HELENA, Mont. — Shaded by hills and rocky cliffs, Yellowstone National Park’s northern approach normally follows the river, taking outside visitors into a very different world teeming with wildlife and otherworldly geothermal features.
But large patches of pavement have now disappeared on this crucial tourist corridor, washed away in a vicious May storm that swelled the Gardner River and sent mud and rocks pouring down its slopes. Some sections of the road had been swept away or left half a lane – if so – with jagged edges that made it look like the river had taken large bites of asphalt.
In its 150th year, Yellowstone, the nation’s oldest national park, finds itself at an existential crossroads in an era of climate change. It will be rebuilt after the flood damage, which forced the two northern entrances to close for months. But the question is how, especially given the likelihood that flash floods, drought, wildfires and heat will drastically change the way the park operates.
“We have a pretty good idea of what’s in store for us,” said Betsy Buffington, the Northern Rockies regional vice president of the National Parks Conservation Association. “What does reconstruction mean in this broader context?”
In the days following the storm, Yellowstone’s superintendent Cam Sholly suggested that climate change has made old disaster gauges obsolete. He described the recent storm as a “thousand-year event, whatever that means today.”
“They seem to be becoming more common,” he added.
The biggest threat is a rapidly changing climate, which experts say contributed to the record flooding. An atmospheric river plus warm temperatures resulted in the equivalent of four to nine inches of rain in combined precipitation and snowmelt, according to NASA. The Yellowstone River, just north of the park, peaked at 13.88 feet, breaking the previous record of 11.5 feet set in 1918.
If, as Mr. Sholly suggests, “thousand-year events” are going to happen much more often, National Park Service officials should think seriously about whether it makes sense to rebuild roads and buildings in the same locations where they were washed away. In places, he said, sections of the road slipped 80 feet into the river.
With more rain-on-snow events, more flooding is expected. “Many of the roads are historic stagecoach roads,” said Cathy Whitlock, a paleoclimatologist at Montana State University in Bozeman and author of a climate change study of the park. “The park needs to think about extreme events, the kind we haven’t seen before, and strengthen its buildings, roads and infrastructure.”
National parks across the country face similar challenges. They are particularly vulnerable because many are located at higher elevations, where the thinner atmosphere leads to warmer temperatures and where disappearing snow results in more ground absorption of heat, according to a 2018 study.
For now, Yellowstone officials are working to ensure that visitors can have a little vacation for the rest of the summer. The southern portion of the park has reopened and the northern portion is set to open on Saturday in time for the holiday weekend, although visitors will not be able to access it from the north.
The Federal Highway Administration has announced $60 million in quick-release funding to allow for temporary repairs in the park, but long-term reconstruction costs will be much higher. The Associated Press recently estimated that the price tag could exceed $1 billion, although the National Park Service has not yet calculated a margin. “I’m not going to give a high-level grade at this point,” said Mr Sholly in an interview. “It’s going to be expensive.”
No decisions have been made regarding the route of the new road between Gardiner, a gateway community at the north entrance, and the park headquarters in Mammoth. Mr Sholly said rebuilding the same river route could be unsustainable as climate change made another catastrophic flood more likely.
He said the sections of the faded road are “probably less than two miles, but they’re in the worst areas for that to happen.” Aerial photos show that in some places flooding has wiped out the entire roadway and reclaimed the river channel.
“I’d rather see that river corridor restored,” he said.
The northeastern entrance to the park will also remain closed after parts of the main route there crumbled in the storm, shutting down the nearby tourist towns of Silver Gate and Cooke City.
Neither entrance is expected to reopen until the fall.
The problem this time was a flood of water, but scientists are also concerned about the opposite. The snowline is creeping higher in the region and the dried-up grasses, shrubbery and tree branches are ready for major wildfires.
Last year, the fuels for wildfires were so dry that the park suspended its policy of letting natural fires burn. The park has been depleting fuels by mechanical means around hotels, shops and other buildings to provide a defensive space if wildfires break out.
“We’ve seen fires burn where we’ve never seen them before,” said Mr. Sholly. “Last year we had some of the warmest water temperatures and the lowest water levels we’ve seen in our rivers and streams.”
The park area, which warmed 2.3 degrees Fahrenheit between 1950 and 2018, is likely to be as warm or warmer than it has been in 20,000 years, according to paleoclimate records cited in Ms. Whitlock’s study. The dominant snow level in 1950 was about 7,000 feet and by 2100 it could be 9,500 feet according to projections.
By 2060 to 2080, the park is expected to be 5 to 6 degrees Fahrenheit warmer than temperatures just before and after 2000, Ms Whitlock’s study shows. Without mitigation, temperatures could rise by as much as 10 degrees by the end of the century.
Higher and drier temperatures can also alter the park’s famous geothermal features, causing them to receive less water. A recent study found that during a mega-drought in the 13th century, the Old Faithful geyser stopped erupting for decades. Geothermal features depend on a balance between water and heat.
Researchers are studying wildlife migration routes outside the park to ensure that Yellowstone’s famed range of species, from grizzlies to antelopes, have ways to exit the park when it gets warmer. “If we want to protect Yellowstone’s iconic wildlife, we need to protect the areas that animals need to migrate, move and maintain genetic diversity,” said Ms. Buffington, vice president of the conservation association.
Cultural properties are also at risk. So far, it appears that the only park building to have been damaged was a 1930s ranger’s cabin that had been washed away, Mr Sholly said. An inventory of archaeological sites is underway to see if they suffered damage in the torrential rains.
When rebuilding the park, they will take into account all the possible consequences of climate change.
“What are the things that we might not have thought about 10 or 20 or 30 years ago but will be thinking in 10, 20 or 30 years?” said Mr. Sholly.