By Don Heppner, Alex Woods, Jennifer Burleigh, Harry Kope and Lorraine Maclauchlan
The current, historically unprecedented outbreaks of mountain pine beetle and Dothistroma needle blight in British Columbia are strong indicators that relationships between pests, hosts and climate are being altered as climate changes. Numerous recent pest epidemics elsewhere in North America provide further strong evidence of the impact of changing climate on forest ecosystems.
The interactions between pests, hosts and climate are complex, have co-evolved over centuries, and in many instances, are not well understood. This, together with the uncertainty associated with how regional climates will change, makes it difficult to predict the responses of specific pests to climate change. However, as climate changes, the environmental parameters under which present forests were established will change. When these changes result in increasingly sub-optimal conditions, trees will become physiologically stressed. Stressed trees are generally more attractive, more nutritious, and less resistant to many forest pests. Changes in thermal and moisture environments, combined with changes to host plant conditions, will interact synergistically facilitating the development of insect and pathogen outbreaks. The incidence of forest decline syndromes is also likely to increase as a result of general reductions in forest health.
Large scale, pest-caused forest decline and mortality will have long-term ecological, social and economic consequences. Timber supplies, water resources as well as other forest resources will be impacted. We anticipate increasing levels of mortality in the standing inventory in many Timber Supply Areas in the province as a result of forest pest activity. Much of the immature growing stock will also be affected by increasing levels of pest-caused mortality, growth losses and regeneration delays. Although the mountain pine beetle epidemic represents a current extreme, in many Timber Supply Areas it is possible that the combined impacts of multiple pests under the influence of climate change could approach a similar magnitude of impact on the remaining timber resource.
Although there is still much uncertainty regarding the severity and extent of climate change, there are strategies, which could be implemented to mitigate the impacts on forest health. We provide concise recommendations that would better track changing forest health conditions, increase our ability to forecast pest related impacts of climate change, increase the effectiveness of forest planning by proactively incorporating forest health issues and improve our abilities to prevent, mitigate and adapt to changing forest pest conditions. The unprecedented and concurrent outbreaks of insects and diseases in BC emphasize the need to expedite an action plan on the following nine recommendations of equal importance:
1. Mandate expanded forest health monitoring for forest health agents at the landscape, watershed and stand level, as a component of ministry responsibility;
2. Build a forest health research section;
3. Implement modelling projects to predict future forest health impacts;
4. Maintain forest health strategies and develop climate change risk assessments for each Timber Supply Area;
5. Review and revise legislation and policy to identify forest health risks and strategies within forest stewardship plans;
6. Institute landscape-level planning for forest health, as well as for other values;
7. Develop and implement hazard- and risk-rating systems for forest insects and diseases;
8. Implement changes to tree species selection and stocking standards to enable facilitated migration;
9. Enable the research and development of products and tactics for the treatment of forest insects and diseases.
The management of forest lands has clearly become more challenging as a result of climate change. We believe that our current forest management paradigm, which assumes stable climates and stable forest conditions, could be improved to better cope with highly uncertain future forest conditions. Forest management needs to respond and adapt to accommodate the diverse and innovative practices we will require to manage our forests into the future.