Florida circa 2100: Global warming's toll
Ludmilla Lelis | Sentinel Staff Writer
June 23, 2008
You might not recognize the Florida that global warming could create by 2100. And the troubles just start at the coast. Beach erosion and coastal flooding worsen. Wells and rivers turn salty. Habitat for endangered animals could be lost. That's what scientists expect as the heated ocean water expands and glaciers melt, causing the seas to rise, potentially by several feet during the next century. How quickly Florida will feel the pressure from a sea-level rise depends on the pace of global warming during the next decade. But scientists warn that some rise will be inevitable, even if greenhouse-gas emissions were controlled today. Here are some of the expected effects:
Our coastal cities would be destroyed
About 387 miles of the state's 825 miles of sandy beach are critically eroded. As the oceans expand and glaciers melt from the changing climate, the seas will rise. Tide gauges show that effect has started, with a documented sea-level rise of 7 to 9 inches this past century.
If the seas rise quickly, those higher levels are expected to intensify the rate and extent of erosion. Waves will wash over the beach, flattening it and making it more vulnerable to the next storm. Storms will flood a larger area and will reach ground higher than before. Meanwhile, storm floods are expected to occur more often.
The immediate shoreline eventually would become permanently inundated, and that would allow the next set of storm floods to reach farther inland.
Our wildlife would suffer
Some of Florida's native flora and fauna might not survive the changes that sea-level rise could bring. Other habitats would transform as the seas push inland. Salt marshes and tidal flats, often the lowest-lying areas along the coastline, would be permanently flooded and lost.
Estuaries, such as the Indian River Lagoon, have developed a unique mix of plants and animals based on the flows of fresh water and salt water. The small invertebrates (such as shrimp) and juvenile fish might not be able to live in that higher salinity.
On the coastline, sea turtles could lose their nesting grounds if beach erosion accelerates and humans respond by building more sea walls. Each summer, tens of thousands of loggerhead turtles dig their nests in the sand dunes.
Florida's beloved manatees would even be at risk to rising sea levels. The endangered sea cows depend on sea grasses as a key food source. Sea grasses thrive where the water is shallow enough to allow sunlight to penetrate the water. If the water becomes too deep in the sea-grass beds, that would make it tougher for the sea grass to grow. Some sea grasses might not grow as well if the water becomes too salty.
Our water would be undrinkable
Sea-level rise is expected to make freshwater wells turn salty.
Most of Florida pumps its drinking water from deep, underground pockets of fresh water in the Floridan Aquifer. The aquifer, however, sits in limestone, which is naturally porous. Along the coastline, there are breaks in the limestone, where the fresh water mixes with the sea.
Seawater is actually heavier and denser than fresh water because of the amount of salt and sediment in seawater. However, a large enough column of fresh water can equalize the pressure from the sea.
As long as the pressure remains constant, that zone where the fresh water and salty sea mix won't move. But that zone can shift depending on how the water pressure changes.
Rising seas will exacerbate that problem. The expanding ocean and the additional meltwater will increase the pressure of the sea as it pushes against the freshwater pockets. Eventually, it would overwhelm the fresh water and infiltrate inland wells.
Our rivers would overflow
Rising seas could change the St. Johns River back into the estuary it was during prehistoric times.
At the mouth of the river in Jacksonville, the Atlantic Ocean pushes into the St. Johns as the river flows out toward the sea. The strength of the river flow and the pressure from the sea determine how far inland the sea water reaches. The leading edge of that sea water is the salt front.
After heavy rains, the additional fresh water can push the salt front farther toward the mouth of the river. During drought, the sea water can push farther inland, penetrating as far as Federal Point, near Palatka in Putnam County.
Our water would be undrinkable
Sea-level rise would mimic the drought years, when the salt front is able to push farther south.
Gradually, that added sea pressure also would push the river beyond its current riverbank. Riverfront property would flood more often, and the low-lying edge would erode.
The St. Johns River could change back to the form it took just before the past ice age, when the seas were 20 feet higher. Back then, the river was a saltwater lagoon, and the high points of Volusia County were isolated islands.
Could this really happen?
The world's prime scientific voice on global warming predicts seas could rise 7 inches to 23 inches by 2100. That's at least double Florida's current rate. However, a growing number of scientists think that's too conservative and project a rise of 3 feet or more by 2100.
Ludmilla Lelis can be reached at firstname.lastname@example.org or 386-253-0964.
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