Saving the Florida Everglades

An alligator lily in Everglades National Park.

Michael Huston is now involved in a high-stakes project whose ultimate success may depend on whether his ideas about species diversity, ecological modeling, and land-use tradeoffs are proven right or wrong. The Clinton administration has made the restoration of Florida Bay, Everglades National Park, and other threatened South Florida ecosystems a national priority. One of the highest scientific priorities in the restoration effort is the generation of information using a computer modeling system based on ideas developed at ORNL and the University of Tennessee at Knoxville (UTK). Use of this individual-based modeling approach pioneered at ORNL has been identified as essential by an interagency task force that includes the Army Corps of Engineers, the U.S. Geological Service, the Environmental Protection Agency, the National Park Service, and the National Biological Service, along with such state and local agencies as the South Florida Water Management District. This multi-institutional collaboration is known as the Across Trophic Level System Simulation (ATLSS).

For the ATLSS project, Huston, Don DeAngelis (now with the U.S. Geological Survey), and Lou Gross (UTK) are linking multiple individual-based models. However, rather than fish and trees, the individuals in these models represent some of the major endangered species of South Florida, including the Florida panther, the Everglades kite, and the wood stork, along with their prey—deer, snails, and fish. In the ATLSS modeling system, virtual panthers stalk their simulated prey on a computerized landscape derived from satellite images. If the virtual water is too deep, the movement of the panthers is restricted, but that of their primary prey, the white-tailed deer, is restricted even more. The depth and distribution of water define the unique properties of the Everglades and Big Cypress Swamp, and restoration of the natural pattern of water availability is the primary method for restoring the ecosystem. The objective of the ATLSS models is to predict the biological effects of different patterns of water availability. Such information will assist the Army Corps of Engineers in formulating the restoration plan.

One of Huston's responsibilities is to use information available from hydrologic models to predict how the ecosystem's vegetation will respond in wet and dry seasons and in wet and dry years. The answers will reveal how much food will be available for the deer and how many deer will be available for panthers to feed on under different scenarios of water availability. The virtually flat landscape of South Florida presents an entirely different challenge to Huston than did the Walker Branch Watershed project for which he performed hydrologic and landscape modeling. The topographic relief on Walker Branch Watershed near ORNL exceeds that of the entire state of Florida, and the slope gradient of the Everglades is only about one inch per mile. "Water still runs downhill in Florida," he says, "but just not very fast."

The deterioration of the ecosystems of the Everglades and Florida Bay has resulted from competing demands for land and water from the rapidly growing urban and agricultural areas around Miami. Resolution of this conflict between man and nature is where Huston's ideas about land use and biodiversity may come into play. The primary agricultural activity is located on the deepest and most fertile soils at the northern end of the Everglades, just downstream from Lake Okeechobee.

"This was a rational land use decision," Huston argues, "and need not lead to a serious loss in biodiversity. Plant diversity in this region was naturally low, and the vast stands of sawgrass have simply been replaced by sugar cane and other crops. This highly productive region is ideal for supporting animal diversity, rather than plant diversity. It may now actually support a higher density and diversity of threatened and endangered predators than it did prior to the coming of agriculture. We saw bald eagles nesting next to sugar cane fields, thriving on rats and rabbits. Other rare predators, such as bobcats, otters, foxes, barn owls, and a variety of hawks—and of course, 'Florida gators'—are also common in the agricultural area, surviving in and around the cane fields."

Although many conservationists see agriculture as the primary evil threatening the Everglades, Huston sees things differently.

Cypress trees in Big Cypress National Preserve.

Although many conservationists see agriculture as the primary evil threatening the Everglades, Huston sees things differently. "The fertile soils of the Everglades agricultural area give it a contrasting and very important role in comparison with the rest of the system." Huston has seen, just as he expected, that the highest plant diversity is found in unproductive "wet prairies" with stunted pines and cypress. "These unproductive wetlands are great for protecting plant diversity, but lousy for most animals, especially the large predators," he says. "Different parts of the system make different contributions to the health of both the environment and the economy of South Florida."

Huston's task now is to convince decision makers who will determine the fate of the Everglades that man and nature can coexist sustainably, to their mutual benefit.



Back to Life on Earth: Why Biodiversity Varies