by Alexandra Syphard, Ph.D., Conservation Biology Institute
Why is housing loss to wildfire relevant?
|Wildland Urbanc Intermix Areas, southern California|
My coauthors and I are concerned about community vulnerability to wildfire, and this paper is the first publication from a much larger project, the USGS Southern California Wildfire Risk Scenario Project. Although one of the main components of this project is to identify the key factors that minimize housing loss, another major goal is to find solutions that balance management of fire hazards with natural resources – and ideally, identify ways to benefit both.
There are a number of reasons why housing loss to wildfire is strongly linked to conservation, and these tend to fall into three main groups.
1. The ecological impact of increased fire frequency in non-forested ecosystems
Throughout the US, particularly in the west, highly successful outreach about the perils of fire exclusion has led to the common belief that more wildfire is needed for its ecological benefits. However, for those of us who study non-forested, crown-fire systems, like the shrublands in southern California, the opposite is true. During the last several decades, human-caused ignitions have escalated due to population growth and urban expansion, and fire frequency has thus skyrocketed in the region. Although many native species in southern California are resilient to periodic wildfire, the vegetation here is actually adapted to a fire regime with much lower fire frequency than in most conifer forest systems. As a result, many species cannot withstand high-recurrence fire, especially if a fire repeats within 5 – 15 years. Increased fire frequency not only contributes to the elimination of native shrubs, but it also imperils the many mammals who depend on shrubland habitat, and furthermore increases the potential for expansion of weedy, highly flammable annual grasslands. As a biodiversity hotspot, southern California is home to the one of the largest numbers of threatened and endangered species in the US.
Because the vast majority of ignitions are caused by humans in California, population growth and urban development have direct effects on the number of fires that occur. If future development occurs in a way that not only reduces risk of home loss, but also reduces the number of fires that start, people and natural resources will both benefit.
2. The ecological impact of fuel treatments and prescribed fire in non-forested ecosystems
The most obvious and accessible approach for dealing with wildfire risk is to manage vegetation, or, the fuels that carry the fire. Thus, reducing the volume and extent of fuels is usually considered to be the most important aspect of fire management. In forested ecosystems, this approach presents few problems for conservation, and is actually mutually beneficial for reducing fire hazard and providing ecological benefits. Unfortunately, this ecological benefit does not extend to non-forested, crown-fire ecosystems. In southern CA, fuel treatment typically involves complete elimination of native shrubs in preference of exotic grasses and low fuel-volume vegetation. These treatments facilitate the expansion of exotic species, and prescribed fire adds more fire to a landscape that is already suffering from an exorbitant amount of fire. Fuel treatments also fragment important habitat for mammals. Aside from the negative ecological impacts, these fuel treatments unfortunately provide insufficient protection to homes during the types of fires that lead to the most home loss – those under extreme weather conditions, with Santa Ana winds. In these weather conditions, fires will not stop at a fuel treatment; in fact, flying embers have been known to jump major multi-lane freeways.
Therefore, our project is seeking solutions to substitute sole reliance on fuel treatments with a combination of approaches that not only provide the maximum public safety, but also reduce resource impacts. We are finding that the best solutions will not only include strategically placed fuel treatments near homes that provide firefighting access, but the addition of land use planning and other measures, like fire-safe landscaping.
3. The ecological impact of housing development
Perhaps the most obvious reason that land use planning and housing loss are related to conservation is the potential for direct habitat loss and fragmentation brought on by development. This is true not only for California, but for any fire-prone region in the world. If new homes are constructed, this will clearly expand the footprint of development and remove habitat to clear the land. And of course, there will simply be more homes available in the landscape to burn. However, given a fixed number of new residences that need to be constructed, our research is finding that the location and pattern of those homes makes a very big difference in whether or not the homes will be destroyed in a wildfire.
In particular, homes in low- to intermediate housing densities, in small, isolated neighborhoods, are the most at-risk, at a landscape scale; however, once a fire reaches a community, there is potential for house-to-house spread if the homes are too close together. Because scattered, low-density housing typically results in larger conversion of habitat, these results imply that building new homes in existing urban areas or in larger, high-density clusters may not only make the homes safer, but can also minimize habitat conversion.
Considering the tremendous economic impact of wildfires, from costs of fuel breaks and firefighting to property loss and fire insurance, we are finding that, like with so many other issues, ecology and economy (and in this case, public safety) really aren’t enemies. In fact, what’s good for one can be good for the other, and we are identifying solutions that are beneficial in all aspects. In southern CA, large wildfires are simply unpreventable. But we believe there are ways we can learn to live with them.