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Climate change looms large over Obama’s Yosemite visit

As the park prepped for President Obama’s visit, experts hope to highlight a park in flux.


When Kelly Martin, the fire chief at Yosemite National Park, heard that President Obama would soon visit her park, she had what seemed like a wild idea. She heard that the Obama family wanted to visit the famous giant sequoia trees in the Mariposa Grove. As it happened, her crew had prepared to set a controlled fire there, in order to help the sequoias regenerate. This could be her big chance, she thought, to try to improve the public’s perception of fire by showing how important fire can be to restoring healthy forests and making them resilient to climate change. So she asked her bosses if she could go ahead with the fire and invite a very special guest to watch.

“Think about how powerful that would be,” Martin told me a few days before the president’s visit.

I was in Yosemite last week, just a few days before the president was scheduled to arrive, as Martin and other park staff were wrestling with something more serious than the predictable frenzy in advance of a presidential visit: In one of the nation’s first parks, climate change is already melting glaciers, killing trees, chasing animals and plants up slope and increasing the likelihood of catastrophic wildfires.

Greg Stock/NPS

So the park’s scientists and resource managers were straining to borrow the president’s bully pulpit to educate the public about a beloved landscape in transition.

“Climate change means that we cannot manage national parks for a little picture of the past to which we cannot return. We need to manage our national parks for possible futures,” Patrick Gonzalez, the principal climate change scientist for the national parks, told me.

That will require overhauling a century of management: After more than 100 years of people putting out fires in Yosemite, the forests are overcrowded with trees and underbrush, which makes the stands more vulnerable to catastrophic fire. Climate change is also increasing the frequency of natural fires sparked by lightning, as more storms roll through and the snowpack, which can prevent fire’s spread, fades.

But fire is the best tool Martin has to reduce the likelihood of major damage to the forests from these more frequent fires. Setting controlled fires to clean out the underbrush and some smaller trees makes it less likely that the next wildfire will rise into the canopy of the biggest trees and wipe out swaths of forest.

She shows me a stretch of forest in the Yosemite Valley that her crew had burned a few years before. The trees are widely spaced. The trunks of the huge ponderosa pines are charred black, but the tops are still green. “These larger trees won’t be destroyed by fire because there is nothing now to let a fire into the canopy of these trees,” says Martin, as she strides through the fire-scoured forest. And the remaining trees have more chance of survival because there’s less competition for water and nutrients.

Kelly Martin inspects a ponderosa pine in a forest in Yosemite Valley burned in a prescribed fire.
Elizabeth Shogren

But visitors don’t like smoke marring the park’s glorious views of waterfalls and massive granite formations like Half Dome and much of the public still views wildfires primarily as a threat. That’s why Martin was so keen to have the president witness a controlled blaze.

The principal climate change scientist for the national parks, who happened to be visiting Yosemite just days before the president’s arrival, learned about Martin’s proposal of setting fire to the Mariposa Grove.

Patrick Gonzalez, principal climate change scientist for the National Park Service, crosses the Merced River in Yosemite.
Elizabeth Shogren

“I actually think it’s a good idea,” says Gonzalez. He is working with Martin and others at Yosemite to redesign their strategy for reducing damage from wildfires by using climate research to decide where to let natural fires burn and set more prescribed fires. “It’s a small investment today that avoids high costs in the future.”

A few days before the president’s visit, a White House videographer arrived in Yosemite to learn from experts about the park and climate change.  Gonzalez says he told him that data from weather stations at Yosemite show that human climate change has caused warming of about 2 degrees Fahrenheit since 1911.

Although Martin hopes a new fire regime can save some of the park from the worst ravages of those high temperatures, Yosemite’s geologist, Greg Stock, has spent his career tracking one of climate change’s likely fatalities: the park’s glaciers. For ten years, Stock has hiked to the remote high peaks of Yosemite to study the two remaining glaciers, Lyell and Maclure. John Muir was the first to document them in 1872 and the U.S. Geological Survey followed in 1883 to photograph and measure them. “The whole northern aspect of that mountain was blanketed in ice and now that’s all gone,” Stock says. “Really there are just small patches of ice tucked up underneath the steepest cliffs where they’re shaded and remain cold enough and even those are dwindling rapidly.”

Greg Stock, Yosemite's geologist.
Elizabeth Shogren
The glaciers are key to keeping the water flowing in the Tuolumne River, an important source of water for San Francisco, after the rest of the snow has melted. But the last four years of drought greatly accelerated their decline. If they keep shrinking at the same pace, Lyell Glacier could be gone within 10 years. Without the glaciers, he fears, the river could run dry during part of the year.

Starting in 2009, Stock put survey stakes in the glaciers to track their movement, since movement is part of what defines a glacier. What he found was sobering: Lyell Glacier was no longer moving. “So maybe we just have one true glacier left in the park now,” he tells me, with clear pain on his face. “What makes the whole thing poignant for me I guess is, arguably, I’m going to be the last researcher to study these glaciers.”

In the end, Martin didn’t get her wish. No fire raged in Yosemite’s Mariposa Grove during the first family’s weekend stay. “It’s almost a missed opportunity,” she says wistfully. But the president did take a break from hiking and sightseeing to address one of Martin's biggest worries about the national parks: “The biggest challenge we’re going to face in protecting this place and places like it is climate change,” Obama said Saturday in a speech in Yosemite Valley. Climate change, he said, is “no longer just a threat. It’s already a reality.”

Elizabeth Shogren is HCN's DC Correspondent.