Humans Drive Wildfires

From the paper. Contribution to 25 year expected fire count by natural and human factors. Contribution of natural (A) and human (B) variables, ceteris paribus, to the expected fire count predicted during the 1976–2000 period. Natural variables are defined as all variants of AET, CWD, lighting, elevation and slope. Human variables include distance to population centers, neighboring maximum housing density, distance to populated places, and distance to campsites. Courtesy: PLOS One and the authors.From the paper. Contribution to 25 year expected fire count by natural and human factors. Contribution of natural (A) and human (B) variables, ceteris paribus, to the expected fire count predicted during the 1976–2000 period. Natural variables are defined as all variants of AET, CWD, lighting, elevation and slope. Human variables include distance to population centers, neighboring maximum housing density, distance to populated places, and distance to campsites. Courtesy: PLOS One and the authors.

Not just climate change: study finds human activity is a major factor driving wildfires. Study weighs human influence in wildfire forecast through 2050. The researchers systematically looked at human behaviors and climate change together, which is unique and rarely attempted on an area of land this large.

From George Washington University

A new study examining wildfires in California found that human activity explains as much about their frequency and location as climate influences. The researchers systematically looked at human behaviors and climate change together, which is unique and rarely attempted on an area of land this large.

The findings suggest many models of wildfire predictions do not accurately account for human factors and may therefore be misleading when identifying the main causes or drivers of wildfires. The newest model proportionately accounts for climate change and human behavioral threats and allows experts to more accurately predict how much land is at risk of burning in California through 2050, which is estimated at more than 7 million acres in the next 25 years.

The paper, “Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California,” appears Thursday in PLOS ONE.

Climate change affects the severity of the fire season and the amount and type of vegetation on the land, which are major variables in predicting wildfires. However, humans contribute another set of factors that influence wildfires, including where structures are built, and the frequency and location of ignitions from a variety of sources–everything from cigarettes on the highway to electrical poles that get blown down in Santa Ana winds. As a result of the near-saturation of the landscape, humans are currently responsible for igniting more than 90 percent of the wildfires in California.

“Individuals don’t have much control over how climate change will affect wildfires in the future. However, we do have the ability to influence the other half of the equation, those variables that control our impact on the landscape,” said Michael Mann, assistant professor of geography at the George Washington University and lead author of the study. “We can reduce our risks by disincentivizing housing development in fire-prone areas, better managing public land and rethinking the effectiveness of our current firefighting approach.”

The researchers found that by omitting the human influence on California wildfires, they were overstating the influence of climate change. The authors recommend considering climate change and human variables at the same time for future models.

“There is widespread agreement about the importance of climate on wildfire at relatively broad scales. At more local scales, however, you can get the story quite wrong if you don’t include human development patterns,” said Max Moritz, a co-author and a University of California Cooperative Extension specialist based at UC Berkeley. “This is an important finding about how we model climate change effects, and it also confirms that getting a handle on where and how we build our communities is essential to limiting future losses.”

Between 1999 and 2011, California reported an average of $160 million in annual wildfire-related damages, with nearly 13,000 homes and other structures destroyed in so-called state responsibility areas–fire jurisdictions maintained by California, according to Dr. Mann. During this same period, California and the U.S. Forest Service spent more than $5 billion on wildfire suppression.

In a model from 2014 that examined California wildfires’ destruction over the last 60 years, Dr. Mann estimated that fire damage will more than triple by 2050, increasing to nearly half a billion dollars annually. “This information is critical to policymakers, planners and fire managers to determine wildfire risks,” he said.

Abstract

The costly interactions between humans and wildfires throughout California demonstrate the need to understand the relationships between them, especially in the face of a changing climate and expanding human communities. Although a number of statistical and process-based wildfire models exist for California, there is enormous uncertainty about the location and number of future fires, with previously published estimates of increases ranging from nine to fifty-three percent by the end of the century. Our goal is to assess the role of climate and anthropogenic influences on the state’s fire regimes from 1975 to 2050. We develop an empirical model that integrates estimates of biophysical indicators relevant to plant communities and anthropogenic influences at each forecast time step. Historically, we find that anthropogenic influences account for up to fifty percent of explanatory power in the model. We also find that the total area burned is likely to increase, with burned area expected to increase by 2.2 and 5.0 percent by 2050 under climatic bookends (PCM and GFDL climate models, respectively). Our two climate models show considerable agreement, but due to potential shifts in rainfall patterns, substantial uncertainty remains for the semiarid inland deserts and coastal areas of the south. Given the strength of human-related variables in some regions, however, it is clear that comprehensive projections of future fire activity should include both anthropogenic and biophysical influences. Previous findings of substantially increased numbers of fires and burned area for California may be tied to omitted variable bias from the exclusion of human influences. The omission of anthropogenic variables in our model would overstate the importance of climatic ones by at least 24%. As such, the failure to include anthropogenic effects in many models likely overstates the response of wildfire to climatic change.

Citation

Michael L. Mann , Enric Batllori, Max A. Moritz, Eric K. Waller, Peter Berck, Alan L. Flint, Lorraine E. Flint, and Empale Dolfi;  Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California; Plus One Published: April 28, 2016 doi: 10.1371/journal.pone.0153589

Source

George Washington University news release.

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