Florida's vegetation has changed its structure over the last century in response to rising atmospheric carbon dioxide and ecologists see the change as a plant-based call-to-arms, heralding dry times to come.
Plants breath in air and breath out moisture through tiny pores called stomata. Comparing a variety of contemporary plants growing in Florida with museum samples and peat bogs dating back 150 years ago, an international team of ecologists found that as the amount of carbon dioxide in the air has increased, the number of stomata on plants' leaves have decreased.
The team of ecologists from Utrecht University in the Netherlands working with David Dilcher of Indiana University in Bloomington published two papers on their work in the recent .
"Our first paper shows connection between temperature, transpiration, and stomata density," Dilcher said in a Indiana University press release. "The second paper really is about applying what we know to the future."
Water evaporates from a plant through its stomata, driving the plant's need to uptake more water from its surrounding soil. Fewer stomata means less water is being released into the air, in the process called transpiration.
"The increase in carbon dioxide by about 100 parts per million has had a profound effect on the number of stomata and, to a lesser extent, the size of the stomata," Dilcher said.
The team predicts that further increases in carbon dioxide will halve the amount of water lost to the atmosphere.
That reduction in water could have serious effects on rainfall and other weather events.
The researchers found that the density of stomata packed on plants leaves has decreased by 34 percent over the past 150 years. The team concludes that while plants can alter the number of stomata on their leaves from season to season, the effects of such long term, sustained changes in stomata numbers are driving changes in the water cycle.
"Our analysis of that structural change shows there's been a huge reduction in the release of water to the atmosphere," Dilcher said.
"The carbon cycle is important, but so is the water cycle," Dilcher said.
America's most famous wetland, the Everglades, already suffer from the loss of groundwater used for agriculture, industry, and human habitation in the north of the state.
"If transpiration decreases, there may be more moisture in the ground at first, but if there's less rainfall that may mean there's less moisture in the ground eventually. This is part of the hydro-geologic cycle. Land plants are a crucially important part of it," Dilcher said.