The effects that climate change will have on the Greater Yellowstone Ecosystem are the focus of a recent study which looked specifically on how the cycle of fire and regrowth will change as temperatures continue to rise over the rest of the 21st century.
“We are following the long-term effects of fire in the Yellowstone area and encountering some lessons and surprises that challenge the way we think about fire in the area,” said Erica A. H. Smithwick, assistant professor of geography and ecology in Penn State’s College of Earth and Mineral Sciences, and principle investigator on the project. “Yellowstone National Park is the first national park in the world and is now a wonderful natural laboratory for studying natural processes.”
The study, which will be published online this week in the journal Proceedings of the National Academy of Sciences, shows that climate change is going to increase the likelihood of large fires in the Greater Yellowstone Ecosystem, to a point that could see a dramatic overall shift in the ecosystem itself; with changes to animal and plant life predicted.
“Large, severe fires are normal for this ecosystem. It has burned this way about every few hundred years for thousands of years,” explains study author Monica Turner, the Eugene P. Odum Professor of Ecology at the University of Wisconsin-Madison and a landscape ecologist who has worked in the Greater Yellowstone area for more than 20 years. “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.”
Centered around the Yellowstone National Park, but encompassing about 20 million acres over Wyoming, Montana, and Idaho, including the Grand Teton National Park, the Greater Yellowstone Ecosystem is predominately made up of lodgepole pine, but includes Douglas fir, Ponderosa pine, whitepark pine, spruce-fir and aspen.
The researchers used historic records of fires in the Yellowstone area and coupled that together with a number of existing climate models to determine how climate change will impact fires in the coming century.
“What surprised us about our results was the speed and scale of the projected changes in fire in Greater Yellowstone,” says lead author Anthony Westerling, a professor of environmental engineering and geography at 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.”
They found that fires large than 500 acres – which were previously a rare phenomenon – will likely be an annual occurrence by 2050. Fire rotation – the time span over which an entire landscape burns – is likely to be reduced from 100 to 300 years to less than 30 years.
“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,” says Turner. “It is critical to keep monitoring these forests and study how they respond to future fires.”
The issue at hand is not the survival of Yellowstone, as Turner notes, but rather what the face of Yellowstone will look like in 50, 75, 100 years. The lodgepole pines which dominate much of the landscape may simply not have enough time to recover from one fire to the next, and if they cannot adapt, they will be wiped from the area, allowing other trees and even shrub- or grass-land to take over.
“The climatic conditions projected for the second half of this century are similar to what we see in areas of the west today that have different forest types from Yellowstone’s,” Westerling said. “We don’t know how fast those species will migrate in response to climate change, though, so the immediate response of the ecosystem is hard to predict. Because of its pristine condition, Yellowstone provides an unparalleled natural laboratory to monitor and learn from fire and ecosystem responses to climate change.”
When this happens, and with the advent in changing climate, the rate of fire rotation will once again change, as fuel and ideal conditions change once again.
“The biggest challenge for us is to understand what can happen when the ecosystem is transformed,” said Westerling. “Our projections also depend on the climate models we are using — for example, if projections for winter snow pack or summer rainfall were to increase significantly, that would change our results.”
“In these model we don’t consider what the vegetation will do under these changing regimes,” said Smithwick. “The forest has been stable for thousands of years, but it looks like it will face changes by 2050.”