Species diversity in the Florida Everglades, USA: A systems approach to calculating biodiversity

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The Everglades, a complex wetland mosaic bounded by human development at the southern tip of the Florida Peninsula, is home to a wide array of species, including 68 threatened or endangered animal species. Species richness within Everglades National Park, at the southern extreme of the Greater Everglades ecosystem, is 1033 plant taxa, 60 reptile taxa, 76 mammal taxa, 432 fish taxa, 349 bird taxa and 38 amphibian taxa. This paper briefly introduces the flora and fauna of the Greater Everglades, focusing on species of special conservation concern and those non-native species that are altering native ecology. While there is conservation utility in cataloging biodiversity, we argue that counts of species alone are inadequate descriptors of ecosystem condition because they fail to effectively indicate emergent ecosystem properties (resilience, productivity). We develop an approach to calculating biodiversity based on systems theory that can be applied across trophic levels to provide a condition benchmark that accounts for food web interactions. The Everglades, for which detailed flow data between ecosystem components have been compiled as part of ongoing modeling efforts (DeAngelis et al., 1998), is among the few ecosystems globally for which this technique is currently feasible. Flow data are coupled with exogenous forcing energies (in emergy units – Odum, 1996) to compute transformity values (Odum, 1988) for biotic and abiotic components of an Everglades graminoid marsh community. We calculate across-trophic level biodiversity using the Shannon information equation applied to ecosystem emergy flows. Results suggest that the graminoid marsh is operating at 42% of theoretical maximum ecosystem flow diversity. By comparing observed flows with theoretical maximum flows, we provide a measure of component conservation value; we observe strong overlap between species with lower than expected emergy-based importance and those known to be currently threatened or endangered. A significant positive association between this conservation value and transformity in the marsh suggests systematic uppertrophic level biodiversity degradation.

Keywords:  Biodiversity - Everglades - transformity - emergy - network analysis - ecosystem

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