ABSTRACT 
 
 
 
 
Title of Thesis: ON THE VERGE: A DESIGN FRAMEWORK 
USING LANDSCAPE ECOLOGY AND EDGE 
DESIGN PRINCIPLES TO RECONNECT 
HABIATAS AND DIVERSIFY VEGETATION 
FOR POLLINATORS IN SE TEXAS 
  
 Audrey Erin Fann, Master of Landscape 
Architecture, 2022 
  
Thesis directed by: David N. Myers, Ph.D. Landscape Architecture 
Program, College of Agriculture and Natural 
Resources  
 
 
 
Pollinators are a crucial part of our ecosystem providing benefits for plant reproduction, plant 
diversity and agricultural crops. Pollinator habitats are constantly under threat due to human 
activity including pesticide use, land use change and development, pollution, and climate change. 
With an increase of development there is also a decrease in connectivity between natural habitats 
which causes habitat fragmentation and a loss of pollinators. This thesis suggests that by using 
landscape ecology principles and other research, a design framework that provides 1) 
connectivity between existing natural areas, and 2) increasing vegetation community diversity 
will lead to increased quantity and quality of pollinator habitat and thus more overall pollinators. 
This design framework is demonstrated in a case study in Hidalgo County, Texas in the Rio 
Grande River basin. 
 
  
 
 
 
 
 
 
 
 
 
ON THE VERGE: A DESIGN FRAMEWORK USING LANDSCAPE ECOLOGY AND EDGE 
DESIGN PRINCIPLES TO RECONNECT HABIATAS AND DIVERSIFY VEGETATION 
FOR POLLINATORS IN SE TEXAS 
by 
 
 
Audrey Erin Fann 
 
 
 
Thesis submitted to the Faculty of the Graduate School of the 
University of Maryland, College Park, in partial fulfillment 
of the requirements for the degree of 
Master of Landscape Architecture  
2022 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Advisory Committee: 
Dr. David N. Myers, Chair 
Dr. Karin Twardosz Burghardt 
Dr. Peter I. May 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
? Copyright by 
Audrey Erin Fann 
2022 
 
 
 
 
 
 
 
 
 
 
 
  
 
Dedication 
To my family, this is for us. 
Para mi familia, esto es para nosotros. 
ii 
 
 
 
Acknowledgements 
Words can?t even begin to express my thanks to Dr. David Myers, for his extensive 
guidance throughout this entire thesis process. Thank you, Dr. Myers for your time, 
your constant reassurance, and for the remarkable structure you provided me.  
I would like to thank my committee members Dr. Karin Twardosz Burghardt for her 
immense knowledge of insects and plants, and Dr. Peter May for his enthusiasm and 
great knowledge of ecological design.  
 
Thank you to my family for helping me develop my project, conduct research along 
my site, and for their endless support of my dreams. Lastly, thank you to my friends 
near and far for keeping me laughing throughout the most difficult of times.  
 
Thank you all.  
 
 
iii 
 
 
 
Table of Contents 
 
 
Dedication ..................................................................................................................... ii 
Acknowledgements ...................................................................................................... iii 
Table of Contents ......................................................................................................... iv 
List of Figures ............................................................................................................... v 
List of Abbreviations ................................................................................................... vi 
Chapter 1: Introduction ................................................................................................. 1 
Chapter 2: Literature Review ........................................................................................ 4 
Chapter 3: Site Inventory and Analysis ...................................................................... 33 
Chapter 4: Design Framework and Design ................................................................. 52 
Chapter 5:  Conclusion and Summary ........................................................................ 77 
Appendices .................................................................................................................. 79 
Bibliography ............................................................................................................... 88 
 
 
 
 
 
 
  
iv 
 
 
 
List of Figures 
Figure 1 Counties of The Rio Grande Valley ............................................................. 34 
Figure 2 Site Context Maps of Texas and the Counties of the Rio Grande Valley .... 34 
Figure 3  Hydrology Map Along Proposed Site ......................................................... 35 
Figure 4 Average Monthly Precipitation in Hidalgo, County..................................... 36 
Figure 5 Average Monthly Rainfall ............................................................................ 36 
Figure 6 Average Wind Direction in Hidalgo, County ............................................... 37 
Figure 7 Annual Growing Season for Hidalgo, County ............................................. 37 
Figure 8 Soil Map in the Proposed Site ...................................................................... 39 
Figure 9 Land Use Type within the Proposed Site ..................................................... 40 
Figure 10 Natural L:and Use within the Proposed Site .............................................. 41 
Figure 11 Farmland Land Use within the Proposed Site ............................................ 44 
Figure 12 Urban Area Land Use within the Proposed Site ......................................... 45 
Figure 13 Main Roads within Proposed Site .............................................................. 46 
Figure 14 Population Change for Hidalgo, County .................................................... 47 
Figure 15 Section A Site Analysis .............................................................................. 48 
Figure 16 Section B Site Analysis .............................................................................. 49 
Figure 17 Section C Site Analysis .............................................................................. 50 
Figure 18 Section D Site Analysis .............................................................................. 51 
Figure 19 Master Plan Section A ................................................................................ 56 
Figure 20 Master Plan Section B ................................................................................ 58 
Figure 21 Master Plan for Section C........................................................................... 60 
Figure 22 Master Plan for Section D .......................................................................... 62 
Figure 23 Four Lane Roads- Street Tree Program ...................................................... 64 
Figure 24 Before and After Implementations of Increasing Vegetation Structure 
Along Two-Lane Roads with Shoulders ..................................................................... 65 
Figure 25 Two-Lane Roads as Is ................................................................................ 65 
Figure 26 Two Vegetation Structure Implementations ............................................... 66 
Figure 27 Three Vegetation Structures Intervention .................................................. 67 
Figure 28  Four Vegetation Structures Intervention ................................................... 68 
Figure 29 Farm Roads as Is ........................................................................................ 69 
Figure 30 Before and After Aerial and Perspective Images of Farmland Roads ........ 69 
Figure 31 One Vegetation Structure Implementation ................................................. 70 
Figure 32 Two Vegetation Structures Intervention .................................................... 71 
Figure 33 Three Vegetation Structures Intervention .................................................. 71 
Figure 34 Before and After Aerial and Perspective Images of Reforesting Farmlands
..................................................................................................................................... 72 
Figure 35 Before and After Aerial and Perspective Images of Urbanizing Farmlands
..................................................................................................................................... 73 
Figure 36 Oxbow Lakes as Is...................................................................................... 74 
Figure 37 One Vegetation Structure Interventions ..................................................... 74 
Figure 39 Two Vegetation Structures Interventions ................................................... 75 
Figure 40 Three Vegetation Structures Interventions ................................................. 75 
 
v 
 
 
 
List of Abbreviations 
RGV- Rio Grande Valley 
RGR- Rio Grande River 
LRGV- Lower Rio Grande Valley 
BSP- Bentsen State Park 
NBC- National Butterfly Center 
SANWR- Santa Ana National Wildlife Refuge 
TPWD- Texas Parks and Wildlife Department 
USFWS- U.S. Fish and Wildlife Service 
NABA- North American Butterfly Association 
TCP- Thornforest Conservation Partnership 
Y2Y- Yellowstone to Yukon 
 
 
vi 
 
 
 
Chapter 1: Introduction 
Pollinators are critical to the preservation of healthy ecosystems. Biodiversity and 
ecosystem services are being lost because of fragmenting natural habitats (Tscharntke 
et al., 2016), and it is important to protect pollinator habitats because ?pollinators 
provide an essential ecosystem service to humankind? (Fontaine et al., 2006). 
Pollinator habitats are constantly under threat due to human activity including 
pesticide use, land use change and development, pollution, and climate change. 
Increasing population directly impacts the need for housing as well as the need to 
devote more land to agriculture. Developing natural land into urban or agricultural 
areas results in both a loss of total pollinator habitat as well as reducing the 
connectivity between remaining natural landscapes. Losing these vital habitats 
decreases the amount of vegetation diversity, thus decreasing the overall number of 
pollinator populations. According to Theobald et al., (2010), we are losing a football 
field of natural areas every 30 seconds in the United States, which adversely impacts 
many species including pollinators.  
This thesis suggests that by using landscape ecology principles and other research, a 
design framework that provides 1) connectivity between existing natural areas, and 2) 
increasing vegetation community diversity will lead to increased quantity and quality 
of pollinator habitat and thus more overall pollinators. This design framework is 
demonstrated in a case study in Hidalgo County, Texas in the Rio Grande River 
basin. Typical land uses in the case study area include residential, commercial, 
agriculture, transportation, recreational areas, and natural areas. Restoration plans and 
1 
 
 
 
designs in the publicly held natural areas in the case study area provide an 
opportunity for connectivity.  
Hidalgo County is experiencing an over 10% growth rate, over the last 10 years, and 
new development for suburbs is displacing natural areas or farmlands. There is a 
competition for space to either grow food or create housing. New urban development 
results as a disconnect between patches of greenspaces like state parks and wildlife 
management areas, a decrease of plant diversity, and a decrease of habitat for 
pollinators (Wenzel et al., 2020). The proposed design framework will address both 
connectivity and vegetation community diversity to support that pollinator habitat is 
conserved, restored, and connected when land around the Rio Grande River develops 
due to the urban and suburban expansion or other land use change.  
The thesis will be organized into five chapters: introduction, literature review, site 
inventory and analysis, design framework, and conclusion and summary. Chapter 2: 
Literature Review will explore principles of landscape ecology, the relation between 
plant diversity and pollinator diversity, roads, stakeholder groups and applied case 
studies. The design framework principles will be derived from the literature, creating 
a framework that will increase habitat and connectivity, increasing the vegetation 
diversity, and therefore, enriching the overall health of pollinator habitats. Chapter 3: 
Site Inventory and Analysis will document the case study's land use, hydrology, 
vegetation, and open spaces, while noting the sites opportunities and constraints. 
Chapter 4:  Design Framework will provide guidelines, plans and designs for 
promoting edge design along roads and farmlands that benefit pollinators. The design 
will create a connection between green spaces using landscape ecology and edge 
2 
 
 
 
design principles, and increase vegetation structural diversity, thus increasing 
pollinator habitat. Chapter 5: Summary and Conclusion provides a review of the 
objectives of the thesis, a conclusion discussing the design framework, benefits, 
limitations, and an overall summary of the thesis.  
3 
 
 
 
Chapter 2: Literature Review 
This thesis will develop a design framework after understanding design principles 
from landscape ecology and edge design, the relation of plant diversity and pollinator 
diversity, roads and their benefits or disadvantages to pollinators, stakeholder groups 
and applied case studies. The literature review is organized into five sections. The 
first section will investigate selected concepts and principles from the landscape 
ecology discipline, such as landscape mosaics: patches, corridors, and edges. The 
second section broadly reviews pollinator types and their food, habitat, nesting and 
water needs, and the influence of plant diversity on pollinator diversity. The third 
section will document benefits or detriments of roads in relation to pollinators and 
pollinator habitat. The fourth section will discuss groups and organizations that are 
stakeholders in the Rio Grande Valley. The last section will investigate precedent 
case studies that are successfully helping pollinator habitats at a variety of scales. 
Section1: Landscape Ecology 
Ecology is the study of interactions among organisms and their environment (Forman, 
1995). Landscapes are ?formed by two mechanisms operating together within its 
boundary specific geomorphological process and specific disturbances of component 
stands? (Forman and Gordon, 1981). Landscape ecology is the study of spatial 
patterns that provides scientific basis for the study and management of landscapes and 
their ecological systems (With, 2019). Landscapes can be studied at any scale and can 
occur in terrestrial systems and even aquatic and marine systems (With, 2019).  
4 
 
 
 
 
Landscape Mosaics 
Landscape mosaics show an ?existence of clear boundaries between neighboring 
patches? (Hansson and Merriam, 2012) from an aerial view. Landscape mosaics, 
especially ones with ?barriers, conduits, and highly heterogeneous areas, determine 
the resistance to flow or movement of species, energy, materials, and disturbance 
over a landscape? (Forman, 1996). In natural areas, boundaries may be less evident 
than in urban areas due to being heavily altered by humans (Hansson and Merriam, 
2012). The overall health of a landscape can be identified by the overall connectivity 
of the natural systems present (Dramstad et al., 1996).  
Forman (1995) suggests that there are three mechanisms which create spatial 
heterogeneity within a landscape? substrate heterogeneity, natural disturbance, and 
human activity. Substrate heterogeneity is related to the soil types, hills and wet spots 
on a landscape which create vegetation patchiness. Natural disturbances are natural 
disasters like tornadoes, fires, and pest explosions, all of which will create 
heterogeneity within a landscape (Forman, 1995). Human activity is also a major 
cause of heterogeneity. Building roads, cutting down woodlots, and plowing fields 
will all cause heterogeneity within a landscape. After alterations in the landscape, 
whether by natural or anthropogenic events, a visual difference will be evident as 
landscape mosaics.  
Landscape mosaics are composed of three characteristics: patches, corridors, and 
background matrix (Forman, 1995). Background matrixes are often developed lands 
5 
 
 
 
like agricultural or urban areas (Bentrup, 2008). Patches are remnants that are 
surrounded by different plants and animal communities (Bentrup, 2008). Corridors 
are the link between patches and are usually valuable and suitable for biodiversity 
(Bentrup, 2008). The arrangement of landscape mosaics can affect the ecological 
systems interacting between them (Hansson and Merriam, 2012). 
Patches 
A patch is a wide homogeneous area that differs from its surroundings (Forman, 
1995). Patches can be diverse in size and provide a variety of benefits for their 
inhabitants. Small patches are able to capture a range of habitats and are able to 
protect biodiversity in areas with limited space (Bentrup, 2008) while large patches 
often provide major ecological benefits (Forman, 1995).  
There are ecological values of both large and small patches. Patch sizes and their 
benefits are often up for discussion; some believe having a single large patch is more 
beneficial for species, while others believe that smaller patches are more beneficial 
(Forman, 1995). Small patches, while valuable, cannot be the sole replacement for 
large patches. Due to the ever-changing landscapes, like development, large patches 
can quickly transform into small patches. The more land a species has to inhabit the 
greater number of species are able to thrive? smaller patches have less resources for 
species. A landscape without large patches gets eviscerated (Forman, 1995) for its 
limited resources, unfortunately smaller patches are the dominant form of natural 
habitat on Earth (Haddad et al., 2015 as cited in Tscharntke et al., 2016). A healthy 
6 
 
 
 
landscape should have large patches with supplemental smaller patches (Forman, 
1995).  
While patch size is important, shape always plays a crucial factor in ecological 
movement and flow. Human activity plays a direct role in the formation of patch 
shapes. Shapes affect the ecological function of patches and there are four attributes 
to the patch shapes: elongated, convolution, interior, and perimeter (Forman, 1995)   
Elongated patches are more efficient than round patches along areas like agriculture 
fields, or forest areas, but are less effective in conserving internal resources of a patch 
(Forman, 1995). Since these patches are long, research suggests that orientation plays 
a key role in the positioning and success of these patches (Forman, 1995). Patches 
perpendicular to an animal's route will slow down their movement because they will 
be more cautious when approaching the boundary (Forman, 1995). Patches placed 
parallel to the movement of the species may enhance their movement (Forman, 1995). 
Convoluted patches have longer perimeters, and more lobes which can cause 
turbulence in water and wind flow (Forman, 1995). The lobes offer benefits by 
forming microclimates, creating shaded areas during the hot days, and blocking wind 
during windy times (Forman, 1995). Interior patches are often protected from solar 
radiation and wind and are generally a critical area for species that require remote 
habitats (Forman, 1995). Perimeter patches are surface boundaries with infinite 
vegetation varieties. They are everything surrounding the interior patch. Identifying 
the elongation, convolution, interior, and perimeters of patches determines the shape 
and ecological characteristics of a patch. 
7 
 
 
 
The further patches are from each other, the less abundant the pollinators are. The 
diversity of pollinators decreases in disconnected habitats (Rahimi et al., 2021). In ag 
land centric areas pollinators are dependent on nearby natural landscape patches 
(Olsson et al. 2015, as cited in Rahimi et al., 2021). A habitat with an abundance of 
natural areas compared to those of agricultural lands would result in species spillover 
to the surrounding fields (Kammerer et al., 2016, as cited in Rahimi et al., 2021).  
Corridors 
Corridors are strips of land that differ from the adjacent land on both sides (Forman, 
1995). Corridors are interconnected landscape elements like wildlife habitats, riparian 
areas, wetlands, and prime agricultural areas (Ndubisi et al., 1995). Corridors help 
increase gene flow and population viability, enable recolonization of patches, and 
provide habitat for a variety of species by creating connectivity between patches 
(Bentrup, 2008).  
Corridors have five functions: habitat, conduit, filter, source, and sink. Corridors are 
habitats to edge and generalist species; rare and endangered species are usually absent 
(Forman, 1995). There are two types of corridor habitats: line corridors and strip 
corridors. Line corridors are narrow and dominated by edge species. Strip corridors 
are wide enough to have interior species (Forman, 1995). The transportation or 
conduit through corridors are like rivers or roads moving things along them. 
Corridors can also function as boundaries; filtering species trying to cross between 
patches (Forman, 1995). Once a corridor has been established, you may find species 
that spread out while utilizing it to cross between patches causing a diversifying 
8 
 
 
 
effect on the matrix (Forman, 1995). Corridors can act like a sink collecting soil, 
water, chemicals, and seeds from the environment (Forman, 1995).  
Corridor widths can vary in size, even within the same corridor. It is useful to 
measure the width at different heights above the ground. Larry Harris and colleagues, 
as cited in Forman (1995), have recommended corridor widths for three different 
objectives. The first being when the movement of individual animals and their 
behavior is well known you can have a corridor width of tens of meters. Secondly, 
when you are considering an entire species and there is a lot of knowledge about 
them, the corridor will be hundreds of meters wide. If there is a lot known about the 
species, they can anticipate them using the corridors more frequently, thus justifying 
the wide width. Finally, when you are considering an entire assemblage of species 
that you know little about and expecting it to function for decades or hundreds of 
years, corridor widths should be measured in kilometers. Not having great knowledge 
of any singular species encourages a larger width to accommodate the variety of 
species that could potentially use the corridor.  
Bentrup (2008), provides suggestions regarding the design of corridors. Managers 
should design corridors to perform well at several scales, and along dispersal or 
migratory routes of species. It is beneficial to have similar vegetation in corridors and 
their connecting patches and preferably have them be wide corridors of a minimum of 
one hundred? for invertebrates. To avoid expanding fragmentation, Bentrup 
recommends using existing corridors like roads or utility corridors, and to focus on 
edge design. While constructing a planting plan for edge design, it's crucial that plants 
9 
 
 
 
closest to the roads are smaller in height to reduce the potential of vehicle-wildlife 
collisions. It is also important to select the correct plants that can survive along busy 
roads and are more tolerant to pollutants.  
Boundaries and Edges 
?Linear habitats such as hedgerows, crop margins, and roadsides have been shown 
to have value to other invertebrate pollinators, primarily butterflies? (Munguira and 
Thomas, 1992). 
Edges are described as the outer portion of a patch that differs from the interior of the 
patch (Dramstad et al., 1996). Often the edge and interior look different and can have 
different species composition and abundance. Boundaries can be political, or 
administrative and divided between inside and out. As human development continues, 
edges will be created dividing what is natural and human made (Dramstad et al., 
1996). The shape of a patch can be defined by its edge and can be manipulated to 
accomplish ecological functions (Dramstad et al., 1996).  
Forman (1995) describes three mechanisms that produce vegetation edges? a patchy 
physical environment, natural disturbances, and human activity. Boundaries can be 
differentiated by being hard or soft. Edges are generally high density and have a high 
diversity of plant species differing from the inner portion of species. To understand 
the boundaries, we recognize three important spatial scales: fine scale, intermediate 
scale, and broad scale. Fine scale boundaries are blown down clearings adjacent from 
grasslands or roads. Intermediate scale boundaries are created by landforms where a 
ridge meets a valley bottom. Broad scale boundaries separate climatic regions, 
10 
 
 
 
tectonic plates, and biomes. Boundary patterns between two ecosystems are 
curvilinear, or straight.  
Edges can influence communities by acting as a filter or barrier, which is particularly 
helpful to reduce invading species (Fonseca, 2008). Some species are sensitive to the 
conditions found in the interior and having that outer edge habitat is crucial to their 
survival (Clift, 2018). The population of species along the edge is normally different 
from those inside the patch (Clift, 2018). Edges are thought to have a higher 
biodiversity than the inner habitat, such as ecotones, which are soft edges with ?a 
gentler transition between two environments? (Clift, 2018). Edge structures will 
diverse horizontal and vertical plantings are richer in species (Dramstad et al., 1996).  
Edges are the first to receive pesticides around agriculture areas due to wind and 
water flow. Conservation buffers can help block the spread of pesticides onto 
pollinator habitats. Bentrup in (2008), recommends when designing buffers to use 
vegetation with a chemical tolerance, to use a mixture of plant sizes to fill in gaps, 
and placing buffers in areas where they would intercept prevailing winds. Plant 
palettes are recommended to have species that- bloom for entire growing seasons, 
natives, mixed plant heights, and plants that do not host pests. To decide where to 
place edge buffers and which plants to plant, sun studies should be taken into 
consideration. Plants should be selected based on their sun needs and their ability to 
get sun after placement 
  
11 
 
 
 
Oxbow Lakes 
According to the Resource Enhancement and Protection Conservation Education 
Program (2019) and the Nature Conservancy, oxbows are U-shaped cut offs of rivers 
because of natural and human activities. Agriculture runoff, drainage improvements, 
and development are all causes of sediment buildup which create blockage between 
river bends. Restoring the riparian edge of an oxbow can improve water quality, 
wildlife habitat and increase flood water storage. It is best to plant native grasses, 
forbs, plant a quick growing nurse crop, and to utilize fallen trees as in-water 
structures for wildlife.  
Section 2: Pollinators 
There are many diverse types of pollinators, each with unique benefits to plants and 
vegetation communities. They are essential to the reproduction of plants and help 
with the production of genetically diverse vegetation. Pollinators play a necessary 
role in our ecosystem, providing ?pollination services to over 180,000 different plant 
species and more than 1,200 crops? (About Pollinators, n.d.). Major pollinators 
groups include butterflies, bees, birds, bats, beetles, flies, and moths.  
Butterflies 
There are more than 700 species of native butterflies in the United States (Marks et 
al., 2005). During the four stages of their life cycle, egg, caterpillar, pupa, and adult, 
butterflies need different things for each stage. Eggs can be on leaves, branches, trees, 
shrubs, wildflowers, grasses, and soil (Marks et al., 2005). Caterpillars will eat host 
plants before they turn into pupas. While pupas don't need to eat, they do need 
12 
 
 
 
protection and will utilize tall grasses, piles of leaves and bush (Marks et al., 2005), 
and butterflies will rely on nectar from flowers.  
Bees 
There are over 4,000 native bee species in the United States (Marks et al., 2005), and 
over 700 species in Texas (Warriner and Hutchins, 2016). Honeybees are essential to 
crop pollination and play an important role in the ecosystem. Bumblebees ?live in 
colonies, share work, and have multiple overlapping generations throughout the 
spring, summer and fall? (Marks et al., 2005). Solitary bees, approximately 90% of 
Texas natives (Warriner and Hutchins, 2016), do not live in hives or colonies, but 
nest in dirt mounds, termite holes, mud, plant resins, and the ground (Marks et al., 
2005).  
Birds 
Birds are the most helpful to plant species that are sparsely distributed (Ford 1985, as 
cited in Sekercioglu, 2011). Birds fertilize plants by transferring pollen from their 
bills from one plant to another. In North America, there are no commercial crops that 
rely on birds for pollination (Cirino, 2016). Birds pollinate wildflowers, but birds are 
suffering due to the decrease in wildflower habitats due to monoculture agriculture 
(Cirino, 2016). Hummingbirds are essential to pollinating many shrubs and vines and 
pollinate flowers as they drink nectar from them (Marks et al., 2005). Hummingbirds 
and other birds visit flowers that are typically tubular, have tubes, funnels, cups, 
supports perching, brightly colored like red, yellow, or orange, odorless, and open 
during the day (About Pollinators, n.d.).  
13 
 
 
 
Bats 
Bats are essential for tropical and desert climate vegetation. Many fruits rely on bats, 
like ?banana, mangoes, dates, figs, peaches, guava, avocado and agaves? (Marks et 
al., 2005). There are 45 species of bats in the United States, with the greatest 
concentrations living in the southwestern states (Marks et al., 2005). Two nectar 
feeding bats, the lesser long-nosed bat, and the Mexican long-tongued bat, which 
migrate north thousands of miles in the spring from Mexico to Arizona, New Mexico, 
and Texas, are federally endangered species (About Pollinators, n.d.) Bats are 
nocturnal, making them beneficial to nocturnal blossoms (Marks et al., 2005). Bats 
typically visit flowers that are large, pale, or white in color, and very fragrant (About 
Pollinators, n.d.).  
Beetles and Flies 
There are over 30,000 beetle species found in the United States (Ley et al., 2018). 
They have a bad reputation because they leave behind a mess and destroy flowers, but 
they still play a role in pollination (Ley et al., 2018). Beetles are important to species 
such as magnolias and spicebush (About Pollinators, n.d.). Beetles visit flowers that 
are open during the day, bowl-shaped, white, dull white, green, strongly scented, 
large solitary flowers, or small bunches of flowers (About Pollinators, n.d.). Flies 
typically visit flowers that are pale, dark brown or purple, have putrid odors like 
rotting meat, carrion, dung, humus, sap, and blood (About Pollinators, n.d.).  
  
14 
 
 
 
Moths 
Moths, while at a glance look like butterflies, have distinct features that tell them 
apart (Ley et al., 2018). Moths are typically less colorful, and hairier than butterflies, 
and they have antennae that are featherlike (Ley et al., 2018). The majority of moths 
are nocturnal, which is important for night blooming flowers (Marks et al., 2005). 
Moths need habitats similar to butterflies. Moths typically visit flowers that are in 
clusters, white or dull in color, open in the late afternoon or evening, and flowers that 
produce ample nectar (About Pollinators, n.d.). 
Plant Diversity Relation to Pollinator Diversity 
In previous decades, declines of pollinator populations have been recorded 
worldwide. This raises concerns about the loss of the important ecological function of 
pollinators for wild plant communities and agricultural systems (Potts et al. 2010). 
One way to combat the decline of pollinator populations around agriculture areas is to 
?enhance plant diversity at multiple spatial scales ranging from local fields to 
surrounding landscapes? (Kremen & Miles, 2012; Kennedy et al., 2013 as cited in 
Isbell et al., 2017). The number of foraging niches positively correlates with the 
number of nectars, pollen profiles, and flower types available (Potts et al., 2003) 
eventually leading to pollinator diversity. 
The relationship between plant diversity and pollinator diversity is mutualistic and 
will directly influence one another. Experimental evidence directly reveals that plant 
communities could be negatively affected by a loss of pollinator diversity (Fontaine et 
al., 2006). The number of pollinators in an area has a direct impact on the ability to 
15 
 
 
 
increase plant population birth rate. Increasing plant species richness will positively 
affect pollinator diversity and pollination services (Orford et al., 2016 as cited in 
Isbell et al., 2017). The richness of a plant palette helps a variety of pollinator species 
because pollinators differ in floral preference and have diverse needs for their 
individual life cycles.  
Diversity of plants is equally as important as the number of plants in one area. In a 
study, conducted by Ebeling et al in 2008, they comprised 82 plots with plants having 
six levels of species richness to determine how plant richness affects pollinator 
richness. They discovered that plots with one flowering plant received around 20 
pollinator visits, where plots with twelve flowering plant species had over 200 
pollinator visits over the same period of time. This shows that having more diverse 
plants provides an increase in floral resources like nectar and pollen. The study's 
results state that ?plant species richness, blossom cover and the presence of attractive 
plant species enhanced the temporal stability in frequency of pollinator visits? 
(Ebeling et al., 2008). High diversity of plants and the frequency of pollinator 
visitations can be critical to the success and stability of plant communities.  
The diversity of crops is also affecting the density of pollinators. A study conducted 
by Raderschall, and colleagues (2021), showed that an increase of crop diversity in 
the landscape enhanced the densities of bumble bees. This study also showed that 
farmland near semi natural habitats supported higher densities of managed and wild 
bees (Raderschall, 2021). Increasing the pollinator densities will benefit crops and 
incentivizes farmers to have agri-environmental schemes.  
 
16 
 
 
 
Food 
Flowers are a great source of food for pollinators because it provides them, nectar, 
and pollination services. Native bees are only able to get food from nectar and pollen 
(Warriner and Hutchins, 2016). Fallen fruit is also food for pollinators like bees, 
beetles, and butterflies. Butterflies need host plants to be eaten by their larvae in the 
early stages of development. Planting diverse plants with a variety of colors, 
fragrance, heights, and bloom periods will attract different pollinator species (Ley et 
al., 2018). Most pollinator species benefit from sites with ?a diverse array of native 
herbaceous and woody plants? (Warriner and Hutchins, 2016), so they will have food 
for a longer period of time.  
Plants and Reproduction 
Pollinators need different plants for different stages of their lives. Sites with diverse 
native herbaceous and woody plants are the most beneficial to pollinators (Warriner 
and Hutchins, 2016). Rich native plant assortments increase the availability of 
suitable egg-laying sites (host plants) for butterflies and moths (Warriner and 
Hutchins, 2016). Host plants play a key role in the ability for pollinators to continue 
multiplying. Some pollinators are reliant on a single species as host plants, while 
other pollinators are able to utilize a variety of plants. For example, Monarch 
butterflies (Danaus plexippus) are dependent on milkweed (Asclepias) plants during 
their egg laying (Warriner and Hutchins, 2016). It's important to plant vegetation in 
groups to increase pollination efficiency (Ley et al., 2018.) 
  
17 
 
 
 
Shelter and Nesting 
To provide pollinators protection from severe weather conditions and predation, it is 
vital to have sites for nesting and roosting. Incorporating plants with varying heights 
like trees, shrubs, and perennials, provide the most opportunities for pollinators to 
find shelter (Ley et al., 2018). Dead trees can be a great nesting site for pollinators 
and should be left alone when possible (Warriner and Hutchins, 2016). Leaving soils 
uncovered in some areas provides nesting sites for insects that are ground nesters 
(Ley et al., 2018). Bees are central place foragers. Female bees collect all their food 
from one central point on the landscape? their nesting site (Warriner and Hutchins, 
2016). The nesting site for bees can be categorized into three categories, ground 
nesters, tunnel nesters, and cavity nesters (Warriner and Hutchins, 2016), which is 
why it's important to ensure space for all their needs. Cavity nesters and generalist 
species usually benefit more from urbanization than ground nesters and specialists 
(Wenzel et al., 2020). Cavity nesters can utilize buildings, while ground nesters have 
less bare soil due to high intensity lawns, and sealed surfaces (Wenzel et al., 2020). 
Water 
Water is a necessity for pollinators, not just for drinking, but for bathing and 
obtaining mineral nutrients (Marks et al., 2005). It is important that fresh water is 
available for pollinators, free from pesticides (Marks et al., 2005), and other 
pollutants. Pollinators get most of their water from food, for example, caterpillars that 
eat plants which are mostly made of water.  
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Section 3: Roads 
In the United States, roadsides encompass more than 10 million acres of land 
(Forman et al., 2003) through agricultural and urban areas. While roads are beneficial 
to humans, they can create a disconnect between habitats for pollinators. Roadsides 
offer several benefits to pollinators, including food, nesting and breeding sites, and 
shelter. Since roads are causing fragmentation through natural areas, roadside 
plantings can provide corridors between patches for pollinators. Road corridors are 
linear surfaces used by vehicles usually with vegetated parallel strips on either side 
(Forman, 1995). These roadside corridors are particularly important for pollinators in 
areas with highly altered landscapes, such as intensely managed agricultural lands and 
urban areas (Remley and Redmond, 2017). Planting for pollinators along roads also 
brings other benefits like ?stabilizing roadsides, reducing stormwater pollution, 
supporting wildlife, and increasing public appreciation of the local landscape? 
(Remley and Redmond, 2017). 
Often, a common concern in creating these diverse habitats along roads is that they 
increase the likelihood of pollinators getting killed by vehicles, but it actually helps 
reduce this issue (Remley and Redmond, 2017). When pollinators do not have the 
abundance, they are looking for on one side of the road they will venture off onto the 
other side to see if there are more resources available? causing them to be within the 
boundaries of fast-moving cars. If we increase the diversity and volume of plants on 
both sides of the road, we reduce the need for pollinators to cross to the other side to 
19 
 
 
 
reap the benefits of flowering plants. There was a study done to evaluate this theory 
of pollinators crossing the road.  
The study was performed, at the University of Michigan in 2021, by doctoral students 
Gordon Fitch and Chatura Vaidya, which evaluated to see how much of an impact 
road had on pollinators? ability to utilize plants along both sides of the roads. Using 
three plants, the students placed two on one side of the road and the third on the 
opposite side; all plants were placed at an equal distance from each other. The side 
with two plants had one of them with a luminous pigment, which was applied to the 
reproductive structures of the flowers. At the end of the day, the plants were brought 
back to a dark room to use an ultraviolet flashlight to see and record the number of 
flowers that had the pigment on them. The study showed that the single plant across 
the road had 50% less pigment than the plant on the same side of the road as the 
pigmented plant. The size of the road also plays a role in the reduction of pollen 
transfer from plant to plant. The more lanes a road had and the wider it was, the less 
pollinators were able to cross. Large or medium size roads obstruct the movement of 
bees and lowers their ability to forage and pollinate on the other side of the road. 
Roads pose a significant barrier for pollinators, and this study was one of the first that 
proved it.  
Depending on the location of the road, pesticides can play a large and detrimental role 
with pollinators. If the roads are along farmlands, it is important to have a buffer 
between the diverse high-volume pollinator plantings, and crops to reduce the amount 
of pesticide going onto the plants. If the roads are just along urban areas, you can 
20 
 
 
 
reduce the effects of pesticides by carefully spot spraying or completely avoiding 
spraying pesticides, communicating with landowners about the effects of drifting 
pesticides, and overall, being more conscientious about the type of pesticides used 
(Remley and Redmond, 2017).  
In addition to pesticides and vehicular tragedies, pollinators also face other issues 
along roads like different forms of pollution. With plantings along roads, we expose 
pollinators to pollutants like ?noise, light, exhaust fumes, dust and metals? (Forman et 
al., as cited in Philips et al., 2020). The more vehicles along roads, the more pollution, 
and the greater risk for pollinators to be poorly influenced. Loud noises from the 
speeds of vehicles and traffic can defer pollinators from foraging along roadsides 
(Phillips et al., 2020). A study performed by Phillips and colleagues sought the 
impacts of pollutants on pollinators along road verges. The results of this study note 
that despite originally thinking road plantings would become ecological traps for 
pollinators, they can have an advantageous impact. The study showed that pollinators 
are willing to and able to move away from pollution. The researchers still 
recommended having at least two meters between the high-density plantings, and 
road edges (Phillips et al., 2020).  
Bentrup (2008), advises plants along roads be made up of a variety of colors, textures, 
form, and height. Areas closer to the road should have the most detail because they 
are what people driving by will see. Plantings for pollinators include ?wildflowers, 
native bunch grasses, shrubs, and trees that provide pollinators with food or shelter? 
(Remley and Redmond, 2017). Bentrup also suggests ensuring safety, by designing 
21 
 
 
 
and placing buffers that will allow view of oncoming traffic at intersections. To 
design near intersections, you need to have a view called the ?site triangle,? whose 
location is determined by the vehicular speed in that area. Setbacks are 70ft at 15 
mph, 90 ft at 20 mph, 170 ft at 30 mph, 195 ft at 40 mph, 245ft at 50 mph, and 285ft 
at 55mph (Bentrup, 2008). 
  
22 
 
 
 
Section 4: Stakeholder Groups 
Farmers 
Farmlands are an essential part of our livelihoods. With the need for food to support 
the growing population, we often choose farmlands at the expense of biodiversity 
(Foley et al., 2005). Farmlands are mostly monocultures or potentially rotated with 
only a few other crops throughout the year. Pollinators play an essential role to the 
success of farmlands. Globally, $577 billion worth of annual food production relies 
on direct contributions by pollinators (IPBES, 2016, as cited in Betts et al., 2019). 
With the decline of pollinators, we can see adverse consequences on food production 
(Winfree et al. 2018 as cited in Betts et al., 2019) and native biodiversity (IPBES, 
2016, as cited in Betts et al., 2019). While the relationship between farmlands and 
pollinators is a mutualistic one, pollinators respond positively to a more diverse 
planting palette. In an area with less natural habitats, pollinators are forced to venture 
out further to forage, utilizing more energy (Maurer et al., 2020, as cited in Rahimi et 
al., 2021). There is evidence supporting the notion that having plant diversity and 
natural areas around farmlands will increase pollinators and help with weed and pest 
suppression (Isbell et al., 2017), increasing crop yield.  
While having an increase of natural habitats and pollinators around farmlands is 
great, it's essential to look at the issues that could arise for them. Farmers often 
choose to protect their crops using insecticides, herbicides, and pesticides. Common 
pesticide concerns are insecticides, pesticide mixtures, fungicides, synthetic-auxin 
herbicides, and soil fumigants (Code et al., 2016). Insecticides are acutely toxic to 
23 
 
 
 
pollinators, specifically neonicotinoids, because of their widespread use and insect 
growth regulators. Pesticides move into habitats in a variety of ways, including 
drifting, volatilization, getting into nearby water systems, and wind erosion (Code et 
al., 2016). One way to have a healthy pollinator habitat near farmlands includes 
adding in a pesticide free buffer to block pesticides from going straight onto 
pollinator plants. The pollinator habitat should be a minimum of 30 feet away from 
farmlands using ground-based pesticide applications, 60 feet from the use of air blast 
sprayers, and 125 feet from crops treated with neonicotinoids (Code et al., 2016) if 
there is no buffer. Design and placement of buffers would be to select a site that is 
upwind of pesticide use, prepare the site by pulling weeds and removing weed seeds, 
do not include plants that are hosts for crop pests, and avoid using pesticide once the 
habitat is established (Code et al., 2016). 
With farming being a business, we cannot expect farmers to willingly give up their 
land to help pollinators. Farmers rely on their land to the full extent it has to offer, 
and they might not be able to financially survive without the crops produced on those 
acres. Other issues that arise could be that the farmers need to invest in new 
equipment and diverse seed mixes (Isbell et al., 2017) to tend to the land they want to 
utilize for pollinators. While land sparing is only beneficial to biodiversity, land 
sharing is beneficial to both farmers and nature (Christmann et al., 2021). One of the 
most readily implemented strategies to increase plant diversity is planting species rich 
hedgerows to border crops (Isbell et al., 2017). Other ways to increase the diversity of 
plants include planting weedy forbs, planting forb strips, perennial hedgerow borders, 
intercrops, and polycultures (Garibaldi et al., 2014, as cited in Forest et al., 2017).  
24 
 
 
 
Pollinator Economic Benefits for Farmers 
To persuade farmers to use pollinator strips along their crops, we need to only use 
marketable habitat enhancement plants (Christmann et al., 2021). These plants can be 
wildflowers that farmers could potentially sell either in bouquets or by having a 
community festival where people cut their own. By having pollinator strips in and 
around farmlands, crop yields can increase which can lead to higher profits (USDA, 
n.d.). Farmers could also earn biodiversity credits by dedicating any acreage of land 
to pollinators and selling the credit to the Biodiversity Conservation Trust (Ecosystem 
Services Market Consortium, 2021). Another way to persuade farmers to plant 
pollinator habitat is by allowing them ?to gain social capital as ?pollinator stewards? 
and potentially charge more for their products? (Burkle et al., 2017).  
 
Conservation Reserve Enhancement Program 
 
CREP is the Conservation Reserves Enhancement Program that helps agriculture 
producers retire land to ?protect environmentally sensitive land, decrease erosion, 
restore wildlife habitat, and safeguard ground and surface water? (USDA, n.d.). The 
USDA?s Farm Service Agency established CREP to provide farmers with financial 
benefits for conserving and enhancing natural resources on their farms. The 
commitment time for the program is 10 - 15 years for non-agriculture production on 
the selected land. CREP supports practices like filter strips and forested buffers to 
?help protect streams, lakes, and rivers from sedimentation and agricultural runoff? 
(USDA, n.d.). There are currently no CREP programs in Texas.  
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American Forests 
The American Forest Organization was established in 1875 to create ?healthy and 
resilient forests, from cities to large natural landscapes, which deliver essential 
benefits for climate, people, water and wildlife? (American Forest, n.d.). American 
Forest has projects all over the country to help plant trees, create policy, and create 
resilient forests. This organization is currently working on projects in the Rio Grande 
Valley like the Thornforest Conservation Partnership, The Reforestation Pipeline in 
the Rio Grande Valley, and the Climate-Smart Forest Restoration. The thornforest 
restoration project is complete, planting over 100,000 trees in the RGV (American 
Forest, n.d.).  
Thornforest Conservation Partnership  
In 2018, the Thornforest Conservation Partnership (TCP) was formed to help guide 
conservation efforts in the LRGV. Their goals are to help communicate the 
importance of the thornforest habitat, educate the public about conservation, and to 
encourage action for stronger public policies and funding. (Thornforest Conservation 
Plan, 2020). The TCP developed a conservation plan to protect existing thornforest 
habitat and potential corridors that link habitats together (Thornforest Conservation 
Plan, 2020). The entire thesis site is within the Thornforest Conservation Partnership 
conservation area.  
 
 
26 
 
 
 
 
National Butterfly Center 
The National Butterfly Center (NBC) is a 100-acre plot of land located in Mission, 
Texas that was formed in 1998. The NBC is a project of the North American 
Butterfly Association (NABA), dedicated to conservation and the study of wild 
butterflies in their native habitat (National Butterfly Center, 2020). The NBC is a 
crucial part of the NABA, because it represents the whole lower Rio Grande Valley. 
The National Butterfly Center brings people together from all over the county to see 
rare butterfly?s endemic to the RGV, which helps the economy via ecotourism. 
Without the NBC there would not be as great of a recorded history of pollinators in 
the RGV. They have great resources explaining the rich diversity of species that 
depend on their land to survive, and even as a stop along monarch butterflies? 
migratory routes.  
 
Section 5: Precedent Case Studies 
The following are well known precedent case studies that have utilized landscape 
ecology principles including a focus on hubs and corridors for conservation planning. 
Three projects include the Maryland GreenPrint Program, The Florida Wildlife 
Corridor, and The Yellowstone to Yukon (Y2Y).  
The Maryland GreenPrint Program is a green infrastructure assessment which 
identifies almost 2 million acres of ecologically significant land (Weber, 2003). The 
changing landscape due to population and development changes is destroying wildlife 
27 
 
 
 
habitat in Maryland. Hubs and corridors were identified as a proposed network for 
plants and animals to maintain connectivity even with the changing landscape (Weber 
et al., 2004). The Florida Wildlife Corridor is a statewide corridor that was created as 
a landscape- scale conservation approach. The corridor encompasses nearly 18 
million acres of land, 9.6 million that are already protected, and 8.1 million that have 
no conservation status (Hoctor et al., 2015). Their goal is to advocate for the missing 
links within the hubs, while educating the public about the importance of land 
conservation. Yellowstone to Yukon (Y2Y) is a national conservation effort 
connecting and protecting habitats from Yellowstone to Yukon. This is a 2,000-mile 
corridor that ?protects habitats, keeps habitats connected and inspires others to engage 
in similar work? (Yukon Conservation Initiative, 2022) Their goal is to bring 
communities together to accomplish linking these landscapes together across 
Northwest America and Canada.  
Texas Department of Transportation (TxDOT)   
The Texas Department of Transportation (TxDOT) began its wildflower program in 
the 1930s. This program is participating in The Texas Monarch and Native Pollinator 
Conservation Plan, recognizing the decline in the population of the eastern North 
American migrating monarchs. TxDOT owns and maintains 1.1 million acres of 
roadway right-of-way in Texas. Eight hundred thousand acres of these rights-of-way 
are vegetated and are in all ecoregions of Texas, having a wide variety of landscapes 
(TPWD, 2016). These landscapes help support over 900 species of wildlife and about 
5,500 species of vascular plants (TPWD, 2016).  
28 
 
 
 
The TxDOT program is to help ?reduce the cost of maintenance and labor? (TPWD, 
2016) while still creating aesthetically pleasing landscapes. Using native wildflowers 
upwards of 2,000 species along roads, attracts tourism while helping the environment, 
biodiversity, pollinator health and even the economy (TPWD, 2016). Because of 
TxDOT?s program, communities have come together to appreciate the blooms and 
hold festivals, arts and crafts shows, and even sporting events. 
The flowers are mowed twice a year and timed properly to ensure seed germination to 
ensure next year's bloom. Texas DOT does not use traditional methods of herbicide 
application but rather, spot spray problemed areas. TxDOT purchases approximately 
30,000 pounds of seeds to be used annually, seeding over 15,000 acres of right-of-
ways (TPWD, 2016). This right of ways can create vegetation corridors helping 
fragmented habitats in urban and agricultural areas (TPWD, 2016).  
?From an ecological perspective, grasses and wildflowers planted and/or protected 
through the Wildflower Program have conserved water, controlled soil erosion, and 
provided habitats for wildlife, including pollinators, across Texas? (TPWD, 2016).  
Texas Parks and Wildlife Pollinator Management Guide 
The Texas Parks and Wildlife has created a guide that best helps manage Texas 
pollinators. Some management techniques include treating only 30% of an area at a 
time (Warriner and Hutchins, 2016). Prescribed burns should only be conducted from 
fall to early spring to avoid burning during the growing season. It is also suggested to 
allow dead trees, rotting logs, and dying branches to stay on site because it can be 
29 
 
 
 
useful for tunnel-nesting bees. Lastly, avoid the use of chemical fertilizers, as they 
can be detrimental to wildflowers.  
Missouri Biodiversity Pilot Project 
Missouri developed a program that benefits pollinator habitat, and corn and soybean 
farmers. The program came as a result of a partnership between Ecosystem Services 
Market Consortium (ESMC) and the Missouri Corn Merchandising Council and the 
Missouri Soybean Merchandising Council. This program will allow farmers to earn 
biodiversity credits by participating in this project to increase conservation habitat for 
pollinators. Farmers can create pollinator habitats ?within existing or new field 
borders, buffers, waterways, or on other non-productive agricultural grounds? 
(Ecosystem Services Market Consortium, 2021). After doing so, farmers can obtain 
biodiversity credits to be purchased by interested buyers or the Biodiversity 
Conservation Trust. Farmers can enroll in this program with any amount of acreage, 
and it costs nothing for farmers to participate (Ecosystem Services Market 
Consortium, 2021).  
Ecosystem Services Market Consortium ?is a non-profit that works to compensate 
farmers and ranchers who improve the environment through their agricultural 
practices. Our market program to reduce greenhouse gases, improve water quality, 
and increase other ecosystem services benefits all of society. - Quote obtained through 
the ESMC Website 
  
30 
 
 
 
College Park in Prince George's County, Maryland 
Residents of Prince George's County in Maryland can be a part of the county wide 
conversation efforts for pollinators. The county distributes seed packets scientifically 
developed with native plantings to help butterflies, birds, bees and more. In 2020, the 
Prince George's Soil Conservation District distributed over 500 seed packets.  
College Park, Maryland developed an initiative called ?No-mow April? to encourage 
their residents to refrain from mowing their lawns to support local pollinators. The 
city worked together with the city's Bee City USA committee to motivate 
homeowners to help pollinators grow and thrive during this part of their lifecycle. By 
mowing less, we can expect to see more colors and variety in the landscapes that 
attract a diverse population of pollinators. After making the pledge, residents can pick 
up a sign to display on their lawn to help educate the local community about the 
benefits of ?no-mow April.? The city also has great resources and guides on how to 
plant in ways that best benefit native pollinators. 
Literature Review Conclusions 
In conclusion, the literature review provides principles and tools to 1) provide 
connections between existing natural areas, and 2) increase vegetation community 
diversity to increase quantity and quality of pollinator habitat and thus promote an 
overall increase in pollinators. Landscape ecology principles inform the design at a 
landscape scale to address the patches and their disconnect by using corridors to 
reconnect these natural areas. Pollinators play a crucial role in our ecosystems, 
31 
 
 
 
including the food we eat and ecosystem services for all organisms. Increasing the 
amount of vegetation diversity will increase the number of pollinators in the 
landscape. Roads, while having detrimental qualities, can also actually provide great 
benefits to pollinators when used as pollinator corridor. Designing on both sides of 
the road can lower the fatalities with cars because they have resources keeping them 
on the same side of the road. Roads can function as corridors to transport pollinators 
from patch to patch giving them a place to rest, eat, and providing them shelter. 
Financial benefits and tools that have been used with farmers include programs like 
the Conservation Reserve Enhancement Program. Farmers may often benefit from 
pollinator habitats by gaining a more productive crop, and by minimizing the usage of 
pesticides. There are many great examples, at the regional, state, community, and 
habitat level that show how both large and small implementations can provide 
benefits for pollinators.  
 
32 
 
 
 
Chapter 3: Site Inventory and Analysis 
Chapter 3 will document the inventory and analysis for the selected case study site 
and local area. The site inventory documents the site context, location, and history. 
The three main attributes documented include abiotic, biotic, and cultural which are 
derived from Ndubisi (1995). Abiotic attributes document the hydrology, climate, and 
soil around the site. Biotic attributes document the native vegetation and native 
pollinators. Last, cultural attributes will document and map the land use including 
natural areas, farmlands, and urban areas, roads, and population demographics. 
Case Study Location 
The Rio Grande Valley (RGV) is made up of four counties? from west to east they 
are Starr, Hidalgo, Willacy, and Cameron County. The southern border for three of 
these counties is the Rio Grande River, which divides Mexico and the United States 
of America. With the climate and relative location to the equator, this area has a semi 
tropical climate creating a hotspot for over 300 species of butterflies (Leslie, 2016) 
and 150 species (Wauer, 2004), which are found solely in this area.  
The case study site is in a wildlife corridor proposed by the U.S. Fish and Wildlife 
Service, which plans to create a corridor within the four counties of the Rio Grande 
Valley to protect biodiversity (Texas Parks and Wildlife Department, 2020). This 
project site is a small section of Hidalgo, County, along the Rio Grande River which 
is in the proposed U.S. Fish and Wildlife Service corridor and was selected because 
33 
 
 
 
of its familiarity with the author and the opportunity to connect major natural 
greenspaces in a selected section.  
The green spaces along the border are crucial to the sustainability of pollinators. The 
western hub of the project site is Bentsen State Park. This park was selected because 
of its large size, popularity among the community and its monitored species diversity. 
The eastern hub of the project site is the Santa Ana National Wildlife Refuge. The 
wildlife refuge was selected because of its large size, management goals, and its 
accessibility. The southern boundary of the site is the Rio Grande River. 
Figure 2 Site Context Maps of Texas and the 
Counties of the Rio Grande Valley Figure 1 Counties of The Rio Grande Valley 
 
History 
The proposed project site is located within Hidalgo County, which is part of the four 
counties that make up the Rio Grande Valley. The Rio Grande Valley has a rich 
recorded history dating earlier than the 16th century before explorers arrived. Today, 
the RGV is home to over 1.4 million people and growing. Agriculture and animal 
husbandry are the leading industries in the Rio Grande Valley. The Rio Grande 
Valley is in a subtropical climate with the ability to grow crops all year round. The 
34 
 
 
 
second and third largest industries are mining and recreation which includes national 
and state parks, fishing and hunting, and summer and winter resorts (Brand and 
Schmidt, 2020). The warm temperatures make the RGV a biodiversity hotspot for 
many rare species of birds and butterflies, which bring in ecotourism.  
The RGV is actively growing and there has been a lot of habitat destruction due to 
development causing habitat fragmentation. To combat the rising issues of habitat 
fragmentation, the U.S. Fish and Wildlife Service plans to create a ?wildlife corridor? 
within the four counties of the Rio Grande Valley to protect biodiversity (Texas Parks 
and Wildlife Department, 2020). 
Abiotic Attributes 
Hydrology 
The Rio Grande River is the southern border of Texas and partially the northern 
border of Mexico. The Rio Grande River is 1,855 miles long and the fifth longest 
river of North America (Brand and Schmidt, 2020). The watershed of the RGR is 
Figure 3  Hydrology Map Along Proposed Site 
35 
 
 
 
close to 336,000 square miles and crosses through Texas, New Mexico, and 
Colorado, as well as Mexican states like Chihuahua, Coahuila, Nuevo Leon, and 
Tamaulipas (Brand and Schmidt, 2020). The river flows into the Gulf of Mexico.  
Climate 
Average Monthly Temperatures 
The Rio Grande Valley has a 
subtropical climate which means 
it's warm to hot most of the year. 
Average temperatures for winter 
are around 52?F - 57?F, and 
Figure 4 Average Monthly Precipitation in Hidalgo, County 
summer temperatures are 92?F - 
98?F. The coolest month is January, and the warmest month is August. Warmer 
temperatures make for a longer growing season benefiting many tropical plants.  
Annual Average Monthly 
Rainfall  
 
Hidalgo County gets an annual 
precipitation of 22.8 inches. The 
wettest month of the year is Figure 5 Average Monthly Rainfall 
September with an average of 3.6 inches of precipitation. The driest month of the year 
is December with an average of 0.7 inches. 
  
36 
 
 
 
Average Wind Direction  
Wind is most often blowing in from the South for 7.1 months between January and 
August, and two months from October to December. Wind coming from the East 
happens for 1.4 
months between 
August and 
October. The 
wind only comes 
Figure 6 Average Wind Direction in Hidalgo, County 
from the North for 1.5 months between December and January.  
Average Annual Growing Season 
The growing season is the longest continuous period of non-freezing temperatures in 
a calendar year. The temperatures are rarely below freezing in the area making the 
growing season very long. 
There are even comfortable 
temperatures in winter months 
like January and December. 
Figure 7 Annual Growing Season for Hidalgo, County 
  
37 
 
 
 
 Soils 
There are twenty-four identified soils within the boundaries of the proposed site. The 
three soils that make up most of the area are Rio Grande silt loam, Matamoros silty 
clay, and Reynosa silty clay loam. Rio Grande silt loam makes up 32.60% (4,103 
Acres) of the site and is the predominant soil type. Rio Grande silt loam is mostly 
cropland soil under cotton, grain, sorghum, and a variety of cool season vegetables. 
Vegetation that best survives in this soil are hackberries, Rio Grande ash, cottontop 
and plains bristle grass (Rio Grande Soil Series, 2009).  
Matamoros silty clay makes up 15.60% (2,710 Acres) of the site and is the second 
most predominant soil type. The Matamoros silty clay is mostly for irrigated cropland 
soil with a less than 1% slope and ?consists of deep, moderately well drained, slowly 
permeable soils? (Rio Grande Soil Series, 2003). Crops using this soil are cotton, 
grain sorghum, sugarcane and ?native vegetation consists of sacaton grass, cottontop 
grass, plains bristle grass, common bermudagrass, hackberry, Rio Grande ash, and 
mesquite trees? (Rio Grande Soil Series, 2003). 
Reynosa silty clay loam makes up 10.20% (1,774 Acres) of the site and is the third 
most predominant soil type within the site. Reynosa silty clay loam consists of deep, 
well-drained soil. The slopes are usually less than 1% but can get up to 3% in some 
areas (Rio Grande Soil Series, 2000). This soil is primarily cropland for cotton, grain, 
sorghum, and also hosts native grasses such as little bluestem, Texas winter grass, and 
bristle grass (Rio Grande Soil Series, 2000). Woody plants that thrive in this soil 
38 
 
 
 
include mesquite trees, sprint hackberry, lotebush, black brush, and common 
hackberry (Rio Grande Soil Series, 2000).  
 
Figure 8 Soil Map in the Proposed Site 
Biotic Attributes 
Vegetation 
The Lower RGV is in the plant hardiness zone 9b (USDA n.d.). The RGV is part of 
the ?brush country? which encompasses the southern end of Texas. Typical plants in 
the brush country include mesquite, black brush, brasil, and other thorny plants 
(Taylor, 1998). The RGV has four counties bordering the Rio Grande River, so there 
are also many vegetation species around its riparian area like willows, hackberries, 
ashes, and mesquite.  
 
39 
 
 
 
Pollinators 
There are over 325 butterfly species in the Rio Grande Valley and hundreds to 
thousands more pollinators like bees, moths, flies, bats, birds, and beetles. The 
National Butterfly Center provides a Butterfly Checklist from 2021 with over 90 
species, out of the 243, that could only be found in the RGV. The RGV is along the 
monarch butterflies? migratory path to and from Mexico.  
Cultural Attributes 
Land Use 
Land use has also caused declines in biodiversity through the loss, modification, 
and fragmentation of habitats; degradation of soil and water; and overexploitation of 
native species (Pimm and Raven as cited in Foley, et al, 2005). There is a total of 
17,387.91 acres within the site boundaries. The three mainland uses on the site are 
natural areas, farmlands, and urban areas. 
 
Figure 9 Land Use Type within the Proposed Site 
40 
 
 
 
Natural Areas 
Natural areas are the most abundant land use on the proposed site. These natural areas 
consist of state, national, county, and local parks, wildlife management areas, as well 
as thornforest habitat. There are 10,551 acres of natural area within the four sections 
of the proposed site. The two end caps of the site are natural areas chosen for their 
similar goals of conserving pollinators and wildlife habitat. The end caps are Bentsen 
State Park to the west and the Santa Ana National Wildlife Refuge to the east. Two 
other well-known management areas are the National Butterfly Center, and 
Anzalduas County Park.  
 
Figure 10 Natural L:and Use within the Proposed Site 
 
  
41 
 
 
 
Bentsen? Rio Grande Valley State Park 
Bentsen State Park is a 797-acre park located in Mission, Texas established in 1962 
and hosts the park headquarters for the World Birding Center. Over 360 bird species 
have been recorded in the park along with butterflies, javelinas, and bobcats. The park 
has a mix of wetland, brush, riparian, and woodland habitats (Texas Parks and 
Wildlife Department, 2020). The park's native plants include trees like the 
Montezuma bald cypress, Sabal palm and Texas wild olive which cannot be found 
anywhere else in North America (Texas Parks and Wildlife Department, 2020). 
Bentsen State Park is the western hub of my site and in section A. 
National Butterfly Center 
The National Butterfly Center (NBC) is a 100-acre plot of land located in Mission, 
Texas that was formed in 1998. The NBC is a project of the North American 
Butterfly Association (NABA), dedicated to conservation and the study of wild 
butterflies in their native habitat (National Butterfly Center, 2020). The primary focus 
of the butterfly center is to educate the public about the importance of biodiversity 
and the key role butterflies have on maintaining a healthy ecosystem. The National 
Butterfly Center is in section A of my proposed site. 
Anzalduas County Park 
Anzalduas Park is a 96- acre grassland park located in Mission, Texas established in 
1951 and is best known for their birding. The area is open to the public for 
recreational and educational events. The site is along a bend of the Rio Grande River 
42 
 
 
 
allowing for fishing and bird watching. The Anzalduas Park is located in section B of 
my site.  
Santa Ana National Wildlife Refuge 
Santa Ana National Wildlife Refuge (SANWR) is a 2,088-acre area located in Alamo, 
Texas and was established in 1943 to aid in the protection of migratory birds (U.S. 
Fish and Wildlife Service, 2020). The SANWR is open to the public and dedicated to 
conserving the area for native plants and wildlife while educating the public about the 
importance of conservation. The refuge also has 14-miles of walking trails to be 
emerged in nature and have better visibility of birds and butterflies. The wildlife 
refuge has approximately ?400 bird species, 450 types of plants and half of all 
butterfly species found in North America? (U.S. Fish and Wildlife Service, 2020). 
The Santa Ana National Wildlife Refuge is the eastern hub of my project's scope in 
section D. 
 
  
43 
 
 
 
Farmlands 
Farmlands is the second largest land use in the proposed site with an area of 4,974 
acres. Crops being grown within the site are grains, citrus, cotton, corn, potatoes, 
sorghum, and sugarcane. Section C, which has the largest urban area, has the least 
amount of farmland. Farmlands are crucial to the economic wellbeing of the Rio 
Grande Valley. 
 
Figure 11 Farmland Land Use within the Proposed Site 
  
44 
 
 
 
Urban Areas 
There are six cities with boundaries within the site from West to East: McAllen, 
Mission, Hidalgo, Pharr, San Juan, and Alamo. The total area of urban land use 
within the site is 1,479.4 acres. There are no urban areas in section D and minimal 
areas in sections A and B. The main city within the site is Hidalgo, Texas, located in 
section C. The urban area is mixed use, having commercial properties as well as 
residential areas. With Hidalgo having a main border crossing from Mexico, this area 
has a lot of imported goods. In Hidalgo County, 67% of the population live in single 
unit family homes.  
 
Figure 12 Urban Area Land Use within the Proposed Site 
 
  
45 
 
 
 
Roads 
This region of Texas does not have a lot of public transportation. Cars are the main 
source of transportation even for everyday necessities; walking to stores, restaurants 
or for recreation is not common. In Hidalgo County, 70% of homes own 1-2 cars, 
20% own 3-4 cars, 2% own more than 5 cars, and only 7% of homes have no cars. 
Within the site, there are 92 miles of road which does not include dirt roads.  
 
 
Figure 13 Main Roads within Proposed Site 
 
 
  
46 
 
 
 
Population Demographics 
The population of the Rio Grande Valley is growing rapidly. In Hidalgo County, from 
the 2010 census to the 2020 census, we saw a population growth of 12.4%, or 95,985 
people. In Cameron County, there was a 3.6% population increase of 14,797 people. 
In Starr County, there was an 8.1% population increase of 4,952 people. In Willacy 
County, population dropped by 1,970 from 2010 to 2020 with a decrease of 8.9%. 
Ethnicity in the RGV is 93.53% Hispanic/ Latino and 6.47% Non-Hispanic/ Latino. 
Race for the total RGV population of 1,402,340 is: White 87.71%, Black/African 
American 0.60%, American Indian/Alaskan Native 0.35%, Asian= 0.71%, Native 
Hawaiian/Pacific Islander 0.02%, Some Other Race 9.18% , 2+ Races 1.43%.  
 
 
 
 Figure 14 Population Change for Hidalgo, County 
Infrastructure  
Due to the location of the site being along the Rio Grande River in South Texas, the 
border wall runs in segments within the boundaries of the proposed site. While issues 
do arise due to the habitat destruction needed to build the wall it will not be taken into 
major consideration for this project because most pollinators are able to go through, 
up, and around the wall.  
47 
 
 
 
Site Analysis 
Section A is the Eastern hub of the proposed site, selected because of the Bentsen 
State Park. Natural areas are enclosed by farmlands on almost every side. There are 
opportunities to reconnect natural areas by utilizing road verges and restoring oxbow 
lakes that lay within farmlands.  
 
Figure 15 Section A Site Analysis 
  
48 
 
 
 
Section B has the second largest natural area of the four site sections. Section B has 
two functioning oxbows, which are recommended to enhance by increasing 
vegetation diversity. This site has the largest intact green space. This section has 
farmlands on either side of its large natural area patch.  
 
Figure 16 Section B Site Analysis  
49 
 
 
 
Section C has the largest urban area of all four sections with a total of 1,143 acres. 
This section has a portion of the city of Hidalgo, which is the main border city 
between Mexico and the United States within the proposed site. The city is 
encroaching on the natural areas to the east and west increasing the space between 
them causing habitat fragmentation. There are opportunities to develop a street tree 
program that allows refuge for pollinators.  
 
Figure 17 Section C Site Analysis 
  
50 
 
 
 
Section D has the largest acreage of natural areas along the proposed site. This 
section is the furthest east and has the Santa Ana National Wildlife Refuge as the hub 
of the proposed site. This section while having the largest amount of natural area, has 
the most disconnect between the patches. The most beneficial way to reconnect them 
is by adding corridors and obtain land through land acquisition. 
 
Figure 18 Section D Site Analysis 
  
  
51 
 
 
 
Chapter 4: Design Framework and Design  
Chapter 4 discusses the design framework used to create designs that could be 
implemented on various parts of the proposed site.  
Vision 
My vision for this proposed site is to create connectivity corridors between natural 
landscapes that are facing detrimental effects of human activity. Within these 
corridors an increase of vegetation diversity is proposed to enhance the vegetation 
increasing pollinator diversity. This design will utilize roads and oxbow lakes to 
make primary corridor connections between natural hubs in each of the four sections. 
Farm roads will be used to make secondary connections between the existing natural 
hubs. Lastly, a program like CREP could be implemented and land acquisition could 
be proposed to increase hub size.  
Design Goals 
The goal of this project is to develop a design framework that will create corridor 
connections, increase vegetation diversity, and increase habitat for pollinators along a 
selected site along the Rio Grande River in Hidalgo County, Texas.  
Goal 1: Increasing Connectivity 
The first goal of this project is to increase the connectivity between fragmenting 
habitats within the site. By utilizing the roads along the site, which are abundant, 
corridors can be created for the transportation of pollinators between existing natural 
52 
 
 
 
habitats and proposed reforested areas. Oxbow lakes also contribute to the 
connectivity between natural habitats, particularly if they are isolated around 
farmlands. Using farm roads along farmlands will also function as corridors allowing 
for pollinators to get from patch to patch.  
 Goal 2:  Diversify Vegetation Structures 
The second goal of this project is to diversify vegetation to benefit pollinators on the 
proposed site. Increasing the vegetation structures along road verges will increase the 
abundance of pollinators. Planting a variety of plant species that can be utilized 
throughout the stages of pollinators' lives is essential.  
Goal 3: Increase Habitat 
The third goal of this project is to increase pollinator habitat and natural areas on the 
site. This goal will be accomplished by doing the first two goals. The corridors, and 
vegetation diversity will increase the pollinator habitats.  
Actions 
The interventions are organized into primary, secondary and tertiary actions. Primary 
actions would be the first steps taken to create landscape scale connectivity. These 
steps will be done if there is a money and support for the implementations. For the 
next step, secondary actions would increase connections at a finer scale and seek to 
increase redundancy and increase connectivity density. This step will be done if there 
is more funding and more support from the community. Finally, provided enough 
resources, tertiary actions focus on policy program and acquisition as tool to 
53 
 
 
 
strengthen corridors and increase overall habitat. This step will only be implemented 
if there a CREP like program where farmers can be financially compensated for their 
participation.  
Master Plan Section A 
The primary actions for this thesis are to create pollinator corridors between existing 
natural patches using road verges, and oxbow lakes. Starting from the furthest point 
West in Section A, to create a connection between Bentsen State Park and the other 
natural areas surrounding the proposed site, 5 roads (Old Military Highway, Levee 
Road, S Schuerback Road, S Greene Road and Bentsen St. Park Road) were selected 
to add roadside verges. A corridor created along Military Road, located above F4, 
creates the connection between Bentsen State Park and N2, in section B.  
The second part of primary actions are to restore oxbow lakes within the proposed 
site. Increasing the vegetation diversity along the edge of oxbow lake #1, which is 
surrounded by farmland, will increase pollinator habitat, and plant diversity. The 
increase of vegetation diversity will attract more pollinators and provide them refuge 
within the farmlands. By diversifying the vegetation of Oxbow #1 (O1) and creating 
road verges along the selected roads, two corridor connections between Bentsen State 
Park in Section A and natural area 2 in Section B will be made.  
The secondary actions are to create fine interstitial corridors by designing along 
farmland roads. The first step will be to utilize large and longer farmland roads along 
the perimeter of the farmlands to reduce the number of acres a farmer would have to 
give up. In section A, there will be two corridors along main farm roads totaling 2.25 
miles. The first one will be below F3 along W. Military Highway and 1.1 miles long. 
54 
 
 
 
The second one will be following the road that is up against the Rio Grande River in 
F4 stretching 1.15 miles long. After using the large roads, smaller roads will be taken 
into consideration to increase the connectivity between patches. In F4, there will be 
nine dirt roads selected for pollinator corridors with a total of 3.66 miles. 
Tertiary actions are to develop policies that allow for land acquisition to increase 
pollinator habitat. These steps will only be done if there is a program in place to 
financially incentives farmer participation. After studying maps and visiting the site, 
areas were selected to help increase patch size. If the given the opportunity, land 
acquisition should occur for F1 and F2 to increase the patch size of Bentsen State 
Park (N1), connecting it with the surrounding natural areas around the proposed site. 
Patch F1 is 190 acres, and F2 is 213 acres, reforesting these areas will increase the 
Bentsen State Park patch (N1) by 303 acres to a total of 2,927 acres.  
Urbanization is predicted to take over farmlands. Suggesting plantings and edge 
designs for pollinators will help ensure benefits for them even after urban 
development. Farm to urban areas is predicted by studying aerial views and visiting 
the site. It is predicted F3 will be converted to a residential neighborhood increasing 
the mobile home patch (U1) by 190 acres to a total of 295 acres. 
55 
 
 
 
 
Figure 19 Master Plan Section A 
  
56 
 
 
 
Master Plan Section B 
The primary actions are to create pollinator corridors between existing natural 
patches. In section B, by using Military Road and Levee Road as corridors, a 
connection between N1 and N2 can be made. On the Eastern end of Section B, to 
create a connection between N2 and N4, a road verge along Old Military Highway is 
proposed to create a corridor. The second part of the primary actions are to restore 
oxbow lakes and diversify the vegetation structures along them. Oxbow #2 has the 
southern side along N2 and its northern side along F6. Purchasing 57 acres of 
farmland in F6 will increase the plant diversity and strengthen the corridor along the 
oxbow. Oxbow #2 is functioning and connected on both ends to the Rio Grande 
River, increasing the vegetation diversity and adding a buffer will reduce pesticide 
runoff into the river. To connect N2 to N4, land acquisition should occur northeast of 
N3. Increasing the vegetation width north of N3 is strengthening the corridor between 
N2 to N4 by utilizing N3. 
Secondary actions are to utilize farm roads that are along the perimeter of farmlands 
to increase the connectivity between patches. To create a secondary connection 
between N2, N3 and N4 there will be one corridor along a main farm road which is 
located right below F6 above N3 which is 1 mile long. In F6, there will be 6 smaller 
dirt roads selected for pollinator corridors with a total of 3.18 miles. 
Tertiary actions are to develop policies that allow for land acquisition to increase the 
overall pollinator habitat. After studying aerial maps and visiting the site it is 
proposed that the eastern portion of F6 be reforested. Reforesting F6 will provide a 
buffer to minimize pesticides from the surrounding farmlands from going into the 
57 
 
 
 
oxbow and into the Rio Grande River. Areas within the site are also predicted to be 
turned into urban residential. The lower portion of F5 (26.5 acres), is predicted to be 
converted to a residential connecting U4 (9 acres) to U5 (35 acres) and creating a 
larger urban area of 70.5 acres. 
 
Figure 20 Master Plan Section B 
 
 
 
  
58 
 
 
 
Master Plan Section C 
 
Primary actions for Section C include creating pollinator corridors along roads to 
connect patches. To create a primary connection with N6 and N7 a road corridor is 
proposed along Old Military Rd, which is the northern boundary of F8. The 
secondary goal of the primary action is to restore oxbow lakes by increasing the 
vegetation diversity. An oxbow lake between N6 and F8 should have an increase of 
plant diversity along its edge. To increase of vegetation diversity along the oxbow, a 
portion of farmland should be obtained to increase the width of the riparian area and 
along the lower edge of F8 along the Rio Grande River. There are no proposals for 
using farm roads in Section C.  
The tertiary actions are to develop policies for land acquisition to increase pollinator 
habitat. By creating a CREP like program we can ask farmers to participate by 
proving those financial incentives. N7 is a 273-acre natural area with farmlands on 3 
sides, F8 on the left and N9 on the right. Land acquisition is proposed on a portion of 
the right side of F8 to increase the patch size of N7. Secondary goals of the tertiary 
action are to predict where farmland will be urbanized. Its predicted F7, which is 59 
acres, will be developed into an urban area connecting U6 and U7. 
59 
 
 
 
 
Figure 21 Master Plan for Section C 
 
  
60 
 
 
 
Master Plan Section D 
 
Primary actions include creating pollinator corridors between existing natural areas. 
This can be done in Section D, by utilizing Military Roads? Road verges to create a 
connection between N7 and N9, and N9 to N10. To create a secondary connection 
between N7 and N8 a proposed corridor along the lower farmland edge of F9 is 
created along the riparian zone of the Rio Grande River. Extending the width along 
the riparian area of the lower edge of farmlands, which touches the Rio Grande River, 
is proposed in F10 to create corridors for pollinators between N8 and N10. Also, 
within the primary actions is to increase the vegetation diversity along the edge of 
oxbow lakes. Oxbow #4 is in the center of F10 and increasing the vegetation diversity 
will help connect N8 and N9 with N10.  
Secondary actions include using farmland roads. Using farm roads along the 
perimeter first will reduce the number of acres a farmer would have to give up. A 
main corridor along S. Cage Blvd is proposed as the main North/South connection in 
F9. Using smaller roads can be done within F9 to increase the edge diversity and 
pollinator patches within farmlands. A farm road corridor in F10 is suggested to 
increase the north/south connection between the road corridor along Old Military 
Road (north) and the riparian zone along F10 (south).  
Tertiary actions are to develop policies that allow for land acquisition to increase 
pollinator habitat if a CREP program can be implemented. Farmland restoration can 
be done in F9, which is between N7 and N8. F9 is the third largest farmland area 
within the proposed site. Two small patches are proposed to be purchased for 
restoration in F9 to create areas of refuge for pollinators within farmlands. F10 is the 
61 
 
 
 
second largest farmland area within the site. Proposed land acquisition is suggested 
between N8 and N9 to increase the patch size and strengthen the connection between 
patches. There are no areas predicted to be turned into urban areas at this time.  
 
Figure 22 Master Plan for Section D 
 
  
62 
 
 
 
Habitat Scale Design Interventions 
After the initial corridors are selected along the entire site, we look down at the 
habitat scale to create a design framework for the implementations. The second goal 
of this project is to diversify vegetation to benefit pollinators on the proposed site. 
The third goal of the project is to increase the pollinator habitat which can be done by 
implementing the first two goals. Planting a variety of plant species that can be 
utilized throughout the stages of pollinators' lives is essential. Design guidelines to 
diversify vegetation were developed by incorporating the materials obtained from the 
literature review. There are design guidelines for seven different landscape types that 
can be utilized in various areas of the site and even combined to best fit the needs of 
the location (Appendix 3). The guidelines were developed for a street tree program, 
two lane roads, farm roads, oxbow lake edge design, farmlands turned urban, and 
farmlands that are reforested (Appendix 3). At the habitat scale, implementations will 
be done alongside roads, and farmlands to create the road verge corridors, increase 
plant diversity and increase pollinator habitats. Plant species were investigated to 
decide the most beneficial species to pollinators, while considering their growing 
conditions regarding sunlight, water, and management needs (Appendix 1 and 2).  
Design interventions will also be accomplished in primary, secondary, and tertiary 
actions following the master plan. Roads will be the primary action for creating the 
initial corridors. The habitat scale interventions will be to increase the habitat width, 
and vegetation structure that best fits the needs of the location, funding, and support 
to implement these designs. The second half of the primary action is to increase the 
63 
 
 
 
vegetation structure diversity along oxbow lakes, particularly those in farmlands. The 
secondary actions are to utilize farm roads along the perimeter of farmlands to add in 
pollinator strips, and the secondary half of the secondary action is to utilize roads 
within farmlands. The tertiary actions will be to purchase land through land 
acquisition that can be reforested or to plan for land that will be developed for 
housing.  
Roads 
A street tree program is recommended to help pollinators in the nearby Hidalgo, 
County. Four lane roads are the typical road type along the natural areas within the 
proposed site. These implementations will allow for a more diverse vegetation and 
allow for pollinators to rest while going from one natural patch to another. Trees 
provide pollinators will pollen, nectar and shelter. Design guidelines for the street tree 
program can be found in Appendix 3.  
 
  
Figure 23 Four Lane Roads- Street Tree Program 
64 
 
 
 
One of the main road types along 
the site are two lane roads with 
and without shoulders. Treatment 
for right of ways will be possible 
whether the two-lane road has 
shoulders or not. Right of ways 
along the site vary from 40ft to 
Figure 24 Before and After Implementations of Increasing Vegetation 
Structure Along Two-Lane Roads with Shoulders 
100ft depending on the area. Any 
of the proposed treatments can be done within the right of way making them more 
feasible because we would not have to obtain land from farmers or developers during 
the primary stages of this case study. 
Roads are a main land use within the project scope distancing over 92 miles of paved 
roads within the proposed site. The total 
miles of roads increase if we consider 
farm roads, and country roads, which 
are not currently noted. There are four 
main road types such as two-lane roads 
with and without buffers, four lane 
roads, and farm roads within the 
proposed site. The main road which the 
implementations will be developed for Figure 25 Two-Lane Roads as Is 
are two lane roads without shoulders. All three vegetation implementations can be 
done along the same mile of road whether in a pattern or just altering between two. 
65 
 
 
 
By incorporated the unique designs we reduce the acres needed while still creating 
essential pollinator habitats. There are palm trees in the right of way along most 
selected roads. Design guidelines for two lane roads can be found in Appendix 3.  
Two Vegetation Structure Intervention 
 
 First, if any implementations can be made given a small amount of money, road 
verges will be utilized for pollinator habitat Research suggests having a minimum 
cleared setback of 6ft to ensure driver visibility and to reduce the sounds, light, and 
vibrations in the pollinator habitat. Pollinator habitats should be a minimum of 20ft 
wide with a variety of herbaceous 
native plants including host plants. 
It is important to have bare areas 
within the habitat to provide nesting 
sites for ground nesters. In this 
intervention the first step will be to 
add herbaceous plants 6ft away 
from the roads and implement a 
20ft wide pollinator habitat. The 
Figure 26 Two Vegetation Structure Implementations 
current vegetation structure along 
the road verge will now be two: herbaceous plants and the large street trees. It is 
important to plant the vegetation properly to ensure they meet their proper sunlight 
requirements. Design guidelines and suggested plantings can be found in Appendix 2 
and 3.  
 
66 
 
 
 
 
Three Vegetation Structures 
Implementation  
 
To increase the vegetation structure 
within the pollinator habitat, the 
secondary intervention include 
widening both the setback and 
pollinator habitat. The setback was 
widened to 10ft to enhance the driver?s 
visibility protecting animals from 
vehicular incidents, and to reduce the 
Figure 27 Three Vegetation Structures Intervention 
pollution going into the pollinator habitat. 
The pollinator habitat will be widened by 5ft making it 25ft and adding shrubs to the 
habitat, increasing the vegetation structure for pollinators. There are now three 
vegetation structures in the pollinator habitat including: herbaceous, large trees, and 
shrubs. It is important to plant the vegetation properly to ensure they meet their 
proper sunlight requirements. Design guidelines and suggested plantings can be found 
in Appendix 2 and 3.  
  
67 
 
 
 
Four Vegetation Structures Implementation 
 Lastly, to increase the plant 
vegetation structures to four layers, 
small trees will be added in the 
pollinator habitat. This 
implementation will widen the 
setback by 5ft increase safety for 
drivers, and pollinators, while 
reducing the pollution going into the 
pollinator habitat. The setback will 
now be 15? wide. The pollinator 
Figure 28  Four Vegetation Structures Intervention 
habitat is also widened by 5ft making 
it 30ft to comfortably add in trees. The total vegetation structures are increased to 
four and will now include: herbaceous, large trees, shrubs, and small trees. It is 
important to plant the vegetation properly to ensure they meet their proper sunlight 
requirements. Design guidelines and suggested plantings can be found in Appendix 2 
and 3.  
 
 
  
68 
 
 
 
Farmland roads 
Farmlands are not hotspots for 
pollinators due to the considerable 
amounts of pesticide usage and being 
monocultures. While pollinators are 
beneficial to crops, they do not 
provide them with all their basic 
needs. Farm roads allow for tractors, 
and trucks to navigate through the 
farm fields without crushing crops. Figure 29 Farm Roads as Is 
They are normally just dirt roads, and they are quite common within the proposed 
site. The dirt roads are 
typically 15ft wide and 
have crops on either side. 
While adding in pollinator 
habitat is beneficial to 
pollinators it is important to 
Figure 30 Before and After Aerial and Perspective Images of Farmland 
consider the pesticides Roads 
being used to maintain the crops. It is helpful to add in a pollinator buffer between the 
crops and the proposed pollinator habitat, because it can reduce the number of 
pesticides going into it. It?s suggested to have a minimum of 60ft away from spray 
pesticides if there is no buffer present, and a minimum of 30ft if there is a buffer. I am 
proposing adding in a buffer strip using plants that are wind pollinated to reduce the 
69 
 
 
 
need for pollinators to venture into the buffer strip. Design guidelines and suggested 
plantings can be found in Appendix 2 and 3.  
One Vegetation Structure 
Intervention  
To increase habitat, and vegetation 
diversity for pollinators I propose 
adding in a pollinator corridor 
alongside a few selected farm roads. 
To ensure we are not creating 
pollinator death traps safety 
precautions must be considered. 
Adding buffers will minimize 
pesticide drift, and research suggests 
Figure 31 One Vegetation Structure Implementation 
having a minimum width of 30 ft. To 
provide protection from cars, studies show a minimum of 6 ft should be cleared 
alongside the road creating setbacks. A minimum of 20ft is suggested for pollinator 
plantings so that is what will be done here. The pollinator vegetation structure will 
now include herbaceous planting, and the buffer will include herbaceous and shrubs. 
It is important to plant the vegetation properly to ensure they meet their proper 
sunlight requirements. Design guidelines and suggested plantings can be found in 
Appendix 2 and 3.  
 
 
70 
 
 
 
Two Vegetation Structures Intervention 
The second intervention includes 
increasing the setback to 10ft to increase 
visibility and safety, increasing the 
pollinator habitat by 5ft to add in shrubs, 
and keeping the buffer width the same. The 
pollinator vegetation structure will now 
include herbaceous planting, and shrubs. 
Figure 32 Two Vegetation Structures Intervention 
The buffer will now include herbaceous, 
shrubs, and trees. It is important to plant the vegetation properly to ensure they meet 
their proper sunlight requirements. Design guidelines and suggested plantings can be 
found in Appendix 2 and 3.  
Tree Vegetation Structures Implementations 
Lastly, to increase the vegetation structure again setbacks will increase by another 5ft 
making it 15ft wide, which will increase the safety for small animals trying to cross 
the street, and for pollinators trying to use 
the pollinator habitats. The pollinator buffer 
will increase to 30ft to now add in small 
trees. These implementations can be done in 
a variety of patterns along the same road to 
meet the needs of the plants, pollinators, and 
road location and the create a more 
heterogenous patterns to provide for 
Figure 33 Three Vegetation Structures Intervention 
71 
 
 
 
increased vegetation structural diversity. The pollinator vegetation structure will now 
include herbaceous planting, shrubs, and small trees. The buffer will include 
herbaceous, shrubs and trees. It is important to plant the vegetation properly to ensure 
they meet their proper sunlight requirements. Design guidelines and suggested 
plantings can be found in Appendix 2 and 3.  
 
Land Acquisition Farmland to Reforested  
 
Obtaining land from farmers would be the most beneficial for pollinators from a 
conservation perspective, but not from an economic one. While reforesting farmlands 
closest to natural areas will strengthen the natural patch size, it will reduce the acres a 
farmer can utilize. A CREP program would need to be implemented to create 
financial incentive for farmers. If there was enough support and money the sites 
selected would aid in the increase of overall pollinator habitat. Design guidelines and 
suggested plantings can be found in Appendix 2 and 3.  
  
Figure 34 Before and After Aerial and Perspective Images of Reforesting Farmlands 
72 
 
 
 
Farmland to Urban 
Due to the growing population, and the ecotourism brought in by the National 
Butterfly Center and Bentsen State Park housing development will more than likely 
be built over what once is farmed land. To best benefit pollinators, there are design 
goals that should be taken into consideration to ensure pollinator habitat. 
Urbanization will happen and its best to create design guidelines to prepare for the 
future with pollinators in mind. Design guidelines and suggested plantings can be 
found in Appendix 2 and 3.  
 
 
 
 
 
 
Figure 35 Before and After Aerial and Perspective Images of Urbanizing Farmlands 
 
  
73 
 
 
 
Oxbow Edge Vegetation Diversity 
There is a total of eight oxbow lakes withing the proposed site. By increasing the 
vegetation along the edges of oxbow lakes we create secondary corridors for 
pollinators. The increase of vegetation diversity will increase the overall number of 
pollinators around the site. Design guidelines can be found in Appendix 3.  
 
Figure 36 Oxbow Lakes as Is 
  
One Vegetation Structure Intervention 
Oxbow lakes can provide a number of benefits to pollinators. Incresing the vegetation 
structure diversity along oxbows will help increase pollinator diversity. The first 
implementation should be to add in a variety of herbaceous plants along the oxbow. 
Since the oxbows are within farmlands, its highly reccommended to add in an buffer 
to decrease the amount of pesticides going into the pollinator habitat and the water 
supply. By doing the first impletmentation the vegetation stucutre will be herbaceous. 
Design guidelines can be found in Appendix 3. 
 
Figure 37 One Vegetation Structure Interventions 
74 
 
 
 
Two Vegetation Structures Intervention 
The next step will be to widen the pollinator habitat to add in shrubs and widening the 
buffer. Widening the buffer will provide more protection for pollinators using the 
habitat and increase the vegetation structure to two. These implementations will 
increase the vegetation structure to two including: herbaceous and shrubs.  
 
Figure 38 Two Vegetation Structures Interventions 
 
Three Vegetation Structure Intervention 
 
Lastly, to increase the vegetation structures further, implementations will be done to 
widen the pollinator habitat to add in trees. Widening the buffer will provide more 
protection for the pollinator habitat. The vegetation structure diversity will now 
increase to three and will include: herbaceous, shrubs, and small trees.  
 
Figure 39 Three Vegetation Structures Interventions 
  
75 
 
 
 
Presentation Boards 
All the preceding figures are organized on a set of presentation boards (Appendix 4) 
where additional information is provided. In addition to the designs, calculated 
metrics for the interventions are also provided. Appendix 4, Board 7 has results of the 
project measuring out all the miles of proposed main roads and farm roads within 
each section and the total throughout the site. For example, to create the first 
vegetation structure in the pollinator habitat along the selected two-lane roads you 
would need 76 acres of road verges. Board 8 also identifies all the acres needed for 
each implementation throughout the site, such as acres of land for proposed 
reforestation, proposed urban development areas, and the difference needed to 
increase the pollinator habitat along the entire site. For example, to reforest the 
selected areas along the entire site we would be increasing pollinator habitat for 1,281 
acres. Further details specific to each section?s implementation metrics can be found 
in Appendix 4. 
 
 
  
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Chapter 5:  Conclusion and Summary  
This thesis suggests that by using landscape ecology principles and other research, a 
design framework that provides 1) connectivity between existing natural areas, and 2) 
increasing vegetation community diversity will lead to increased quantity and quality 
of pollinator habitat and thus more overall pollinators. The case study provides a 
demonstration of the design framework that will contribute to the creation of corridor 
connections between natural landscapes along the Rio Grande River. The project 
complements and supports the corridor proposed by the U.S. Fish and Wildlife 
Service which plans to create the corridor within the four counties of the Rio Grande 
Valley. Creating these connections and restoring and creating diverse vegetation 
communities will help pollinators as they navigate the landscape for food, shelter, and 
nesting. At the landscape scale, the design framework provides a minimum of two 
corridors between existing natural hubs creating the redundancy needed to insure 
connectivity. At the habitat scale, the proposed design interventions diversify 
vegetation structure for a variety of locations, needs, and available resources. Using a 
design framework that provides the prioritization of primary, secondary, and tertiary 
actions, provides decision makers a prioritized road map to take steps to support a 
pollinator corridors and creation of pollinator habitats.  
Assumptions and Limitations 
Site visits were impacted by COVID-19 and the political environment surrounding 
the National Butterfly Center which resulted in its closure while this project was 
undertaken. I am a Texas native and raised 10 miles east of my site in the Rio Grande 
77 
 
 
 
Valley. During the COVID-19 pandemic. I moved home and decided to choose a 
local thesis site. I was able to drive along all ~20 miles of my site while being home. 
Due to the political climate surrounding the National Butterfly Center, I was unable to 
make connection with Center managers. This was a limitation when documenting an 
additional species information for my site. High border security along my site was 
also a limitation on how much of the site I could observe and understand. Issues 
related to the border wall were beyond the scope of this study. Climate change is 
critical, important, and a subject that would influence the case study area but is 
beyond the scope of this study. The design and plans proposed would still benefit 
pollinators even with the rising temperatures and changes in moisture regimes.  
Further Research 
This design thesis proposes to create initial connections between fragmenting natural 
habitats and diversify vegetation at a habitat scale in a selected site along the Rio 
Grande River. Pollinators are critical to overall sustainability of ecosystems and 
should be treated as such. This research is intended to support further work that needs 
to be undertaken to support pollinators in the Rio Grande Valley.  
 
 
 
 
 
 
 
 
 
puro pinche 956 
  
78 
 
 
 
Appendices 
 
Appendix 1. From Section 7 - Selecting Wildflower by Natural Vegetation Region, in the 
Roadside Vegetation Management Manual from TxDOT (2018) 
Individual 
Common Percent Rates Per 
Name Scientific Name Per Mix Acre General Information 
State flower of Texas. Blue with white trim on 
spikes. Most common wildflower on roadsides 
and pastures. Legume family (nitrogen fitting). 
Bluebonnets Lupinus texensis 42% 20lbs 
Needs well drained soil and prefers full sun. 
Blooms from March-May. 12-24 inches high. 
13,500 seeds per pound. 
Hardy annual that is easily established. Red 
Gaillardia flowers with yellow trim. Needs well drained 
Indian Blanket 19% 10lbs 
pulchella soil and full sun. Blooms from May-July. 1?-2 
feet. 153,000 seeds per pound. 
Hardy annual. Blooms are red, pink, white and 
Phlox shades of rose. Likes dry soil and full sun. 
Annual Phlox 18% 8lbs 
drummondii Blooms from February-June. 8-24 inches. 
234,000 seeds per pound. 
Annual or short-lived perennial. Purple blooms. 
Prairie Verbena Prefers full sun. Popularly planted with Pink 
6% 3 bs 
Verbena bipinnatifida Evening Primrose. Blooms from April-November. 
4-12 inches. 450,000 seeds per pound. 
Hardy annual. Yellow flower petals clasp around 
Clasping Rudbeckia stem with black cone center. Likes dry or wet 
6% 1lbs 
Coneflower amplexicaulis soils with full sun. Blooms from April-June. 1?- 
2 feet. 800,000 seeds per pound. 
Hardy annual. Heavy bloomer. Prefers full sun, 
Plains Coreopsis 
5% 2lbs but will tolerate wet or dry soil. Blooms from 
Coreopsis tinctoria 
March-July. 1-3 feet. 1,400,000 seeds per pound. 
Hardy perennial. Soft pink four petalled flowers. 
Pink Evening Oenothera Popularly planted with Prairie Verbena. Blooms 
3% 1-3lbs 
Primrose speciosa from March-November. 8-16 inches. 864,000 
seeds per pound. 
Annual, perennial or biennial. Blooms red with 
color variations of purple, orange, pink, yellow, 
Indian Castilleja 
1% 1/4lb white, etc. throughout the state. Needs well 
Paintbrush indivisa 
drained soil and full sun. Blooms from March 
May. 6-18 inches. 5,100,000 seeds per pound. 
79 
 
 
 
Appendix 2. Proposed Plant Palette: 
Herbaceous: 
? Awnless Bush Sunflower (Simsia calva) Perennial February - December 
? Indian Blanket (Gaillardia pulchella) Annual/Perennial February - December 
? Mexican Hat (Ratibida columnifera) Annual/ Perennial April - September 
? Milkweed (Asclepias spp. and Cynanchum spp.) Perennial March ? December  
? Scarlet Sage (Salvia Coccinea) Annual March - December 
Shrubs: 
? Rio Grande Butterflybush (Buddleja sessiliflora) Annual, April - July 
? Spiny Hackberry Celtis pallida Perennial February - May 
? Texas Lantana (Lantana urticoides) Perennial April ? October 
? Night Blooming Jasmine (Cestrum diurnum) Evergreen  
Trees: 
? Cedar Elm (Ulmus crassifolia) Perennial, July - August 
? Southern Hackberry (Celtis larvigata) Perennial, February - April 
? Anacua (Ehretic anaua) Perennial, April  
? Honey Mesquite (Prosopis glandulosa) Perennial, February ? September  
Wind Pollinated Trees and Shrubs for Buffer: 
? Live Oak (Quercus virginiana) Perennial, March - May 
? Bur Oak (Quercus macrocarpa) Perennial, March - May 
? Bald Cypress (Taxodium distichum) Perennial, April  
? False Willow (Baccharis neglecta) Perennial, August- October 
? Black Willow (Salix nigra) Perennial, April- May 
  
80 
 
 
 
Appendix 3. Design Guidelines: 

 Roadsides along Farmland  
o Design Guidelines 
 Vegetation buffer to protect from pesticides 
? Use plants that do not provide pollinator resources like 
wind pollinated trees and shrubs 
? Pollinator Habitat at least 60ft from pesticides if there is 
no buffer 
? Minimum of 30ft if buffer is present  
? High-volume pollinator plantings in buffer between 
pollinator habitat and crop fields  
? Buffer and Pollinator Habitat should be upwind from 
pesticide use 
 Pollinator Habitats should provide pollen, nectar, and nesting 
habitats for a variety of bloom seasons 
? Wildflowers 
? Native plants 
? Host plants  
? Do NOT use pest host plants  
? Keep old trees (nesting) 
? Leave some open areas for ground nesters 
o Maintenance Plan 
 Mow annually 

 Roadsides along Natural Areas 
o Design Guidelines 
 Plants to use: 
? Variety of colors, forms, textures, heights 
? Native plants 
? Meadow plants (Low Maintenance) 
? Wildflowers 
? Weedy forbes strips 
? Perennial hedgerows 
 Place smaller plants closest to the roads 
 Avoid spraying pesticides (spot spray if necessary) 
 Prep site beforehand by pulling weeds 
 Keep at least 2m (two meters) between the high-density 
plantings and road edges  
 Ensure plants are placed where they meet their proper sunlight 
needs 
o Maintenance Plan 
 Mow twice a year 

 Four Way intersections 
o Design Guidelines 
81 
 
 
 
 Plant a variety of colors, forms, textures, and heights 
 Place smaller plants closest to the roads 
 Ensure visibility with a ?site triangle? 
? Setback of 90ft for 20mph 
? Setback of 170ft for 30mph 
? Setback of 195ft for 40mph 
o Maintenance Plan 
 Mow annually 

 Pollinator Patch/Strips within Farmlands 
o Design Guidelines 
 Hedgerows for windbreaks 
 Single stem wildflowers  
 high plant species richness and complementarity of different 
seed mixture 
 the sowing of multiple flower strips in the landscape with a 
total extent of 10% in 50 ha study areas to avoid effects of 
fragmentation of food and nesting resources. 
o Maintenance Plan 
 Mow Annually 
o Community Involvement 
 Create cutting and harvesting events welcomed to the public to 
cut their own flowers/ create their own bouquets  

 Farmland turned Urban  
o Design Guidelines 
 Use native plants 
 Use pollinator plants 
 Minimal maintenance yards 
 Diversity lawn vegetation 
 Add pocket parks/ or empty lots 
 Walking trails 
 No pesticide uses 
 Grow a garden 
 Care for current trees  
 Create a native plant pocket garden 
 Allocate land use to ensure accessibility to green spaces within 
walking distance  
 Promote urban agriculture  
 Preserve biodiversity 
o Maintenance Plan 
 Mow annually  

 Farmland turned Reforested  
o Design Guidelines 
 Row, planting seedlings 
? typically, spiny native brush ? ebony, Huisache, 
retama, catclaw acacia, anacua  
? Drought tolerant  
82 
 
 
 
 Plant in 10? intervals  
 Maintenance Plan 
o Prescribed burns  
 Mow 

 Restoring Oxbow Lakes 
o Design Guidelines 
 high plant species richness and complementarity of different 
seed mixtures to provide food also for specialist pollinators 
(bees, butterflies, and butterfly larvae). 
 perennial species mixtures to ensure the provision of a high 
variation of food over the year as well as hiding and nesting 
sites.  
Policies: 
Land acquisition  
CREP 
o If farmers plant any acreage of pollinator habitat, they should be 
financially compensated. 
o They can gain a label and leverage to sell their produce for more if 
they are labeled as ?pollinator stewards? 
o They should be able to gain incentives or credit  
o They can sell products grown from pollinator habitat or buffers 
seasonally  
 
83 
 
 
 
Appendix 4: Project Boards 1-8 
 
 
 
 
84 
 
 
 
 
 
 
 
 
85 
 
 
 
 
 
 
 
 
86 
 
 
 
 
 
 
 
 
87 
 
 
 
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