Dead trees, many at least a half-century old, may be victims of too much water being pumped into the swampy headwaters of the Myakka River to be used for farm irrigation.
Even though experts think they have figured out what is responsible for a massive tree die-off in an ecologically vital area known as the Flatford Swamp, the situation is so complex they are not sure what to do about it.
The swamp plays a key role in the Myakka River ecosystem, soaking up floodwaters, filtering pollutants and providing habitat for fish and other wildlife. The Myakka, in turn, is the second-largest source of fresh water for Charlotte Harbor, one of the most productive estuaries in the state.
"If we are right, we need to decrease the amount of water in the system," said Jim Guida, a supervisor with the agency that regulates water resources in the region. "It's going to take time to figure out answers. We want to do it as rapidly as possible."
The district has spent more than $2-million to preserve 2,357 acres in the Flatford Swamp.
The Southwest Florida Water Management District had a public meeting Thursday to discuss results of a six-month, $150,000 investigation into the tree die-off in eastern Manatee County.
The study found that the amount of the 5-square-mile swamp affected by the tree die-off more than doubled since 1990, to a total of about 1,000 acres. Upland species such as oaks and pines, and wetland trees normally tolerant of changing water levels, have been affected.
The average age of the dead trees was 57. One survived as long as 100 years.
Most of the trees appear to have died since 1990, though their cores showed some had problems as early as the 1980s.
"We feel very, very strongly that rising water level is the cause of the mortality in the area," said University of Florida forestry pathologist Thomas Miller.
David Tomasko, the water district scientist who coordinated the study, said, "We believe there is evidence humans have changed the hydrology in the area."
Part of that change is an increase in farming, which relies on groundwater for irrigation. Between 1990 and 1995, the acreage devoted to citrus and vegetable crops in the Flatford Swamp basin increased 41 percent.
The district said it plans to conduct more tests and work with landowners on farming techniques, rather than order cutbacks in water use.