By Kelly April Tyrrell, University of Wisconsin
In August 2016, areas of Yellowstone National Park that burned in 1988 burned again. Shortly after, in October 2016, ecologist Monica Turner and her team of graduate students visited the park to begin to assess the landscape.
“We saw these areas where everything was combusted and we hadn’t seen that previously,” says Turner, a professor of integrative biology at the University of Wisconsin–Madison who has closely studied Yellowstone’s response to fire since 1988. “That was surprising.”
In a study published this week [May 20, 2019] in the Proceedings of the National Academy of Sciences, Turner and her team describe what happens when Yellowstone — adapted to recurring fires every 100 to 300 years — instead burns twice in fewer than 30 years. Yellowstone as we know it faces an uncertain future, the researchers say, and one of the big questions they hope to answer is whether the forests can recover.
“We were essentially able to reconstruct what the forest looked like before the fire happened, how many trees there were and how big they would have been,” Braziunas says. “Because we also measured nearby stands (of trees) that didn’t burn, we could compare what happens after the reburns and game out the scenarios in the model.”
The estimate, she and Turner say, represents a best-case, conservative scenario. With a warming climate and increased frequency of drought, the forests are likely to burn again in short intervals.
However, the forest has long shown itself to be resilient.
“The landscapes are going to look different than they have in the past,” says Turner, “but that doesn’t mean they won’t be beautiful. There will be species that benefit and species that see their ranges contract.”
“Change is going to happen and change is going to happen more quickly than we thought it would,” she adds. “We are learning how the system responds, but we don’t know to what degree it will be resilient or adapt in the future. But I am not ready to write it off. We have been surprised in the past.”
By Brett French
If there’s a plant-based poster child for wildland fire in the subalpine forests of Yellowstone National Park, it would be the cone of the lodgepole pine tree.
“All of these forests evolved with fire after the last glacial retreat,” said Roy Renkin, a vegetation specialist for Yellowstone National Park. “Different species have evolved different mechanisms to deal with fire.”
The Douglas fir has thick bark meant to resist low-intensity fires. Fireweed spends a lot of time spreading its roots out so it can sprout after fires remove competition. And the lodgepole pine’s specially devised cones will open to release seeds only when heated to 104 to 122 degrees.
“This green forest over here looked like that black forest many times,” he explained.
Renkin is one of the few people still on staff at Yellowstone who was around when the 1988 fires swept across roughly one-third of the park, charring more than 793,000 acres. Since then, he’s been witness to the rebirth of the park’s vegetation following what many at the time thought would be a legacy of scorched earth and a slow rebound.
“You guys will be lucky to have a meadow there in 100 years,” let alone a forest, he remembers one group of “ologists” concluding after visiting a heavily burn site. Thirty years later some of the trees that repopulated the area are 25 feet tall. Elk sedge that took root has grown “as big as basketballs.”