Disturbing forest disturbances

Abstract

The forest sector in Canada makes a significant contribution to the wealth of the nation. Many of our forest ecosystems, like the phoenix, need fire for rebirth and renewal. In contrast, other forests rely on a cool, wet disintegration driven by insects and their commensal fungi feeding on trees to effect this renewal. This disparity has a manifest difference in the character of these forests and how they have developed and evolved over thousands of years. While there are characteristic natural temporal and spatial patterns to these disturbances, recent work has shown that they are being perturbed by global change. Compounding these perturbations is the emergence of extensive anthropogenic disturbances in these forests. If humans continue trying to manage complex natural systems as though they were machines, problems with unknown consequences will compound. For example, we have only recently begun to understand that changes in disturbance regimes can generate positive feedbacks leading to what could amount to sudden and drastic change for certain forest communities. Systems-based techniques aimed at adapting to these consequences are emerging and will need to be implemented in a timely fashion to minimize the risks and maximize the opportunities associated with sustainable forest management under a changing climate.Key words: insects, diseases, fire, disturbances, climate change, adaptation, FireSmart, partial harvesting RÉSUMÉ Le secteur forestier du Canada constitue un élément significatif de la richesse de la nation. Plusieurs de nos écosystèmes forestiers, comme le phénix, ont besoin du feu pour renaître et se renouveler. Par contre, d'autres forêts comptent sur la désintégration froide et humide générée par les insectes et leurs champignons commensaux qui s'alimentent sur les arbres pour mettre en oeuvre ce renouvellement. Cette disparité se répercute de façon manifeste dans le caractère de ces forêts, leur développement et leur évolution au cours de milliers d'années. Même s'il existe des patrons caractéristiques naturels, temporels et spatiaux associés à ces perturbations, les études récentes ont démontré qu'elles sont affectées par les changements mondiaux. En plus de ces perturbations, on note l'émergence de perturbations anthropogéniques de plus en plus importantes au coeur des ces forêts. Si les humains continuent d'essayer de gérer ces systèmes naturels complexes comme s'il s'agissait de machines, les problèmes dont les sont conséquences sont inconnues se multiplieraient. À titre d'exemple, nous avons commencé que récemment à comprendre que les changements dans les régimes de perturbation peuvent entraîner des retombées positives menant à ce qui pourrait culminer en un changement soudain et drastique dans le cas de certaines communautés forestières. Les techniques reposant sur des systèmes visant à s'adapter à ces conséquences sont en cours de développement et devront être implantées au bon moment pour minimiser les risques et maximiser les opportunités associées à l'aménagement forestier dur...

Risk of natural disturbances makes future contribution of Canada's forests to the global carbon cycle highly uncertain

“…This enabled us to evaluate both the range of potential future outcomes and their probabilities. Six disturbance agents-(i) fire, (ii) spruce budworm (Choristoneura fumiferana Clemens), (iii) mountain pine beetle (Dendroctonus ponderosae Hopkins), (iv) aspen defoliators (Malacosoma disstria Hü bner, Choristoneura conflictana Walker, and Operophtera bruceata Hulst), (v) jack pine budworm (Choristoneura pinus Freeman), and (vi) hemlock looper (Lambdina fiscellaria fiscellaria Guené e)-have historically had the greatest impact on forest dynamics in Canada (46,(63)(64)(65)(66). We developed separate regional probability density functions (PDFs) for each of these disturbance agents based on 1959 -2000 natural disturbance statistics.…”

Climate change impacts on drought-prone forests in western Canada

“…Lakes, wetlands and peatlands would be profoundly affected, and forest productivity could be greatly reduced, especially following periods of drought-induced dieback and mortality, or when conifers fail to regenerate naturally after disturbances such as fire. Drought-stressed forests are also likely to become more susceptible to damage by insects and diseases, especially those whose life cycles are favoured by warmer temperatures (Volney and Hirsch 2005 Although drought is the primary mechanism acting to constrain growth and distribution of trees in a water-limited landscape, fire is one agent by which change may take place rapidly at the landscape level. Across Canada, the composition of the boreal forest is already shaped by the fire regime with the gradual decrease in the abundance of fire-intolerant balsam fir (Abies balsamea (L.) Mill.)…”

Remote sensing of forest pest damage: a review and lessons learned from a Canadian perspective

“…The combined effects of insects and fire, for example, can reportedly transform a forested region from a carbon sink to a source (Kurz et al 2008). As the climate of the planet continues to change, the direct and indirect effects of warming and natural disturbances threaten the sustainability of Canada's forest sector (Volney and Hirsch 2005). Indeed, evidence of such impacts is accumulating quickly in Canada and beyond (Gauthier et al 2015;Girardin et al 2015;McDowell et al 2015a).…”