Programmatic Biological Assessment, Conference Report, and Conservation Strategy for Impacts from Transportation Improvement Projects on Select Sensitive Species on Colorado's Central Shortgrass Prairie. 

Lee Grunau, Anne K. Ruggles, Marie Venner, Chris Pague, Renee Rondeau, Jerry M. Powell
Posted on: 7/18/2022 - Updated on: 11/07/2023

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The purpose of this Biological Assessment (BA), Conference Report (CR), and Conservation Strategy is to determine whether the Colorado Department of Transportation’s (CDOT) routine maintenance and upgrade activities on existing transportation corridors of eastern Colorado over the next 20 years are likely to affect any of the threatened and endangered, proposed, candidate or sensitive species listed below, and to describe conservation measures that CDOT will take to mitigate those impacts.

CDOT has three goals: 1) proactive conservation of declining species in the central Shortgrass Prairie Ecoregion of Colorado; 2) compensation for potential impacts to atrisk species from transportation improvements on the existing transportation corridor network and to existing bridges in eastern Colorado; and 3) improved efficiency and effectiveness of environmental assessments associated with CDOT projects over the next 20 years. To achieve these goals, CDOT is proposing a large-scale, planned conservation effort, rather than addressing possible impacts to listed and currently non-listed species on a project-by-project basis. This will make a more effective contribution to the recovery of declining species and result in improved management of high quality priority habitats. At the same time, uncertainty in planning and implementation of CDOT projects will be minimized.

The concept for this programmatic agreement was developed in cooperation with USFWS, FWHA, CDOW, TNC, and CNHP. The project focuses on the Colorado portion of the Central Shortgrass Prairie ecoregion as modified by TNC (1998) from Bailey et al. (1994). For the purposes of this project, TNC’s CSP boundary was further modified to include all segments of I-25 within Colorado. The total project area includes the entire eastern prairie in Colorado (~27,520,863 acres) and has a western boundary roughly coincident with Interstate 25 (Figure 1). It is dominated by shortgrass, mixed-grass, and sandsage prairie spread across rolling plains, tablelands, canyons, badlands, and buttes (TNC 1998).

The impact analysis was conducted using GIS and the best available scientific data in conjunction with expert review. The core project team consulted with experts in each taxonomic group (herpetofauna, birds, fish, mammals, invertebrates and plants) to select a list of species likely to be affected by CDOT activities in the CSP over the next 20 years (Grunau and Lavender 2002). Three lists of plant and animal species (terrestrial and aquatic species) were developed: species currently listed as threatened or endangered under the ESA (Table 3), proposed or candidate under the ESA (Table 4 and Table 5), and those ranked by a conservation entity as sensitive (at risk of rangewide or local imperilment) (Table 6). The experts also helped refine existing range and distribution data and define impact zones within existing transportation corridors for each species across the range of CDOT transportation improvements. The experts suggested that potential impacts from most routine CDOT maintenance activities would likely have only temporary effects (Grunau and Lavender 2002). However, because the experts identified 4 habitat loss as the most important potential impact, they concurred that any construction project resulting in permanent loss should be mitigated (Grunau and Lavender 2002).

CNHP calculated the maximum potential impact for each species, and then eliminated overlap among species to arrive at the total amount of habitat for targeted species within the project area that could potentially be impacted by CDOT activities: 15,160 acres (Grunau and Lavender 2002). Based on input from experts, the core project team concluded that on-site mitigation using best management practices, rather than off-site mitigation, was the most appropriate conservation strategy for aquatic species, butterflies, and some plants.

The Conservation Strategy section of this document describes actions that will be taken to offset impacts to targeted species from the Colorado Department of Transportation’s (CDOT) full suite of transportation improvements and routine maintenance on the eastern plains of Colorado over the next 20 years. Details on Best Management Practices (BMPs) and some sample land protection projects that could, if implemented, meet offsite mitigation requirements, are included. The off-site mitigation strategy is based upon the acquisition of property rights (especially conservation easements) over high-quality habitat blocks that: a) contribute to the integrity of populations of targeted species, and b) allow use of an appropriate suite of management tools (e.g., prescribed fire, grazing regimes) to achieve conservation objectives, and c) are located where conservation in perpetuity is most likely to be achieved (i.e., either adjacent to other permanent conservation areas, or large enough to achieve this effect in and of themselves).

CDOT anticipates that these conservation measures for currently listed species, as well as target species that may be listed in the future, will be in effect in perpetuity. These conservation measures will satisfy CDOT’s and FHWA’s section 7 consultation requirements for listed species, and may satisfy future section 7 consultation requirements for target species should they become listed in the future, over the 20 years following acceptance of this Biological Assessment and Conservation Strategy, and issuance of a Biological Opinion by the U.S. Fish and Wildlife Service (USFWS).


Grunau, L., Ruggles, A.K., Venner, M., Pague, C., Rondeau, R., Powell, J.M. (2003). Programmatic Biological Assessment, Conference Report, and Conservation Strategy for Impacts from Transportation Improvement Projects on Select Sensitive Species on Colorado's Central Shortgrass Prairie. 

Affiliated Organizations

Colorado Natural Heritage Program, Bear Canyon Consulting Group, Venner Consulting, Colorado Department of Transportation

Affiliated Organizations

The Nature Conservancy is the leading conservation organization working around the world to protect ecologically important lands and waters for nature and people.