2023-063 Wildlife Corridors Date: September 8,2023 Report No. 2023-063
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
Wildlife Corridors and Mapping
BACKGROUND:
The Denton 2040 Comprehensive Plan as approved on March 22, 2022, established Key Action
#127 - Identify and map wildlife corridors throughout the City to be addressed within three years
of Plan adoption.
Work Plan Timeline Summary
March 2022-In advance of the Denton 2024 Comprehensive Plan a Habitat Connectivity Map was
provided in the March 18,2022,Friday Report(II.C. and Attachment A). This map took a different
look at the Preferred Land Preservation Map (Figure 2.3 of the 2040 Comp Plan).
June 2022— Staff provided ISR 2022-038, which staff recommended definition for wildlife
corridors as "greenspace and manmade structures/improvements that allow wildlife to move
between larger areas of existing habitat." The term wildlife corridor was not previously defined
within the Denton 2040 Comprehensive Plan,but was recommended within this ISR.Additionally,
the ISR outlined a two-pronged approach to identify and map the wildlife corridors. The first step
was to generate an overall greenspace map that pulls information from existing City of Denton
resources.
December 2022— Staff provided ISR 2022-077,which included an update on the greenspace map
in support of identifying and mapping wildlife corridors. That update included graphic images of
the greenspace map and its components as well as outlined the next step of working with a wildlife
working group to finalize a wildlife corridor map.
May 2023- Formation of the Wildlife Working Group which met five times and concluded work
on July 26, 2023. The University of North Texas and the City of Denton worked through the final
model description and graphics throughout August 2023.
DISCUSSION:
Staff have used geographic information system (GIS) layers as well as non-GIS data to augment
GIS layers to better identify potential wildlife areas. This effort refined the greenspace map and
provided a visual of lands within the City that the City controls, have existing conservation
restrictions, and/or are covered under the Environmentally Sensitive Areas (ESA)requirements of
the Denton Development Code (DDC).
Date: September 8,2023 Report No. 2023-063
The working group was assembled after informal communication with such entities as the Texas
Parks and Wildlife Department, University of North Texas, Texas Women's University, master
naturalists and others. Staff spent time with the working group reviewing the data used to create
the greenspace map (attached) as well as providing information on the ESA requirements.
Through the review of the City data(i.e., greenspace map), the group was able to discuss wildlife
movement in general. UNT representatives offered to perform a flow analysis using Linkage
Mapper.
Flow analysis offers a dynamic framework to model intricate connections and pathways among
focal regions on diverse landscapes.By combining geographic, environmental,and ecological data
researchers can visualize overall connectivity of a landscape and model the effects that different
human land uses have on landscape connectivity (Balbi et al. 2021). The use of flow analysis can
provide insights useful for landscape planning, conservation efforts, and sustainable resource
management, and contribute to a more comprehensive understanding of the complex interplay
between nature and human activities (Balbi et al. 2021). The Linkage Mapper Toolbox is a
commonly used statistical model used to implement flow analysis (McRae et al. 2023).
Linkage Mapper is an open-source software built upon Circuitscape and specialized for wildlife-
centric flow analysis within Esri software, like ArcPro (Anantharaman et al. 2020, McRae et al.
2023). Both Linkage Mapper and Circuitscape are free to use and available to download online
(Anantharaman et al. 2020, McRae et al. 2023). Linkage Mapper uses a user-provided cost image
to calculate the most likely paths between areas of interest,mapping all potential wildlife corridors
and highlighting the Least Cost Path (LCP) between areas. The LCP was the route with the least
difficulty for wildlife movement.
The two main requirements of the tool are a feature layer with points indicating areas of interest
and a cost image. Ten greenspaces were chosen to be areas of interest based on their size, location,
and local knowledge of habitat. For this analysis,the main assumption was that these greenspaces
provide adequate wildlife habitat, and that wildlife will want to connect from greenspace to
greenspace.
Three datasets were used to create a cost image (i.e., difficulty or ease of wildlife movement
through the area) for the analysis. The Normalized Difference Vegetation Index(NDVI)was used,
otherwise known as a greenness index, to account for spatial differences in vegetation structure
and cover. Land cover data from the National Land Cover Database was used to account for land
use and its effects on wildlife movement. Finally, City of Denton specific data to include areas
with some sort of government oversight, such as Environmentally Sensitive Areas and
Conservation Easements. These three datasets were combined into a single cost image depicting
the relative integrity of the landscape.
Date: September 8,2023 Report No. 2023-063
Once the datasets were ready, UNT ran the"Build Networks and Map Linkages"tool. The outputs
shared included potential corridors (attached) and Least Cost Paths (attached).
The final Wildlife Corridor Map (attached) will now be integrated into the City's online
interactive mapping tool. Similar to the Future Land Use Map, the Wildlife Corridor Map will be
used as a planning tool when reviewing and recommending future land uses.
Literature Cited
Anantharaman, R., Hall, K., Shah, V. B., & Edelman, A. (2020). Circuitscape in Julia: High
Performance Connectivity Modelling to Support Conservation Decisions. Proceedings of the
JuliaCon Conferences, 1(1), 58. https:Hdoi.org/10.21105/jcon.00058
Balbi, M., Croci, S., Petit, E. J., Butet, A., Georges, R., Madec, L., Caudal, J.-P., & Ernoult, A.
(2021). Least-cost path analysis for urban greenways planning: A test with moths and birds across
two habitats and two cities. Journal of Applied Ecology, 58(3), 632-643.
https:Hdoi.org/10.1111/1365-2664.13800
McRae et al.Linkage Mapper. Accessed 2023. https://Iinkagemapper.org/
USGS. (2019).National Landcover Database. hLtps://www.usgs.gov/products/data
USGS. (2023). Landsat Missions I U.S. Geological Survey. https://www.usgs.gov/landsat-
missions
ATTACHMENTS:
1. Greenspace Map
2. Corridors for Wildlife Movement Map
3. Least Cost Pathways for Wildlife Movement Map
4. Wildlife Corridor Map
STAFF CONTACT:
Michael A. Gange
Director of Environmental Services & Sustainability
Michael.gange@cityofdenton.com
(940) 349-7165
REQUESTOR: Staff Initiated
STAFF TIME TO COMPLETE REPORT: 80 hours
PARTICIPATING DEPARTMENTS: Environmental Services & Sustainability, Development
Services, Animal Services, Drainage, and Parks & Recreation
Attachment 1 — Greenspace Map
The different land types that could be incorporated into a wildlife corridor program. Visual of lands within the City that
the City controls, have existing conservation restrictions, and/or are covered under the Environmentally Sensitive Areas
(ESA) requirements of the Denton Development Code (DDC).
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Attachment 2 — Corridors for Wildlife Movement Map
The University of North Texas provided the City with the output from Linkage Mapper. The green lines represent the
most likely paths between areas of interest. These lines represent the general corridor where wildlife movement is
expected.
Legend
Wildlife Corridor
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Attachment 3 — Least Cost Pathways for Wildlife Movement Map
The University of North Texas provided the City with Least Cost Path Mapping from Linkage Mapper. The Least Cost
Path is the route with the least difficulty for wildlife movement. The general wildlife corridors are also shown as the
darker green lines on this map.
Legend
Wildlife Corridor
- Greatest Cost Path
Least Cost Path
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Attachment 4 — Wildlife Corridor Map
The Wildlife Corridor Map combines the greenspace map efforts with the Linkage Mapping outputs for corridors and
least cost paths. This map will be integrated into the City's online interactive mapping tool. The specific lines mapped as
"wildlife corridors" simply reflect a direct path while the overall least cost paths are the general areas expected to
support wildlife movement.
Legend
+Wildlife Corridor
Green Space
Greatest Cost Path
Least Cost Path
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