Jump to main content.

Guidance for Defining the Potential Area In Which a Species Is Likely to Be Adversely Affected or Critical Habitat May Be Destroyed or Adversely Modified


April 21, 2010

SUBJECT: Guidance for Defining the Potential Area In Which a Species Is Likely to Be Adversely Affected or Critical Habitat May Be Destroyed or Adversely Modified

FROM: /s/ Donald J. Brady, Director, Environmental Fate and Effects Division, Office of Pesticide Programs

TO: All Managers and Staff of the Environmental Fate and Effects Division

I am providing this guidance on defining the potential area in which a listed species is "likely to be adversely affected" or critical habitat may be destroyed or adversely modified. Further this guidance addresses projecting future use relative to listed species assessments. This guidance which is effective immediately, is being issued consistent with recommendations from the EFED Endangered Species Registration Review Workgroup.


The Office of Pesticide Programs (OPP) uses the 2001 National Land-Cover Dataset (NLCD) as the first step for defining the area in which a listed species or critical habitat is likely to be adversely affected. The NLCD represents the best available source of nationally consistent landcover data. OPP matched individual and aggregated land cover classes from the 2001 NLCD to general pesticide label uses. For example, selected agricultural crops (e.g., corn) are assumed to be represented by the cultivated crops class (Class 82 cultivated crops) within the 2001 NLCD Definitions. Other generalized use patterns currently represented by NLCD classes in OPP risk assessments are orchard/vineyards (included in Class 82 cultivated crops), forestry (Classes 41 deciduous forest, 42 evergreen forest, and 43 mixed forest), pasture/hay (Class 81), and turf/residential (e.g., urban & suburban homeowner uses).

Additional general landcover class associations are under development. Turf is represented by an amalgamated landcover class blending four NLCD classes (Class 21 developed open space, 22 developed low intensity, 23 developed medium intensity, and 24 developed high intensity) and the 2001 NLCD impervious surface coverage. This turf product is proposed for public release in 2010. An additional class for rights-of-way is under development from a source other than the NLCD (e.g. TeleAtlas). OPP is in the process of developing an association list that links labeled pesticide uses with individual NLCD landcover classes using the recent preliminary development work in the California red-legged frog (CRLF) assessments; this list will be made available to risk assessors when available. Finally, because the NLCD is updated on a periodic basis, OPP will revisit these designations with each update, including the 2006 update, which is still under development.

The individual land cover class is used as the "starting point" or "footprint" of potential use sites for a given class and is described as the initial area of concern in previous OPP endangered species risk assessments (e.g., California red-legged frog). The potential area in which a species or habitat is likely to be adversely affected is defined using this initial area of concern plus any additional area deemed appropriate based on the fate, transport (e.g. drift and downstream dilution) and effects observed in data available for the risk assessment. For example, a pesticide used on corn will have an initial area of concern represented by the cultivated crops NLCD category. Assuming the risk assessment determines that the greatest distance where effects may be expected (using all available data) via spray drift is 500 feet, the potential area of Likely to Adversely Affect (LAA) effects will be the cultivated crop NLCD class plus 500 feet. Thus, this area represents the greatest extent where effects from the labeled use of the registered pesticide have the potential to adversely affect listed species.

Where more detailed land cover or crop-specific information is available (e.g., Washington State Department of Agriculture crop distribution data), it will be used as a refinement in risk characterization; however, this type of information is not to be used to define the initial area of concern, unless the data are available nationally. In addition, the United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) is developing cropland data layers that represent individual crops (e.g., sugarcane), although to date layers are only available for selected states. When these data become available nationally, OPP will consider how to use these in place of the generalized NLCD data. In addition, OPP will create a catalog of available crop-specific data sets for risk assessors to consider on a case by case basis until more refined nationally consistent data sets are available.


The Services have pointed out that projections of future use are an important component of "determining whether listed species are likely to be adversely affected by the addition of the pesticide products and, if so, an analysis of the extent of effects over the reregistration period." (Letter of January 14, 2009 from Marjorie Nelson to Arty Williams). In general, there is an increasing trend of continuous growth in urban and non-urban areas; however, the impact of continuous growth in terms of the effect on individual listed species is generally unquantifiable. OPP currently accounts for potential future use of registered agricultural uses by assuming that all of the cultivated cropland within the NLCD class represents the use site, including land in the Conservation Reserve Program (CRP). The CRP is a program administered by the USDA that takes cropland out of production. Lands currently in the CRP were by definition cropped at the time of imagery acquisition for the 2001 NLCD. Therefore, the cultivated cropland layer in NLCD represents these areas and any future conversion of CRP land to cultivated cropland.

OPP believes these assumptions result in a highly conservative estimate of where an individual crop (e.g., corn) may be grown and likely captures the locations where a given crop may either be rotated into, or where new uses would be expected to expand into. OPP also believes it is reasonable to assume that forestry, pasture/hay, and orchard/vineyard uses will also be over-represented by the respective land cover class within the 2001 NLCD because each of these use sites represents a significant sub-set of sites within each class.

Other uses, such as the residential and turf, may not be representative of future expansion within the NLCD land-cover types. At this point in time, OPP is unaware of any peer-reviewed methodology for estimating the locations and extent to which potential future expansion of turf and residential use sites will occur. At the December 2007 West Virginia meeting between OPP and the Services, it was agreed that the Services would provide a relevant example (i.e., large scale assessment) of how projections of future growth in residential uses should be addressed in future Biological Opinions. OPP has agreed to evaluate any approach submitted by the Services; however, it is OPP's position that any approach should be vetted through an external peer review process, such as the Federal Insecticide, Fungicide, and Rodenticide, Act (FIFRA) Scientific Advisory Panel, prior to being implemented in OPP's ecological risk assessment process. OPP and the Services have agreed to work together to develop and vet such an approach as deemed appropriate for OPP risk assessments. The Services have agreed to use an approach for estimating future growth in residential and turf areas in all "pipeline" consultation packages, until such time as a peer-reviewed methodology is agreed upon by both the Services and OPP. Pipeline consultations include all assessments previously submitted by OPP to the Services, as well as any assessments submitted prior to development of a peer-reviewed methodology acceptable to both OPP and the Services is implemented.

Any questions should be directed to Mark Corbin or other members of the Workgroup.

Endangered Species Reregistration Workgroup

Mark Corbin, EFED
Kevin Costello, PRD
William Eckel, EFED
Cathy Eiden, PRD
Stephanie Irene, EFED
Edward Odenkirchen, EFED (Co-Chair)
Melissa Panger, EFED
Anita Pease, EFED
Mohammed Ruhman, EFED
Dana Spatz, EFED
Thomas Steeger, EFED
Ingrid Sunzenauer, EFED (Co-Chair)
Michelle Thawley, EFED
Katrina White, EFED

Publications | Glossary | A-Z Index | Jobs

Local Navigation

Jump to main content.