Impacts of climate, CO2 levels and human activity on the spatial distribution of global fire regimes
Le 03 Mai 2024
11h30 Hybrid - online and Salle Louis Thaler, bat 22 UM
Olivia haas & sandy harrison
Leverhulme Wildfires Centre, Imperial College London, London, United Kingdom
University of Reading, Reading, United Kingdom
Link to seminar:
https://umontpellier-fr.zoom.us/webinar/register/WN_imS2T4YmQ1iVRzphj73s5Q There is growing concern of increasing large and intense wildfires in many regions because of climate change. Whilst some regions have seen increases in the last few years, satellite observations show that area burnt has declined globally over the last two decades, most notably in the tropical savannas of South America and Africa. Part of the complexity in understanding how wildfires will change in the future is the fact that they are driven by multiple factors, including climate, vegetation and human activity. An added complication is that atmospheric CO2 levels affect vegetation independently from climate, however how this effect may influence fire regimes is difficult to quantify from observations alone. In this seminar, we present three global empirical models of burnt area, fire size and a measure of fire intensity and show how they can be used to explore the global sensitivity of fire regimes to changes in climate, atmospheric CO2 and human activity. By making use of a coupled biogeography-biogeochemistry model (BIOME4) and a productivity model (P model) that both include climate and CO2 levels as inputs, we provide a new way to explore the interaction of CO2-enduced changes on vegetation and fire regimes using sensitivity analysis. We show simulations of fire regimes under very different climate conditions, both in the past and in the future. At the Last Glacial Maximum we show fire activity consistent with evidence from sedimentary charcoal records, but only when directly accounting for the effect of low CO2 on vegetation. Simulation of future fire regimes under low- and high-mitigation scenarios indicates a global shift in wildfire patterns by 2100 CE with burning reduced in tropical regions but larger and more intense wildfires in extra-tropical regions. Under low mitigation, increases in burnt area worldwide overwhelm the current human-driven declining trend, with fire size and intensity increasingly limited by dryness and vegetation fragmentation. These model experiments highlight the distinct controls of different fire properties. Whilst burnt area is driven by fuel availability and dryness, fire intensity is limited by fuel build-up, and fire size by fuel continuity. This decoupling occurs because of the different temporal and spatial scales on which the controls of burnt area, fire size and fire intensity operate. These findings have immediate implications for the improvement of process-based fire models, which currently do not take these distinctions into account.
Watch previous seminars on our YouTube channel: https://www.youtube.com/channel/UCrX4IsZ8WIFcDa0ZmC7rcQg
Contact:
Isabelle CHUINE (UMR CEFE) : isabelle.chuine@cefe.cnrs.fr
