BOZEMAN (AP) -- Negatives such as unhealthy forests, rapid population growth and decreasing water could converge into a nasty mix for the Rocky Mountain West, says a report issued by Colorado College.

''The combination of prolonged drought and continuing rapid population growth are key ingredients to a regional perfect storm,'' says the State of the Rockies Report Card, prepared by faculty and students at the private, liberal arts college. The report produced annually since 2004 focuses on Montana, Idaho, Wyoming, Colorado, Utah, Nevada, Arizona and New Mexico.

Concerns cited include 21 million acres of diseased forests in the Rockies, plus the social and environmental consequences of rapid energy development in a region with 11 percent of the nation's proven oil reserves and 31 percent of the natural gas reserves.

The population of the Rocky Mountain West grew by an ''alarming'' 9 percent between 2000 and 2005, more than four times the national growth rate, the report says. If that rate continues, Montana stands to see a population increase of 40 percent by 2030.

Eighty-three percent of the regional population lives in cities or towns, but the growth has occurred largely on land not developed previously, much of it forested. That adds to the expense and complexity of fighting wildfires, the report says.

Fire vulnerability increases in forests with diseased and insect-infested trees. In the eight Rocky Mountain states, eight of the 10 counties ranked highest for unhealthy forests are in Montana. Those counties are Flathead, Sanders, Mineral, Ravalli and Missoula.

''The immediate economic costs of devastated forests are potentially enormous to regional tourism, land developers and natural ecosystems,'' the report says.

Greater population also is likely to bring heightened arguments about water in the arid or semiarid West, it says.

Regionally, 87 percent of water drawn from streams and underground aquifers goes to agriculture. In Montana, the figure is 96 percent. As the population rises, the report says, demand for water to satisfy nonagricultural uses stands to increase.

''Conservation and creative water sharing methods can potentially benefit the Rockies' people, land and environment, but the demands of a growing population will likely create new tension,'' the report says. ''How this limited, variable and potentially shrinking supply is managed ... will largely determine not only the sustainability but also the livability of the Rockies so valued by millions of residents and visitors alike.''

A more optimistic report from The Sonoran Institute, a conservation group with offices in Bozeman and Tucson, Ariz., outlines some regional successes.

''Compared with much of the country, residents of the Northern Rockies are blessed with a unique opportunity to learn from the mistake of others,'' says the Sonoran report, which presents examples of development that Sonoran researchers say adds to communities instead of detracting from them.

The examples in the report released last week are a ''relatively tiny percentage of the development that is going on,'' said Dennis Glick, director of Sonoran's Bozeman office. However, he said, they indicate what could be the beginning of a trend that moves away from sprawl and focuses on preserving open space and wildlife habitat, with affordable housing part of the mix.

Case studies include a 310-acre, Bozeman subdivision with 30 percent of the area dedicated to open space, trails and water features. The subdivision has four miles of trails.