Forest Health in a Changing Climate

• Study resources have been provided to assist with learning about Forest Health in a Changing Climate.

Forest health in a changing world

• Globalization and climate change effects on forest insect and pathogen impacts are becoming more common.
• Expanding international trade has facilitated the invasion of insects and pathogens into new regions.
• Invasive species are causing substantial forest damage and economic impacts.
• Climate change is affecting the geographic distribution of host trees, and resulting increased pest impacts.
• Interactions between invasive pests and climate change outcomes are poorly understood and difficult to predict.
• Sustainable forest management, global trade networks and an increase in the volume of traded goods have had a considerable impact on tree populations.
• Emerald ash borer has been devastating ash trees in North America, while Phytophthora ramorumis causing dieback and mortality of a wide range of tree species in Europe and North America.

How Wildfire Impacts Wildlife and Forests

• Wildfires are inevitable, but not all fires are harmful to forests.
• Low-intensity fires can naturally "clean" and thin forests, and reduce large-scale high-severity fires.
• High-severity fires across large landscapes can be devastating for wildlife, forests and surrounding communities.
• High-severity fires may destroy nearby communities while low-intensity fires help maintain forest health.
• Loss of habitat and food sources is a result of high severity fires.
• Runoff containing ash and debris from high severity fires degrades water sources.
• Native re-vegetation and ashes enrich soils after low-intensity fires.
• Tree trunks and roots stay intact in low-intensity fires, keeping forests and minimizing soil erosion.

Forest Pest Management

• Native insects and diseases play an essential role in the ecological balance of Canada's forests.
• Forest insects and micro-organisms contribute to change and regeneration in forest ecosystems.
• Insects and diseases renew forests, recycle nutrients, provide new habitats, and food sources.
• Forest insects and diseases sometimes make national news when infestations are severe.
• Severe infestations may destroy commercially valuable forests, or infest Canadian forest products.
• Mountain pine beetle, spruce budworm, and Dutch elm disease are examples of forest pests causing significant losses.
• Forest insects and diseases in Canada are classified as: native, alien, and invasive.
• Native species have existed in Canada for years, alien species introduced recently.
• Invasive species are insects/diseases that spread beyond their known usual range.
• Native forest insects and diseases are of little concern when they exist at non-damaging population levels.
• Ecological or economic damage results when native species increase beyond an acceptable threshold.
• Forest resource managers is required to assess the risks posed by potential outbreaks and apply risk-based decision-making to manage outbreaks.

Biotic Pathogens

• Bacteria are single-celled organisms that lack a true cell nucleus but have a single chromosome.
• Only a few pathogenic bacteria attack trees.
• The majority of forest pathogens are fungi, belonging to Basidiomycotina, Ascomycotina or Deuteromycotina divisions.
• Deuteromycotina reproduce asexually by producing conidia on conidiophores or within special structures.
• Ascomycotina reproduce sexually by producing 4-32 ascospores inside sacs or asci, within structures called ascomata.
• Ascomata may be cup-shaped (apothecia), bottle-shaped (perithecia), or balloon-shaped (cleistothecia).
• Basidiomycotina reproduce sexually by forming basidia, which produce four basidiospores on a structure called ascoma.
• Rusts are Basidiomycotina that function as obligate parasites and have a complex life cycle that requires a host.

Forest Pests and Climate Change

• Many of Canada's forest pests and diseases have become household names in recent years.
• The emerald ash borer has aggressively attacked eastern Canada's Green Ash trees.
• The mountain pine beetle destroyed British Columbia's Lodgepole Pine trees from the late 1990s-2010s.
• Dutch elm disease is slowly stripping cities and towns across eastern and central Canada American Elms away.
• Forest pests and tree diseases act as disturbance agents but climate change is worsening the situation.
• Warmer winters and summers are leading to the massive insect damage.
• Climate change has resulted in less mortality of mountain pine beetles.
• Mountain pine beetles are attacking jack pine and forestry researchers see climate change as a risk.
• Hotter summers allow ash borer populations to undergo two reproductive cycles.
• Deep winter cold spells that are needed to limit many pests outbreaks, and tent caterpillars are a thing of the past.
• The warming climate is making it easier for pests to reproduce and spread.
• Increasing drought means trees are less resilient to the effect of insects and disease.
• Trees are more likely to die when faced with an onslaught of insects during drought.
• The city of Winnipeg, and Manitoba have strategies to reduce Dutch elm disease.
• Alberta and Saskatchewan have strategies that target mountain pine beetle spread.
• Climate change will bring unforeseen disturbances, which means forest managers must prepare.

Shape-shifting forests

• North American forests are showing adaptation, resilience, renewal and are in a state of hope.
• A change is occurring from mature forests towards ecosystems dominated by shrub and herbs.
• In the Northwest Territories, pine trees have surrendered their reign to grasses and stunted aspens.
• Places with short interval reburns see the conifer forests replaced by open stands of aspens.
• In Alberta, the number of extreme short interval reburns increased as the climate grew drier/warmer.
• Western and northern parts of Canada and the Southwestern United States are most affected.
• Areas lack nearby sources of seeds for trees to regrow as soil seed banks destroyed, and seedlings cannot survive.
• Areas are showing ongoing shifts away from old-growth tree species like spruce to shorter-lived trees.
• Forests aren't inherently the superior ecosystem, rebalancing is sometimes needed where they have invaded.
• It is noted that forests are starting to lose the "safe operating space" needed to be resilient to disturbances.
• The loss of large, old-growth trees is causing consequences for creatures that thrive in mature forests and are disrupting the ecosystem.
• Actions have far-reaching impacts on shared ecosystems: strategies include fuel treatments/controlled burning.

Drought

• Drought is expected to become more frequent and severe in Canada.
• Drought is defined as a shortage of precipitation over an extended period.
• Drought threatens Canada's forests by limiting water needed for tree survival.
• Weakened trees are at higher risk with impacts on the Canadian forest industry.
• Climate Moisture Index (CMI) measures annual precipitation and the expected water amount that evaporates.
• The SeedWhere program predicts where climates will be located under scenarios/timeframes.
• Select planting stock best suited to the predicted drought conditions.
• A substantial drought was experienced in Canada between from 1951-2010 (most notably the 2001-2002 drought)
• Prairie conditions are expected to shift northwards resulting in changes to the southern boreal forest.
• Regions such as the Pacific/Atlantic coastal areas are expected to be less affected.