How a global biodiversity hotspot, the North American Coastal Plain, went unrecognized

Background/Question/Methods

Biodiversity hotspots, threatened areas where conservation values are concentrated, are priorities for conservation action. To qualify as a global hotspot by Conservation International’s definition, a region must meet two criteria: at least 1500 species of vascular plants (> 0.5 percent of the world’s total) endemic to the region and a loss of at least 70 percent of original habitat. Biologists within the region increasingly recognize the Atlantic and Gulf Coastal Plain of the United States and northeastern Mexico as a major center of speciation and endemism that has experienced extreme levels of habitat conversion and degradation. For example, longleaf pine savannas and woodlands, the dominant matrix vegetation of the southeastern portion of the North American Coastal Plain, have experienced >97% loss of area since Euro-African settlement. Nevertheless, the Coastal Plain has not been recognized internationally as a global biodiversity hotspot. We sought to document the level of endemism of vascular plants and vertebrates, estimate levels of habitat loss region wide, and determine why the North American Coastal Plain has failed to achieve global recognition as a hotspot. We hypothesized that conceptual biases have blinded ecologists and conservationists as to the hotspot status of this region.

Results/Conclusions

The North American Coastal Plain contains 6170 native vascular plant taxa, of which 1748 (28.3%) are endemic. Of the 1133 terrestrial and freshwater vertebrates, 18.4% and 32.4% are endemic at species and subspecies levels. Estimates that <5% of primary vegetation remains place the region among the global hotspots most imperiled by habitat loss. Ecological biases and ignorance thwarted recognition of this region as a hotspot. The species-rich, phylogenetically distinct flora is now better known. Fine-scale richness of vascular plants (30-50 species/m²) in some pine savannas and other grasslands is among the highest in the world. New region-wide data for plants and vertebrates have improved understanding of the development of endemism and high biodiversity in a flat (maximum elevation <250 m) and historically frequently burned region. Old concepts of plant succession and community classification systems based on trees have been replaced by appreciation of the role of recurrent disturbances such as fires and hurricanes in generating and maintaining biodiversity. This paradigm shift needs to be matched by changes in management of remaining natural areas, and ultimately global recognition of the North American Coastal Plain as a hotspot, to ensure biodiversity conservation in this region during a time of rapid environmental change.