Climate change to shrink Montana’s forests, challenge species

Temperatures across the state are projected to increase by as much as 6 degrees by the middle of the century while summer rainfall grows scarce – two trends driven by the planet’s shifting climate, a University of Montana scientist said Monday.

For western Montana, the results could alter the landscape, causing a reduction in forested areas, a shift in species distribution, a greater number of severe wildfires and a generally unfamiliar climate.

“What does our (weather) future look like from a geographical perspective? It’s like Denver, eastern Colorado or southwestern Nebraska,” said Nick Silverman, a researcher with the Montana Climate Office at the University of Montana’s College of Forestry and Conservation. “Things are shifting and changing, and we have to think about everything that comes about from that.”

Silverman joined several other UM and Montana State University scientists, along with the Montana Wildlife Federation, on campus Monday night to discuss the impacts of climate change on the state’s future.

Scientific models suggest temperatures across the state will increase nearly 6 degrees by 2050, accompanied by drier summers and nearly an entire month of additional days over 90 degrees. The results will force species to adapt, move or die, and it will likely lead to a contraction of Montana’s forests.

“Seasonality really matters – a tree is growing at a certain time and needs water at a certain time,” said Alisa Wade, a conservation scientist and spacial ecologist at UM. “The growing season has been increasing and will continue to increase, but hot weather makes things dry up. There’s going to be increased mortality, and there’s really no benefit there. Hot temperatures kills trees.”

Wade said the impacts of climate change will depend on the underlying health of Montana’s forests and other unpredictable factors like La Nina and El Nino.

While forest regeneration could see positive gains at high elevations, hot and dry conditions at lower elevations are projected to cause a reduction in forested areas, Wade said.

“There is such a thing as CO2 fertilization, so with increased CO2 in the air, you get more productivity,” she said. “But when you have water limitation, there is an extreme reduction in growth and productivity. You have the potential for a faster range contraction than expansion, leading to an overall loss of forested area in Montana.”

A mismatched snowshoe hare stands out with its winter coat against a snowless background. (Scott Mills research photo)

Warming temperatures will also impact the state’s wildlife, creating what Scott Mills described as “winners and losers” in the fight for survival.

Mills, the associate vice president of research for global change and sustainability at UM, said climate is a powerful driver of species’ distribution and abundance, and it will change the type of plants and animals found in any particular place.

“We’ve seen range shifts historically, and we see a lot more range shifts happening now,” said Mills. “Species are responding. Species of all types are moving to the north.”

If animals can survive by moving or adapting, Mills said some may attempt the latter by adjusting their size, appearance, diet or behavior. Others will adapt through classic evolution driven by natural selection.

That happens most rapidly when populations are large, when they’re connected, and when the stressors occur one at a time, Mills said.

“I have a great deal of confidence if asked the question of what will happen to wildlife under climate change. I’m 100 percent certain species will move, adapt or die,” Mills said. “There will be winners and losers as this climate envelope changes.”