Florida Everglades
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Florida Everglades, not what it used to be

When the Europeans first set foot on North America, the Everglades were part of a 5.2 million-acre (8,100 square miles) watershed that covered a third of what is now Florida. The Florida Everglades wetlands occupied about three million acres. They extended from Lake Okeechobee southward to the ocean. So habitable land was restricted to thins strips along the east and west coasts of the state. Those glory days are a distant memory, but the grassy wetlands of the Everglades still occupy and impressive 1.5 million acres in the form of the Everglades National Park.

Lake Okeechobee defines the northern edge of the original Florida Everglades. The lake covers an area of 730 square miles, making it the second-largest freshwater lake entirely within the United States. But the lake is shallow, and in most areas, the water depth is less than six feet. Both the lake and the Everglades exist due to a process called differential compaction. 

A clay-rich geological formation covers the central portion of Southern Florida. However, sandstones underlie the coastal areas, and both of these formations rest on top of Oligocene to Miocene age limestones. Over time the clays in the central portion of the state of compacted more than the coastal areas. This difference in compaction turned south-central Florida into a shallow depression. 

At one point, water in this shallow basin extended over most of southern Florida. But the Everglades wetland areas grew, forming thick peat deposits that eventually covered south-central Florida. Now, Lake Okeechobee is the remaining bit of open water, and the watershed to the north of the lake is the source of the lake’s freshwater.

A changing world

The Everglades is also known as the “River of Grass.” The same freshwater that feeds Lake Okeechobee eventually moves from the lake into the Everglades. This constant drainage creates a thin sheet of water that slowly flows over the flat lowlands. As the water flows, it causes the sawgrass to ripple in huge waves of green.

But the Florida Everglades are a snapshot in geological time. When sea levels were lower during and immediately following the last ice age, Central Florida was all dry land. As sea levels rise in the future, Central Florida will become a shallow reef below the ocean’s surface. The Everglades can only form when the flat lowlands of Florida exist in a precarious balance with sea level.

However, it doesn’t take climate change to affect the Everglades. Human development over the past several hundred years removed half of these wetlands. One million acres are captured in the Everglades Agricultural Area, where commercial farming, mostly sugarcane, takes place. Another half a million acres contain dams, dikes, and canals as part of a water control system.

Carbon Sequestration

Coastal wetlands and their associate peat deposits are extremely effective carbon storage reservoirs. Carbon sequestration within these systems is an important part of the global carbon cycle. However, the Everglades ecosystem contains more than sawgrass. It also provides habitat for extensive mangrove forests. Recent research demonstrates that mangroves are very efficient at carbon sequestration. They capture carbon in the biomass above ground, and they also feed carbon into the soils, trapping the carbon below the waters of the swamp.

Despite their reduction in size by fifty percent over the past several hundred years, the Everglades is still an impressive example of wetlands. But as sea levels rise and human development continues, this ecosystem will come under increasing amounts of stress.    


ArcheanWeb:

The Everglades water wars (Source: ArcheanWeb) – https://archeanweb.com/2020/04/09/the-everglades-water-wars/ Also:

Coastal wetlands (Source: ArcheanWeb) – https://archeanweb.com/2019/12/27/coastal-wetlands/ Also:

Saltwater invades Florida’s water supplies (Source: ArcheanWeb) – https://archeanweb.com/2019/12/09/saltwater-intrusion-florida-water-supplies/ Also:

Sources:

  Lake Okeechobee Geology (Source: Access Genealogy) – https://accessgenealogy.com/florida/lake-okeechobee-geology.htm Also:

Florida Everglades (Source: Earth System Science) – http://www.cotf.edu/ete/modules/everglades/FEeverglades1.html Also:

Feature Image: Everglades Pa-Hay-Oke Swamp (By Daniel Kraft) (Modified) – By Daniel Kraft – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=84416351

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.