Get Used to the American West in Flames: What Living With the 'New Normal' Will Mean
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It seemed likely that the Las Conchas record would last years, if not decades. It didn’t. This year the Whitewater Baldy fire in the southwest of the state burned an area almost twice as large.
Half Now, Half Later?
In 2007, Tom Swetnam, a fire expert and director of the laboratory of Tree-Ring Research at the University of Arizona, gave an interview to CBS’s 60 Minutes. Asked to peer into his crystal ball, he said he thought the Southwest might lose half its existing forests to fire and insects over the several decades to come. He immediately regretted the statement. It wasn’t scientific; he couldn’t back it up; it was a shot from the hip, a WAG, a wild-ass guess.
Swetnam’s subsequent work, however, buttressed that WAG. In 2010, he and several colleagues quantified the loss of southwestern forestland from 1984 to 2008. It was a hefty 18%. They concluded that “only two more recurrences of droughts and die-offs similar or worse than the recent events” might cause total forest loss to exceed 50%. With the colossal fires of 2011 and 2012, including Arizona’s Wallow fire, which consumed more than half-a-million acres, the region is on track to reach that mark by mid-century, or sooner.
But that doesn’t mean we get to keep the other half.
In 2007, the Intergovernmental Panel on Climate Change forecast a temperature increase of 4ºC for the Southwest over the present century. Given a faster than expected build-up of greenhouse gases (and no effective mitigation), that number looks optimistic today. Estimates vary, but let’s say our progress into the sweltering future is an increase of slightly less than 1ºC so far. That means we still have an awful long way to go. If the fires we’re seeing now are a taste of what the century will bring, imagine what the heat stress of a 4ºC increase will produce. And these numbers reflect mean temperatures. The ones to worry about are the extremes, the record highs of future heat waves. In the amped-up climate of the future, it is fair to think that the extremes will increase faster than the means.
At some point, every pine, fir, and spruce will be imperiled. If, in 2007, Swetnam was out on a limb, these days it’s likely that the limb has burned off and it’s getting ever easier to imagine the destruction of forests on a region-wide scale, however disturbing that may be.
More than scenery is at stake, more even than the stability of soils, ecosystems, and watersheds: the forests of the western United States account for 20% to 40% of total U.S. carbon sequestration. At some point, as western forests succumb to the ills of climate change, they will become a net releaser of atmospheric carbon, rather than one of the planet’s principle means of storing it.
Contrary to the claims of climate deniers, the prevailing models scientists use to predict change are conservative. They fail to capture many of the feedback loops that are likely to intensify the dynamics of change. The release of methane from thawing Arctic permafrost, an especially gloomy prospect, is one of those feedbacks. The release of carbon from burning or decaying forests is another. You used to hear scientists say, “If those things happen, the consequences will be severe.” Now they more often skip that “if” and say “when” instead, but we don’t yet have good estimates of what those consequences will be.
Ways of Going
There have always been droughts, but the droughts of recent years are different from their predecessors in one significant way: they are hotter. And the droughts of the future will be hotter still.