Biological Resources

Biological resources are evaluated during project planning, design and construction phases. During the design phase of transportation projects EPG determines what biological resources may occur within or near the study area. A general description of the habitat in the project area is prepared and other initial data are collected from sources, such as literature and agency databases. Biological resources that are typically evaluated may include:

  • Special status species, regulated by federal, state and local law, regulation or policy
  • Native Plants
  • Habitat and vegetative communities
  • Wildlife connectivity

Through the design phase, EPG works with the design team to avoid and minimize impacts on biological resources. Where avoidance is not possible, mitigation measures are implemented to safeguard species and their habitats during project construction and operation. A thorough description of the protocol followed during the analysis of biological resources and the role of the EPG and contractor biologist can be found in the ADOT Environmental Planning Group - Development Program Consultant Biological Procedures.

Biological study and documentation process

biological study and documentation process

For additional information on the BE process and Section 7 consultation, see the USFWS Section 7 of the ESA.

Special Status Species

Special status species are plant and wildlife species that are listed, or proposed for listing, as threatened or endangered by the U.S. Fish and Wildlife Service (USFWS) or National Marine Fisheries Service under the provisions of the Endangered Species Act of 1973 (ESA). During project planning and design, a qualified biologist reviews the USFWS species list (Endangered Species list) to determine if special status species may occur in the project area.  If it is determined that special status species have the potential to occur and could be affected by the project, coordination with the USFWS may be warranted. Section 7 of the ESA requires Federal agencies to use their existing authority to conserve threatened and endangered species. A Section 7 consultation with the USFWS allows federal agencies to determine that actions they authorize or fund are not likely to jeopardize the continued existence of listed species or adversely modify critical habitat. Critical habitat has been designated by USFWS for certain threatened or endangered species and is also protected under the ESA. It is a geographic area with certain characteristics that is deemed essential for the conservation of a species and may require special management and protection. In the event that a special status species does not occupy critical habitat, the area is still protected because it may be essential for a species’ recovery. Private entities are involved in Section 7 consultation only when their action requires federal lands, permits or funding.

The USFWS also provides data that are specific to Arizona and maintains lists of species for each county (USFWS-AZ Ecological Services). If a project is proposed on US Forest Service (USFS) or Bureau of Land Management (BLM) lands, other federal land or tribal land, a review of agency or tribal species lists is required. In addition, the State of Arizona has a designation of special status species for species that occur throughout Arizona. Biologists should use the Arizona Game and Fish (AGFD) Environmental Review on-line tool for obtaining a list of special species and/or critical habitat known to occur within 2 or 3 miles of the project vicinity. However, use of a species list does not take the place of formal or informal consultation; it is used as a starting point for project research. Once a species list is developed for a project, specific analysis is required to identify potential effects of the proposed action on each species and its habitat. The results of this analysis will determine the need for additional coordination with federal, tribal, state or local agencies. Following is a list of some of the federal, state, tribal and local laws and regulations that address the protection of plant and wildlife species, it is not inclusive of all applicable laws and regulations.


EPG evaluates projects for impacts to protected native plants per the Arizona Native Plant Law (Title 3: Agriculture, Chapter 7: Arizona Native Plants), administered by the Arizona Department of Agriculture(AZDA). There are five categories of protected plants in Arizona:

  • Highly Safeguarded (essentially endangered species)
  • Salvage Restricted (cacti, ocotillo, etc.)
  • Export Restricted
  • Salvage Assessed (the common desert trees)
  • Harvest Restricted (firewood, bear grass, yucca)

These plants are protected by law and cannot be removed from any lands without a permit from the AZDA. This applies to plants that are owned by a private entity or managed by a government agency. The ADOT Roadside Development Group has specific evaluation guidelines for native plant salvage and replanting.

Invasive Plant Species and Noxious Weeds

Project areas may also support invasive plant species. Invasive plants are introduced species that can thrive in areas beyond their natural range of dispersal. They are characteristically adaptable, aggressive and have a high reproductive capability. This combined with a lack of natural enemies often leads to a rapid spread of the species. The introduction of invasive plants causes or is likely to cause economic or environmental harm, or harm to human health.

Noxious weeds are native or non-native plants designated by a federal, state, or local government as causing economic harm or harm to public health, agriculture, recreation, wildlife or property. To help preserve the integrity of native vegetation throughout the state, EPG evaluates each project area for the presence invasive plants and noxious weeds, and prescribes mitigation measures to remove and prevent introduction of such species.

A list of invasive species that is a compilation of AZDA, USFS and BLM designated species maintained by ADOT Roadside Development. The ADOT Natural Resources Management Section (NRMS) surveys and manages plants that are documented on the AZDA prohibited, regulated, and restricted weed list. When on Forest Service lands, ADOT also may survey and manage species found on the USDA Forest Service Invasive Species list. The BLM also has policies regarding noxious and invasive weeds. The EPG document Development Program Consultant Biological Procedures provides more information on the protocol for surveying and documenting the presence of invasive species that may be encountered on a project site. The protocol for implementing mitigation measures is also discussed in the document.

Wildlife Connectivity

When wildlife habitat becomes fragmented, viable habitat is lost which may contribute to a decline in species numbers and diversity. Fragmented habitat not only affects wildlife movement, but can have a negative impact on ecosystem health and native plant species. Population decline becomes a critical issue when species are no longer able to move between areas of suitable habitat due to transportation infrastructure and urbanization. Reduced wildlife connectivity may limit or remove access to natural habitat, breeding areas, food, shelter and migration; isolated populations tend to have a decrease in genetic diversity. Wildlife connectivity may also help aide in the re-establishment of populations that have been reduced or eliminated due to disease or natural occurrences such as fire or drought.

ADOT is committed to maintaining and improving connectivity, where possible, within its infrastructure projects. ADOT incorporates wildlife crossings and tunnels as part of its wildlife connectivity mitigation measures to support plant and wildlife diversity. ADOT has been involved in the development of Arizona Wildlife Linkages Group, and has developed a linkages map to identify, maintain and improve connectivity. A review of the maps facilitates the determination of whether a project has any identified wildlife linkages within the project area. If linkages are present, the AGFD and adjacent tribes must be contacted for additional recommendations.