North American Forests Could Face Increased Pest Damage From Climate Change

Rising global temperatures and shifting rainfall patterns could amplify tree pests and diseases across more than 80 per cent of North American forests within decades, according to a study published in Nature Ecology & Evolution. The research indicates that insects present the most immediate threat. More than 60 per cent of the examined areas are projected to experience 30 per cent more insect pressure by mid-century.

Pest Pressure and Forest Vulnerability

Species like the spongy moth are already causing heavy damage in Canadian forests and could expand significantly across eastern North America over the coming decades. Dr. Zihui Wang, a researcher in the Department of Botany at the University of British Columbia, explained the physiological mechanisms driving this vulnerability.

Wang noted that warm winters help overwintering pests survive in place, while concurrent heat and drought place additional stress on forest canopies. Stressed trees become far more susceptible to insect outbreaks and fungal pathogens.

The Intersection of Wildfires and Smoke Hours

Weakened and dry trees do not merely attract pests; they also create tinderbox conditions that intensify wildfire risks. Wang pointed out that dry wood provides a prime opportunity for fires, establishing a direct link between pest infestations, timber mortality, and blazes.

North American Forests Could Face Increased Pest Damage From Climate Change — Photo: Tree Frog creative

An increase in wildfire activity reliably translates into heavier smoke, which degrades regional air quality. Terri Lang, a meteorologist with Environment and Climate Change Canada, explained that the distinctive topography of British Columbia exacerbates this problem.

Environment Canada defines a smoke hour as any period when smoke reduces visibility to 10 kilometres or less.

City	2017 Smoke Hours	2018 Smoke Hours	2021 Smoke Hours	2026 Smoke Hours ( YTD )
Penticton	354	376	—	302
Kamloops	449	—	541	305

While daytime temperatures often help lift smoke and temporarily improve visibility, shifting wind patterns can spread wildfire smoke over vast distances and intensify fire behaviour.

Redefining Forest Management

The compounding pressures of disease, insects, and fire mean that historical approaches to conservation are no longer viable. Dr. Jonathan Davies, the senior author of the research, emphasized that rapid ecological transformation is already underway.

Climate change forestry — Photo: Ctvnews

This ongoing shift threatens critical carbon sinks, local air quality, and the broader forestry economy. Experts suggest that while no single remedy exists to reverse these trends, adaptive management can help mitigate future damage.

Wang noted that forest managers can monitor high-risk areas more closely and make intervention decisions earlier to protect vulnerable stands before outbreaks overwhelm them.