Citizen science predicts the distribution of the treeline in the Fennoscandian Arctic

Abstract

Abstract Context The effects of climate change in the Arctic are particularly pronounced since temperatures have risen nearly four times as fast as in the rest of the planet. Shifts in climatic patterns enable the expansion of temperature-limited vegetation at a global-scale to higher latitudes and elevations. Objectives The purpose of this study is to predict the distribution of the main tree species in the treeline across Fennoscandia by drawing from three distinctive datasets. I ask which method used to collect data is better at predicting the distribution of the treeline? How will the distribution of the treeline respond to climate change in the next 50 years? Methods Three tree datasets together with environmental data were used to spatially model the treeline. The first dataset was compiled by setting up a network of vegetation plots in Fennoscandia. The second belongs to the Swedish National Forest Inventory and the third is from a Swedish online portal where citizens report their species observations. Environmental data was sourced from the Coupled Model Intercomparison Project. Results The citizen science dataset was superior in predicting treeline distribution due to the large-number and wide-spatial distribution of observations. The probability of treeline presence increased with temperature and decreased with precipitation, meaning that the treeline will expand in distribution to higher elevations. These responses are tree species-specific. Conclusion The conservation of the tundra is threatened by the encroachment of the treeline which is driven by climate, and citizen science holds unique importance for wide spatial and temporal ecological research.