Climate change is likely to cause more frequent wildfires and may transform the forests and ecosystem of the iconic Yellowstone national park in the coming decades, a US study said Monday.
Dense forests dominated by narrow lodgepole pines trees are currently a dominant feature of the picturesque tourist destination which straddles Idaho, Montana and Wyoming.
But more open spaces, grasslands and forests populated by different kinds of fir trees and shrubs could characterize it in the future, said the study in the Proceedings of the National Academy of Sciences.
Years when no wildfires break out will become rare by 2050, and fires like the historic one in 1988 that ravaged 1,200 square miles (311,000 hectares), affecting more than one third of the park, will become the norm by 2075.
US university researchers made the forecasts by examining climate data from 1972 to 1999 and creating statistical patterns by combining those data with figures on the size and frequency of Rocky Mountain fires in the same period.
The study authors then projected how climate change of up to one degree Celsius annually, combined with the snowmelt which is arriving earlier each spring, would affect fires in Yellowstone through 2099.
"What surprised us about our results was the speed and scale of the projected changes in fire in Greater Yellowstone," said professor Anthony Westerling of the University of California, Merced.
"We expected fire to increase with increased temperatures, but we did not expect it to increase so much or so quickly. We were also surprised by how consistent the changes were across different climate projections."
After 2050, the average annual area burned was nearly 400 square miles (100,000 hectares), the study said. The fire pattern became remarkably similar to that currently seen in the US southwest.
"Large, severe fires are normal for this ecosystem. It has burned this way about every 100 to 300 years, for thousands of years," said co-author Monica Turner of the University of Wisconsin, Madison.
"But if the current relationship between climate and large fires holds true, a warming climate will drive more frequent large fires in the Greater Yellowstone Ecosystem in the future."
That could mean that lodgepole pines will have less time to recover in between blazes, and they may be replaced by faster-growing varieties of shrubs and trees like aspen and Douglas fir. Wildlife will certainly be affected, too.
Some experts say it takes up to 90 years for lodgepole pines to recover when a massive blaze wipes out a forest.
"More frequent fires will not be catastrophic to the area - Yellowstone will not be destroyed - but they will undoubtedly lead to major shifts in the vegetation," said Turner.
"It is critical to keep monitoring these forests and study how they respond to future fires."