The New Cost of Sprawl

Once again, wildfires of extraordinary scale and magnitude swept across the western states and coast of California this past summer. Some of the deadliest in U.S. history, they have destroyed both natural lands and residential communities. For many of those impacted, the trauma is compounded by the fact that they didn’t know they were in danger. Last year’s stories of families in the Napa Valley leaving their homes at a moment’s notice, only to return hours or days later to find them completely destroyed, were both heart-breaking and shocking.

The Wildland-Urban Interface or WUI is the zone of transition between unoccupied wildlands and human development, currently defined as acreage with a minimum residential density of 1 home per 40 acres located within or in close proximity to wildlands. The WUI, which is mapped every ten years in conjunction with the national census, locates and quantifies the residential structures potentially at risk from wildfires.

The commingling of vegetated areas and housing pose an increased wildfire threat for two reasons. The first is that at least fifty percent of wildfires are caused by human activity; consequently more residential development in the vicinity of wildlands means more fires – a fact sadly borne out by the Thomas fire, the largest of last summer’s California fires. The second is something now referred to as “ember attacks,” where sparks from wildfires are blown by high winds into developed neighborhoods, either setting their housing or the landscape planted around them aflame.

A quick glance at the map of the WUI clearly indicates that fires on the scale of the past few summers may not be freak occurrences. Between 2000 and 2010, the WUI has grown exponentially, and is currently equivalent to a land area the size of the state of Washington, including some 44 million homes, or one out of every three houses in the United States. Not surprisingly, the contours of the WUI run along the limits of low-density residential sprawl. Combined with more intense summer storms and longer drought seasons, which some argue are a result of global warming, the WUI forecasts a new cost to this low-density pattern of development – that of human lives and livelihoods.

In the aftermath of the fires, most communities have focused on near term emergency efforts – banning fires, creating evacuation routes and warning systems, educating home-owners or mitigating the risk through new code requirements. The larger public policy issues – whether or not to rebuild, or if limits should be placed on the growth of the WUI – have been little addressed. Embedded in this is the Achilles heel of residential sprawl – the property rights that go along with the development pattern, making the discussion, let alone any changes, enormously difficult, and at great personal cost to those affected.

As planners and architects, however, it is our responsibility to engage in that discussion, and advocate for the policies and practices that are sustainable, not only environmentally, but as they protect and preserve us against the changing landscape of natural catastrophe. Our resiliency efforts need to expand to include not only the threat from the rising seas, but also the escalating ravages of wildfires.

We should also focus on controlling the forces that contribute to the expansion of the WUI. Low-density development around high-cost urban centers such as San Francisco are in part a response to the housing crisis, as families push every further away from the center in search of reasonably priced dwellings. Policies that promote affordable housing, infill development, or the densification of our existing suburbs, will help curtail the growth of the WUI.

And we should not lose sight of the wildfire’s devastating impact on our natural environment. They have destroyed untold acres of wildlands as well as the animals and habitats they support, wiping them out for decades if not generations to come. Firefighting efforts now consume more than fifty percent of the budget of the Forest Service, whose primary mission is to protect and preserve our natural environment. Our advocacy should also allow a return to their primary mission.