The major objective of the USGS's ATLSS (Across Trophic Level Systems Simulation) Project is to compare the relative differences between alternative hydrologic scenarios on the biotic components of the greater Everglades ecosystem. The goal is to provide a rational, scientific basis for ranking the hydrologic scenarios as input to the planning process, and through this to aid development of appropriate monitoring and adaptive management schemes.

ATLSS is constructed as a multimodel, meaning that it includes a collection of linked models for various physical and biotic systems components of the greater Everglades (fig. 1). This landscape modeling approach is the work of USGS scientists and collaborators from several universities. The ATLSS models are all linked through a common framework that allows for the necessary interaction between spatially explicit information on physical processes and the dynamics of organism response across the landscape.

The ATLSS hierarchy starts with models which translate coarse resolution hydrologic information to a finer resolution appropriate for biotic components that operate at a spatial extent much smaller than the 2-mile resolution of the South Florida Water Management Model, which provides hydrologic input to ATLSS. The development of such a high resolution hydrology uses GIS vegetation maps and the hydroperiods associated with vegetation types, to characterize a 28.5 meter resolution topography (pseudotopography) of water derived from the 2-mile resolution hydrology model.

The ATLSS hierarchy next includes Spatially Explicit Species Index (SESI) models that make use of the spatially explicit, within-year dynamics of hydrology to compare the relative potential for breeding and/or foraging across the landscape. SESI models have been constructed and applied during the Central and Southern Florida Comprehensive Review Study (Restudy) to the Cape Sable Seaside Sparrow, the Snail Kite, Short and Long-Legged Wading Birds, and White-tailed Deer, with an additional model for Alligators now near completion.

Considerably more detailed models have been developed for the distribution of functional groups of fish across the freshwater landscape. This model considers the size distribution of large and small fish as important to the basic food chain which supports wading birds. It has been applied to assess the spatial and temporal distribution of availability of fish prey for wading birds. Individual-based models, which track the behavior, growth and reproduction of individual organisms across the landscape, have been constructed for the Cape Sable seaside sparrow, the snail kite, the white-tailed deer, the Florida panther, and various wading bird species. The models include great mechanistic detail, and their outputs may be compared to the wide variety of organism distribution data available, including that from radio collared individuals. An advantage of these more detailed models is that they link each individual animal to specific environmental conditions on the landscape. These conditions (e.g., water depth, food availability) can change dramatically through time and from one location to another, and determine when and where particular species will be able to survive and reproduce. ATLSS models have been developed and tested in close collaboration with field scientists who have years of experience and data from working with the major animal species of South Florida.

The most important need in greater Everglades restoration is the ability to predict the relative effects of different alternative restoration plans, compared with the base case of no restoration. The ATLSS integrated suite of models has been used extensively for that purpose in Everglades restoration planning. In particular, it has been used in the evaluation of the effects of Restudy, ModWaters, and C-111 hydrology scenarios on key biota. The role of USGS's ATLSS Program is to predict the effects of changes in water management on greater Everglades species and biological communities, as an aid to identifying and selecting those changes most needed and most effective for the restoration effort. The suite of ATLSS models can be used in parallel with monitoring and adaptive management during and after implementation of a restoration plan.

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(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report (PDF, 8.7 MB))

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