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Rescuing the Everglades

Don DeAngelis ‘66 builds mathematical models of Florida wetland habitats in a bid to save threatened species.
June 23, 2009

Leading the way along the Anhinga Trail, an elevated boardwalk that twists and turns for half a mile through the Florida Everglades National Park, Don DeAngelis ‘66 stops suddenly and points out a full-grown alligator sunning itself 20 yards ahead. When the gator’s jaws groan open in what appears to be a monster-sized yawn, he chuckles with delight.

“I think it’s pretty clear that the alligator population of the Everglades is doing okay,” says DeAngelis, a theoretical ecologist with the U.S. Geological Survey (USGS), who has spent two decades building complex mathematical models to evaluate the viability of south Florida’s threatened animal species. “In recent years, I’ve counted up to 50 alligators during a single walk along this trail.”

That’s a welcome change. As two more gators emerge from a murky creek, DeAngelis recalls that the alligators of the Everglades were on the federal endangered-species list from the mid-1960s until the mid-1980s. Today their survival is no longer at issue.

“Unfortunately, that can’t be said about some other Everglades species, such as the Florida panther and the wood stork,” he says. “Right now, we’ve got at least a dozen species that are very much in peril because of continuing pressure from agriculture, development, and sometimes ineffective water management policies.”

DeAngelis’s computer-generated simulation models of animal habitats are playing a critical role in the effort to save Florida’s endangered species through the Comprehensive Everglades Restoration Plan (CERP), a 30-year, $9.5 billion federal program. “The state and the federal government are making progress in restoring some parts of the Everglades since CERP began in 2000,” he says. “But I’m still concerned about the long-term future of this ecosystem. We’ve made important gains, but I’d say the jury is still out on how healthy the Everglades will be in 50 years.”

As DeAngelis treks along the trail through a vast freshwater region of shallow saw-grass marshlands and areas of deeper water known as sloughs, he finds himself eyeball to eyeball with at least a dozen alligators (he guesses that perhaps 35,000 now roam the 2,000 square miles of Everglades National Park’s wetlands, which stretch from Miami south to Florida Bay), as well as other creatures whose habitats he studies. Finally, he leads the way to a swampy tract covered with three inches of “sheet flow,” the barely moving surface water that typifies the great saw-grass marsh.

“The deeper areas of this sheet flow provide a habitat for apple snails, which are the only food source for the snail kite,” he says, referring to a threatened bird species. Drought, faulty water management, and surging development have reduced water levels, depriving them of their food supply. “Right now the total Everglades population of snail kites is way down, and that’s disturbing,” he says.

In fact, DeAngelis notes, the hydrology of the entire Everglades has changed significantly during the past four or five decades. Nearby sugarcane farming and other forms of agriculture have encroached on the area as the population of south Florida has soared from about 1.3 million to nearly 4.5 million people. “There’s been relentless pressure from population growth, which has led to building numerous dikes and canals that can interfere with normal water flow,” he says. As a result, the 5,000-year-old Everglades have shrunk from an original 8,000 square miles to slightly less than half that today.

Since the early 1990s, DeAngelis has coördinated the building of habitat and population models that the environmental agencies involved in CERP can use to evaluate how various water management scenarios might affect threatened species such as the snail kite. An international team of scientists and students works on the project, known as Across Trophic Level System Simulation (ATLSS).

To build the USGS-sponsored models of Everglades habitats, DeAngelis and his team first gather huge amounts of empirical data on day-to-day water levels, vegetation, temperatures, and the life cycles and behavioral characteristics of different animal species. (This information has been collected over the years by biologists in the field.) Then, with the help of advanced modeling techniques and specialized computational software, they use the data to create a habitat suitability index for threatened species in each of 70,000 500-by-500-meter “cells” in their specialized map of the Everglades.

“What we do, essentially, is to translate the empirical data into algorithms and then calculate how suitable each particular cell will be for a particular threatened species under various conditions in the future,” DeAngelis explains. Some of the models are so detailed that they simulate populations individual by individual, projecting what would happen to each one under different CERP hydrology plans and other ecological scenarios. The goal is to help regional land-use planners make decisions that will better protect the hundreds of animal species in the complex Everglades ecosystem.

“We successfully simulated the observed increase in snail kites from near extinction in the 1970s to a high population of about 3,000 some years ago,” DeAngelis says, “and now we’re using the model to try to understand the more recent declines of these threatened birds.” His team has also used its models to simulate population change in about a dozen other endangered species, including the Florida panther, the wood stork, and the Cape Sable seaside sparrow.

“Don is known worldwide for his mathematical modeling in ecology,” says Douglas Donalson, an ecologist with the U.S. Army Corps of Engineers in Florida. “He’s a meticulous scientist, and I don’t think there’s any doubt his work is having a significant impact on the effort to restore the Everglades.”

Adds Leo Sternberg, a professor of biology at the University of Miami and an expert on Florida vegetation: “Don’s models are an indispensable component of any discussion of Everglades restoration. They’re also extremely elegant. Somehow, he has this ability to take extremely complex data and reduce it to a few key factors. What Don does is like taking a very complicated story and translating it into a beautiful haiku.”

Raised in the Washington, DC, suburbs as the son of a project manager with the U.S. Army Corps of Engineers, DeAngelis chose plasma physics over quantum theory at MIT after surviving what he calls his toughest course: fourth-year classical mechanics. “I struggled pretty hard,” he says, “but by the end of the semester, I realized I wanted to do classical physics as a career.”

After earning a PhD in engineering and applied physics at Yale, however, DeAngelis discovered that there “weren’t any jobs” in his specialty. So he applied for–and won–a presidential internship in environmental science at Oak Ridge National Laboratory in Tennessee. To his surprise, he discovered that he liked ecology even better than physics. For most of the next 22 years, he worked as a staff ecologist at Oak Ridge, where he began to develop the habitat models that he makes for the USGS today. During the late 1980s, while still at Oak Ridge, DeAngelis and colleagues started developing a series of Everglades models for Everglades National Park. The National Biological Service (now part of the USGS) recognized the importance of the modeling for its own continuing assessment of the wetlands and recruited him to Florida in 1994.

DeAngelis, who teaches ecology and conducts related research at the University of Miami, also serves as editor of the American Naturalist. Though he has an active family life (his wife of 12 years, Lie Lo, is a south Florida real-estate agent with four grown sons), he often puts in 12-hour days. “Working in Everglades restoration is an enormously complicated and time-consuming job,” he says.

Still, he’s convinced that it’s worth the effort. “The Everglades are still threatened by runaway development, and they face real danger if we don’t make the correct choices up ahead,” he says. “I’ve spent a lot of years working on these habitat models, because I think the stakes are very high. We absolutely have to get this right.”

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