That sinking feeling

How rising sea levels threaten the Everglades

The sea level rise expected in the coming century will swamp the Everglades unless current management is adjusted or climate change is curbed.

Today, the sea level is rising at a rate of about 30 centimeters per century. Although some of that increase results from melting glaciers and ice sheets, most comes from the expansion of seawater as it warms, Harold R. Wanless, a geologist at the University of Miami in Coral Gables, Fla., said today during a briefing in Fort Lauderdale during a meeting of the American Geophysical Union.

The rate of increase is accelerating, he noted: The Miami-Dade County Climate Change Task Force is expecting sea level to rise about 45 centimeters by 2050 and between 90 centimeters and 1.5 meters by the end of the century.

Many parts of the Everglades include layers of peat, which is about 1 meter thick in spots. That material acts like a sponge in the rainy season, Wanless said. A continuing threat to the Everglades is the loss of fresh water during seasonal draining for agriculture in many cases. If the peat dries out for an extended period, it could collapse and allow saltwater to flood into the area. Alternatively, he notes, maintaining adequate levels of fresh water in the Everglades would keep ground levels from falling and would stop salt water from intruding.

Another way to reduce the rise in sea level would be to lower the atmospheric concentrations of greenhouse gases such as carbon dioxide. By quickly reducing those concentrations from today’s 380 or so parts per million to 350 ppm, a substantial part of the expected rise in sea level could be forestalled, he speculates. “That [action] won’t stop sea level rise, but it could avert catastrophe,” he said.

A 1-meter rise in sea level “would seriously impact the lowest parts of the Everglades, but the other parts would have a chance at survival if we get our act together,” he added.

A rise in sea level would have adverse effects beyond the Everglades, said Jayantha Obeysekera, a hydrologist at the South Florida Water Management District in West Palm Beach, Fla. If the sea level rises just 48 centimeters — about the amount expected in the next 40 years or so — salt water will infiltrate many of the aquifers along Florida’s eastern coast, thereby contaminating the wells that serve the area’s residents. And moving those wells isn’t an option, he noted: “If we move the wells inland, we could drain the Everglades.”

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