Determining Target Salinity Values for Restoration of the Estuaries of the Greater Everglades

Science Center Objects

The Greater Everglades Ecosystem, which includes Everglades National Park and Biscayne National Park, experienced significant alterations in the 20th century with the construction of canals to divert water, water management practices, growth of agriculture, and the rapidly expanding urban population of Miami and south Florida.  In the 1990s a federal, state, and local effort to restore the Greater Everglades Ecosystem was initiated; however, a significant problem for resource managers was lack of information on what the system looked like prior to the 20th century.  Our project addresses the questions of freshwater availability and salinity in the natural ecosystem prior to canal construction.  Results from our research are used by resource managers to set goals and targets for restoration of the Everglades.

An image of a microscopic freshwater snail. It's length is approximately 3mm.

Microscopic (length ~3 mm) adult snail in the Hydrobiidae family. Click on the image to learn more! (Credit: G. Lynn Wingard, USGS. Public domain.)

Project Lead: G. Lynn Wingard

FBGC Project Members: Bethany Stackhouse, Bryan Landacre, Christopher Bernhardt

Other USGS Project Members: Andre Daniels, Marci Marot

Collaborator: Frank Marshall, Cetacean Logic Foundation


The Greater Everglades Ecosystem, located in southern Florida, is a unique environment that includes freshwater wetlands, cypress domes, one of the world’s most extensive mangrove coastlines, estuaries, and the only reef tract in the continental United States. Everglades National Park is a significant part of this ecosystem and has been designated a World Heritage Site, an International Biosphere Reserve, and a Wetland of International Importance. The seasonal rainfall and flat landscape make the area vulnerable to flooding, so beginning in the late 1800s, as the population of south Florida grew, there was a demand for protection from flooding and for additional water and land for agriculture and the increasing population. These demands led to construction of extensive canal systems to divert water and roads and railways to make travel through the relatively undeveloped region easier. These built features, however, divided up the landscape and significantly changed the natural flow of freshwater through the wetlands to the estuaries and coastal ecosystems. 

The Comprehensive Everglades Restoration Plan (CERP) was developed in the 1990s and was authorized by Congress as part of the Water Resources Development Act of 2000 (U.S. Public Law 106-451). The CERP outlines the need for science to guide restoration of the Everglades and the driving principle of the CERP is “to get the water right,” which means to restore as much of the natural hydrology and ecological functioning as possible. To accomplish these goals, resource managers need to understand how the natural ecosystem functioned prior to significant human alteration. The problem is that few scientific or anecdotal records exist for the early 20th century. Moreover, ecosystems change over hundreds or even thousands of years so to be able to restore an ecosystem and to develop management plans that include adaptation to future change, resource managers need to understand how the ecosystem responds to long-term forcing factors (for example, storms, climate, sea level). 

Our research is designed to answer these questions for the resource management agencies (National Park Service, U.S. Fish & Wildlife Service, Army Corps of Engineers, and the South Florida Water Management District, and others). The clues to what the past environment was like are contained in the sediments formed and deposited in the region, so we collect sediment cores from throughout south Florida. The sediments, plant and animal remains, pollen, isotopes, and geochemistry of the cores are analyzed and the ages of the sediments are determined through geochronology (radio-isotopes) and pollen biostratigraphy. The basis of our work is the principal that “the present is the key to the past.” We study the present-day environment of south Florida and learn how the plants and animals live (for example, what is the salinity, pH, or depth of the water) to interpret the information in the cores. As a result of our work, managers have a better understanding of how much freshwater flowed through the system before the canals were built, how the freshwater influenced the salinity of the estuaries in the natural system, and how the plants and animals have responded to these changes. They use this information on the past to set targets and performance measures for hydrologic restoration of the Everglades.