A single, devastating California fire season wiped out years of efforts to cut emissions. Scientists found evidence of human activity in ash from fires at two remote locations in the Sierra Nevada mountains.
There are few things in the natural world that are as hard to study as the past. This is especially true of past events, since human activities have a way of changing the environment—and changing your life—in a big way.
A new study finds evidence of human activity in ash from fires in the Sierra Nevada mountains—evidence consistent with human influence, but no smoking gun to confirm that humans are guilty of the fires.
Why did the scientists look for evidence of fossil fuel use in the ash? There are two reasons. First, the California fires have been a big deal: They’ve killed hundreds of people and millions of acres of protected land, forced millions of people to evacuate, and destroyed dozens of homes. Second, the Sierra Nevada are some of the most sensitive locations in the world to changes in climate.
The researchers wanted to test whether the ash samples they found contained evidence of burning—or maybe “leaking” from a nearby power plant—before going to the trouble of excavating and sifting through hundreds of tons of ash to find it.
For two years, scientists ran the tests at two remote locations to see if the ash contained evidence of burning from the fires. They found evidence that one of the ashes contained fossil fuel residues from an underground storage area used to store nuclear waste until the mid-1980s, as well as evidence that the second ash contained residues from a nearby chemical factory that burned to eliminate toxic chemicals from the air. The researchers also found that the dust from the first fire contained evidence of human activity.
“Both of the fires were quite substantial in terms of loss of human and ecological values, and they were within a mile of each other,” said study co-author Elizabeth Roper, a senior research scientist at the Woods Hole Oceanographic Institution. “That led us to believe that the presence of a human related debris in their ash would be quite likely to be associated with either the first fire or the second fire.”
Another scientist involved in the study said the findings are consistent with the fires being caused by human activity.
