Biodiversity colonisation of the Arctic under climate change: impacts on land, sea and people

Abstract

Climate change is driving a redistribution of species worldwide. The Arctic is a particularly vulnerable ecosystem which is affected by climate change at a much greater rate than the rest of the world. Both terrestrial and marine systems are under pressures of climate-driven species range shifts, and it is imperative to understand how these ecosystems and communities may change in the future. Despite the magnitude of changes, the Arctic remains relatively understudied and the consequences of novel species shifting into the Arctic remain relatively unknown. By addressing these critical knowledge gaps, this thesis offers comprehensive insights into the impacts of climate-driven species redistribution on terrestrial and marine ecosystems in the Arctic, alongside its repercussions for people. Using species distribution models (SDMs), I find a high potential for novel species assemblages to emerge in the Arctic, particularly in the high and low Arctic which are the northernmost Arctic regions situated above 75° and between 75°-65° North, respectively. I show, however, that species’ dispersal abilities and habitat availability limit range shifts, constraining the capacity of terrestrial species to track suitable climate. Marine ecosystems exhibit significant variations in species responses to climate change, with projections indicating over 50% losses of marine fish and mammal species by 2100 from the Greenland Sea, Norwegian Sea and Barents Sea regions in the Arctic. Additional indicators of biodiversity change, such as functional and phylogenetic diversity, provide nuanced insights into the impacts of range-shifting species on Arctic communities. I project increases in functional diversity driven by the influx of novel species with traits distinct from those of current Arctic communities, potentially reshaping community structure and function. Despite significant increases in novel colonists, I find significant implications from concurrent losses of native Arctic species. These losses disrupt ecosystem functioning and emphasise the importance of considering both species gains and losses in biodiversity assessments. Then, by combining SDMs and food-web models, I explore the emergence of novel ecosystems in the North Water Polynya, one of the most productive ocean ecosystems in the world. I find that incoming species decrease energy transfer to higher trophic levels, suggesting climate change could completely disrupt a marine Arctic food web. Finally, I find that climate change disproportionately impacts local Arctic communities, with effects on their livelihoods and cultural identities being far greater than the effects experienced at national or international levels, as their lives are deeply intwined with native species. While novel species may offer new trade opportunities, especially of marine fish, the loss of native species may outweigh these gains, particularly in terrestrial systems. Together, my results from this thesis significantly advance our understanding of the impacts of biodiversity colonisation in the Arctic on land, sea and people. This thesis highlights the urgency of adopting future-oriented conservation approaches to safeguard Arctic biodiversity in the future, support resilient ecosystems, and address the multifaceted challenges posed by ongoing environmental change. Engaging stakeholders, including local communities, scientists, policymakers and industry representatives, in collaborative research and decision-making processes will be crucial to ensuring the relevance and effectiveness of conservation and management efforts in the Arctic.