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Associated PressLeaving South Florida wetlands alone might have deterred hard freezes and avoided millions in damages, three researchers say.
Some crop-damaging freezes in South Florida might have been milder or avoided if wetlands in those areas hadn't been drained years ago for farming, a new study suggests.
Roger Pielke Sr. and Curtis Marshall of Colorado State University and Louis Steyaert of the U.S. Geological Survey report on the study in today's issue of the journal Nature.
They focused on an unexpected 1997 freeze in southern Florida areas that used to be wetlands. The freeze cost vegetable and sugarcane growers about $300-million.
Starting with weather conditions recorded from before the freeze, they ran a computer program to simulate what would have happened if the areas had remained wetlands. Then they asked what would happen assuming the land-use conditions were the same as those in 1993. (Conditions in 1993 were chosen as the latest available estimate of what the land was like in 1997.)
The simulations indicated that if the wetlands had remained untouched, temperatures in most areas would have stayed in the mid to upper 30s, avoiding a freeze. In other wetlands areas, there would have been freezing but it would have been milder and briefer than the outcome calculated with the land switched over to agriculture.
The researchers got similar results when studying crop-damaging freezes in South Florida that occurred in 1983 and 1989.
Wetlands can ward off freezes in two ways, the researchers said. First, standing water moisturizes the atmosphere, which can then better trap heat that radiates away from the ground at night. Second, wetlands retain warmth better than drained lands and release heat when wetlands start to freeze.
Jim O'Brien, Florida's state climatologist, said the study's conclusions were no surprise. "To me, it's just common sense."
O'Brien also said that while wetlands can ward off freezes that happen when the land gives up heat, they are ineffective when cold air masses roll in from somewhere else.
The researchers agreed, but Marshall said the majority of freezes south of Lake Okeechobee are due to the heat radiation effect.