The missing pieces for better future predictions in subarctic ecosystems

Arctic and subarctic ecosystems are undergoing substantial changes in response to climatic and other anthropogenic drivers, and these changes are likely to continue over this Century. Due to the strong linkages between the biotic (vegetation and carbon cycle) and abiotic (permafrost, hydrology and local climate) ecosystem components, the total magnitude of these changes result from multiple interacting effects that can enhance or counter the direct effects. In some cases, short-lived extreme events can override climate-driven long-term trends. The field measurements can mostly tackle individual drivers rather than the interactions between them. Currently, a comprehensive assessment of the drivers of different changes and the magnitude of their impact on subarctic ecosystems is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years and encompasses the 12% of all published papers and the 19% of all study citations across the Arctic. In this study, we summarize and rank the direct and indirect drivers of ecosystem change in the Torneträsk area, and propose future research priorities identified to improve future predictions of ecosystem change. First, we identified the direct and indirect changing drivers and the multiple related processes and feedbacks impacting the local climate, permafrost, hydrology, vegetation, and the carbon cycle based on the existing literature. Subsequently, an Expert Elicitation with the participation of 27 leading scientists was used to rank the short- (2020-2040) and long-term (2040-2100) future impact of these drivers according to their opinions on the relative importance and novelty. These two key evaluation matrices form the basis for identifying the current research priorities for subarctic regions. The relatively small size of the Torneträsk area, its great biological and geomorphological complexity, and its unique datasets is a microcosm of the subarctic and the rapidly transforming Arctic ecosystems that can help understand the ongoing processes and future ecosystem changes at a larger circumpolar-scale. This in turn will provide the basis for future mitigation and adaptation plans needed in a changing climate.