The emergence of novel disturbance in Jasper National Park – evaluating the causes and implications of 100 years of landscape change using repeat photography
Date
2025
Authors
Tricker, James
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Abstract
Recurring disturbance has a strong influence on the bounds of ecosystem variability. The concept historical range of variability (HRV) describes these bounds, providing a sense of the range of ecosystem characteristics exhibited in response to disturbance and recovery over time and space. Altered and novel disturbances can drive changes in ecosystem composition and configuration that depart from the HRV and lead to regimes shifts. In Jasper National Park, a systematic set of historical and repeated oblique photographs depict montane landcover in the aftermath of extensive fires in 1915 and a mountain pine beetle (MPB) outbreak in 2020/22. However, the MPB disturbance is historically unprecedented, and raises important questions about whether the characteristics of this event are within the HRV of the montane ecosystems. The focus of this dissertation is to apply a new workflow for deriving landcover maps from oblique photographs to evaluate the landcover changes that have occurred in the park’s montane ecoregion over the last 105 years. The workflow comprises a deep learning algorithm that automates the classification of landcover evident in grayscale and color oblique photographs and a georeferencing tool that incorporates these data into a GIS. I report on the accuracy of the data produced by the workflow (Chapter 2) and quantify the changes in composition and configuration of broad landcover types after the two disturbance events for a study area in the montane ecoregion (Chapter 3). A scenario planning exercise is then undertaken to evaluate the uncertainty surrounding the implications of these changes and the potential for future novel disturbance events (Chapter 4). Georeferencing accuracy using root-mean-square error for a subset of 7 images was 4.6 m and overall classification accuracy for the landcover map produced from oblique photographs using the new workflow was 68%. The change analysis in the montane ecoregion indicated that the MPB outbreak has returned a version of heterogeneity evident in 1915 to the landscape by reducing the dominance of mature conifer (both in composition and configuration) across the landscape. Four scenarios then describe alternative futures in the park based on different levels and combinations of ecological novelty and management intervention. The value of this research is to validate the development of a new workflow for analyzing historical and repeat photographs, increase the temporal depth of ecological monitoring in the park, and allow managers and restoration practitioners to develop a better understanding of how and where novel disturbance is altering ecological processes and could reoccur in the future.
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Keywords
Jasper National Park, Repeat photography, Novel disturbance, Historical range of variabililty, Mountain Legacy Project