Ecosystems of the Western Hemisphere

In order to support continental-scale assessment of terrestrial ecosystem distribution and condition, we developed a distribution map of the potential location and extent of vegetation types for North America, Meso America, and the Caribbean. NatureServe ecologists lead efforts to develop internationally standardized classifications for terrestrial ecosystems and vegetation. One classification approach is with existing vegetation. The International Vegetation Classification, or EcoVeg approach (Faber-Langendoen et al. in press), grew out of USA federal standards, defining vegetation concepts at multiple thematic levels. Vegetation systems are defined as “moderate sets of diagnostic plant species and diagnostic growth forms that reflect biogeographic differences in composition and sub-continental to regional differences in mesoclimate, geology, substrates, hydrology, and disturbance regimes.” Building from prior national and regional ecological classifications from the area (see Josse et al. 2003; 2007), a hierarchical classification was established for existing vegetation types describing natural upland and wetland conditions. National and regional maps of current extent were reconciled to the standard classification and provided georeferenced locations for use in spatial modeling. Spatial modeling used climate, geophysical data layers, and satellite spectral data, in a sequential process to map potential distributions at several levels of the vegetation classification hierarchy. Inductive modeling in sequential steps, followed by expert review and refinement, resulted in a map of 147 vegetation macrogroups for the North American continent & the Caribbean. This map depicts the location and extent of each macrogroup had there been no intensive human land uses in recent centuries. Initial validation of the map, using a separate, randomized set of labeled sample areas of 0.5km2vs. 1km2vs. 5km2 indicated high agreement at finest spatial resolutions, suggesting that the map is suitable for use in applications requiring a pixel resolution of 270 x 270m2and higher.