Science in Support of Everglades Restoration—Some Contributions from the USGS in Florida
by Matthew Cimitile
Today's Everglades may still seem vast and wild, but more than a century of dredging, canal and levee building, agriculture, and other human activities in the region has greatly undermined the ecological functions of the largest subtropical wilderness area in the United States. To reverse this trend, the Comprehensive Everglades Restoration Plan (CERP) was signed into law by President Bill Clinton in 2000. The plan outlines initial ecosystem-wide steps to restore the Everglades back to as natural a state as possible. Of primary importance is restoring natural freshwater flows. "To do so requires water managers to figure out the correct quantity, quality, timing, and distribution of freshwater that persisted before major landscape changes, in order to maintain a healthy and productive ecosystem today," said U.S. Geological Survey (USGS) biologist Barry Rosen. The USGS is a crucial partner in providing information and data toward this effort.
By the early 1900s, South Florida was becoming a prime destination for settlers. The region was an expanse of freshwater that farmers and settlers wanted to transform into farmable land. Canal-dredging projects drained water out of the Everglades (known as the River of Grass) and changed wetlands into land ready to be developed and farmed. As land opened up for such crops as sugar cane, tomatoes, beans, and potatoes, more settlers were attracted to the area, leading to further drainage. By 1927, 440 miles of canals, 47 miles of levees, and 16 locks and dams had been constructed throughout the region, according to CERP.
The hurricane of 1928 accelerated changes in the Everglades. The storm's landfall resulted in massive flooding, saltwater intrusion, and thousands of deaths. Calls for federal assistance were immediate and prompted future projects that removed more water from the Everglades and built additional flood-protection structures to prevent such destruction from happening again. The Everglades as it had existed for centuries was drastically altered. The River of Grass would eventually shrink to half the size it was at the beginning of the century, according to the Southwest Florida Water Management District.
At about the same time, a grassroots effort developed into a political movement to protect what remained of the natural environment in South Florida. In 1934, Congress authorized creation of a national park in the Everglades, and in 1947, Everglades National Park was established "to conserve the natural landscape and prevent further degradation of its land, plants, and animals". But the infrastructure that was draining and channeling the region's wetlands by altering freshwater flow had already set in motion a series of disturbances that continue to affect the park's ecosystem today.
To begin restoration of the Everglades, scientists must first piece together the region's natural conditions before drainage. A USGS database of historical maps, charts, and aerial photographs has given scientists a glimpse of the changes that have taken place over the past century and a half. The database contains charts and maps that document explorations into the region from the mid- to late-19th century. Aerial photographs date back to a U.S. Army Air Corps survey of the region in 1928. Additional surveys took place in 1940, 1952, and 1964. All such maps and surveys are electronically scanned into the database, and through a process known as georeferencing, researchers pinpoint precise locations among each map, chart, and aerial photograph through the years.
Georeferencing allows researchers to see gradual and, in some cases, sudden changes to the landscape. One clue comes in the form of ecotones, boundaries between two ecological systems. By tracing shifts in ecotones, scientists can view landscape change in terms of ecology. "Using these photos and maps and charts, we can pinpoint where alterations took place and separate out the human signals from the natural signals to determine why these systems changed," said USGS ecologist Tom Smith of the Southeast Ecological Science Center in Gainesville, Florida.
Along with deciphering changes to ecotones, scientists must also look for clues that reveal what the water conditions were like a century ago. Coral heads are long lived and record seawater conditions as they grow; thus, they can be used to calibrate reconstructions of past salinity and temperature. In September 2009, USGS scientists investigated a section of Florida Bay for the coral species Solenastrea bournoni, which is found in shallow turbid environments. Solenastrea bournoni is the only coral species that can tolerate the large temperature and salinity swings that frequently occur in Florida Bay. Finding a large coral head would provide proxy data to combine with other historical data to better estimate past temperature and salinity.
"We are trying to understand historical sea-surface temperatures through the use of strontium/calcium ratios in the skeletal material of the corals," said USGS geologist Chris Reich of the St. Petersburg Coastal and Marine Science Center in St. Petersburg, Florida. "If we find a big enough coral head, we can see back 100 to 150 years and pick out the salinity swings that occurred in Florida Bay before any of the canals and other modifications in the Everglades took place."
Using a noninvasive observing system called the Along-Track Reef-Imaging System (ATRIS), USGS scientists acquired georeferenced, color digital images and water-depth measurements. They collected more than 360,000 images. Although no large coral head was discovered during the fieldwork for use in a calibration study, Reich hopes the study will spur further opportunities. "With the interest in this study, we are hoping other opportunities will come up to use the ATRIS system as a tool for looking for additional coral heads or for observing seagrass restoration or storm impacts on restoration initiatives."
While restoration motivates researchers to look to the past, concerns about climate change cause them to look forward. One project is trying to better understand the likely response of vegetated shorelines to predicted sea-level rise. Smith's team of scientists, including Paul Nelson, Ginger Range, Karen Balentine, and Gordon Anderson, monitor mangrove and marsh vegetation plots throughout the year. Year-round sampling of upstream freshwater sites, brackish sites, and coastal mangrove sites allows for measurements of mangrove forest growth and production in relation to various hydrologic conditions, such as dry versus wet season. The group also measures rates of elevation change in sediment surfaces, as well as soil accretion or loss on the shoreline where coastal mangrove forests and brackish marshes occur. The resulting data allow the team to determine rates and patterns of local sea-level and sediment fluctuations over time scales ranging from less than a year to a decade and longer.
"We are trying to answer—if predictions of sea-level rise follow expected rates—'Can mangrove forests keep up?'" said Nelson. "The mangrove shoreline will migrate inland, in which case mangroves die off and sea-level rise is winning; or the mangroves will migrate upward, or vertically, and thus the shoreline remains relatively stable; or they will move seaward if more sediment becomes available."
Another project, known as "La Florida" (Land of Flowers), looks toward the years 2040-70 to project what might happen to two of Florida's charismatic watersheds, the lower Suwannee River basin and the Everglades, if climate-change predictions hold true. A collaborative effort among the USGS, the University of Florida, and Florida State University, La Florida is scaling down global-climate models to a resolution that allows researchers to ask detailed questions about future changes in regional weather patterns. Data such as yearly rainfall are integrated with inputs from various ecological and hydrological models to forecast changes to the Everglades ecosystem. By estimating potential future evapotranspiration rates and vegetative responses, researchers can begin to infer how habitat changes may in turn cause shifts in wildlife ranges. The project seeks to understand what will happen to rain patterns under different climate-change scenarios and whether populations of certain species will increase or decrease.
"We decided on projecting to 2040-70 because we wanted the information to be useful to resource managers in our lifetime," said Smith.
There are more USGS projects in the Everglades pertaining to hydrology, ecosystem studies, invasive species, and climate change than can be mentioned here. Fortunately, the USGS Greater Everglades Priority Ecosystems Science (PES) has helped organize this flood of data in an information-management system known as SOFIA. Short for "South Florida Information Access," SOFIA includes an extensive publication database and a diverse collection of data and metadata; it contains information on approximately 200 projects, including past projects and those currently being conducted in South Florida.
"SOFIA is where scientists and the public can access Everglades data and information in one place," said USGS information technology specialist Heather Henkel, who maintains the SOFIA system at the St. Petersburg Coastal and Marine Science Center. "It is designed to ensure that data resources are carefully managed and that the results from the various studies are archived after projects have ended."
Another platform that stores a wealth of information and supports biological and ecological assessments in the Everglades is the Everglades Depth Estimation Network (EDEN). The EDEN project, managed by Pamela Telis of the USGS Florida Water Science Center, brings together real-time water-level, ground-elevation, and water-surface modeling to provide scientists and managers with current water-depth information for the entire freshwater part of the Greater Everglades. Information is integrated and then presented on a 400-m2 grid that provides a consistent and documented dataset.
Scientists and managers can use both SOFIA and EDEN to help guide field operations, integrate data about hydrologic and ecological responses, and support assessments that measure ecosystem responses to restoration implementation.
The data accumulated from all these projects provide the baseline information that resource managers will need to guide restoration efforts and to evaluate performance after various restoration steps are completed. "It was essential to have the foundational data gathering and work before we began to construct the CERP components," said Rosen. After a decade of conducting research and developing guidelines and regulations pertaining to restoration efforts, Everglades restoration has begun.
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