MEETING REPORT: Creating Defensible Spaces in the Age of Megafires



By Lynn Langley.

With the first real rain of the season falling outside during our January meeting, Gary Ferguson, author of Land on Fire, shared some of his extensive knowledge of California fires. He began with some sobering facts: there have been 9,000 fires since July, 2017; nearly $500 million has been spent to fight fires in California in the past six months; the federal government has spent more than $300 billion on natural disasters in 2017.

To Gary, the forces of fire profoundly shape the landscape. These forces determine the types of flora and fauna growing in an area, as well as the spacing and shape of trees. Due to California's dry climate, fire is the only way for biomass to get back into the soil. After a healthy fire, there is 20-22% more enrichment in the soil. Plants and animals depend on this additional enrichment to assist in fire recovery. After the big fires in Yellowstone National Park, lodgepole pines were found to be reseeding at 100,000 trees per acre. Animal mortality is also not as high as previously thought. Most animals were able to move away from the Yellowstone fires—as few as forty-four elks died. Birds and insects were the first to reinhabit the burned out areas, taking advantage of tree trunks with newly available spaces for nesting and feeding. Healthy fire cycles had been the norm until recently. We have moved into the megafire era, which is an entirely different situation.

Megafires (fires encompassing at least 100,000 acres) are becoming more prevalent. The last twelve years have seen a dozen or more megafires each year. Megafires can sterilize the soil, making it impossible for plants to reseed. They can also create hygrophobic soil that can’t absorb water. These fires burn hotter, can create their own weather, and are more difficult and dangerous for firefighters. Since the 1970s, megafires have caused a death rate among wildfire fighters that is six times that of urban firefighters.

Gary sees two primary reasons for this change from healthy fire cycles to megafire cycles. The first is the seventy years of fire suppression policy followed by the U.S. Forest Service. As a result, there are now over 300 million acres of excess fire fuel in forests in the western United States. The second reason for the shift to more megafires is climate change. There has been a seventy-five-day increase in the length of the fire season in the west since the 1970s. In 2018, for the first time ever, the California fire season will be year-round. Since 1985, human caused climate change has almost doubled the number of acres burned annually in the drought-ridden American west. Continuing in this way, by 2050 there is an 80% chance that drought cycles in California could last 25-30 years.

Warmer temperatures and less rainfall due to the changing climate is and will profoundly affect California. In 2016, sixty-two million trees were lost in the state. The ongoing drought has not only killed trees outright, but weakened millions of others, making them more susceptible to disease and infestations of pine bark beetles. Invasive species (like cheat grass) come into freshly burned areas, crowd out native species, and become fuel for new fires. It is more important than ever for defensible fire spaces to be created. Gary ended his presentation by introducing a representative from Fire Safe Council of San Diego County, who provided several sources to learn how to create defensible fire spaces. Cal Fire and the California Native Plant Society also provide fire-resistant landscaping ideas, including plant recommendations.

#201802

  

Our Mission  To inspire and educate the people of San Diego County to grow and enjoy plants, and to create beautiful, environmentally responsible gardens and landscapes.

 

Our Vision   To champion regionally appropriate horticulture in San Diego County.

  • Facebook Social Icon

© 2019 San Diego Horticultural Society