Why Worse Wildfires part 2

What’s Natural?

Why Worse Wildfires?  Part 2

Fighting the Ranch Fire

Why worse wildfires? The short answer is more humans cause more wildfire ignitions in altered landscapes. Since 1970, California’s population doubled, adding 20 million people. As more human habitat was developed, the increasingly disturbed landscape quickly became covered in easily ignitable invasive grasses (see part 1). To protect human habitat, fires were suppressed and ground fuels increased. Development also expanded a vulnerable electric grid. Furthermore, more people increased the probability of careless fires and more innocent accidents. And sadly, a larger population added more arsonists.

During a typically warm and dry July day, a rancher was innocently driving a stake into the ground to plug a wasp’s nest. Surrounded by dry grass, the hammer’s spark ignited a devastating inferno named the Ranch Fire. Despite sensationalist’s hype, global warming had not made the grass drier. Grass becomes highly combustible in just a few hours of dry weather. And like most of northern California, there has been no warming trend for maximum summertime tempertures. Based on Western Regional Climate Center data, maximum summer temperatures in the Mendocino area had cooled by 3°F since the 1930s. The rapidly spreading Ranch Fire soon merged  with a different fire to form the Mendocino Complex Fire, California’s largest documented fire.

Similarly, a highway accident sparked roadside grasses that kindled northern California’s 7th largest fire, the Carr Fire. 

Summertime cooling trend at Ukia,  Mendocino County, California

Careless fires cannot be considered accidents and offenders should be held accountable. A hunter’s illegal and improperly attended campfire caused the August 2013 Rim Fire, centered around Yosemite National Park. It was California’s 5th largest fire. 

Governments and utility companies should likewise be held accountable for carelessly maintaining our electric grids. An electric spark ignited California’s deadliest fire, the Camp Fire which destroyed the town of Paradise and killed 85 people. As a 2018 research paper estimates, “Since the year 2000 there’ve been a half-million acres burned due to powerline-ignited fires, which is five times more than we saw in the previous 20 years.” 

More disturbing is the number of fires started by arson. According to the U.S. Fire Administration, nationally, as in California, one in every five brush, grass, or forest fires since 2007 were intentionally set. Arsonists have been recently charged for some of California’s 2019 fires. Arson accounted for 55% of Kentucky’s fires and is the leading cause of Florida’s fires. Because arson is so difficult to prove, arson statistics are probably underestimated. So, experts in Australia combine arson and “suspicious” fires to argue half of Australia’s fireswere likely intentionally set. That means each year 31,000 Australian bushfires are intentionally ignited. And as in the American west, Australia’s bush fires have been increasingly fueled by invasive grasses like Buffel grass.

Wildfires caused by natural lightning ignitions, peak during the summer months of July and August, and become virtually non-existent in the autumn and winter. In contrast, human ignitions have created year-long fire seasons. Counter-intuitively, California experiences the most dangerous fire weather during the cooler and wetter seasons.  As seasonally cold air settles in over the high mountain deserts in autumn and winter, episodes of high winds, known as the Santa Ana and Diablo winds, flow downslope. Sinking air warms 5°F for every 1000-foot drop in elevation so these downslope winds can raise lowland temperatures 25°F in just a few hours. That warming causes relative humidity to fall, so these winds rapidly suck moisture out of whatever vegetation it passes over. In combination with faster spreading embers, fires burn 2 to 3 times more area during high wind events.

Human vs Lightning Wildfire Ignitions from Balch 2017

Under natural conditions, seasonally extreme winds never coincided with the season of abundant lightning. But due to human ignitions there has been an increased probability of more ignitions occurring during strong cool-weather winds. California’s 2nd biggest fire, the Thomas fire, was ignited in December by a downed power line during high winds. The third largest fire, the Cedar Fire was ignited in October by a lost hunter who carelessly lit a signal fire. California’s deadliest fire, the Camp Fire, was ignited by a powerline and fiercely spread due to a November high wind event.  

Climate change does not ignite fires. Climate change does not affect how quickly dead grasses and bushes can dry. Climate change may affect the winds, but any warming, natural or human, would reduce those extreme winds. Regards California’s worst fires, a US Geological Survey’s wildfire expert states, “Some will argue that it’s climate change, but there is no evidence that it is. It’s the fact that somebody ignites a fire during an extreme [wind] event.”

Jim Steele is Director emeritus of San Francisco State’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Contact: naturalclimatechange@earthlink.net 

Why Worse Wildfires? Part 1

What’s Natural?

published in the Pacifica Tribune, November 20, 2019

Why Worse Wildfires? Part 1

SAGE GROUSE LEKKING

There are several theories trying to explain the recent uptick in wildfires throughout the western USA. Some scientists blame increased human ignitions. Others suggest accumulating surface fuels due to a century of fire suppression. Others argue landscape changes and invasive grasses have amplified the amount of easily ignited vegetation, while still others blame climate change. What’s the Sage Grouse connection? Like human communities, the Sage Grouse’s habitat is being threatened by fast spreading wildfires, and that increase in bigger wildfires in sagebrush country is due to invading annual grasses, like cheatgrass.

Historically hot dry sagebrush habitat rarely burned (just once every 60-100 years) because slow growing, patchy sagebrush only provides scant surface fuels incapable of supporting large and frequent fires. But the invasion of introduced annual grasses, like cheatgrass, has changed all that. As one wildlife researcher lamented, “The color of Nevada has changed from a sagebrush silver gray to a cheatgrass tawny brown since the 1990s”.  Likewise, in the 1800s California’s hills were covered with perennial grasses that stayed green during the summer. Now California’s hills are golden brown as highly flammable annual grasses have taken over.

Cheat grass-dominated sagebrush habitat now burns every 3-5 years, up to 20 times more frequently than historic natural conditions. Extensive research on the effects of cheat grass found habitats with high cheat grass abundance are “twice as likely to burn as those with low abundance, and four times more likely to burn multiple times between 2000-2015.” What makes cheatgrass such a problem?

Invading annual grasses germinate earlier in the season and deprive the later-germinating native grasses of needed moisture. These foreign grasses die after setting seed, leaving highly flammable fuels that can burn much earlier in the year and thus extend the fire season. Eleven of the USA’s 50 biggest fires in last 20 years have been in Great Basin sagebrush habitats, where invasive cheatgrass is spreading. Nevada’s largest fire was the 2018 Martin Fire. Rapidly spreading through the cheat grass, it burned 439,000 acres, a burned area rivaling California’s largest fires in recorded history. 

Cheatgrass in Juniper Woodland

The 2012 Rush Fire was California’s 4^th largest fire since 1932, burning 272,000 acres of sagebrush habitat in northeastern California. It then continued to spread burning an additional 43,000 acres in Nevada. The 2018 Carr Fire was California’s 7^th largest fire and threatened the town of Redding, California. It started when a towed trailer blew a tire causing its wheel rim to scrape the asphalt. The resulting sparks were enough to ignite roadside grasses. Grassfires then carried the flames into the shrublands and forests, where burning grasses served as kindling to ignite less-flammable trees. Likewise, grasses were critical in spreading northern California’s biggest fires. In southern California, as humans ignite more and more fires, shrublands are being converted to more flammable grasslands.

Wildfire experts classify grasses as 1-hour fine fuels, meaning dead grass becomes highly flammable with just one hour of warm dry conditions. When experts estimate impending fire danger, they calculate the extent of a region’s fine fuels to determine how fast a fire will spread. The amount of small diameter fuels like grasses that can dry out in an hour, as well as twigs and small branches that dry out within 10 to 100 hours of dry weather, determine how fast the winds will spread a fire. It does not matter if it was wet and cool, or hot and dry during previous weeks or years. Just one hour of warm dry fire weather sets the stage for an explosive grass fire. Decades of climate change are totally irrelevant.

Some scientists point out that certain logging practices also spread “invasive grasses”. For that reason, California’s Democrat congressman, Ro Khanna, has been arguing that the U.S. Forest Service policy to clear cut after a wildfire is making California’s forest fires spread faster and burn hotter by increasing the forest floor’s flammable debris. Khanna warns, “Because we don’t have the right science, it is costing us lives, and that is the urgency of getting this right.” 

Bad analyses promote bad remedies and blaming climate change has distracted people from real solutions. The “cheatgrass” problem will continue to cause bigger fast-moving fires no matter how the climate changes. But there are several tactics that could provide better remedies. Holistic grazing that targets annual grasses before they set seed is one tactic. Better management of surface fuels via prescribed burns is another, as well as more careful logging practices. And re-seeding habitat with native perennial grasses or sagebrush could help shift the competitive balance away from cheatgrass. In combination with limiting human ignitions, (see part 2), all those tactics may ensure healthy populations of Sage Grouse living alongside safer human communities.

Jim Steele is Director emeritus of San Francisco State’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Contact: naturalclimatechange@earthlink.net