Data from: Current and projected cumulative impacts of fire, drought and insects on timber volumes across Canada

Canada’s forests are shaped by disturbances such as fire, insect outbreaks and droughts that often overlap in time and space. The resulting cumulative disturbance risks and potential impacts on forests are generally not well accounted for by models used to predict future impacts of disturbances on forest. This study aims at projecting future cumulative effects of four main natural disturbances – fire, mountain pine beetle, spruce budworm and drought - on timber volumes across Canada’s forests using an approach that accounts for potential overlap among disturbances. Available predictive models for the four natural disturbances were used to project timber volumes at risk under aggressive climate forcing up to 2100. Projections applied to the current vegetation suggest increases of volumes at risk related to fire, mountain pine beetle and drought over time in many regions of Canada, but a decrease of the volume at risk related to spruce budworm. When disturbance effects are cumulated, important changes in volumes at risk are projected to occur as early as 2011-2041, particularly in central and eastern Canada. In our last simulation period covering 2071 to 2100, nearly all timber volumes in most of Canada’s forest regions could be at risk of being affected by at least one of the four natural disturbances considered in our analysis, a six-fold increase relative to the baseline period (1981-2010). Tree species particularly vulnerable to specific disturbances (e.g., trembling aspen to drought) could suffer disproportionate increases in their volume at risk with potential impacts on forest composition. By 2100, estimated wood volumes not considered to be at risk could be lower than current annual timber harvests in central and eastern Canada. Current level of harvesting could thus be difficult to maintain without the implementation of adaptation measures to cope with these disturbances.

加拿大的森林由火灾、虫害暴发与干旱等干扰塑造，这类干扰往往在时间与空间上相互叠加。当前用于预测干扰对森林未来影响的模型，通常未能充分考量由此产生的累积干扰风险及其对森林的潜在影响。
本研究旨在通过考虑干扰间潜在叠加效应的研究方法，预测加拿大全国森林范围内四种主要自然干扰——火灾、山松甲虫（mountain pine beetle）、云杉芽虫（spruce budworm）与干旱——对木材蓄积量的未来累积影响。
研究采用现有四种自然干扰的预测模型，在直至2100年的强气候强迫情景下，预估面临风险的木材蓄积量。
针对当前植被的模拟结果显示，加拿大诸多区域中，与火灾、山松甲虫及干旱相关的风险蓄积量将随时间推移上升，而云杉芽虫相关的风险蓄积量则会下降。
当叠加考量各类干扰的效应时，研究预测风险蓄积量的显著变化最早将于2011-2041年出现，尤以加拿大中部与东部区域为甚。
在2071至2100年的最后一个模拟时段内，加拿大多数林区的几乎全部木材蓄积量都可能面临本研究分析的四种自然干扰中至少一种的影响，相较于基准期（1981-2010年），这一数值增长了六倍。
对特定干扰尤为脆弱的树种（如颤杨对干旱），其风险蓄积量或出现不成比例的增长，进而对森林群落组成产生潜在影响。
至2100年，加拿大中部与东部区域被预估为无风险的木材蓄积量，或低于当前年度木材采伐量。因此，若不实施适应措施以应对此类干扰，当前的采伐水平将难以维持。