Computer models estimate impact of climate change on Ozarks

Sunday, September 21, 2008 | 6:01 p.m. CDT

JOPLIN — Models used to predict the impact of climate change suggest that the Ozark forest will change in the future, but they don't agree on what those changes will be.

One forecast suggests the oak and hickory that dominate the forest will be replaced by pines, while another says the forest could evolve into savanna or even grassland.

A third possibility is a tangle of undergrowth dominated by woody vines, such as honeysuckle and poison ivy, choking out trees by mid-century.

"I certainly would expect forests to change," said John Shannon, state forester with the Arkansas Forestry Commission and a technical adviser to the Arkansas Governor's Commission on Global Warming.

The Ozarks region has been forested for 35 million years, said Cindy Sagers, a plant ecology and plant biology teacher at the University of Arkansas in Fayetteville and a member of the commission.

She said the forest likely will survive, but it will be different.

"What we do know is that vegetation zones are shifting," she said, "so that things that grow in southern Arkansas can now be planted in northwest Arkansas. "There is probably going to be some forest here, but whether it is pine or savanna..."

The National Wildlife Federation has put together models that forecast temperature increases of as much as 7 degrees for Missouri by 2100 if global warming goes unchecked, and that would "alter the composition of the state's forests, with southern pines replacing oak and hickory currently prevalent in southern Missouri and the Ozarks."

"Global warming could cause 40 to 60 percent of Arkansas' forests to be replaced by grasslands as slightly warmer temperatures push trees currently suited to the state's climate northward," the wildlife federation concluded.

An Environmental Protection Agency analysis found temperatures rising an average of 1 to 4 degrees in Missouri and Arkansas during the summer and 1 to 7 degrees in winter.

"If conditions become drier, the current range and density of forests could be reduced and replaced by grasslands and pastures," the EPA report on Missouri noted. "Even a warmer and wetter climate could lead to changes; trees that are better adapted to warmer climates, such as (some) oaks and southern pines, would prevail. Under these conditions, forests could become more dense."

"These changes could occur during the lifetime of today's children," the EPA report on Missouri concluded.

In Arkansas, southern pine forests advance northward, and scrub timber and noncommercial varieties of oaks would also expand their range, the EPA noted.

A third analysis, this one in 2006 by Jacqueline Mohan, then a scientist with the Marine Biological Laboratory at Woods Hole, Mass., forecasted that rising carbon dioxide levels will lead to the proliferation of vines, such as poison ivy and Japanese honeysuckle, in forests around the country, which will damage or kill many trees.

Doug Inkley, senior scientist with the National Wildlife Federation, said all of the models for the region find rising temperatures but are not as certain about the rainfall forecast. Less rainfall would mean a drier Ozarks, while more rainfall would cause an expansion of the range for southern pine species, for example, he said.

But even if rainfall increases, soil moisture likely would decline because of warmer temperatures, he said.

If the future is wetter, species of trees now associated with southern states, such as the southern magnolia, might migrate northward, Shannon said.

Loblolly pine is another species that might march toward Missouri, he said.


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