A Clearer Picture for Preservation
David L. Hart
Staff Writer, UGA Office of Research Communications
Infrared aerial photo courtesy of EOSAT Company
Roy Welch and Marguerite Remillard map plant communities on an aerial photograph of the Everglades. Photo by Rick O'Quinn
ATHENS, Ga. -- It's been 400 years since Amerigo Vespucci drew his first maps of the New World, so you'd expect that every square inch of the United States has been mapped nine ways to Sunday by now.
And you'd be right, give or take four or five million acres in Florida.
"The first explorers landed at the tip of Florida -- De Soto was there, Ponce de Leon -- and went around the Everglades and on up. [Eventually] the whole United States was all mapped, except this blank area of the Everglades," said Marguerite Remillard, an associate research scientist with the UGA Center for Remote Sensing and Mapping Science.
The Everglades remained a blank spot because ground-based surveying methods weren't well-suited for the wet terrain, and the demand for economic development wasn't sufficient to overcome the geographic obstacles, said Roy Welch, UGA research professor of geography and the center's director. Until now, photomaps from the 1960s and hand-drawn vegetation maps remained the most detailed pictures of the region.
"The Everglades has a fantastic history with pirates hiding out there, a lot of drug dealing -- even today, planes will go down and be left there. We flew over and we'd see these remnants of a fuselage just lying out there," Remillard said. "It's amazing that it's 1995 and [the area] hasn't been mapped yet in any great detail."
That's been a problem for the National Park Service as they work to protect three neighboring areas in south Florida -- Everglades National Park, Big Cypress National Preserve and Biscayne National Park -- in the face of invasions by humans, exotic plants and hurricanes.
"We're making major changes to the park by doing prescribed burning, nature's making changes like Hurricane Andrew, we're making large water modification changes to the park, and we don't know what's happening to our vegetation resources," said Bob Doren, the assistant research director at Everglades National Park. "A map can be used for us to set some long-term goals about how we look at these things and how we monitor them for change. That's really the point."
For all this, they need more than a map; they need a brand new way to create one.
Keeping tabs on the vegetation, including the cypress, mangrove and melaleuca trees, on such a large scale has as much to do with computers and satellites as it does with plant ecology. By bringing together the technologies of a geographic information system (GIS) and remote sensing, the center is piecing together not just a map, but a digital database of some of the last unspoiled wetlands in the United States, a stone's throw from the Miami suburbs.
"We believe that the data we can provide is fundamental to understanding the dynamics of what is taking place and also to establishing policies that will benefit the natural environment well into the 21st century," said Welch, who leads the project.
Although the Everglades has been under constant pressure from external disturbances for many years, the major impetus for getting this project rolling can be pinpointed to a particular day: Aug. 24, 1992. The impetus had a name -- Hurricane Andrew -- and wind speeds of more than 140 miles per hour.
Andrew ripped across the southern tip of Florida, razing towns and cutting wide swaths through the pine forests, mangrove thickets and cypress swamps of the three parks in what ecologists euphemistically call a "broad-scale disturbance." Andrew disturbed the living daylights out of the Everglades. But in Florida, hurricanes happen.
"This area is hit by hurricanes and has been for eons, so these plants are adapted to them," Remillard said. "They're very intense disturbances, but they're natural disturbances and they do reoccur over time."
Under normal conditions, then, the plants have evolved to recover from the worst nature can dish out. However, with all the changes humans have made over the years, no one is sure just what the normal conditions are any more. For example, in the mangrove area where the hurricane did a lot of damage, the mangroves normally would grow back, given enough time. However, an imported species, the Brazilian pepper, puts a wrinkle in this scenario. This South American shrub tends to invade disturbed areas, choking off all other plants and evicting the wildlife that live there. The park service is worried that, if left unchecked, the Brazilian pepper will take over the mangrove communities.
The park service also is at war with melaleuca, an Australian tree introduced in the 1930s to dry up the Everglades, before people understood the importance of wetlands. It worked, but now the melaleuca are spreading out of control. As it turns out, the worst way to manage a stand of melaleuca is to cut it or burn it down, because the species immediately "drops its seeds and reproduces like crazy," Remillard said.
Similar management problems occur with human disturbances, such as water-flow changes as the coastal cities siphon off water and the rising nutrient levels as agricultural runoff flows into the watershed. The map might reveal that one area is beyond help and that the park service would make better use of its limited resources on another.
"All of a sudden there's a lot of concern over the environment and what's taking place there -- what the expansion of Miami and the agricultural areas is causing as they butt up against the Everglades," Welch said. "We're developing maps and a geographic information system database oriented toward modeling the vegetation and the environment, both for now and into the future."
What they need is a multilayer jigsaw puzzle that covers more than 6,600 square miles in and around the three parks. This huge task, more simply known as the Everglades project, uses GIS methods to organize and analyze plant community details and remote sensing data.
Welch founded the Center for Remote Mapping and Sensing Science in 1984 to investigate just this sort of application of remote sensing and GIS methods. Remote sensing describes any data recorded from a distance -- by satellites, planes or even hand-held cameras. Geographic information systems use computers to manage and analyze all sorts of data tied to geographic locations -- from dirt samples to satellite images.
The bottom layer of the Everglades puzzle is a mosaic of eight French satellite images, anchored to control points from a global positioning survey. This "digital image mosaic" underpins the entire project.
"Any time we point to a pixel -- or picture element -- in that digital mosaic, we can also recover the ground coordinates of that point," Welch said. "That will give us the control that we need to fit the aerial photographs to that digital image mosaic." Now that the digital image mosaic is complete, the long process of laying out the upper layers has begun.
"It's a labor-intensive phase," he said. "We'll take somewhere between 400 and 500 color infrared aerial photos and extract details from them. When these details are aligned to the same points from the global positioning system, every pixel in the image will be accurate to within 30 feet of the actual ground location."
The aerial photographs, from the U.S. Geological Survey, provide the resolution needed to identify the roads, water flow and plants in the area. The researchers will produce layers of information about the region's transportation and hydrology, and another layer will show which plants grow where in the parks.
Roads are roads, but there are hundreds of different plants. Rather than picking out every individual species in the region, the researchers developed a classification system that identified the major plant communities found in the three parks.
"You have to match the classification system with what can be identified from the aerial photographs," Remillard said. "If you were right there on the ground, you could identify each of the species and say, This is saw grass, and this is mule grass,' and make a list of species, but you can't do that over the entire park. We try, first, to group the species into associations and then the associations might be grouped together into communities." Some of the major communities in the Everglades include wet prairie and forests of black, red and white mangrove.
The vegetation groupings also indicate whether the plants in an area have been influenced by human activities. In aerial photos, signs of humans range from agricultural fields to all-terrain vehicle trails and even airboat tracks.
"I think the most difficult part is deciding what you can and can't see in a photograph and going out in the real world and saying Yes, what's on the photograph is what I actually see on the ground,'" Doren said.
To translate the colors and textures in the aerial photos into plant communities, they need something to work with -- a pixel-to-plant dictionary, so to speak. They have to confirm that what they think they see in the aerial photos is actually there. "But the bigger problem is how to figure out where we are when we're collecting this data," Welch said.
Welch and his colleagues at the center have addressed this problem by developing a new procedure that links a satellite global positioning system (GPS) to a laptop computer displaying the digital image mosaic, all while the researchers are flying around in a helicopter.
As the helicopter moves from location to location, its position is displayed on the satellite image, and the center's researchers can easily find themselves on the more detailed aerial photographs they carry with them. Then they land and visually confirm which plants grow at that point. Back at the lab, they use this "ground truth data" to identify the plant communities in the photos.
"This technique blends modern aviation, new GPS technology, digital image processing on laptops and old-fashioned field data collection," Welch said.
By integrating these plant communities and remote sensing sources, the GIS database will be a digital model of south Florida, not just a photograph. The computer functions as a high-tech camera, taking snapshots and making maps from the layers of information in the database.
Researchers can put on a wide-angle lens and see a panoramic, high-altitude satellite view of the whole area. They can zoom in and see a smaller area, but this time in greater detail. They can change lenses and look at the networks of roads and canals in a particular area. If they change lenses again, they can see the plant communities that populate a specific place. Time-Lapse Ecology
While initially the project will provide a detailed and unprecedented snapshot of Everglades National Park, Biscayne National Park, and Big Cypress National Preserve, that's only the beginning. The park service and a host of other organizations will find it even more useful when the GIS database can show how the parks change over time.
"If they have the geographic information system, the image data and a record of what's there at one point in time, compared with either what happens in the future or compared with historical photographs, they can get a better feeling for what might happen if they change things," Remillard said.
The park service has aerial photos from years before Andrew, but the project is so huge that park service managers will have to pick and choose which regions they want to target for a time-lapse view. The areas most heavily damaged by Andrew, and areas where they know pollution is entering the park, top the list, Doren said.
"We will take snippets of the map -- insets if you will -- and we'll monitor them over short periods of time, and maybe we can afford once every 20 years to redo the entire map," he said.
The park service is not the only group that stands to benefit from the project. "Right now this whole region is receiving a great deal of attention from the government," Welch said. "It seems like every time you turn around, there's a different agency involved."
The U.S. Fish and Wildlife Service will use the database, because the Florida Panther Refuge will be included. The state of Florida and the Florida Game and Freshwater Fish Commission also have expressed interest in the effort. The South Florida Water Management District is cooperating with the project to create its own GIS database for an adjacent conservation area. Even groups like the Audubon Society, for example, might be able to use it to look at how plant communities affect the way birds forage in different habitats.
"I have a feeling that once it's done, a lot of universities and other organizations that do research, including the conservation organizations, will be very interested in having a copy of it," Doren said. "I have a feeling they'll find all kinds of uses for it."
It has taken a long time to get from hand-drawn vegetation maps to a precisely digitized and flexible tool for managing the embattled plant communities of south Florida. Once the National Park Service and other groups charged with preserving the Everglades have their map, they will have a much better idea of where the Everglades is heading.
"I think it's going to be one of the most valuable management tools that we have for the long term," Doren said. "We plan on making this map not just a static picture on the wall, but a very dynamic, three-dimensional image. We've got nothing like that now."
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