Mountain ecosystems serve as sentinels of change, and those in the Canadian Rocky mountains have undergone an exceptional shift over the past century. This change has been driven by management practices, disturbance regimes and anthropogenic climate change. With more than a century of strong human influence, have we ensured that ecosystem novelty will prevail? Can historic references predating the 20thcentury, be used to identify boundaries and thresholds of change? We present quantitative analyses of 100 high-resolution image pairs of systematic historic survey and repeat photographs of mountain habitats acquired in the Canadian Rocky Mountains, measuring treeline advance, changes in forest cover, and extent of forest regeneration. With a time lapse of 70 to 100 years between image pairs, these photographs contain critical information about relatively long-term ecological change that cannot be found elsewhere. This data-rich and spatially extensive approach offers unique insight into these dynamic mountainous landscapes. We use these ecological data to inform our reinterpretation of novelty and historic references by identifying boundaries to recovery and restoration that have emerged from this century.
Results/Conclusions
In the 220 km of mountain habitat examined, we found high levels of variability in the ecosystem dynamics across the Canadian Rocky Mountains, although general patterns of increased coniferous cover and an altitudinal advance treeline were prominent. To explain the processes driving the observed patterns, we disentangle climate-driven ecosystem responses from changes in disturbance and land-use history. Just over half of the ecosystems captured by the images responded in the direction predicted (i.e., upward advance of the treeline ecotone and infilling of forest cover). Also, disturbance plays a surprisingly large role in both historic reference and contemporary images. These results are discussed from the perspective of emerging novelty in mountain ecosystems and the implications for conservation and restoration.