Ecosystems in the continental maps were geospatially delineated as facets of the landscape generated through biophysical stratification of bioclimate, biogeography, lithology, landforms, surface moisture, and land cover. This approach was framed on the understanding that the biodiversity that occurs in any area is largely the result of a biotic response to physical environmental potential and local dynamic processes, and that unique physical settings tend to give rise to unique assemblages of biodiversity. Implementation was based on the mapping and integration of fundamental ecosystem structural elements like land surface forms, surficial lithology, bioclimates, topographic moisture potential, and land cover as a proxy for vegetation. This methodology was developed during a Nature Conservancy and NatureServe collaboration for mapping ecosystems in South America, and then further refined in USGS ecosystems mapping efforts for the conterminous United States and Africa.
Global Ecosystems Viewer
South America
The biophysical stratification approach for modeling ecosystems was developed during a Nature Conservancy and NatureServe collaboration to map ecosystems for South America. This approach was based on the acquisition or generation of five base layers - bioclimate (WorldClim, 2004 and TNC, 2005), landform (SRTM, 2000 and WWF-Hydrosheds, 2005), landcover (GLC, 2000), elevation (SRTM, 2000), and geology (TNC and GDS, 2005) - followed by the integration of these layers into a set of 659 unique ecological combinations. This set of ecological combinations was then mapped and used to represent the local-scale terrestrial ecosystems for South America at the finest spatial resolution (450-meters) ever attempted for the continent.
Additional information:
Terrestrial Ecosystems of South America article
Conterminous United States
USGS used the same biophysical stratification approach in its first continental project, modeling the distribution of terrestrial ecosystems for the conterminous United States. Four major structural components for ecosystems – isobioclimates, land surface forms, surficial lithology, and topographic moisture potential – were modeled and then spatially combined into a set of biophysical settings to represent the unique ecosystems.
Bioclimate was modeled using the Rivas-Martínez global bioclimatic classification system that quantifies key bioclimatic indices reflective of vegetation distributions. Implementation utilized the Daymet temperature and precipitation data to generate four climate layers: macroclimates, bioclimates, thermotypes, and ombrotypes. Then the single climate layer needed for the model was created by a combination of the thermotypes and ombrotypes, determined as the best choice to achieve the required climate variations. Combination of the ombrotypic regions (dry/wet gradients) and the thermotypic (warm/cold) regions resulted in 127 unique combinations to represent bioclimates.
Land surface forms were modeled using the Missouri Resource Assessment Partnership (MoRAP) methodology that is based on slope and local relief. Once this methodology was applied to the USGS 30-meter National Elevation Dataset (NED) a total of eight land surface classes were generated. Then based on further investigation into the initial set of classes a modification was applied that redefined the original low mountains class into two; low mountains or high mountain/deep canyons. And as a final step an additional class of drainage channels, derived independently to identify wet and dry river channels, was added to produce a final set of 10 classes: flat plains, smooth plains, irregular plains, escarpments, low hills, hills, breaks/foothills, low mountains, high mountains/deep canyons, and drainage channels.
Surficial lithology was derived from a generalization and reclassification of the 28 lithology classes of the USGS map "Surficial Materials in the conterminous United States" into a set of the 18 lithologies that typically control or influence the distribution of vegetation types.
During this first USGS modeling effort an additional base layer, topographic moisture potential, was added to help contribute substrate moisture regimes into the ecosystems model. The four topographic moisture potential classes in this layer – periodically saturated or flooded land, mesic uplands, dry uplands, and very dry uplands - were based on the derivation of ground moisture potential using a combination of computed topographic characteristics (CTI, slope, and aspect) and mapped National Wetland Inventory boundaries.
The final ecosystems layer was produced by combining these four layers, each at a 30-meter spatial resolution, into the 49,168 unique physical environments that characterize the abiotic (physical) potential of the environment. This initial set was further refined by applying a minimum pixel count threshold (20,000 pixels) that reduced the set of unique physical environments down to 13,482. This final set of 13,482 classes were then aggregated into the 419 NatureServe ecosystems using a semi-automated labeling process based on rule-set formulations for the attribution of each ecosystem.
Additional Information:
Conterminous United States Terrestrial Ecosystems data
A New Map of Standardized Terrestrial Ecosystems of the Conterminous United States article
Africa
Modeling the terrestrial ecosystems for Africa was USGS’s final continental implementation of the ecosystem mapping methodology. Three base layers - isobioclimates, land surface forms, and surficial lithology – were modeled for Africa and then spatially combined into a set of biophysical settings representing unique ecosystems.
Isobioclimates were generated using the spatial algorithms developed during the United States effort (with minor adaptations) applied to the WorldClim climatological source data to model the separate climate layers. Then the resulting ombrotypes and thermotypes layers were combined to produce the final set of 157 composite classes.
The land surface forms layer for Africa consisted of seven classes - smooth plains, irregular plains, escarpments, hills, breaks, low mountains, and high mountains/deep canyons. The MoRAP classification was applied to 90-meter elevation source data, created by void-filling and re-sampling the 30-meter SRTM elevation data provided by the National Geospatial Intelligence Agency, to generate the initial eight classes. Next the previously defined USGS refinement was used to identify the nineth class, high mountains/deep canyons. Finally, resulting from further investigation, flat plains and smooth plains were combined into a single class, and low hills were merged into hills producing the final product of seven land surface form classes.
Surficial lithology was a map of parent materials - a mix of bedrock geology and unconsolidated surficial materials classes. It is a compilation and reclassification of twelve digital geology, soil, and lithology databases into nineteen surficial lithology classes delineated based on geology, soil, and landform. Due to the varying spatial and classification resolutions of the geologic source data, this surficial lithology map varies in spatial complexity and classification detail across Africa.
The base layers, which were generated from source data of differing origin and coarser spatial resolution than the United States effort, were combined to produce a 90-meter spatial resolution map of the unique physical environments that characterize the abiotic (physical) potential of the environment. These unique footprints of the physical and biological landscape were then reviewed by regional vegetation and landscape ecology experts and attributed (labeled) to an intermediate scale African ecosystem class.
Additional information:
Africa Terrestrial Ecosystems data
A New Map of Standardized Terrestrial Ecosystems of Africa article
- Overview
Ecosystems in the continental maps were geospatially delineated as facets of the landscape generated through biophysical stratification of bioclimate, biogeography, lithology, landforms, surface moisture, and land cover. This approach was framed on the understanding that the biodiversity that occurs in any area is largely the result of a biotic response to physical environmental potential and local dynamic processes, and that unique physical settings tend to give rise to unique assemblages of biodiversity. Implementation was based on the mapping and integration of fundamental ecosystem structural elements like land surface forms, surficial lithology, bioclimates, topographic moisture potential, and land cover as a proxy for vegetation. This methodology was developed during a Nature Conservancy and NatureServe collaboration for mapping ecosystems in South America, and then further refined in USGS ecosystems mapping efforts for the conterminous United States and Africa.
Global Ecosystems Viewer
South America
The biophysical stratification approach for modeling ecosystems was developed during a Nature Conservancy and NatureServe collaboration to map ecosystems for South America. This approach was based on the acquisition or generation of five base layers - bioclimate (WorldClim, 2004 and TNC, 2005), landform (SRTM, 2000 and WWF-Hydrosheds, 2005), landcover (GLC, 2000), elevation (SRTM, 2000), and geology (TNC and GDS, 2005) - followed by the integration of these layers into a set of 659 unique ecological combinations. This set of ecological combinations was then mapped and used to represent the local-scale terrestrial ecosystems for South America at the finest spatial resolution (450-meters) ever attempted for the continent.
Additional information:
Terrestrial Ecosystems of South America article
Conterminous United States
USGS used the same biophysical stratification approach in its first continental project, modeling the distribution of terrestrial ecosystems for the conterminous United States. Four major structural components for ecosystems – isobioclimates, land surface forms, surficial lithology, and topographic moisture potential – were modeled and then spatially combined into a set of biophysical settings to represent the unique ecosystems.
Sources/Usage: Public Domain.Isobioclimates for the Conterminous United States Bioclimate was modeled using the Rivas-Martínez global bioclimatic classification system that quantifies key bioclimatic indices reflective of vegetation distributions. Implementation utilized the Daymet temperature and precipitation data to generate four climate layers: macroclimates, bioclimates, thermotypes, and ombrotypes. Then the single climate layer needed for the model was created by a combination of the thermotypes and ombrotypes, determined as the best choice to achieve the required climate variations. Combination of the ombrotypic regions (dry/wet gradients) and the thermotypic (warm/cold) regions resulted in 127 unique combinations to represent bioclimates.
Land surface forms were modeled using the Missouri Resource Assessment Partnership (MoRAP) methodology that is based on slope and local relief. Once this methodology was applied to the USGS 30-meter National Elevation Dataset (NED) a total of eight land surface classes were generated. Then based on further investigation into the initial set of classes a modification was applied that redefined the original low mountains class into two; low mountains or high mountain/deep canyons. And as a final step an additional class of drainage channels, derived independently to identify wet and dry river channels, was added to produce a final set of 10 classes: flat plains, smooth plains, irregular plains, escarpments, low hills, hills, breaks/foothills, low mountains, high mountains/deep canyons, and drainage channels.
Surficial lithology was derived from a generalization and reclassification of the 28 lithology classes of the USGS map "Surficial Materials in the conterminous United States" into a set of the 18 lithologies that typically control or influence the distribution of vegetation types.
During this first USGS modeling effort an additional base layer, topographic moisture potential, was added to help contribute substrate moisture regimes into the ecosystems model. The four topographic moisture potential classes in this layer – periodically saturated or flooded land, mesic uplands, dry uplands, and very dry uplands - were based on the derivation of ground moisture potential using a combination of computed topographic characteristics (CTI, slope, and aspect) and mapped National Wetland Inventory boundaries.
Sources/Usage: Public Domain.Terrestrial Ecosystems for the Conterminous United States The final ecosystems layer was produced by combining these four layers, each at a 30-meter spatial resolution, into the 49,168 unique physical environments that characterize the abiotic (physical) potential of the environment. This initial set was further refined by applying a minimum pixel count threshold (20,000 pixels) that reduced the set of unique physical environments down to 13,482. This final set of 13,482 classes were then aggregated into the 419 NatureServe ecosystems using a semi-automated labeling process based on rule-set formulations for the attribution of each ecosystem.
Additional Information:
Conterminous United States Terrestrial Ecosystems data
A New Map of Standardized Terrestrial Ecosystems of the Conterminous United States article
Africa
Modeling the terrestrial ecosystems for Africa was USGS’s final continental implementation of the ecosystem mapping methodology. Three base layers - isobioclimates, land surface forms, and surficial lithology – were modeled for Africa and then spatially combined into a set of biophysical settings representing unique ecosystems.
Sources/Usage: Public Domain.Terrestrial Ecosystems for Africa Isobioclimates were generated using the spatial algorithms developed during the United States effort (with minor adaptations) applied to the WorldClim climatological source data to model the separate climate layers. Then the resulting ombrotypes and thermotypes layers were combined to produce the final set of 157 composite classes.
The land surface forms layer for Africa consisted of seven classes - smooth plains, irregular plains, escarpments, hills, breaks, low mountains, and high mountains/deep canyons. The MoRAP classification was applied to 90-meter elevation source data, created by void-filling and re-sampling the 30-meter SRTM elevation data provided by the National Geospatial Intelligence Agency, to generate the initial eight classes. Next the previously defined USGS refinement was used to identify the nineth class, high mountains/deep canyons. Finally, resulting from further investigation, flat plains and smooth plains were combined into a single class, and low hills were merged into hills producing the final product of seven land surface form classes.
Surficial lithology was a map of parent materials - a mix of bedrock geology and unconsolidated surficial materials classes. It is a compilation and reclassification of twelve digital geology, soil, and lithology databases into nineteen surficial lithology classes delineated based on geology, soil, and landform. Due to the varying spatial and classification resolutions of the geologic source data, this surficial lithology map varies in spatial complexity and classification detail across Africa.
The base layers, which were generated from source data of differing origin and coarser spatial resolution than the United States effort, were combined to produce a 90-meter spatial resolution map of the unique physical environments that characterize the abiotic (physical) potential of the environment. These unique footprints of the physical and biological landscape were then reviewed by regional vegetation and landscape ecology experts and attributed (labeled) to an intermediate scale African ecosystem class.
Additional information:
Africa Terrestrial Ecosystems data
A New Map of Standardized Terrestrial Ecosystems of Africa article - Maps
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