Experts: Warming displacing species


Published: Friday, January 3, 2003 at 6:01 a.m.
Last Modified: Friday, January 3, 2003 at 2:01 a.m.

With the world's temperatures rising annually, many of Florida's plants, animals and insects are relocating in search of new food sources, breeding grounds and suitable winter climates, University of Florida ecologists said Thursday.

From the flowering dogwood tree to the monarch butterfly, habitat shifts in state species may be part of a global trend, the scientists said.

According to two separate studies published in the journal Nature this week, global warming is forcing species worldwide to relocate. Variations in habitat and range in some cases are disrupting ecosystems through competition of native and introduced species.

Climate experts say the studies, which outline habitat variations and document species' shifts by 60 miles or more in recent decades, are two of the strongest examples yet that fluctuation in the biological world may be caused at least in part by temperature variations brought about by human activity.

In Florida, butterflies may be one of most visible examples of fluctuating habitats, said Thomas Emmel, director of the university's endangered species labs and soon to be director of UF's new McGuire Center for Lepidoptera Research.

Considered excellent environmental indicators, the absence or proliferation of butterfly species often indicates subtle variations in ecological conditions. At least three varieties of butterflies have appeared in North Central Florida in recent years, species once found only in southern reaches of the state, Emmel said.

The migration is to be expected. As global temperatures increase - by some estimates as rapidly as 1 degree per century - and regional weather patterns in the southeastern United States become more temperate, the northern extent for many traditionally tropical species, including butterflies, is moving north.

For example, populations of the polydamas swallowtail, a butterfly once native to southern parts of the state, are appearing more frequently and in increasing numbers in Gainesville.

The monarch, another butterfly that once bred intermittently in Alachua County, is now breeding up to 11 months a year, Emmel said.

"I saw one yesterday, on New Year's Day, right here in Gainesville," he said. "That's very unusual. It used to be that they would stop breeding in September and start again in April."

In addition, the black-and-yellow-striped zebra longwing, Florida's state butterfly, which once appeared only in mid-summer, is now common in Alachua County year-round.

But butterflies aren't the only species packing their bags as regional and global temperatures climb.

Mangroves, trees dependent on warm water, also have been moving north on both coasts in recent years, said David Steadman, climate expert and curator of ornithology at the Florida Museum of Natural History.

Birds common in Florida like the cardinal, mockingbird and Carolina wren have steadily moved farther north, and are now found regularly in New England and Canada, he said.

And the Cuban anole, a red-brown lizard native to Cuba, has established itself in Gainesville, once only found in the deepest reaches of South Florida.

"I think you could make a case that warmer climate is part of the equation," Steadman said.

Still, while spikes in regional temperatures have expanded the range of some state species, the habitat shifts have not been trouble free. Increased competition between native and non-native anoles, for example, has led to local varieties being squeezed from prime territories, Steadman said.

The flowering dogwood, once a staple of Gainesville's spring-time bloom, has also suffered as regional temperatures have climbed.

"We are at the southern end of dogwoods' natural range," said Meg Niederhofer, the city's arborist.

"As global warming proceeds, trees at the southern end of their range have a more and more difficult time," she said. "The environmental stress is exacerbated."

Greg Bruno can be reached at 374-5026 or greg.bruno@ gvillesun.com.

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