Biodiversity in the Yukon: patterns, dynamics, and disturbances

Reid, Kirsten Anne (2023) Biodiversity in the Yukon: patterns, dynamics, and disturbances. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Northern ecosystems are in a period of significant change. Combined, global climate change and human land use are rapidly and significantly changing the structure, function, and resilience of northern ecosystems. In Yukon, Canada, air temperatures have increased by 2°C over the past 50 years with further increases of up to 3.7°C expected by the end of the century. At the same time, large-scale industrial development is ongoing throughout the Territory. Ecosystems here are faced with the amalgamation of these changes: an increasing number, intensity, and combination of pressures. In this thesis, I investigate the structure of Yukon’s ecosystems, focusing on past pressures and changes as well as future changes likely to arise from both natural and anthropogenic pressures. I review documented changes to vegetation communities throughout Yukon, assessing the vulnerability and resilience of different regions and vegetation structures and highlighting knowledge gaps that will direct future research to provide an in-depth understanding of Yukon’s changing vegetation. Through a large-scale field experiment, I identify the dominant controls on biotic community composition throughout northern Yukon. Vegetation communities have increased species richness at more northern study locations, a pattern counter to global biodiversity theory. The length of the snow season plays an important role in this relationship; as winter precipitation patterns continue to change, vegetation communities and ecosystem functioning may be negatively affected. Finally, focusing on the Eagle Plains ecoregion in Northern Yukon, I synthesize the ways that natural, anthropogenic, and cumulative disturbances are significantly changing the landscape, shaping the future trajectories. An integrated approach is required to direct future land management, conservation, and use. The results highlighted in this thesis contribute to a dynamic understanding of the current state of subarctic ecosystems, highlighting the complex and adaptive nature of Yukon’s ecosystems. Yukon’s ecosystems are inherently resilient but current and future pressures are likely to challenge this resilience, potentially forcing state changes with numerous cascading effects.

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