USA–– As a climate scientist, you can talk about seasonal change in precipitation.
Or you can say the Smokey Bear fire danger signs will read high to extreme 22 to 30 days a summer, instead of the current 15, by 2040.
Presenting the latest predictions for western Montana and Idaho because of hotter summers and rainier winters was one goal of Fridays Northern Rockies Climate Change Workshop in Missoula.
But finding a way to relate the hard science to the interests of forest managers, lumber mill owners, trout fishermen and downhill skiers requires some research of its own.
Were trying to explain that these things are already with us, said Penny Morgan, a fire ecologist with the University of Idaho who led the Northern Rockies research team at the workshop. This is a chance to communicate how does it play out in the Bitterroot Valley or around Missoula? Were trying to show people whats vulnerable to change.
For the past 2 1/2 years, team members have been poring over a centurys worth of data forest fire records, snow-depth logs, dates of first and last frosts, spring runoff peaks, plant inventories and wildlife surveys. Theyve looked for patterns that repeat over the years or decades, and conditions that help some things and hurt others.
For example, one pattern thats shown consistent progress is the change in winter weather. The Lolo National Forest got 90 percent of its winter precipitation as snow between 1970 and 2000. By 2046, 76 percent of its territory will see a mix of snow and rain.
Rainy winters mean smaller snowpacks and earlier spring runoffs. In turn, that means drier summers and lower rivers and streams, where fish will find warmer water temperatures because the cold snowmelt has disappeared earlier.
In the Bitterroot Valley, that means snow that used to reach almost to the valley floor will retreat nearly to the peaks of the Bitterroot and Sapphire mountain ranges by mid-century.
Looking at forest fire data from 1890 to 2008, graduate student Kerry Kemp found Idahos fire season has grown by 32 days in the past 25 years. Fire sizes also have grown. If the trend continues, she said, the mountains south of Missoula into central Idaho could see their annual median burned acreage grow 500 percent by 2040.
That does not mean that every fire will be five times bigger. Kemp said the pattern keeps its mix of big and small fire years. Theres also the strong possibility that toward the middle of the century, forests may actually run low on fuel to burn.
Or the changing moisture could trigger disappearance of larch forests and expansion of ponderosa pine territory, two ecotypes that burn very differently.
All these changes affect U.S. Forest Service managers decisions about where to log, improve wildlife habitat or fight fires. They might also influence where river rafting companies set up shop, how ski resorts manage their snowmaking and where homeowners can affordably buy flood insurance.
In an area like Missoula where lots of people like to recreate outdoors, these management decisions filter down to the public, Kemp said. So they must be understandable and defensible.
Theres strong evidence for changing climate that will continue in our future, Morgan said. We can do something about it, but it may mean using the tools weve got in different ways. Some things that regenerate now might not in the future.
Reporter Rob Chaney can be reached at 523-5382 or at firstname.lastname@example.org.