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IUCN Definitions

Published Jun 21, 2011

A summary of the relationship between GAP Status Codes and IUCN Definitions

This is not a crosswalk between IUCN Categories and GAP Status Codes, but it helps summarize their definitions and relationship.  Only GAP Status Codes 1 and 2 meet the definition of protected by IUCN as, “A clearly defined geographical space, recognized, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values”.

GAP Status Code 3 and 4 lands cannot be assigned an IUCN Category.  While IUCN Ia, Ib, II are more likely to be GAP 1, many of these areas cannot permit natural disturbance events to persist and are GAP 2.  Similarly, there are many IUCN Category III, IV and V protected areas that are managed as GAP 1.  USGS GAP maintains an approved crosswalk to assign IUCN Categories to US protected areas based upon their management designation, landowner, GAP Status Code and size.  Contact Lisa Johnson for the most current version.

IUCN Category/Definition GAP Category/Definition
Category Ia: Strict Nature Reserves are strictly protected areas set aside to protect biodiversity and also possibly geological/geomorphological features, where human visitation, use and impacts are strictly controlled and limited to ensure preservation of the conservation values. Such protected areas can serve as indispensible reference areas for scientific research and monitoring. GAP Status 1: An area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a natural state within which disturbance events (of natural type, frequency, intensity, and legacy) are allowed to proceed without interference or are mimicked through management..
Category Ib: Wilderness Areas are protected areas are usually large unmodified or slightly modified areas, retaining their natural character and influence, without permanent or significant human habitation, which are protected and managed so as to preserve their natural condition.
Category II: National Park protected areas are large natural or near natural areas set aside to protect large-scale ecological processes, along with the complement of species and ecosystems characteristic of the area, which also provide a foundation for environmentally and culturally compatible spiritual, scientific, educational, recreational and visitor opportunities.
Category III: Natural Monument or Feature protected areas are set aside to protect a specfic natural monument, which can be a land form, sea mount, submarine caverns, geological feature such as caves or even a living feature such as an ancient grove. They are generally quite small protected areas and often have high visitor value. GAP Status 2: An area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a primarily natural state, but which may receive uses or management practices that degrade the quality of existing natural communities, including suppression of natural disturbance.
Category IV: Habitat/species management protected areas aim to protect particular species or habitats and management reflects this priority. Many category IV protected areas will need regular, active interventions to address the requirements of particular species or to maintain habitats, but this is not a requirement of this category.
Category V: Protected landscape/seascape protectected areas occur where the interaction of people and nature over time has produced an area of distinct character with significant ecological, biological, cultural and scenic value
Category VI: Protected area with sustainable use of natural resources are generally large, with much of the area in a more-or-less natural condition and wherea a proportion is under sustainable natural resource management and where such exploitation is seen as one of the main aims of the area.
Not applicable GAP Status 3: Area having permanent protection from conversion of natural land cover for the majority of area. Subject to extractive uses of either broad, low-intensity type (eg. Logging) or localized intense type (eg. Mining). Confers protection to federally listed endangered and threatened species throughout the area.
Not applicable GAP Status 4: No known public/private institutional manadates/legally recognized easements.
Permanently unassigned Holdings that do not meet the IUCN definition of a protected area or are not GAP Status 1 or 2.

Conduct the ANALYSIS

Published May 27, 2011

The analysis step is the point at which we determine how much of a vertebrate species’ or a land cover’s distribution occurs in areas managed for the long-term maintenance of biodiversity.

Distribution of Lark Bunting in the United States

Protected Status of Lark Bunting in the United States

To calculate this, maps showing the location of plant and animal habitats are overlaid with other maps that show where protected areas are. If predicted plant and animal habitats are in the same place as protected areas, those animals are considered to be protected.

By the time the gap analysis process is completed, a valuable suite of map and data products has been assembled.

Products from a typical Gap Analysis include:

  • Digital land cover maps
  • Digital animal distribution maps
  • Digital protected areas maps
  • Identifications of “conservation gaps”
  • Identifications of species-rich areas
  • Downloadable datasets in multiple formats
  • Assessments of the conservation status of vertebrate species in the United States

Mapping Protected Areas

Published May 27, 2011

“Stewardship” is not the same as ownership — when we talk about stewardship, we are talking about how lands are being managed, from a conservation perspective.

A map of public land ownership might look like this:

Protected Areas by Owner

A stewardship map is created by looking at the extent to which the publicly-owned lands are managed with conservation in mind. As part of the gap analysis process a conservation ranking is applied to each land parcel in the database. GAP Status Code 1 and 2 lands have the highest degree of management for conservation, while status 3 lands support multiple uses, including resource extraction (forestry, mining, etc.). Status 4 lands are either unprotected or of unknown management intent.

GAP bases its analysis of species protection on GAP Status Code 1 and 2 lands only. In assigning a stewardship ranking, the gap analysis process emphasizes the managing entity over the owner, and bases the ranking on the expressed long-term intent of the managing entity instead of focusing on short-term processes. The criteria for assigning a ranking include:

  • Permanence of protection from conversion of natural land cover to unnatural land cover such as human-induced barren, arrested succession, or cultivated exotic-dominated landscapes).
  • Amount of the tract protected, with a 5% allowance for intensive human use.
  • Inclusiveness of the protection, i.e., is protection focused on a single feature such as a wetland or particular species or does it encompass all biota and habitat.
  • Type of management program and degree that it is mandated or institutionalized.

A map of GAP stewardship codes applied to public lands might look like this:

Map showing conservation status of public lands in the US

Map showing conservation status of public lands in the US

See our Protected Areas Datababase of the United States viewerto explore Protected Areas data online.

Mapping and modeling SPECIES ranges and distributions

Published May 27, 2011

Knowing where species occur is vital to biodiversity protection, climate change research, and conservation planning. Because we are unable to know all the places in which a species occurs, we use computer models that can help us predict where a species occurs based on what we know about its habitat preferences.

To create a predicted distribution model for a species, we first define that species’ range, which is the general area within which that species can be found.  Currently, GAP is creating national species range maps and distribution models for most of the mammals, birds, reptiles, and amphibians that occur within the U.S.

Distribution of Lark Bunting in the United States

Protected Status of Lark Bunting in the United States

Each species range map is based on 12-digit HUCs (i.e., hydrologic units).  Each HUC within a species’ range is attributed with seasonal range information such as breeding, winter, or migratory.  A separate species distribution model is created for each species for each season because animals use different habitat during each season.  Each species range map is reviewed by expert biologists to ensure the accuracy of the data.

Species distribution models depend on known species habitat relationships or species observation records.  A wildlife habitat relationship database (WHRDB) is used to store and maintain the extensive information on species habitat relationships acquired from the published literature.  In addition, spatial data are compiled that describe the relationship between a species’ habitat and other elements such as land cover and elevation.  For each species, these spatial data are used as model inputs based on the habitat preferences stored in the WHRDB.

A predicted distribution map for each species is created based on the model inputs, which are based on the WHRDB and spatial data.  This map is reviewed by expert biologists and revisions are made based on their comments.  Each species’ predicted distribution is based on the best available data and is a binary representation of where a species is likely to occur.

Species modeling outputs include:

  • 12-digit HUC range maps showing seasonal use for each species;
  • Spatial data as model inputs that include the entire US;
  • WHRDB that include species common name, scientific names, habitat relationships, life history characteristics, etc.;
  • Species observation records;
  • Binary (presence/absence) representation of species distribution across US.

See our Species viewerto explore Land Cover data online>>

Mapping the LAND COVER of the dominant ecological systems

Published May 24, 2011

The first step of gap analysis is to create a land cover map that depicts the ecological systems in the area being studied. Ecological systems are defined as “groups of plant community types that tend to co-occur within landscapes with similar ecological processes, substrates and/or environmental gradients: (Comer et al. 2003). Ecological systems are used because the patterns of natural terrestrial land cover are a reflection of the physical and chemical factors that shape the environment of a given land area.

Land cover map for Florida

Vegetation communities are also determinate for overall biological diversity, because their structures and composition significantly affect species-level interactions.
Land cover is mapped using 2001 Landsat ETM+ satellite imagery from the Eros Data Center’s Multi-Resolution Land Characteristics Consortium (MRLC) program. MRLC is the federal consortium for obtaining, processing, and archiving satellite imagery. To facilitate the interpretation of the satellite imagery, we collected field data. Sufficient data were collected to assign an ecological system label to the plot. Knowing how these plots appeared in satellite imagery, enabled us to interpret the remainder of the satellite imagery.
We used a variety of other datasets to help with the land cover classification process. Digital elevation model-derived data sets (which included elevation, slope, aspect and landform) were used, along with digital data on soils, geology, stream and wetland location, point locations for rare plant communities and fire and tree harvest information. Locations of agricultural areas and developed lands were pulled in from the GAP land cover maps directly from the National Land Cover Database 2001. To read a more detailed description of the land cover mapping process, click here.
See our National Land Cover viewer to explore Land Cover data online.

Ancillary Data

Published May 19, 2011

Regions used for species modeling

The lower 48 states of the U.S. were divided into six regions for modeling purposes. Each of the ancillary data layers are split into these six regions and models were run within a region and regional model output were compiled to create a complete distribution model across a species range. The regions are based on grouped MRLC zones. The regions are shown on the map below. You can download the regional boundaries data layer here:

Select a region and then click on the links below to download the regional data layers. Regions used for species modeling

The lower 48 states of the U.S. were divided into six regions for modeling purposes.
Each of the ancillary data layers are split into these six regions and models were
run within a region and regional model output were compiled to create a complete
distribution model across a species range. The regions are based on grouped MRLC
zones. The regions are shown on the map below. You can download
the regional boundaries data layer here:

Select a region and then click on the links below to download the regional data
layers. Descriptions of the data layers follow the links.

regions

Region

Great Plains Northeast Northwest Upper Midwest Southeast Southwest

Hydrography (description)

Grid Name Salinity(s) Water Type(t) Velocity(v) Mask(n) Description
s0t1v0n0 All (0) Flowing (1) All (0) None (0) All types of flowing water with no masks
s0t1v0n1 All (0) Flowing (1) All (0) Standing (1) All types of flowing water with standing water masked out
s0t1v1n1 All (0) Flowing (1) Fast Only (1) Slow & standing (1) All types of fast flowing water with slow & standing water masked out
s0t1v2n0 All (0) Flowing (1) Slow Only (2) Fast (0) All types of slow flowing water with fast water masked out
s0t1v2n1 All (0) Flowing (1) Slow Only (2) Fast & standing (1) All types of slow flowing water with fast water & standing water masked out
s0t2v0n0 All (0) Standing (2) n/a (0) None (0) All types of standing (open) water with no masks
s0t2v0n1 All (0) Standing (2) n/a (0) Flowing (1) All types of standing (open) water with flowing water masked out
s0t3v0n0 All (0) Wet Veg (3) n/a (0) None (0) All types of wet veg with no masks
s1t1v0n0 Fresh (1) Flowing (1) All (0) Brackish standing water & brackish wet veg (0) Fresh, flowing water with brackish standing water and wet veg masked out
s1t1v0n1 Fresh (1) Flowing (1) All (0) All standing water & brackish wet veg (1) Fresh, flowing water with all standing water, and brackish wet veg masked out
s1t1v1n1 Fresh (1) Flowing (1) Fast Only (1) Slow & standing (1) Fresh, fast flowing water with slow water & standing water masked out
s1t1v2n0 Fresh (1) Flowing (1) Slow Only (2) Fast (0) Fresh, slow flowing water with fast water masked out
s1t1v2n1 Fresh (1) Flowing (1) Slow Only (2) Fast & standing (1) Fresh, slow flowing water with fast water & standing water masked out
s1t2v0n0 Fresh (1) Standing (2) n/a (0) Brackish flowing water & brackish wet veg (0) Fresh, standing water with brackish flowing water and wet veg masked out
s1t2v0n1 Fresh (1) Standing (2) n/a (0) All flowing water & brackish wet veg (1) Fresh, standing water with all flowing water and wet veg masked out
s1t3v0n0 Fresh (1) Wet Veg (3) n/a (0) Brackish (0) Fresh wet veg with brackish water masked out
s2t1v0n0 Brackish (2) Flowing (1) All (0) Fresh standing & fresh wet veg (0) Brackish flowing water with fresh standing water, & fresh wet veg masked out
s2t1v0n1 Brackish (2) Flowing (1) All (0) All standing water & fresh wet veg (1) Brackish flowing water with all standing water and fresh wet veg masked out
s2t2v0n0 Brackish (2) Standing (2) n/a (0) Fresh flowing & fresh wet veg (0) Brackish standing water with fresh flowing water & fresh wet veg masked out
s2t2v0n1 Brackish (2) Standing (2) n/a (0) All flowing water & fresh wet veg (1) Brackish standing water with all flowing water & fresh wet veg masked out
s2t3v0n0 Brackish (2) Wet Veg (3) n/a (0) Fresh standing, flowing, & wet veg (0) Brackish wet veg with fresh flowing, standing water, & wet veg masked out

Layer Descriptions

Human impact avoidance

Environments dominated by human disturbance such as roads, cities, and the constructed materials that support human habitation have profound effects on species. For most species, this data layer was used to exclude species from a portion of the landscape. However, some species respond favorably to human habitats, therefore this data layer was used in an inclusionary manner.

Model Report: If a species’ model uses the model variable for human impact avoidance, then downloading these ancillary data will provide the level of avoidance described below.

Level of avoidance

High – For species that are very intolerant of human disturbance. All portions of the landscape identified as being directly influenced by human disturbance are eliminated from the predicted distribution.

Medium -For species that are moderately intolerant of human disturbance. Only portions of the landscape identified as being highly or moderately influenced by human disturbance are eliminated from the predicted distribution.

Low – For species that are partially intolerant of human disturbance. Only portions of the landscape identified as being highly influenced by human disturbance are eliminated from the predicted distribution.

No selection of this parameter indicates the species’ model is not contingent on an index of human disturbance.

Elevation

Some species respond to environments directly related to altitudinal variation. Elevation (e.g., DEM) is easily implemented in spatial modeling by limiting the model to the minimum and maximum values explicitly stated in the literature. DEMs are utilized directly and are measured in meters above mean sea level.

Model Report: If a species’ model uses elevation as a model variable, then download the ancillary data for elevation.

Hydrographic information

Water and its location on the landscape is a very important aspect of species habitats. The source for hydrographic data was the USGS National Hydrography Dataset (NHD).

Model Report: If a species’ model report uses any of the hydrographic information, see the Hydrography table for the correct file. Each downloadable file in the table contains information with regards to salinity, water type, and velocity.

Types of water

Flowing Water – Flowing water represents hydrographic features such as streams, rivers, springs, seeps, ditches with moving water, etc.

Standing Water – Standing water represents hydrographic features such as lakes, ponds, reservoirs, bays, inlets, estuaries, ocean, ditches with stagnant water, etc.

Wet Vegetation – Wet vegetation represents hydrographic features such as swamps, marshes, Carolina bays, etc. This includes a collection of map units representing seasonally or tidally inundated woody and non-woody plants.

Salinity

Water salinity is a major factor when considering habitat conditions for many species. However, the dynamic and complex nature of water systems makes the development of a highly refined and reliable data layer challenging. Therefore, we developed three general categories to include in species habitat models for species requiring water.

Freshwater Only

Brackish/Salt Water Only

All Water (i.e., both brackish/salt water and freshwater)

Stream velocity

For some aquatic species, this is an important aspect of their habitat, such as oxygenation levels, presence of invertebrate prey, and amount of sediment within the water column and on streambed substrates. Stream velocity (i.e, stream gradient) was derived from a combination of streams and slopes calculated from a digital elevation model (DEM), which created three categories for stream gradient.

Slow Only – For species that require slow moving or almost stagnant sections of streams or rivers. Typically these are areas where the underlying topography is flat (0 % gradient).

Fast Only – For species that require high velocity sections of streams or rivers. Typically these are areas where the underlying topography is steep. A threshold of > 5 % gradient was used.

All Types – For species that can utilize either fast or slow sections of streams or rivers.

Distance into and from type of water

Distances from a type of water were:

>4000 m

2000-4000 m

1000-2000 m

500-1000 m

250-500 m

120-250 m

60-120 m

30-60 m

0-30 m

Distances into a type of water were:

0-30 m

30-60 m

60-120 m

120-250 m

250-500 m

500-1000 m

1000-2000 m

2000-4000 m

>4000 m

Land cover information

Land cover

The ecological systems mapped in the GAP National Land Cover Data were used as ‘map units’ to describe habitat types preferred by species.

Model Report: If a species’ model uses map units as a model variable, then download the ancillary data for land cover. Map units are designated as either primary or secondary. Primary maps units are defined as those ecological systems critical for a species’ reproduction and survival. Secondary map units are those ecological systems generally not critical for reproduction and survival, but typically are used in conjunction with primary map units for foraging, roosting, and/or sub-optimal nesting locations. Secondary map units are selected only when located within a specified distance from primary map units.

Patch Size

The type and size of clusters of habitat can be assessed with spatial modeling. We used patch size to indicate minimum amounts of contiguous habitat needed for a species. This variable requires the generation of cluster sizes in the actual modeling code during post processing. In other words, these model variables are not independent ancillary data layers.

Model Report: If a species’ model uses patch size, this variable is generated in the actual modeling code during post processing. Any cells that do not form a minimum contiguous patch are eliminated. There are no specific ancillary layers for this variable.

Contiguous Patch

Minimum size (ha) – This parameter is set using the most conservative values explicitly stated in the species literature.

Forest and Ecotone Habitats

The ecotone (i.e., edge) between forested and non-forested environments can be a critical aspect of habitat. We grouped map units into forested, non-forested, and shrubland/woodland land cover types to create unique data layers. These data layers can then be buffered at specified distances to identify species habitats. Aggregated map units can be compared and contrasted to identify areas of transition between these broad categories. They can also be used to identify core areas or contiguous blocks of similar type (i.e., interior) through buffering.

Forested map units included deciduous forest, evergreen forest, mixed forest, palustrine forested wetland, and estuarine forested wetland (Homer et al. 2004).

Non-forested map units were defined as water, pasture/hay, agricultural areas, urban/developed, marshes, beaches, etc.

Woodland/shrubland map units were defined as those ecological systems and land uses containing a majority of short, scrubby, woody vegetation or sparsely canopied treed vegetation (Homer et al. 2004).

Forest Edge

This data layer constitutes unique aggregations of forest and non-forest map units.

Model Report: If a species’ model uses “edge type” as a model variable, then download the ancillary data for forest edge.

Ecotone type and width

Forest/Open Ecotone Only – This data layer represents the transitional areas between forest and open, non-forested habitats.

Model Report: If a species’ model “edge type” is set as forest/open ecotone only, then download the ancillary data for for forest edge.

Forest/Open Ecotone + Woodlands/Shrublands – The forest/open only ecotone does not consider environments with sparse canopies or scrubby vegetation, therefore this data layer includes woodland and shrubland map units that would otherwise be ignored.

Model Report: If a species’ model “edge type” is set as forest/open ecotone + woodlands/shrublands , then download the ancillary data for forest/open ecotone + woodlands/shrublands.

Ecotone Width – This distance represents a symmetrically buffered edge. For example, an ecotone width of 500 meters includes 250 meters into forest and 250 meters into open.

Buffer Distances –

Distances into forest from forest edge: >4000, 4000, 2000, 1000, 500, 250, 120, 60, 30, and 0 meters

Distances away from forest edge: >4000, 4000, 2000, 1000, 500, 250, 120, 60, 30 and 0 meters

Model Report: If a species model uses ecotone width, this variable is applied to the corresponding ecotone(s) described above (see EcotoneType).