Researchers studying water quality in the Fraser River found wildfires are boosting the concentration of heavy metals, such as arsenic, lead and other materials, like nitrogen and phosphorus, with potential health impacts to the river and Salish Sea.
A recent University of British Columbia study analyzed water quality in the Fraser River Basin north of Hope, along with two decades of wildfire data up to 2023, said lead author Emily Brown, at UBC’s Institute of Oceans and Fisheries.
Wildfires were found to be responsible for more than a 16 per cent change in water quality, Brown said. The Fraser River system is so large it naturally experiences water quality variances, but finding that wildfires alone created such a large change was unexpected, she said.
Water in the form of rain or melted snow transports wildfire ash, topsoil and other elements from burned areas into the river system that eventually empties into the Salish Sea.
Wildfires are a natural part of a healthy ecosystem and contribute in positive ways like introducing nutrients, such as nitrogen and phosphorus, into freshwater and marine environments vital for plant and animal growth, Brown said.
“We need wildfires to help cycle these nutrients and compounds through the environment,” she said.
However, the increasing frequency and severity of wildfires aggravated by climate change may be tipping the scales the wrong way.
“Too much of a good thing is a bad thing, you know?” Brown said. “We can have too much of these compounds and that can cause issues.”
Excessive nitrogen or phosphorus can trigger harmful algae blooms that can strip oxygen from the water and be toxic to other aquatic life like frogs or fish. Heavy metals like arsenic and lead also occur naturally, but at elevated levels are poisonous or lethal for aquatic life, she added.
“Some of the metals we identified are close to the thresholds of harm for freshwater life like fish or invertebrates living in the river.”
Increased levels of toxic metals in the Fraser can also find their way into the Salish Sea where they can accumulate in shellfish, which is potentially harmful to human health, she said.
Fires burning close to the Fraser impacted water quality in short order, Brown said.
But water quality from blazes farther away is still affected as much as a year later because wildfire residue and contaminants can get trapped under snow and later find their way into the watercourse during spring melts.
Climate change may also be changing the ocean’s capacity to sink the carbon generated by wildfires in the seabed — which prevents it entering the atmosphere and boosting global warming, another study by Brown suggests.
“Our research is showing that as climate change is changing the hydrology of the Fraser River, then we could see more of black carbon being a source of carbon dioxide to the atmosphere than sinking into the sea floor.”
Black carbon, a by-product of burning trees, was typically thought to travel down the Fraser to the ocean before sinking to the seabed of the Salish Sea to be stored in sediment.
But as global warming advances, the Fraser is becoming a river fed by rain rather than melting snow — changing the type of black carbon transported downriver, Brown said.
Smaller particles that break down more easily are now being transported by the Fraser, Brown said. And instead of sinking, they float.
“They kind of sit at the top of the ocean and get degraded and can re-enter the atmosphere as CO2.”
More research is needed to understand how climate change is shifting the transport of black carbon and how it might be stored, the study determined.
Both studies underscore the connection of land and water systems and the need to better understand how major terrestrial disturbances, like wildfires, have important ripple effects in rivers and oceans, she said.
“Research is often focused on one area with people looking at land, rivers or oceans separately,” Brown said.
“This [research] shows it’s really important we are thinking across these boundaries and that managers of land and water systems should be considering how events on land, including wildfire, can affect aquatic ecosystems.”
Rochelle Baker / Local Journalism Initiative / Canada's National Observer
Comments