the vicious relationship that humans must end
As the 2021 wildfire season begins to unfold, memories of seasons past linger – in the lungs of people, in the communities and landscapes that have burned down, and in the atmosphere, where greenhouse gases forest fires continue to warm our planet.
Forest fires have wreaked havoc around the world over the past year. In Australia, the bushfires spanning the period 2019-2020 caught public attention as videos of burnt koalas and wallabies circled the internet.
Fires burned in Arizona and Colorado during the first waves of COVID-19. In Siberia, boreal forests and tundra fires burned down in the far north. And with the onset of fall, Washington and Oregon began to burn, with the consequences felt in the United States and Canada, with smoke and COVID-19 keeping people inside.
When it comes to climate, forest fires occupy an unusual space: they are fueled by climate change and help to drive it. As this vicious cycle unfolds and predictions of future extreme fire seasons continue, the need for human intervention to interrupt this cycle has never been clearer.
Greenhouse gas release
Climate change is raising average global temperatures, resulting in longer droughts, with cascading effects on forests and forest fires. These impacts are highly location dependent – they are determined by an ecosystem’s ecology and its history of disturbances, such as forest fires, insect outbreaks or logging.
In many types of forests, rising temperatures and droughts dry out fuels, including vegetation such as dead trees and fallen branches, more quickly and completely, causing them to burn.
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In some forests in California and British Columbia, the effects of weather can reduce the snowpack and accelerate spring snowmelt, which can lead to even drier vegetation and increase the risk of fires. In drought-prone ecosystems, such as parts of the southwestern United States, long stretches without rain can kill trees and leave dead wood ready to burn.
As a driver of climate change, forest fires release huge amounts of greenhouse gases into the atmosphere. In British Columbia, the extreme fire years in 2017 and 2018 each produced three times as many greenhouse gases as all other areas of the province combined. While trees can and do grow back after a fire, replenishing carbon takes time, which is precisely what we are lacking in the fight against climate change.
This does not mean that climate change is the only cause of massive forest fires, and that greenhouse gas emissions are not the only consequence. People, especially European colonizers in North America, created and perpetuated conditions that increase the risk of large-scale fires. We are just one of the many species that suffer the consequences.
An interrupted fire cycle
Fire has long played an important role in maintaining the health of many types of forests. For example, lodgepole pine depends on fire to reproduce by melting the resin that releases its seeds.
In the early part of the 20th century, the ban on Indigenous controlled burning and fire suppression policies interrupted the fire cycle that forests evolved in and eliminated the fires that regularly occurred in forest areas.
Excluding fire from temperate landscapes has disrupted ecosystem mosaics and recently burned areas that had once moderated the spread and behavior of fires. Logging and timber practices, such as clearcutting and replanting, have also altered the risk of fire by favoring evergreen stands of almost the same age that can quickly carry and spread fire.
As the consequences of 20th century forest management unfold, people continue to alter fire regimes by unintentionally starting fires and developing previously wild areas. By continuing to burn fossil fuels, humans further exacerbate climate change and fire risks, independent of forest management.
How do forest fires alter the carbon sink?
The growing expectation of governments and policymakers that forests and trees will offset and compensate for our continued use of fossil fuels further complicates the grim picture of wildfires. Increasingly serious and larger fires could derail this plan.
Most forests are carbon sinks, which means they absorb more carbon than they release, with the amount of carbon absorbed varying with age. As plants photosynthesize, they extract carbon dioxide from the atmosphere and incorporate it into their leaves, roots, and biomass. Over time, this leads to significant carbon stocks in forests, stored in vegetation and, above all, in soils. In cold high latitude environments, even more carbon is stored in permafrost soils.
Fires, along with other disturbances, release this carbon into the atmosphere, reducing the carbon stocks that have built up over time. Forest fires can also initially reduce a forest’s ability to extract carbon from the atmosphere, also known as “sink force”. Severe fires can inhibit the regrowth of forests and change the species composition of the forest. Overall, forest fires increase the amount of carbon leaving forests and can reduce the amount entering.
Forest fire season forecast
While predicting the intensity of fire seasons is not foolproof and has its own limitations, many parts of Canada and the United States face higher than average fire risk this summer, according to forecasts. . Extreme drought is raging in the western United States and the Canadian prairie provinces, the effects of which are reflected in the high fire risk forecast for these same coastal and southwestern regions.
Despite these projections, forest fires are not an anomaly and, for many landscapes, they are a critical process that maintains ecosystem health. But the forest fires of the past burn differently from the forest fires of the present, and now humans and wildlife are in great danger.
Humans, however, can also intervene to interrupt this cycle, with practices like prescribed burning and thinning of forests that can increase the resilience of forests. This is an active area of research and many scientists, including a team from Canada and the United States, are working to develop scientifically sound interventions.
Climate change doesn’t work like an on / off switch, which means forest fires are not part of a ‘new normal’. We are experiencing the effects of climate change, but they will not be consistent or uniform. Climate change is more like a slide, and when it comes to forest fires, we are spiraling down quickly.
Carly Phillips, Researcher-in-Residence, Pacific Institute for Climate Solutions, University of Victoria
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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