Strength-Diverse Wildfires May Encourage Biodiverse Landscapes

Source: Quanta Magazine

By Sophie Zhu

Above is a photograph of the Lassen and Plumas National Forests nine years after the 2000 Storrie Fire. Surprising to most, the area is thriving with resprouting black oaks and live conifers. 

Similarly, four years after the second-most terrorizing wildfire in California, the Tubbs Fire, ravaged through wine ecnoomies and homes, relics of the disaster go unnoticed by most. They are difficult to find—the forest quickly rebuilt. 

It turns out that regular controlled fires drive an area’s biodiversity. For over a hundred years, the US government has maintained its “fire suppression” policy. Now, biologists are revising their beliefs as studies of NorCal, South Africa, and Australia support the idea that fires inspire ecological growth. Of course, megafires would wrack nearby human civilization with loss and only do more harm than good, so laid-back, controlled fires are the ideal way to naturally encourage a little change.

The theory behind this is called the patch-mosaic hypothesis. Although any species or biocommunity needs stability to survive, too much stability can result in stagnation. Consistent but small interruptions in this idyllicity can divide the expansive landscape into “patches,” each of which becoming new microhabitats. For example, a couple trees falling down would open up the canopy and thus allow sunlight to reach dormant plants that lay on the forest floor. Disease outbreaks could locally eliminate a plant that, for years, has overpowered a smaller plant, creating an abundance of opportunity. 

Evan Furness, a Ph.D. student in ecology at Imperial College London, used a computer program called REvoSim with several colleagues to show that disturbance-structured biodiversity climaxed when habitats experienced both overall stability and micro-disturbances. 

This regrowth is not just restricted to plants. Critters that rely on underdog plants would thrive if overpowering ones are locally burnt to ash. Then there are other animals, such as certain birds species, that rely on these critters—an entire chain of animals would rise to the top. Ecologist Brett Furnas with the California Department of Fish and Wildlife noticed bigger increases in carnivore species and counts after low-severity fires.

However, the world’s current policy-molded conditions guarantee that only large, severe wildfires will occur. Combustible material has built up so much that any small fire would easily spread over tens of thousands of acres. 

Plus, many areas have been cultivated by humans to become a monoculture. For instance, Sonoma County has transformed from a forest of oaks and redwoods into thousands of rows of grapevines. The lack of biodiversity only spurred the area’s wildfires; pyrodiversity, which is the phenomenon that fire-dependent landscapes rely on fires of every size, is the key. With different areas of the landscape having different local plant and animal life, fires seep into those “patches” at different speeds. This way, the intensity of wildfires is fractured and controlled.

Of course, scientists warn that not all landscapes are fire-dependent. They emphasize that policy should not be vaguely imposing encouragement or repression of wildfires on all regions. Instead, it should require localized and specific studies of relevant forests that determine whether or not fires are necessary, and if they are, how control should be implemented.