Wildfires and their lesser-known impact on water

Forest fires can impact the water as well as the air | CBC News

This summer, Northwestern Ontario experienced a large number of forest fires. The skies were cloudless, and the air reeked of a campfire for days on end. With climate-changing altering precipitation patterns, it’s projected that what we experienced this summer is only the beginning.

Most of the talk around wildfire impacts is around air quality. Throughout this summer in Thunder Bay, there were multiple air quality warnings which were coupled with low visibility and the smell of smoke. Air quality is a major concern with wildfires due to soot, ash, and other particles and compounds that are released into the air as a result of the burning forests.

Wildfires in western North America have made global headlines in recent years due to their size and level of destruction. These disasters displace residents and impact ecosystems. Wildfires are a natural disturbance and they can help regenerate ecosystems, but only to a point.

A warming climate is leading to more frequent, more severe, and larger forest fires that are causing more damage to ecosystems than regeneration. Air quality has always been a major concern with forest fires, but water quality issues due to forest fires are going to become more and more prevalent.

In Waterton Provincial Park in Alberta, Cameron Falls typically runs clear but after a large wildfire that was then followed by a large storm event, the clear blue falls turned to black. The blackness of the water is due to a large amount of soot, ash, burnt and burnt woody debris. Water levels become elevated with dissolved organic carbon, sediments, and toxins such as mercury that are found naturally in soils and tree trunks but become concentrated in the water when fires and storms come together.

Cameron Falls runs black with soot and charred debris on June 21 one year  after a fire burned … | Waterton lakes national park, Parks canada,  Landscape photography
Cameron Falls running black after wildfires and storms

In areas such as Fort McMurray where wildfires have nearly decimated the town, the wildfires have caused issues for drinking water facilities. When dissolved organic carbon and chlorine mix they can create carcinogens such as trihalomethanes (THMs) and haloacetic acids (HAAs) that are often beyond the capacity of the facility to handle.

Researchers in Waterton have looked at sediments in the park and found high levels of nitrogen and phosphorous in the black muds that form after an event. High levels of nitrogen and phosphorous are precursors for algae blooms which have their own laundry list of negative impacts on oligotrophic aquatic systems.

Wildfires do have beneficial impacts on aquatic ecosystems through increasing coarse sediments and nutrients that are important for many fish species. Although increased nutrients and good habitat from large sediments are beneficial, mercury contamination can become a concern. As mentioned above, mercury stored in the soils and tree trunks gets released in forest fires and concentrates in the water. The increase in other nutrients leads to a plethora of other organisms such as invertebrates. Mercury bioaccumulates and fish such as trout and herring tend to have high mercury levels following wildfires due to feasting on the abundant invertebrates.

Many cities around the world rely on forest watersheds for their drinking water. Increasing intensity and frequency of forest fires are not only going to negatively impact air quality, but coupled with large precipitation events are also going to cause many problems relating to drinking water and aquatic environments.

Climate change is a wicked problem that isn’t going anywhere. The impacts are far-reaching for human and environmental health. Many impacts of climate change are still to come and our systems currently don’t have the capacity to cope with the changes expected to come. Clean water is essential for life and wildfires threaten communities that rely on forest watersheds.

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