Longer heat waves in summer. Little snow in winter. Higher sea levels. Scientists say there's another predicted effect of climate change to add to that list: Stands of treasured hardwoods in New Hampshire could be replaced by cheaper hickory, the kind that now grows in Tennessee.

That could cost the state its character and billions of dollars.

About 360 scientists, foresters, timberland owners and climate-change advocates gathered in Concord yesterday to talk about how global warming could affect New Hampshire forests and what could be done to use the state's acres of carbon-consuming trees to slow the effects. Among those attending were former New York governor George Pataki and Rafe Pomerance, president of the Climate Policy Center and a U.S. negotiator on the Kyoto Protocol.

"Things are going to change," State Forester Phil Bryce said at the start of the event. "The engagement of the forest industry is going to be essential to that change."

During the all-day event, experts talked about on-the-ground questions, such as whether landowners will need to increase the size of culverts. Other questions, such as how to mitigate the more than $7 billion in direct losses to forest industries that climate change could cause, seemed harder to solve.

More than 8,000 people work in New Hampshire's forest industries, many of them in rural areas. Steve Hamburg, director of the Global Environment Program of the Watson Institute for International Studies, said "climate change is real" in the forests that support those jobs.

"It's getting warmer," he said. "It's been getting warmer for 50 years-plus."

Hamburg pointed to longer mud seasons in recent years and stalled winter logging. Loggers need the ground to freeze to move heavy equipment into forest that may be otherwise impossible to reach. He also pointed to the out-of-state migration of spruce trees, which were once one of the most important species here. Weather stressors like the ice storm of 1998 could become more frequent, he said.

Though some individual scientists dispute the human cause or scope of climate change, no skeptics spoke up yesterday. One audience member asked the presenters, who repeatedly said they did not want to sound alarmist, to give the worst-case scenario.

Eric Kingsley, vice president of Innovative Natural Resources Solutions and former director of the New Hampshire Timberland Owners Association, said that continued warming could change the makeup of the forest.

Kingsley prepared a report assuming that carbon concentrations in the atmosphere would double in 100 years. He said scientists debate whether that benchmark will be reached sooner or later. But using that figure, he predicted that lesser-valued oak and hickory trees will gradually replace hardwoods, which would migrate north, following the cooler climate.

"You don't often go to someone's house and admire their beautiful hickory table," Kingsley said. "Hickory is a commercial species. It's not a trash species. But it's also not maple."

In the last six months of 2006, New Hampshire mills paid an average of $641 per 1,000 board feet - or feet of board produced at the mill that is an inch thick and a foot wide - for sugar maple sawlogs, according to Kingsley's report. In the same period, hickory logs delivered to mills in Tennessee averaged $274 per 1,000 board feet.

That change alone could cost New Hampshire's harvest $3.34 billion in the next century. Add another $1.9 billion in losses from a growing mud season, he said. That figure assumes that warming will add one day per decade to the average 20 days that soggy forest floors keep out loggers. Kingsley said it will add more.

From species shift and changes to the mud season, New Hampshire communities could lose $340 million in taxes on the timber taken off the land in the next century, Kingsley said. Maple sugaring would nearly disappear.

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