Wildfires are expanding into areas of our American landscape beyond forests, beyond cities…areas that experts call “the wild land-urban intermix.” This intermix is a transition zone between human development and wild lands such as forests, grasslands and scrublands where housing and vegetation comingle.

In 2010, there were +12.7M more houses and +25M people living in these interface zones than in 1990. In California alone, more than one million homes were built in intermix zones during this same period. In other places, New England is a good example, the numbers of people increased in intermix zones as forestland was “retaken” by abandoned farmland.

Some people are motivated to move to intermix zones in order to live closer to nature. Others move to avoid government regulations. And some move to wildland-urban intermix zones in hopes of finding a lower cost of living. Also, indigenous communities and people who work the land move to intermix zones for their livelihoods and their culture, according to Travis Paveglio, assistant professor of natural resource sociology at the University of Idaho.

Since 1991, structures built in wild land-urban intermix zones “…have to be made up of non-combustible materials, roofs and closed eaves,” said Jonathan Cox, division chief with the California Department of Forestry and Fire Protection. These regulations are in addition to local building codes, regulations and requirements but the problem, of course, is that the average age of houses, according to Zillow, is 50 years old. There weren’t any regulations as to how and with what materials houses/buildings were built or rebuilt in intermix zones prior to 1991.

Though building materials are regulated, retrofit programs in fire prone areas are non-existent.“What we don’t have are retrofit programs,” said Max Moritz, cooperative extension specialist in wildfires at the Bren School of Environmental Science and Management at UC Santa Barbara. “We retrofit for earthquake safety. And there’s public funding for mitigating flood exposure. But we don’t do that for fire.”

Obviously, wildfires happen in every part of the country (think Montana, Idaho, Wisconsin, etc.) But, is there something unique about California that makes its wildfires so catastrophic?

Yes, said Chief Cox.

  1. Climate change impacts – Like most of the West, California gets most of its moisture in the fall and winter. The vegetation then spends the spring and summer growing and drying out due to lack of water and warmer temperatures. Of the largest fires in California since 1932, 9 of them occurred since 2000, 5 of them occurred since 2010 and 2 of them have occurred this year alone.
  2. People – “Many of these large fires…are human caused,” said Nina S. Oakley, assistant research professor of atmospheric science at the Desert Ranch Institute. People cause sparks and sparks cause fires, particularly in dry, warm conditions.
  3. Fire suppression – For the last century, we’ve fought fires; now the Forestry Service is doing controlled burns.
  4. Santa Ana winds – The June – September fire season is driven by drier, warmer weather. The October – April fire season is fueled by the Santa Ana winds. “Fires spread 3 X faster when driven by the Santa Ana winds and are responsible for 80% of the fire losses over the decades since 1990,” said Cox.