Fri Apr 10, 2015 7:13am BST

Predicted climate changes bringing warmer and drier conditions to Yellowstone National Park will likely fuel catastrophic wildfires, cause declines in mountain snows and threaten the survival of animals and plants, scientists said on Thursday.

Warming that is expected in the American West over the next few decades would transform lands in and around Yellowstone from a wetter, mostly forested Rocky Mountain ecosystem to a more open landscape akin to the arid U.S. Southwest, the researchers said in a special issue of a park report.

Such dry conditions have not been seen in the area for the past 10,000 years, said the report, "Ecological Implications of Climate Change on the Greater Yellowstone Ecosystem," compiled by more than 20 university and government scientists.

Destructive wildfires like one in 1988 that charred thousands of acres of the park are predicted to become more common, the researchers said, while years without large fires would become rare.

The increasing frequency of such fires would likely convert dense mountain forests of pine and spruce in Yellowstone, which spans parts of Wyoming, Montana and Idaho, into woodlands intersected by shrubs and grasses, the report said.

Drought would likely hasten the decline of native trees such as aspen and whitebark pine, which are an important food for grizzly bears, and warmer streams will give an edge to non-native fishes at the expense of natives such as cutthroat trout, it said.

The study updates climate-based research first conducted for the park in 1992, before advances in computer-driven data collection and modeling, and before the concept of climate change was broadly accepted or understood, two of the report's authors said.

"In 1992, the potential for global warming driven by (human-caused) emissions of atmospheric greenhouse gases was hypothesized but not yet demonstrated," wrote William Romme, professor emeritus of ecology at Colorado State University, and Monica Turner, president of the Ecological Society of America.

"Today, there is no question that Earth's climate has warmed ... and will continue to throughout the 21st century," they wrote.

The report predicted less mountain snow, but did not spell out impacts of that on iconic Western wildlife such as lynx, wolverines and mountain goats whose survival depends on deep snows at high elevations.