When a severe wildfire transforms tens of thousands of acres of forest into a massive burn scar, the torched trees and charred homes are just the beginning of the problem. Long after the flames have been extinguished and the smoke cleared, the burned landscape can still threaten people living nearby in a number of serious ways.
As of last week, wildfires had torched more than 1.2 million hectares of land across the US this year. Fires are burning right now in California, Oregon, Washington, Montana, Idaho, and Alaska. Arizona, Colorado and Nevada suffered their share of massive blazes earlier this summer, including the deadly Yarnell Hill fire that killed 19 of Arizona’s top firefighters.
In Canada, the northern boreal forest has been burning for months, but the wildfire season there has only just kicked into high gear. There were at least 100 lightning-related wildfires in north-central British Columbia over the August long weekend alone, with the fire danger rating set to “extreme” in some areas.
The recent upward tick in fire frequency and area burned has been attributed to a number of factors. First and foremost is climate change, which has brought both drought and insect infestation, priming the forests for fire. Combined with expanding human development and long-term forest management approaches that have altered natural fire cycles, the table is set for large mega-fires with major effects on humans.
Wildfire and water
It’s a cruel reality that severe wildfire – which results from hot, dry conditions that are exacerbated by climate change – can cause serious water availability and water quality problems. Mountain regions are particularly sensitive to post-fire water problems due to the combination of steep terrain, relatively shallow soil, and high-intensity events like spring snowmelt and summer thunderstorms.
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Picture a severely burned and an unburned forest side-by-side. The unburned forest is a green net strung across the landscape, catching falling rain and snow and slowly transferring it to the ground. The burned forest, however, is a tangle of standing snags and fallen trees, a monochromatic landscape of silver and black trunks pointing up at the sky with minimal ability to catch raindrops or snowflakes.
In the winter, burned forests collect far more snow than unburned forests, which is then stored in the snowpack for the following spring. Without a protective tree canopy to provide shade, the stored snow melts earlier in the spring, and is much more likely to melt all at once. A large wildfire in the summer, then, can set the stage for dangerous flooding the following spring.
It’s not only trees that burn during a wildfire, though. The soil itself turns into a patchwork of water-repellent burned soils and obliterated organic matter. Instead of soaking into the ground to replenish groundwater reservoirs, rain and snowmelt run across the burned land into streams and rivers to be carried downstream. This can lead to flooding – and even drinking water shortages – down the line.
In 2012, after fire tore through the area around Manitou Springs, Colorado, the town was inundated by mudslides and floods. Earlier this month, flash flood warnings were issued for areas of New Mexico downstream of the May 2013 Jaroso burn scar.
It’s not just the volume of stream runoff that is an issue: The dirt and debris it carries can cause its own problems. In New Mexico, irrigation ditches are clogging with wildfire ash washed out of the mountains by monsoon rains. For residential water providers, debris-laden water – and the contaminants that come with it – may not be treatable without major upgrades to water treatment infrastructure. Following the High Park and Hewlett Gulch fires of 2012, drinking water quality in Fort Collins and other Colorado communities took a serious hit. In the aftermath of the 2002 Hayman fire, the Denver Water utility was forced to invest $17m in dredging the Strontia reservoir, which was clogged with downed trees and wildfire debris.
With death and destruction driving the conversation, it becomes ever more important that we don’t lose sight of the ecosystem benefits of less severe fires.
Each year, billions of dollars are spent fighting wildfires. Given recent US budget cuts, future fires will need to be attacked quickly and hard to keep them from spreading, and resources will likely need to be siphoned from other programmes to cover the costs.
With the immediate spectacle of catastrophic wildfire looming over their communities, people can’t be blamed for wanting no cost spared to save their homes, livelihoods and communities.
But though they may breathe a sigh of relief when the flames are out and the smoke clears, their troubles – and the associated costs – have only just begun.
Fires are not all bad
Although severe, high-intensity wildfires have been dominating the headlines in recent weeks, moderate fires can actually be good for the landscape, and, by extension, for humans. When managed as a natural part of the environment, less intense fires can actually increase the health of the environment and build resilience to larger fires by reducing fuel buildup and renewing forest growth. In the past, groups of First Nations, or indigenous Canadians, burned swaths of forest to maintain their food supplies. As reported recently by the CBC, a northern British Columbia First Nation group is bringing fire back to the landscape to help local wood bison.
The trick is to find the balance between forests and people in a highly sensitive landscape stretched to the limit by suburban development, and to build the political will to support unpopular policy decisions around wildfire management and development in fire-prone regions. The US Department of Agriculture’s Forests to Faucets initiative is a bold step forward in this direction, designed to maintain overall forest health in order to manage water supplies. It even includes a “payment for watershed services” programme, in which local residents can be reimbursed for maintaining watershed health for downstream users.
Climate change and its associated insect infestations and drought, as well as rapid development in fire-prone regions, are increasing the frequency, intensity and human cost of large wildfires. With death and destruction driving the conversation, however, it becomes ever more important that we don’t lose sight of the ecosystem benefits of less severe fires, or the cascading effects of wildfire on water quantity and quality.
After all, even after the fire’s out, the problems have just begun.
Sarah Boon, PhD is a hydroecologist and science writer and editor. Her research focuses on forest and water management in western Canada.
Follow Sarah Boon on Twitter: @SnowHydro