Ron and Mary Bitner took a chance when they started growing grapes for wine in Caldwell 29 years ago.

That's because Idaho's Snake River Valley, the highest elevation and coolest viticulture region in the Northwest, had winters too cold and a growing season too short for red wines. They started with just white wines, but since the launch of Bitner's Vineyards, Idaho's winters have warmed and the threat of winter freeze has reduced.

The growing season has gotten 20 to 30 days longer, and for the past 17 years the Bitners have been growing both reds and whites.

"It does seem like our red varieties like it," Bitner said of the changing climate. "We weren't able to grow the reds in Idaho when we started, and now we are."

Boise's average temperature has risen nearly one degree in the last century, triggering a series of changes inIdaho rivers, forests, range and farmland. You don't have to believe - as most of the world's scientists do - that the change is caused by increased levels of greenhouse gases in the atmosphere brought on by human activities - to realize something is happening.

Winters are warmer and the spring runoff begins two to three weeks earlier today than it did 50 years ago. Millions of acres of the state have burned in intense forest fires over the past 20 years, filling valleys with smoke and shutting off access to people's favorite backcountry haunts.

Streamflows are higher in March but lower in July, and in August many tributaries of Idaho's rivers dry up, leaving trout and salmon with reduced habitat. The rivers themselves are warmer, too, often reaching temperatures too high for trout to survive.

"We're seeing the effects of global warming right now," said Boise State University stream ecologist Pete Koetsier.

Those effects are both positive and negative, said Richard Slaughter, a consultant from Boise with the University of Washington.

For the Pacific Northwest's wine industry, global warming has been a boon, said Gregory Jones, a professor and research climatologist in the geography department at Southern Oregon University in Ashland. "Arguably, 40 to 50 years ago, it was very challenging to grow economically viable good- quality wine grapes in the Pacific Northwest," Jones said.

The longer growing season and warmer winter also increase wheat yields. When Margaret Lauterbach, the Idaho Statesman's garden columnist, moved to Boise in 1971 she was told she was "moving to the banana belt."

Then in 1974, winter temperatures dropped to 20 degrees below zero. It's been getting steadily warmer, and she has watched as vines like Virginia creeper have spread all over the area.

The shift has made the area better for plants that thrive in warmer, longer seasons, she said.

"There are some hardy bananas we could grow here," Lauterbach said.

Extra water now runs through Idaho Power Co.'s dams in the spring - when the company already has more than it needs and when state reservoir operators can't capture it all for storage. Streamflows are lower in the summer when power demand spikes as people turn on their air conditioners and run them longer than they did two decades ago.

New studies by Daniel Issak of the U.S. Forest Service's Rocky Mountain Research Station show that in seven of 10 years since 1993, Boise River tributary stream temperatures have risen above 68 degrees, the threshold that stresses trout and salmon.

Before 1990, research shows, the Boise River's temperatures reached the 68-degree mark only once every 10 years. In those seven of 10 years since 1993, fish have had to live in this warm water for up to nine days a year. That will continue to rise and perhaps accelerate, Issak said.

Rainbow trout have held their own so far but have moved around the basin as forest fires have caused different river segments to warm up. But bull trout, already a threatened species, have been losing 8 to 16 percent of their habitat due to dropping streamflows and rising temperatures.

The warmer winters have caused ski hills across the region to open later more often, costing the resorts an early season seen as key to a successful skiing business.

"You need snow early to get people excited," said Jack Sibbach, a spokesman for Sun Valley Ski Resort.

Sun Valley and other resorts, like Tamarack, have installed snowmaking equipment to help, but they still need natural snow and cool-enough temperatures. Last year, Sun Valley didn't open until Dec. 10.

The entire industry is working to come to grips with global warming, Sibbach said.

"I think in the industry people are realizing it is affecting them all over the globe, affecting getting people into the sport," he said.

Idaho's hunters, fishermen, campers, boaters and hikers have had to adjust their lives to the changing conditions. Forest fires have increased 400 percent since 1980, and 600 percent more acres have burned since then, said Tom France, regional director for the National Wildlife Federation.

The Bruneau River, a popular desert floating destination, has had only five average or better water years since 1985 and the last one was 1999, said Ron Abramovich with the U.S. Natural Resources Conservation Service.

"The desert is sensitive to change much more than the high elevations," he said.

So what's next?

"The one thing people have to understand is that the warming won't stop," the Climate Impacts Group's Slaughter said.

That means some of the positive attributes will turn negative somewhere down the line, he said. For anglers it means trout and salmon may disappear in the low elevations and be replaced by smallmouth bass.

Elk could become even more numerous, France said, but mountain goats could disappear. Forests will change from species like whitebark pines (a crucial food source for grizzly bears) to Douglas fir in the higher elevations - and to grasslands and brush in forests along the Boise Front. Invasive species like cheatgrass will continue to force out natives like sagebrush, and tropical diseases like malaria may even show up.

Even if the world reduces greenhouse gases, it will be more than a century before the warming stops, Slaughter said. "We've already bought into a lot of climate change," he said.

Rocky Barker: 377-6484