Wildfires are increasingly recognized not only for their immediate destruction on landscapes and communities but also for their profound and complex impact on aquatic ecosystems. Recent research from the University of British Columbia (UBC) has illuminated the insidious ways in which forest fires affect water quality and carbon cycling within major river basins, with potential far-reaching consequences on marine environments and climate dynamics. This groundbreaking study, led by Dr. Brian Hunt, professor at the Institute for the Oceans and Fisheries (IOF), alongside research scientist Emily Brown, sheds light on the cascading effects of wildfires on freshwater systems and the ocean’s ability to act as a carbon sink.
Focusing their investigation on the expansive Fraser River basin in British Columbia, the team analyzed two decades of environmental monitoring data collected by Environment Canada. Their analysis revealed a clear connection between wildfire events in the basin and the subsequent deterioration in water quality, marked by sharply increased concentrations of toxic compounds such as arsenic and lead. Alongside these heavy metals, nutrients like nitrogen and phosphorus also surged after fire events, creating a nutrient imbalance that threatens aquatic life.
The researchers quantified that wildfires account for up to 16.3 percent of the variations in water quality within the Fraser River system. Considering the river’s inherently high natural variability, attributing such a significant fraction of change to a single factor like wildfire disturbance is both striking and concerning. Although the majority of the Fraser River water is not directly used for drinking, and treatment processes mitigate human health risks, the downstream ecological repercussions may be severe. Enhanced nutrient loads can trigger harmful algal blooms, including toxic varieties, which deplete oxygen levels and devastate fish, shellfish, and other aquatic fauna.
Brown further highlights that the spatial and temporal effects of fire on water quality differ based on proximity to waterways. Fires burning in immediate riparian zones caused prompt changes in water chemistry due to rapid mobilization of ash, contaminants, and nutrients. In contrast, fires occurring further from rivers manifested delayed impacts, sometimes emerging up to a year after the event. This nuanced temporal pattern complicates monitoring and management efforts but underscores the prolonged influence wildfires exert on hydrological systems.
The intensity and frequency of wildfires across British Columbia are intensifying as climate change progresses. Increased wildfire activity may therefore worsen water quality conditions in the Fraser basin and similar ecosystems, threatening biodiversity and the stability of regional aquatic food webs. Simultaneously, this dynamic raises questions about the ocean’s role in global carbon cycling, particularly concerning black carbon and dissolved organic carbon export downstream.
Black carbon, a particulate residue of incomplete combustion of organic material during wildfires, undergoes a notably slow cycling process in the environment. When transported via riverine networks to coastal oceans, black carbon can become buried, potentially sequestering carbon for extended periods and acting as a sink that mitigates atmospheric CO₂ levels. However, the researchers caution that this natural carbon sequestration process may be at risk due to changing hydrological regimes driven by a warming climate.
According to Brown and Hunt, the Fraser River currently depends heavily on snowmelt to feed its waters, which supports the transport of more stable forms of black carbon. Climate projections suggest a projected shift toward rain-dominated flows in the future, subsequently increasing the export of more labile, rapidly degradable dissolved black carbon. This change could accelerate the breakdown of carbon compounds, releasing carbon dioxide back into the atmosphere and diminishing the ocean’s capacity to mitigate greenhouse gas levels efficiently.
This emerging understanding places greater urgency on integrating wildfire impacts into broader environmental and climate resilience planning frameworks. Dr. Hunt emphasizes the need for interdisciplinary research that comprehensively examines the chain reactions initiated by wildfire occurrences—from terrestrial landscapes through riverine networks, to coastal marine ecosystems. Identifying sensitive indicators of wildfire effects enables more precise water quality monitoring post-fire, helping stakeholders anticipate and manage environmental risks.
Moreover, the research foregrounds the importance of Indigenous knowledge and fire stewardship practices in shaping sustainable landscape management. Historically, Indigenous nations in the Fraser River basin have used fire strategically for millennia to maintain ecosystem health and protect communities. However, colonial fire suppression policies have disrupted these natural fire regimes, leading to an unnatural accumulation of combustible materials and setting the stage for more severe fires today.
Brown advocates for a restoration of natural fire cycles through increased support for Indigenous-led cultural and prescribed burning initiatives. Removing bureaucratic obstacles related to jurisdiction and permits, providing sustained funding for training and equipment, and empowering Indigenous governance frameworks represent critical steps toward fostering resilient landscapes and water systems under a warming climate.
As British Columbia grapples with escalating wildfire seasons, these findings call for urgent policy responses that recognize fire as a multifaceted ecological driver. Water quality degradation, shifts in carbon sequestration potential, and ecosystem health are intricately linked to wildfire regimes, demanding integrated management strategies that span forestry, hydrology, and oceanography.
This research breaks new ground by illuminating the hidden yet powerful role of wildfires in shaping not only terrestrial but aquatic and atmospheric processes. The implications extend beyond the Fraser River basin, offering a valuable lens through which other regions vulnerable to fire-climate feedback loops can examine and prepare for their changing environmental futures.
In conclusion, UBC’s investigation into wildfire impacts on water quality and carbon dynamics underscores the complexity of climate change effects on interconnected natural systems. Better understanding these links is pivotal for developing adaptive, science-based approaches to ecosystem management. Equally important is honoring and revitalizing Indigenous fire stewardship traditions that historically balanced fire’s destructive and regenerative potentials.
As wildfire incidence and severity are projected to increase globally, such comprehensive research is essential for safeguarding water resources, protecting biodiversity, and ultimately mitigating climate change impacts through informed, culturally respectful stewardship and scientific insight.
Subject of Research: Impact of wildfires on water quality and ocean carbon sequestration in the Fraser River basin
Article Title: Not provided
News Publication Date: Not provided
Web References:
- https://www.sciencedirect.com/science/article/pii/S0048969725010538
- https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024JG008627
References:
- Journal: Science of The Total Environment
- DOI: 10.1016/j.scitotenv.2025.179416
Image Credits: Not provided
Keywords: Water quality, Wildfires, Climate change, Anthropogenic climate change, Climate change effects, Black carbon, Dissolved organic carbon, Atmospheric carbon dioxide, Nitrogen, Phosphorus, Chemical elements, Ocean chemistry, Oceans, Carbon sinks
