At our campsite one evening, Iniguez unfolded an aerial map that charted Whitewater-Baldy's severity in minute pixels; the green and light-blue dots indicated low and moderate severity, respectively. "As (Whitewater-Baldy) came out of the Glenwood district to the east, it burned into the Bear Fire from 2006," Iniguez explained. "The fire ran into it and dropped to the ground. Then, Iron Creek -- which had burned three times -- didn't stop it, but it went from high to low severity." A more detailed map gauging the fire's precise effect on vegetation will be available next year, when it's clear which trees have survived.
Most of the high-severity patches, roughly 14 percent of the total area, were just where Iniguez expected them -- in elevations above 8,500 feet, where the spruce-fir forests historically experienced centennial stand-replacing fires. The size of those patches concerns him, though. His colleague, Ellis Margolis, from the University of Arizona's Laboratory of Tree-Ring Research, found that in the Gila, patches of spruce-fir up to 2,500 acres historically burned at high severity. Whitewater-Baldy, however, scorched up to 5,000-acre holes in the forest. Iniguez and Margolis suspect fuel buildup has created conditions that cause bigger swaths to burn.
Although the scientists drew some preliminary conclusions, more research is planned. Matt Rollins, also from the USGS, would like to compare sizes and patterns of burn patches in the high elevations with the forest's historical norms. Carol Miller, research ecologist from Missoula's Aldo Leopold Wilderness Research Institute, wonders whether a fire-resilient forest like the Gila's is also a drought-tolerant forest. Despite a desire to know more, future research here is hampered by competition over funds. Most money goes to study mechanical thinning's effects, because treatments are costly and federal administrators want to know if they're paying off.
The Gila's managers hope research will also help them encourage a more adaptable forest as the climate changes. "The Gila is a good experiment in climate change because it's a relatively healthy ecosystem, and so if you think of climate change as a disease that's coming, then the most healthy individuals should get through it a lot better," says Iniguez. But while the Gila's resilience may help it stave off some threats from climate change, it may not be able to avoid them entirely.
By lantern-light and red wine at the Snow Lake campground, after touring the burn, Allen prodded Park Williams, bioclimatologist from Los Alamos National Laboratory, about the effects of climate change on the Gila and other Southwestern forests. Allen and other scientists worry that in the future, the Southwest's forests may not recover after fires. If larger areas burn at high severity, killing all the trees for miles, the distance to seed sources may prevent new trees from sprouting. And young trees struggle to grow under drought and increased temperatures.
Earlier that day, we'd visited a mid-elevation Douglas fir site that burned in 1998; not a single new seedling had regenerated. Instead, gooseberry and grass were taking over. Williams pointed out that climate models predict average temperatures will rise two to three degrees Fahrenheit in the next 40 years, so "trees will essentially be trying to grow on a different planet." This October, he published a grim paper connecting temperature rise to moisture extraction in plants and soil, which could cause widespread tree mortality as the hot atmosphere sucks the forests dry.
Allen described what happens if, say, a tree species like ponderosa can no longer grow. "If the dominant tree species on the site can't live there climatically anymore, that whole ecosystem is going to have to reorganize. Everything's going to change," he said. So in the Gila, and in other Southwestern forests, pines may be replaced by juniper, oak or other low-elevation shrubs more tolerant of heat and drought. "This will further drive ecosystem changes in understory grasses and forbs, wildlife habitat, food webs, patterns of fire, water balances, erosion, nutrient cycling -- you name it," he later emailed.
Despite the wine, the night ended soberly.
"The Gila's not immune to climate change," said Iniguez. "The fact that there was a whole lot of low-severity (fire during the Whitewater-Baldy burn) in the low country suggests that it could come out pretty good. But the drought could just be the tip of the iceberg. It might just get worse and worse. In that case, whether you're the Gila or (any other forest), you might come out looking like another beast."