Fanning the flames: Past and future links between climate change and fire activity across boreal forests

Boreal forests are experiencing unprecedented environmental change, with increasing fire activity posing significant ecological and climatic challenges. This thesis investigates past, present and future interactions between climate and fire across the boreal biome, combining reanalysis datasets, burned area products and machine learning to examine drivers of fire occurrence and project potential changes in future burned area. Chapter 2 evaluates the reliability of three reanalysis datasets across Siberia by comparing six climate variables related to fire activity with in situ observations from meteorological stations. The datasets are mostly good representations for the studied variables but also show notable regional biases and inconsistencies, highlighting the importance of bias correction in the boreal region. Chapter 3 evaluates twelve satellite imagery-derived burned area products across Arctic-boreal North America and Russia from 2001 to 2020, identifying consistent patterns in North America but major discrepancies in southern Siberia, and highlighting the strengths, limitations and suitability of each product for various research and monitoring applications. Chapter 4 develops machine learning models to project burned area across boreal and tundra biomes from 2025 to 2100 under different climate change projections using climate model outputs. Results show strong scenario- and region-dependent increases in burned area, particularly in North America, suggesting that climate change will intensify fire regimes in many areas. The final discussion chapter combines these findings, emphasising that climate-fire relationships are non-uniform and modulated by vegetation, topography and climate. It discusses the implications of increasing fire activity for carbon accounting, ecosystem resilience and climate feedbacks, and highlights the need for adaptive fire management and further research into vegetation-fire-climate feedbacks in boreal systems. Together, the thesis provides a novel approach to understanding boreal climate-fire dynamics and underscores the urgency of addressing fire risk in a warming world.