Stephens stated that wildfire can be destructive but is necessary for healthy forest regeneration. Credit: UC Berkeley / Scott StephensLightning-sparked fires in Yosemite’s Illilouette Creek Basin, which have been burning for nearly 50 years, have been a constant feature of the landscape. They are closely monitored but not controlled. They might ignite into heat plumes that can burn entire hillsides or burn the underbrush for several months.It is approximately 60 miles of forest, which is quite different from other Sierra Nevada areas. Instead of dense wall-to-wall trees, the result of over a century of fire suppression, the landscape is made up of patches of grassland shrubland and wet meadows that are filled with wildflowers, more plentiful than other parts. These gaps in the canopy can often be punctuated with the blackened husks from burned trunks, or the new green of young pines.Scott Stephens, co-director of Berkeley Forests and a professor of environmental policy and management at Berkeley University, said, "It really gives a glimpse into the Sierra Nevada 200 years ago."Stephens is the senior author in a new study. It combines decades of research to show how wildfire's return has affected the ecology of Yosemite National Parks' Illouette Creek Basin, Sequoia and Kings Canyon National Parks Sugarloaf Creek Basins. The parks adopted policies in the basins at Illouette Creek in 1972 and Sugarloaf Creekin 1968 to allow lightning-ignited fires.Although the idea of smoke rising from Half Dome is a concern for politicians and tourists, Stephens' research shows that the presence of fires in these basins has many ecological benefits. This includes increased plant and pollinator diversity, lessening the intensity of wildfires, and increasing water availability during droughts. The research shows that all these benefits will likely make the forest more resilient in the face of climate change's warmer and drier conditions."In many ways fire has been successfully restored to Illilouette and it has made for complex mosaics of vegetation with cascading effect on water," said Brandon Collins, study co-author and joint appointment with Berkeley Forests Research Scientists and the U.S. Forest Service. You can find patches of young trees that have been regenerated from fires 15 years ago or large, old trees with a lot of spacing. It's possible to have fire in areas that aren't burned, like near a creek or at the edge of a field. This complexity can be achieved in a very short time.These findings come at a crucial time in fire season. Drought conditions across the west have already caused numerous large wildfires in the West, including the Dixie Fire which was, as of August 8, the second-largest wildfire in California's history. Stephens stated that climate change may have contributed to the increased severity of these fires. However, Illilouette Creek Basin is an example of how the Sierra's current forest conditions, which are largely the result of decades of fire suppression, are also driving these large-scale blazes.Stephens stated that climate change is not more than 20-25 percent responsible for the current state's fire problems. The majority of the problem is due to the state's forests. "Illilouette Basin, which has no evidence of any changes in fire severity or fire size, is one of few places in the state that can provide this information. Even though climate change is affecting the ecosystem, the feedbacks it has on fire are so powerful that they don't alter the fire regime.Yosemite: Returning fireWildfires that were sparked by lightning or ignited by Native American tribes have been a constant feature of the American West for millennia. They not only cause destruction but also trigger necessary cycles of rebirth, and regeneration. The arrival of European colonists in late 1800s and the formation of the U.S. Forest Service (1905) marked the beginning of a new era where fire was seen as an enemy of both humans and forests.In the 1940s and 1950s, ecologists and forest managers began to question the wisdom and effectiveness of fire suppression. They noted that it was destroying valuable wildlife habitat and increasing fire severity by allowing fuel accumulation for decades. A. Starker Leopold was an acclaimed conservationist who is also a professor of zoology at UC Berkeley. Harold Biswell is a professor at UC Berkeley’s School of Forestry.Leopold's 1963 foundational report prompted the U.S. National Park Service to change its policy in 1968. Lightning fires were allowed to burn within designated fire management zones. These are remote areas at high elevations where danger to human settlements is low. In 1968, Sequoia National Parks and Kings Canyon National Parks created the first fire management zones. Yosemite National Park followed in 1972.This patch of wet meadow was created by a high-severity fire and is now full of wildflowers. Credit: UC Berkeley / Scott StephensCollins stated that "I believe it was finally acknowledged that fire is an integral part of these ecosystems and there were some key people who were willing the take the risk of letting these flames happen.""It's not always clean and it's sometimes not nice."Between 1973 and 2016, Illilouette Creek Basin experienced 21 fires larger than 40 hectaresapproximately equal to 75 football fieldswhile Sugarloaf experienced 10 fires of that size. The result of Illilouette is a forest today that looks messy but has a lot resilience."When people visit Illilouette they say, "Look at all these dead tree!" Stephens stated. Stephens said, "I think that we believe forests should be constantly green and populated only with big trees. It turns out, no forest can do this. It must be able regenerate and grow new trees. Illilouette does that, but it isn’t always clean and it isn’t always nice.Wildfire in Illilouette has provided a wider range of habitats for animals such as bees and bats while also allowing plants to thrive. Foresters have valuable information about the effects of wildfires on vegetation and landscapes in Illilouette."Fires can be set free in Illilouette. We could examine what happens when two fires burn close together: When does the second flame enter the same area as the first? And when does it stop at that perimeter? Collins said. Collins said. Fires that have been lit for less than nine years almost never burn into the fire line from a previous fire.Collins stated that Illilouette also gave forest managers the unique opportunity to examine how wildfire behaves in a variety conditions rather than just at its worst."One thing that is kind of perverse with the fire suppression policy, is that fires are only allowed to burn in the most extreme conditions. Collins stated that a mellow fire is a good time for putting it out. As a result, they burn only when we are unable to extinguish them. These fires can burn in Illilouette, so they're able experience all weather conditions. Some of these fires can really produce a good plume even on bad days. They can also burn in more moderate conditions and produce really diverse effects.The paradoxical effect of returning fire to Illilouette also increased the availability of water within the basin. This is a crucial finding in California's drought-prone year.Gabrielle Boisram (assistant research professor at Desert Research Institute, Nevada) is co-author of the study. She began studying water in Illilouette while completing her Ph.D. in environmental engineering at UC Berkeley. These simulations and measurements show that wildfires created small gaps in the tree canopy, which allowed water from snow and rain to reach the ground, and also reduced the number of trees competing with each other for water resources. Soil moisture in Illilouette rose by as much as 30% in 1969 to 2012, likely contributing to low tree mortality during drought years 2014 and 2015.Also, streamflow from Illilouette Creek Basin appears to have increased slightly since the managed fire program started. However streamflow from other watersheds in Sierras has decreased. It is possible to increase the flow of water downstream, which will benefit both humans and aquatic ecosystems that depend upon this precious resource.Boisram stated that there is more research being done on the effects fire has on hydrology. However, most of the other research focuses on the impacts of large-scale fires that have decimated entire forests. "We are the only western U.S. researchers that study a restored fire system. We're not looking at one fire but many fires of different severity that occurred over time. Because Sugarloaf was the first area in California to allow fires to burn, Illilouette is the only place that can study the long-term effects.The forest ecosystem at Illilouette Creek Basin has been transformed by frequent fire over the years, allowing for more variety in animal and plant life. Credit: Gabrielle BoisramFighting for the fireThe majority of U.S. national parks allow fire to be used, but not for full suppression. In 1974, the National Forest Service changed its policy to allow fires on its lands. However, fire use is rare within this agency. These federal fire use policies, however, have not been able to establish a foothold due to the inherent risks associated with managing wildfire.The study showed that even though Sugarloaf Creek Basin has seen many fires, there was significantly less fire suppression than Illilouette. The ecological benefits of Sugarloaf are therefore not as strong as those in Illilouette.Collins stated that one of the most important things to remember is that Illilouette's landscape was unique because it is higher than many of the forests we manage. It already had a mixture of vegetation and patches of rock, which I believe gave managers more freedom to let fires happen there. Because it lacks continuity, it doesn't have enough potential to generate a massive megafire.Although both prescribed and naturally-sparked fires can help the Sierra forests become more resilient to drought and high severity fires, there is strong opposition to California's national "let it Burn" policy. California state and local fire departments often prefer the safety of fire suppression.Both Stephens and Collins acknowledge that wildfire management is more difficult than ever because of the high fuel density in the Sierra. This, in addition to the warmer, drier climate triggered by climate changes, was the case when Yosemite forest managers allowed fires to burn in 1972. They argue that fire suppression won't work in the long-term because wildfires can become catastrophic if they are not sparked quickly."To allow this to occur, public and political institutions must be open to accepting risk because of the unpredictability. Stephens stated that there will be more fires and more intense burning in areas that have not had any fires for over a century. We can't promise that Illilouette will be the new outcome because it began when climate change wasn't nearly as severe. That means that political institutions will need to be flexible. Or else, the program will end with the first fire that does not do what we want.Stephens and Collins also support more aggressive prescribed burning and restoration of the Sierra to ensure that the forests can burn more safely.Stephens gives credit to Jan W. van Wagtendok (study co-author) for his strong leadership at Yosemite. He received a Ph.D. in 1972 from UC Berkeley and continued to be a researcher at Yosemite throughout his career.Stephens stated that although it has been 50 years since then, the lessons we have learned help us to see what is possible. We have 10-20 years to alter the state's forest ecosystems. If we don't, they will change in 10-20 years. It's important to keep doing this work.Sally Thompson of University of Western Australia, Lauren C. Ponisio of University of Oregon Eugene, Ekaterina Rakmatulina and Jens Stevens of UC Berkeley, and Zachary L. Steel of UC Berkeley are also co-authors of the study. Kate Wilkin of San Jose State University is also a co-author.Continue reading to learn how years of fighting wildfires have helped to fuel the Western megafires todayAdditional information: Scott L Stephens and colleagues, Fire, water and biodiversity in Sierra Nevada: A possible triple win, Environmental Research Communications (2021). Scott L Stephens and colleagues, Fire, water and biodiversity in Sierra Nevada: A possible triple win (2021). DOI: 10.1088/2515-7620/ac17e2
