Wildfire Smoke May Be Disrupting Ocean Carbon Storage

New research from the University of British Columbia reveals that wildfires could be fundamentally altering how our oceans store carbon, potentially turning a crucial climate ally into a source of atmospheric carbon dioxide.

The study analyzed 20 years of water quality data from Canada’s Fraser River basin, finding that fires explained up to 16.3% of water quality changes—a surprisingly large impact for such a vast river system.

Delayed Effects Pack the Biggest Punch

The research uncovered something unexpected: while fires near waterways affect water quality immediately, the most dramatic changes occur 7-10 months later during spring snowmelt. “Using monitoring data collected by Environment Canada over the last 20 years, we calculated that up to 16.3 per cent of the variation in water quality could be attributed to wildfires,” said Dr. Brian Hunt, professor in the Institute for the Oceans and Fisheries.

This timing matters because it coincides with when rivers flush massive amounts of material into coastal waters. The study found that this delayed flushing carries elevated levels of nitrogen, phosphorus, and toxic metals like arsenic, cadmium, and lead into marine ecosystems.

The Carbon Storage Problem

Perhaps most concerning is how fires might be disrupting the ocean’s role as a carbon sink. Black carbon formed when trees burn normally cycles slowly in marine environments, helping sequester carbon from the atmosphere when buried in ocean sediments.

But climate change is shifting the game. “Most of the water in the Fraser River currently comes from snowmelt, but with climate change, this could shift to being more rain-driven in the future,” explained Emily Brown, research scientist at the Institute for the Oceans and Fisheries. This change could lead to “more rapidly degradable dissolved black carbon being exported to the ocean,” meaning carbon sequestration may weaken and black carbon could become an additional source of atmospheric CO2.

Marine Food Webs at Risk

The study revealed that fire-driven changes cascade through entire ecosystems. Increased nutrient loading can trigger excessive algae blooms that ultimately deplete oxygen levels and harm fish, shellfish, and other marine animals. This poses particular challenges for the Salish Sea, where the Fraser River deposits its contents.

What makes this research particularly significant is its scale. Previous wildfire-water quality studies focused on small streams near burn sites. This analysis examined cumulative effects across an entire major river basin—the Fraser drains one-quarter of British Columbia’s land area.

An Indigenous Solution

The researchers point to Indigenous fire management as part of the solution. “Indigenous nations have applied fire to these landscapes for millennia to manage resources and protect their communities,” Brown noted. Colonial fire suppression has led to dangerous fuel buildup across the province.

The study calls for returning British Columbia to more natural fire regimes through Indigenous-led stewardship, including increased cultural and prescribed burning, removal of regulatory barriers, and establishment of Indigenous-led governance structures.

Future Implications

As fire seasons intensify globally, understanding these water-ocean connections becomes critical. The Fraser River system influences the biogeochemistry of its receiving waters in the Salish Sea, making these findings relevant for coastal ecosystems worldwide.

Researchers emphasize that while drinking water treatment protects human health, the downstream marine impacts could worsen as fire frequency and intensity increase. This research provides a new lens for understanding how terrestrial disturbances ripple through interconnected Earth systems—from forest to river to ocean.