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This section of the ESA-FHWA Web tool provides a glossary of key terms often encountered when researching and writing Biological Assessments.  In addition, the U.S. Fish and Wildlife Service also maintains a helpful glossary of key terms  related to the Endangered Species Act.  If there are terms you do not find here that you'd like to see added to the glossary, or terms already in the glossary that could use further clarification, please let us know. ( Contact Us

303(d) list
Section 303(d) of the federal Clean Water Act requires States to periodically prepare a list of all surface waters in the state for which beneficial uses of the water (drinking, recreation, aquatic habitat, and industrial use) are impaired by pollutants. These are water quality limited estuaries, lakes, and streams that fall short of state surface water quality standards, and are not expected to improve within the next two years.

Action (50 CFR §402.02)
An activity or program of any kind authorized, funded, or carried out, in whole or in part, by a Federal agency in the United States or upon the high seas, such as: (a) an action intended to conserve listed species or their habitat; (b) the promulgation of a regulation; (c) the granting of a license, contract, lease, easement, right-of-way, permit, or grant-in-aid; or (d) an action directly or indirectly causing modification to the land, water, or air.
Action agency
The federal agency proposing to undertake a major construction project (action).
Action area (50 CFR §402.02)
All areas to be affected directly or indirectly by the federal action and not merely the immediate area involved in the action.
Adjacent (33 CFR §328)
Means bordering, contiguous, or neighboring. Wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes and the like are adjacent wetlands.
To affect (a verb) is to bring about a change (example: The proposed action is likely to adversely affect piping plovers nesting on the shoreline). The effect (usually a noun) is the result (example: The proposed highway is likely to have the following effects on the Florida scrub jay). Affect appears throughout Endangered Species Act Section 7 regulations and documents in the phrases may affect and likely to adversely affect. Effect appears throughout Section 7 regulations and documents in the phrases adverse effects, beneficial effects, effects of the action, and no effect.
Aquatic bedlands (33 CFR §328)
The area waterward of and below the line of navigability on non-tidal rivers and lakes, below the extreme low tide mark in navigable tidal waters, or below the outer harbor line where a harbor has been created. Means bordering, contiguous, or neighboring. Wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes and the like are adjacent wetlands.
Aquatic shorelands
The shore areas of non-tidal navigable lakes or rivers between the ordinary high water line and the line of navigability unless otherwise established.
Aquatic tidelands
The area between the ordinary high tide line and extreme low tide line (unless otherwise established).

Background conditions
The biological, chemical, and physical conditions of a water body outside the area of influence of the discharge considered in the permit application.
Any land surface above the ordinary high water line that adjoins a body of water and contains it except during floods. Bank also includes all land surfaces of islands above the ordinary high water line that adjoin a water body and that are below the flood elevation of their surrounding water body.
The starting point for analysis; ambient conditions from which to measure and compare potentially altered conditions caused by project activities.
Batched biological assessment
A biological assessment that provides collective coverage for groups of similar types of projects or for projects that take place in a similar geographic location.
Batched biological evaluation
The term used by U.S. Army Corps of Engineers for informal biological assessment.
The land below the ordinary high water lines of state waters. This definition shall not include irrigation ditches, canals, storm water run-off devices, or other artificial watercourses except where they exist in a natural watercourse that has been altered by man.
Beneficial effects
Contemporaneous positive effects without any adverse effects on the species or habitat. By definition, beneficial effects cannot be considered to have no effect.
Best Management Practices (BMPs)
Methods, facilities, built elements, and techniques implemented or installed during project construction to reduce short- and long-term project impacts on listed and sensitive species and habitat. These measures are included as part of the federal agency's proposed action.
The variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.
Biological assessment (50 CFR §402.02)
The information prepared by or under the direction of an action agency to determine whether a proposed action (major construction activity) is likely to affect listed and proposed species and designated and proposed critical habitat that may be present in the project action area, including the evaluation of potential effects of the action on such species and habitat. The outcome of the biological assessment (BA) determines whether formal consultation or a conference is necessary.
Biological opinion (50 CFR §402.02)
A document stating the opinion of FWS or NOAA Fisheries on whether or not a Federal action is likely to jeopardize the continued existence of listed species or result in the destruction or adverse modification of critical habitat.
Brackish waters
Waters with a salinity intermediate between seawater and freshwater, usually showing wide salinity fluctuations.
Any structure that transports traffic or materials across a navigable water, including pipelines and conveyor belts.
A vertical or nearly vertical erosion protection structure placed parallel to the shoreline consisting of concrete, timber, steel, rock, or other permanent material not readily subject to erosion.

Candidate Conservation Agreement (CCA)
A voluntary agreement between FWS or NOAA Fisheries and other Federal or non-Federal landowners that identifies specific conservation measures that the participants of the agreement will undertake to conserve species covered by the agreement, none of which are listed under the Endangered Species Act, with the intention of preventing any need to list the species.
Candidate Conservation Agreement with Assurances (CCAA)
A voluntary agreement between FWS and a non-Federal property owner who agrees to manage lands or waters to remove threats to candidate or proposed species, with assurances that the property owners' conservation efforts will not result in future regulatory obligations that exceed those agreed to at the time the agreement is signed; it authorizes take if the species is later listed.
Candidate species (candidate)
A species for which the Service has on file sufficient information on biological vulnerability and threats to support a proposal to list it as threatened or endangered. Until a proposed rule is issued to list a candidate species, authors of biological assessments are not required to address the species, although it is recommended.
The 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora, regulating or prohibiting international commerce for plant and animal species believed to be harmed by or that may be harmed by international trade. The authority to implement this is under section 8 of the ESA. Read more...
A process of early interagency cooperation involving discussions between an action agency and the Services pursuant to Section 7(a)(4) of the Endangered Species Act regarding the likely impact of the agency's proposed action on proposed species or critical habitat. Conferences are intended to help identify and resolve potential conflicts between an action and species conservation early in project planning, and to develop recommendations to minimize or avoid adverse effects (50 CFR §402.02, 50 CFR §402.10).
Conservation banking
A method used to offset impacts occurring elsewhere to the same listed species. “Bank” consists of non-Federal land containing natural resource values conserved and managed in perpetuity.
Conservation measure (CM)
Activities or measures that help recover listed species.
Conservation recommendations
The Services may provide with the biological opinion a statement containing discretionary Conservation Recommendations. These are advisory and are not intended to carry any binding legal force [50 CFR §402.14(j)].
Conserve, Conserving, and Conservation
The use of methods and procedures necessary to bring any endangered or threatened species to the point at which the measures provided under the Endangered Species Act are no longer necessary; includes research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transportation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.
The process required of a Federal agency when any activity authorized, carried out, or conducted by that agency may affect a listed species or designated critical habitat; consultation is with FWS or NOAA Fisheries and may be either informal or formal.
Critical habitat
Specific geographical areas that possess physical or biological features that are essential to the conservation of listed species. These designated areas may require special management consideration or protection.
Cubic yard (cu yd)
A measure of volume computed by multiplying length by width by depth (1 yard x 1 yard x 1 yard). 1 cubic yard = 27 cubic feet.
Cumulative effects (50 CFR §402.02)
For purposes of consultation under the ESA, the effects of future State or private activities not involving Federal activities, that are reasonably certain to occur within the action area of an action subject to consultation. Cumulative effects are defined differently for purposes of the National Environmental Policy Act (NEPA).

To remove an animal or plant species from the list of endangered and threatened wildlife and plants.
When a species is no longer listed under the ESA. See also Recovered Species.
Destruction or adverse modification (50 CFR §402.02)
A direct or indirect alteration that appreciably diminishes the value of critical habitat for both survival and recovery of listed species, including an alteration to physical or biological features that were the basis for determining the habitat to be critical.
Direct effects
Impacts resulting from the proposed action.
Discharge of fill material
Placing fill material into waters of the United States.
Discountable effects
Potential effects of a proposed action that are extremely unlikely to occur. Based on best judgment, a person would not expect discountable effects to occur.
Distinct population segment (DPS)
A subdivision of a vertebrate species that is treated as a species for purposes of listing under the Endangered Species Act. To be so recognized, a potential distinct population segment must satisfy standards specified in a FWS or NOAA Fisheries policy statement (See the February 7, 1996, Federal Register, pages 4722-4725). The standards require it to be separable from the remainder of and significant to the species to which it belongs. This is equivalent to the NOAA Fisheries evolutionarily significant unit (ESU) classification.
The removal of bed material using other than hand held tools.

A dynamic and interrelating complex of plant and animal communities and their associated nonliving (such as physical and chemical) environment.
Ecosystem approach
A philosophy of resource management that focuses on protecting or restoring the function, structure, and species composition of an ecosystem, recognizing that all components are interrelated.
See Affect/effect.
Effects, insignificant and/or discountable
See Insignificant effect and/or Discountable effects.
Effects of the action
The direct and indirect effects of a federal action on listed species or critical habitat, together with the effects of other interrelated and interdependent activities. Direct effects are those resulting from the proposed action. Indirect effects are those caused by the proposed action later in time, but still reasonably certain to occur. Interrelated actions are part of a larger action and depend on the larger action for their justification. Interdependent actions are those that have no independent utility apart from the action under consideration.
Essential Fish Habitat of the Magnuson-Stevens Fishery Conservation and Management Act sections (50 CFR §600.10).
EFH assessment
Document requirement for any Federal action that may adversely affect EFH, Federal agencies must provide NOAA Fisheries with a written assessment of the effects of that action on EFH [50 CFR §600.920(e)].
Where emergency circumstances mandate the need to consult in an expedited manner, consultation may be conducted informally through alternative procedures that the Director determines to be consistent with the requirements of section 7(a)-(d) of the ESA. This provision applies to situations involving acts of God, disasters, casualties, national defense or security emergencies, etc. (50 CFR §402.05)
Endangered species
A species that is in danger of extinction throughout all or a significant portion of its range. In comparison, a threatened species is a species which is likely to become an endangered species within the foreseeable future.
Endangered Species Act (ESA)
Is a federal law passed by congress in 1973. The ESA is a powerful environmental law intended to slow the rate at which plants and animals are going extinct in the United States. Its goal is to conserve and restore native species for future generations of U.S. citizens to enjoy and use. The ESA is administered by the Department of Interior (U. S. Fish and Wildlife Service) for land-based and fresh-water species, and by the Department of Commerce (U.S. National Marine Fisheries Service, or NOAA Fisheries) for marine species.
Endangered species permit
A document issued by FWS or NOAA Fisheries under authority of section 10 of the ESA allowing an action otherwise prohibited under section 9.
Endemic species
A species native and confined to a certain region; generally used for species with comparatively restricted distribution.
Enhancement of Survival Permit
A type of permit issued by the Service under the authority of section 10(a)(1)(A) of the Endangered Species Act. It permits an otherwise prohibited action that benefits the conservation of a listed species (Endangered Species Act).
Environmental baseline
The environmental baseline includes the past and present impacts of all Federal, State, or private actions and other human activities in the action area, the anticipated impacts of all proposed Federal projects in the action area that have already undergone formal or early section 7 consultation, and the impact of State or private actions that are contemporaneous with the consultation in process.
Essential experimental population
An experimental population whose loss would appreciably reduce the prospect of survival of the species in the wild. All other experimental populations are nonessential.
Estuarine waters
Waters that are semienclosed by land but have open, partly obstructed, or sporadic access to the ocean, and in which seawater is at least occasionally diluted by freshwater runoff from land. Estuarine waters of the state include adjacent tidal flats and beaches up to the limit of tidal inundation or wave splash.
Evolutionarily Significant Unit (ESU)
A Pacific salmonid stock that is substantially reproductively isolated from other stocks of the same species and which represents an important part of the evolutionary legacy of the species. Life history, ecological, genetic, and other information can be used to determine whether a stock meets these two criteria. NOAA Fisheries uses this designation. This is equivalent to the U.S. Fish and Wildlife Service distinct population segment (DPS) classification.
Experimental population
A population (including its offspring) of a listed species designated by rule that is wholly separate geographically from other populations of the same species. An experimental population may be subject to less stringent prohibitions than are applied to the remainder of the species to which it belongs.
Extinct species
A species that no longer exists. For ESA, a species currently believed to be extinct.
Extirpated species
A species no longer surviving in regions that were once part of its range.

Federal action agency
Any department or agency of the United States proposing to authorize, fund, or carry out an action under existing authorities. This agency is responsible for formally submitting a biological assessment for the proposed action to the Services for review and informal or formal consultation. Federal agencies and organizations, as well as Executive Orders and other Presidential Documents.
Federal nexus
A project with a federal nexus either has federal funding, requires federal permits, or takes place on federal lands.
Federal Register
The official daily publication for actions taken by the Federal government, such as Rules, Proposed Rules, and Notices of Federal agencies and organizations, as well as Executive Orders and other Presidential Documents.
Fill material
Any material that will change the bottom elevation of an aquatic area, wetland, or water body.
Fish life
All fish species, including but not limited to food fish, shellfish, game fish, and other nonclassified fish species and all stages of development of those species.
Formal consultation
The required process between FWS or NOAA Fisheries and a Federal agency or applicant conducted when a Federal agency determines its action is likely to adversely affect a listed species or its critical habitat; used to determine whether the proposed action is likely to jeopardize the continued existence of listed species or adversely modify critical habitat. The process concludes with the Service's issuance of a biological opinion under Section 7(b)(3) of the ESA (50 CFR §402.02).
Frequently flooded areas
Lands in the floodplain subject to a 1 percent or greater chance of flooding in any given year. These areas include, but are not limited to, streams, rivers, lakes, coastal areas, and wetlands.


The place or environment where a plant or animal naturally lives and grows. Habitat for a particular plant or animal consists of the elements it needs to survive and may be tied to temperature, water, soil, sunlight, source of food, refuge from predators, places to reproduce, and other living and non-living factors.
Habitat Conservation Plan (HCP)
A plan that outlines ways of maintaining, enhancing, and protecting a given habitat type needed to protect species; usually includes measures to minimize impacts, and may include provisions for permanently protecting land, restoring habitat, and relocating plants or animals to another area. Required before an incidental take permit may be issued.
Harass (50 CFR Part 17)
An intentional or negligent act or omission that creates the likelihood of injury to wildlife by annoying to such an extent as to significantly disrupt normal behavior patterns, which include but are not limited to breeding, feeding, and sheltering.
Harm (50 CFR Part 17)
In the definition of take in the Endangered Species Act, an act that actually kills or injures wildlife, including habitat modification or degradation that significantly impairs essential behavioral patterns such as breeding, feeding, or sheltering.
Historic range
The geographic area where a species was known to or believed to occur within historic time.
Hydric soil
Soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions that favor the growth and regeneration of hydrophytic vegetation (US Department of Agriculture-Soil Conservation Service 1985). Hydric soils that occur in areas having positive indicators of hydrophytic vegetation and wetland hydrology are wetland soils.

Implementation schedule
An outline of actions, with responsible parties, estimated costs and timeframes, for meeting the recovery objectives described in a species recovery plan.
Incidental take
A take of listed species that results from an action but is not the direct purpose or intent of the action, as defined under the Endangered Species Act. Incidental take can be authorized through Section 7 consultation or through Section 10 conservation planning, such as a habitat conservation plan (HCP).
Incidental take permit
A permit issued under section 10(a)(1)(A) of the ESA to a non-Federal party undertaking an otherwise lawful project that might result in the take of an endangered or threatened species. Application for an incidental take permit is subject to certain requirements, including preparation by the permit applicant of a conservation plan, generally known as a “Habitat Conservation Plan” or “HCP.”
Incidental take statement
The part of a non-jeopardy biological opinion that estimates the amount or extent of incidental take of listed species likely to result from the action subject to consultation and exempts that take from section 9 take prohibitions. Per section 7(o)(2) of the ESA, actions that are conducted in conformance with the terms and conditions of an incidental take permit are exempt from the section 9(a)(1) prohibitions on take.
Indirect effect
An effect caused by a proposed action that takes place later in time than the action, but is still reasonably certain to occur.
Informal consultation
An optional process that includes all discussions, correspondence, etc., between FWS or NOAA Fisheries and the Federal agency or the designated non-Federal representative prior to formal consultation, if required.
Insignificant effect
An effect that should never reach the scale where take occurs. Based on best judgment, a person would not be able to meaningfully measure, detect, or evaluate insignificant effects.
Interdependent action
An action having no independent utility apart from the proposed action.
Interrelated action
An action that is part of a larger action and depends on the larger action for its justification.
Is likely to jeopardize the continued existence of a proposed species or adversely modify proposed critical habitat
When the action agency or the Services identify conditions where the proposed action has this result, a conference is required.
Is not likely to adversely affect
The appropriate finding in a biological assessment (or conclusion during informal consultation) when effects on listed species are expected to be discountable, insignificant, or completely beneficial.

Classification given to an action that reasonably would be expected to directly or indirectly reduce the likelihood of both survival and recovery of a listed species in the wild by reducing the reproduction, numbers, or distribution of that species.
Jeopardy biological opinion
A FWS or NOAA Fisheries section 7 biological opinion determining that a Federal action is likely to jeopardize the continued existence of a listed species or result in the destruction or adverse modification of critical habitat.
Jeopardize the continued existence of (50 CFR §402.02)
To engage in an action that reasonably would be expected, directly or indirectly, to reduce appreciably the likelihood of both the survival and recovery of a listed species in the wild by reducing the reproduction, numbers, or distribution of that species.


A lake is a still body of fresh or brackish water larger than 20 acres. Most of its area is too deep for plants to grow on the bottom.
Lead agency
An agency from among two or more agencies involved in a proposed Federal action that is assigned lead responsibility for a consultation. When a federal action involves more than one Federal agency, the agencies may coordinate to designate a lead agency for purposes of consultation with the FWS or NOAA Fisheries.
Lead office
FWS field office responsible for coordinating all or most actions taken to study, propose, list, conserve, and delist a species. The lead office is given the lead responsibility over the entire range of a species, including anywhere it occurs in other regions.
Lead region
FWS region responsible for coordinating all actions taken to study, propose, list, conserve, and delist a species.
Listed species
A species, subspecies, or distinct population segment that has been added to the Federal list of endangered and threatened wildlife and plants. Listed species are found in 50 CFR 17.11-17.12. Under the statute, the two types of species are treated in virtually the same way.
The formal process through which FWS or NOAA Fisheries adds species to the Federal list of endangered and threatened wildlife and plants.
Listing priority
A number from 1 to 12 indicating the relative urgency for listing a plant or animal species as threatened or endangered, using criteria that reflect the magnitude and immediacy of threat to the species, as well as its relative taxonomic distinctness or isolation.

Major construction activity
A construction project (or other undertaking having similar physical effects) that is a major federal action significantly affecting the quality of the human environment, as referred to in the National Environmental Policy Act (NEPA, 42 USC 4332 (2)(c).
Relating to the seas and oceans.
May affect, likely to adversely affect
The appropriate finding in a biological assessment (or conclusion during informal consultation) if any adverse effect on listed species may directly or indirectly result from the proposed action or its interrelated or interdependent actions, and the effect is not discountable, insignificant, or beneficial. If the overall effect of the proposed action is beneficial to the listed species but is also likely to cause some adverse effects, then the proposed action is likely to adversely affect the listed species. If incidental take is anticipated to result from the proposed action, a determination of likely to adversely affect should be made, requiring initiation of formal Section 7 consultation.
May affect, not likely to adversely affect
The appropriate conclusion when effects on listed species are expected to be discountable, insignificant, or completely beneficial.
Mean High Water and Mean Higher High Water Tidal Elevations
The determination of tidal elevation is obtained by averaging each day's highest tide at a particular location over a period of 19 years, measured from mean lower low water, which equals 0.0 total elevation.
Mean Lower Low Water
The 0.0 tidal elevation, determined by averaging each day's lowest tide at a particular location over a period of 19 years. It is the tidal datum for vertical tidal references in the salt water area.
Minimization measure
Measures that reduce the impact of the project on listed species.
Mixing zone
The area of a water body next to an effluent outfall where the effluent is diluted by mixing with the receiving water.

National Pollutant Discharge Elimination System (NPDES)
The provision in the federal Clean Water Act that requires point source dischargers of pollutants to obtain permits, called NPDES permits.
No effect
The appropriate conclusion when the proposed action will not affect a listed species or its critical habitat.
Non-jeopardy biological opinion
A FWS or NOAA Fisheries section 7 biological opinion that determines that a Federal action is not likely to jeopardize the existence of a listed species or result in the destruction or adverse modification of critical habitat.

Occupied critical habitat
Critical habitat that contains individuals of the species at the time of the project analysis. A species does not have to occupy critical habitat throughout the year for the habitat to be considered occupied (e.g., migratory birds). Subsequent events affecting the species may result in this habitat becoming unoccupied.
Ordinary High Water Mark or Line
The visible line on the banks of a water body where the presence and action of water is so common that it leaves a mark on the soil or vegetation. If the ordinary high water line cannot be found, it is measured as the line of mean higher high water adjoining saltwater and the elevation of the mean annual flood adjoining freshwater.

Participation plan
A plan describing the means to carry out one or more tasks outlined in the implementation schedule of a recovery plan.
Performance measure
An observable or measurable benchmark for a particular performance objective against which a project can be compared. If the standards are met, the related performance objectives are considered to have been fully achieved. It is something quantifiable. Standards should be measures, not actions and should be: 1. Achievable, and 2. Capable of being monitored.
Performance-based biological assessment
A type of biological assessment usually written early in the design phase of a project. Because detailed information on the project description and design is lacking at that stage, they establish habitat and species safeguards by defining actions that will not be included in the project or impacts that will be avoided.
A formal request that a species be listed, reclassified, or delisted, or that critical habitat be revised for a listed species under ESA. Critical habitat can be petitioned for designation under the Administrative Procedures Act.
A pond is a body of still fresh or brackish water shallow enough for sunlight to reach the bottom, allowing rooted plants to grow anywhere across its area.
Primary constituent element
A physical or biological feature essential to the conservation of a species for which its designated or proposed critical habitat is based on, such as space for individual and population growth, and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, rearing of offspring, germination, or seed dispersal; and habitats that are protected from disturbance or are representative of the species historic geographic and ecological distribution.
Programmatic biological assessment
A biological assessment that establishes conditions allowing specific activities that occur within general programs to proceed without individual concurrence from the Service (or allowing a shortened concurrence timeline).
Programmatic biological evaluation
Term used by U.S. Army Corps of Engineers for an informal programmatic biological assessment.
Programmatic consultation
Consultation addressing multiple actions of an agency on a program-wide, regional, or other basis.
The formal process of publishing a draft Federal regulation in the Federal Register and establishing a comment period for public input into the decision-making process. Plants and animals must be proposed for listing as threatened or endangered, and the resulting public comments must be analyzed, before the FWS or NOAA Fisheries can make a final decision.
Proposed species
Any species of wildlife, fish, or plant that is proposed in the Federal Register to be listed under Section 4 of the ESA as threatened or endangered.


The geographic area a species is known to or believed to occupy.
Percentage probability of an effect.
Reasonable and prudent alternative (RPA) (50 CFR 402.02)
A recommended alternative action identified during formal consultation that can be implemented in a manner consistent with the intended purpose of the action, that can be implemented consistent with the scope of the Federal agency's legal authority and jurisdiction, that is economically and technologically feasible, and that FWS or NOAA Fisheries believes would not jeopardize the continued existence of listed species or the destruction or adverse modification of designated critical habitat.
Reasonable and prudent measure (RPM) (50 CFR 402.02)
An action that FWS or NOAA Fisheries believes necessary or appropriate to minimize the impacts (the amount or extent) of incidental take caused by an action that was subject to consultation.
To change a species' official status from threatened to endangered or vice-versa.
Recovered species
Under the ESA, a species is "recovered" when it is no longer requires protection under the ESA and thus is delisted.
Action that is necessary to reduce or resolve the threats that caused a species to be listed as threatened or endangered.
Recovery outline
The first FWS or NOAA Fisheries recovery document provided for a listed species. While brief, the document serves to direct recovery efforts pending the completion of the species' recovery plan.
Recovery permit
A permit issued under section 10(a)(1)(A) of the Endangered Species Act for scientific research and other activities benefiting the recovery of federally listed species; allows for research pertaining to species recovery, such as taking blood samples from a peregrine falcon for genetic analysis, or conducting surveys of freshwater mussel beds to determine species status and distribution.
Recovery plan
A document drafted by FWS, NOAA Fisheries, or other knowledgeable individual or group, that serves as a guide for activities to be undertaken by Federal, State, or private entities in helping to recover and conserve endangered or threatened species.
Recovery priority
A rank, ranging from a high of 1C to a low of 18, whereby priorities are assigned to listed species and recovery tasks; assignment of rank is based on degree of threat, recovery potential, taxonomic distinctiveness, and presence of an actual or imminent conflict between the species and development activities.
Recovery unit
A sub-unit of the listed entity, geographically or otherwise identifiable, that is essential to the recovery of the entire listed entity; conserves genetic or demographic robustness, important life history stages, or other feature for long-term sustainability of the entire listed entity. Recovery units are optional, but, where used, should collectively encompass the entire listed entity. Recovery criteria for the listed entity should address each identified recovery unit, and every recovery unit must be recovered before the species can be delisted.
Riparian areas
The transition area between land and water environments. It is the upland area adjacent to streams, lakes, wetlands and marine waters that can support the proper functioning of those water bodies and provide habitat for wildlife. If there is a stream or creek running through a property, there are riparian areas on each side.
A fairly large, moving body of fresh or brackish water that travels within a channel.

Safe Harbor Agreement
A voluntary agreement signed by FWS or NOAA Fisheries and a property owner and any other cooperator that (a) sets forth specific management activities that the non-Federal property owner will undertake or forgo to provide a net conservation benefit to species covered by the agreement, and (b) provides the property owner with the Safe Harbor assurances described within the agreement and authorized in an enhancement of survival permit.
Scientific name
A formal Latin or latinized name applied to a taxonomic group of animals or plants. A species' scientific name is a two-part combination consisting of the genus followed by the species. For example, the scientific name of the little brown bat is Myotis lucifugus. If a species has been further divided into subspecies, a third part is added to the scientific name. The Arizona bat is Myotis lucifugus occultus; “occultus” distinguishes the Arizona subspecies from other subspecies of the little brown bat.
Scientific take permit
See Recovery permit.
Section 4(d) rule
A regulation developed by FWS or NOAA Fisheries establishing prohibitions that apply for a threatened species. Any prohibitions adopted must be those necessary and advisable to provide for the conservation of the species.
Abbreviated term for the U.S. Fish and Wildlife Service and NOAA Fisheries.
Similarity of appearance
A species may be treated as endangered or threatened if it in appearance a species which has been listed under section 4 and enforcement personnel would have difficulty distinguishing between the listed and the unlisted species; if the effect of this difficulty is an additional threat to the listed species; and if such treatment of the unlisted species would improve protection for the listed species. A similarity of appearance listing must be formalized by rule.
Special Rule
See Section 4(d) rule.
For purposes of the Endangered Species Act, this term includes any species or subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.
Species of concern
A species, usually thought to be in decline, that may be considered for federal candidate status in the future. This may include species for which the Services have determined, following a biological status review, that listing under the ESA is "not warranted," pursuant to ESA section 4(b)(3)(B)(i), but for which significant concerns or uncertainties remain regarding their status and/or threats. Species can qualify as both "species of concern" and "candidate species."
A taxonomic rank below that of species, usually recognizing individuals that have certain heritable characteristics distinct from other subspecies of a species. Such species receive no legal protection and use of the term does not necessarily imply that a species will eventually be proposed for listing. A similar term is “species at risk,” which is a general term for listed species as well as unlisted ones that are declining. Canada uses the term in its Species at Risk Act.
Suitable habitat
The area where an organism, including a plant, animal or fish, naturally or normally lives and grows.

To harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct; may include significant habitat modification or degradation if it kills or injures wildlife by significantly impairing essential behavioral patterns including breeding, feeding, or sheltering.
Terms and Conditions
Required actions described in an Incidental Take Permit or Incidental Take Statement.
Threatened species
An animal or plant species likely to become endangered within the foreseeable future throughout all or a significant portion of its range. In comparison, an endangered species is any species, which is in danger of extinction throughout all or a significant portion of its range.
A marked or measured line or strip at a project site along which environmental samples are collected.
Trend line
In technical analysis, a line or two parallel lines that indicate the direction in which a measurable effect is moving, and the direction in which it will continue to move.
A stream or river that flows into a larger stream or river.
The clarity of water expressed as nephelometric turbidity units (NTU) and measured with a calibrated turbidimeter.

Unoccupied critical habitat
Critical habitat that is not occupied (i.e., not permanently or seasonally occupied) by the listed species at the time of the project analysis. The habitat may be suitable, but the species has been extirpated from this portion of its range. Conversely, critical habitat may have been designated in areas unsuitable for the species, but restorable to suitability with proper management, if the area is necessary to either stabilize the population or assure eventual recovery of a listed species. As recovery proceeds, this formerly unoccupied habitat may become occupied. Some designated, unoccupied habitat may never be occupied by the species, but was designated since it is essential for conserving the species because it maintains factors constituting the species' habitat. For example, critical habitat may be designated for an upstream area maintaining the hydrology of the species' habitat downstream.
Any area that does not qualify as a wetland because it does not have the characteristics associated with wetlands.


Warranted but Precluded
A 12-month petition finding that a petitioned action should be undertaken, but cannot because the resources necessary to do so are being devoted to actions with higher priority.
Waters of the U.S.
Includes lakes, rivers, ponds, streams, inland waters, underground water, salt waters, estuaries, tidal flats, beaches, and lands adjoining the seacoast of the state, sewers, and all other surface waters and watercourses within the jurisdiction of the U.S.
Wetlands generally include swamps, marshes, bogs, and similar areas. They are areas that are inundated or saturated by surface water or ground water at a frequency and duration sufficient to support and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.



 For questions or feedback on this subject, please contact Dan Buford at 202-366-8168.

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