Climate-induced events can spark more intense wildfires at a higher frequency, says study
Temperatures in California are soaring: the US state has warmed by about three degrees Fahrenheit over the past century. A warming climate has a bearing on the increasing wildfires recorded worldwide. Shedding light on how climate change influences wildfires, a new study claims that climate change has been controlling wildfires over the past 1,400 years in California's Sierra Nevada region and the frequency of such climate-induced events may increase in the future.
The past two decades have seen the hottest and driest years in the state and 15 of the 20 largest fires in California history have occurred since 2000. “We find that warm and dry conditions promote fire, which in light of climate model predictions, suggests that future fires may be more extensive than we have observed in the last century”, said Richard Vachula, a Ph.D. student in Brown University’s Department of Earth, Environmental and Planetary Sciences and the study’s lead author, in a press release.
Impact of climate change on wildfires
To study the effects of the climate on wildfires, the team of scientists peered into the bottom of Swamp Lake, located toward the northern edge of Yosemite National Park in Sierra Nevada region. In the lake, they looked for sediments: smoke plumes from the wildfire release charcoal, which finds its way to the bottom of the lake, settling as sediments.
By examining the size of the charcoal particles, the team traced the source of these particles - whether its source was from a regional or local fire activity. Regional fire activity happens in roughly a 90-mile radius and releases lighter particles that can travel farther in the air while local fire activity occurring within a 15-mile radius, gives rise to larger particles that do not travel far.
With this information, scientists compared the charcoal data with the existing climate records, including temperatures and rainfall patterns. They found correlations between climate and fire over time. The researchers also factored in the data aimed at measuring the effects of direct human forest management, either by indigenous populations or by the US government.
While their results revealed that the regional activity was closely associated with the climate patterns, meaning warmer and drier climates correspond to periods of increased regional fire activity, local activity had more to do with human interventions.
For human-induced local activity, the team used archeological records to track the size of Miwok Native American populations - a group native to Northern America - over time. The Miwoks primarily feed on acorns. To aid the growth of acorn-producing oaks, they used fire to check the growth of underbrush. "The study showed that when the Miwok population was large, burning increased at the local level, even when the climate was adverse to burning. At the regional level, however, the influence of climate remained dominant", said the press statement. And in the past 1,400 years, according to the authors, climate change has been having an increasing impact on wildfires.
But there is an exception to the finding. Between 1900 and 1970, human activity appeared to have replaced climate as a regional influence on wildfires. This was when the National Parks Service systematically suppressed fire throughout Yosemite, which seemed to reduce fire despite climate conditions favoring increased activity.
Speaking about the impacts of climate change in the future, Vachula, said, "Future climate change is sure to have an impact on wildfires, forests, and in turn, human health. Recent fire seasons have been impacting air quality in California. This is likely to be a persistent problem in the future."
However, wildfires can be managed. According to Vachula, we have a number of strategies to mitigate wildfires. He added, "These include prescribed burning, fuel removal, and letting natural fires burn. I think the key is to remember that fires are essential parts of these ecosystems. So, I would suggest that we ought not strive to reduce burning but rather seek to facilitate it in a way that minimizes its effects on the health or well-being of humans."