Yosemite Creek Basin Case: When a Wildfire Isn’t That Bad 

Yosemite Creek Basin Case: When a Wildfire Isn’t That Bad 

When we hear the word ‘wildfire’, usually all we can imagine is the catastrophic aftermath, the smokes, the blaze, the poor wildlife, and the people relentlessly trying to stop it.  

But what if wildfires aren’t all that bad? What if can actually be good? 

Scott Stephens is the senior author of a new study that gathers together decades of research documenting how the return of wildfire has shaped the ecology of Yosemite National Park’s Illilouette Creek Basin and Sequoia and Kings Canyon National Parks’ Sugarloaf Creek Basin. 

In 1972 and 1968 at Illilouette Creek and Sugarloaf Creek, the parks allowed lighting-ignited fires to burn. While it’s worrying to see smoke, Stephens and his colleagues stated that frequent fires to burn in these basins has brought undeniable ecological benefits. 

In this case, wildfires can boost plant and pollinator biodiversity, limit the severity of wildfires and increase the amount of water available during periods of drought. Moreover, these benefits may make the forest more esilient to the warmer, drier conditions brought by climate change. 

Coauthor Brandon Collins said, “n many ways, fire has successfully been restored to Illilouette, and it has made for a complex mosaic of vegetationwith cascading effects on things like water. 

“In Illilouette, you can have patches of young, regenerating trees from a fire 15 years ago, or areas where a classic understory burn has resulted in big, old, widely-spaced trees.  

“You can even have areas where fire has missed because there’s more moisture, such as adjacent to a creek or on the edge of a meadow. All this complexity can happen in a really short amount of space.” 

The idea of wildfires vs reality 

Stephens agreed that climate change has played a role in increasing the severity of the fires. But he also stated that decades of fire suppression can drive these massive blazes. 

“I think climate change is no more than 20 to 25% responsible for our current fire problems in the state, and most of it is due to the way our forests are. Illilouette Basin is one of the few places in the state that actually provides that information, because there is no evidence of changes in fire size or in the severity of fires that burn in the area. 

“So, even though the ecosystem is being impacted by climate change, its feedbacks are so profound that it’s not changing the fire regime at all.” 

Before, wildfires were so common because of lightning or burning by Native American tribes. They did cause destruction, but at the same time they encouraged necessary cycles of rebirth and regeneration. 

In the late 1800s, followed by formation of the U.S. Forest Service in 1905, fire in forests were considered bad and so the majority of wildfires were quickly put out.  

It was only decades later, around the 40s to 50s, some forest managers and ecologists had begun to question the wisdom of fire suppression. They stated that it had been eliminating valuable wildlife habitat and increasing the severity of fires by allowing decades of fuel buildup. 

Therefore, in 1968, the U.S. National Park Service changed its policy, allowing lightning fires to burn within special fire management zones (remote regions at high elevations) where danger to human settlements was low.  

Collins said, “I think it was finally recognized that fire is an integral piece of these ecosystems, and there were a few key people who were willing to take the risk of letting these fires happen.” 

Sight of dead trees and devastation? 

Between 1973 and 2016, Illilouette Creek Basin experienced 21 fires larger than 40 hectares while Sugarloaf experienced 10 fires of that size. After letting all that fire ablaze, the forest we see today may look unfavorable. But according to the researchers, it holds a lot of resilience. 

Stephens said, “When some people visit Illilouette, they say, ‘Look at all these dead trees!’ I think we have this idea that forests need to be green all the time and made up with only big trees.” 

“But it turns out that no forest can do that. It has to be able to grow young trees and regenerate. Illilouette is doing that, but it isn’t always clean, and it’s not always nice.” 

In Illilouette, wildfire has created a more diverse array of habitats for animals like bees and bats, while allowing a variety of plant life to flourish.  

The detailed history of wildfires in Illilouette has also provided foresters with valuable information on how the impact of one wildfire on landscape and vegetation can influence the trajectory of the next wildfire. 

Collins stated that Illilouette has also given forest managers a unique opportunity to study how wildfire behaves under a variety of conditions, rather than only at its most dire. 

“By letting these fires burn [in Illilouette], they’re able to experience the full range of weather conditions. On bad days, some of these fires have really put up a pretty good plume. But on the flip side, they also get to burn under more moderate conditions, too, and it makes for really varied effects,” said Collins. 

Trying to bring fire back… 

Even though most U.S. national parks now practice some form of fire use, rather than full fire suppression, these policies have struggled to gain a foothold, largely because of the inherent risks involved in managing wildfire. 

The study found that in Sugarloaf Creek Basin, where many fires have been allowed to burn, there has also been significantly more fire suppression than in Illilouette. As a result, the ecological benefits in Sugarloaf are not as evident as those in Illilouette. 

Collins said, “I think one of the key things to recognize is that the landscape in Illilouette was already somewhat unique, partly because it is at slightly higher elevation than a lot of the forests we manage. 

“As a result, it already had a mix of vegetation with patches of meadows and rock, and I think maybe that gave managers a little more ease in letting fire happen there. It doesn’t have the potential to really push off a giant megafire because it lacks the continuity that some of these other areas have.” 

…amidst strong opposition to letting wildfires burn 

Moreover, there’s been a strong opposition to let wildfires be, particularly in California. Both local and state fire agencies often favor the safety of fire suppression.  

Stephens and Collins agreed that the current fuel density in much of the Sierra, mixed with the hotter, drier conditions already triggered by climate change, has made managing wildfire even riskier than it was. 

But they argued that fire suppression will never succeed in the long term, because the longer that forest fuel sources are allowed to build up, the more likely it becomes that wildfires will turn catastrophic when they are finally sparked. 

Stephens said, “In order to actually allow this to happen, political and public institutions need to be willing to accommodate risk, because there will be some unpredictability. There are going to be fires that get larger, and more severe burning in places that have had very little fire for a century or more. 

“We can’t guarantee that Illilouette is going to be the new outcome, because it started when climate change was not nearly as severe. So, political institutions will have to accommodate that, or the first fire that doesn’t do exactly what we hope will shut down the whole program.” 




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