Wildfires
Wildfires burn ~350-400 million hectares globally each year — about 4% of vegetated land area. Carbon emissions from fires average ~7.5 Gt CO₂ per year, with high interannual variability. The 2023 Canadian wildfire season alone emitted ~1.2 Gt CO₂. Fire regimes are shifting under climate warming: longer fire seasons, larger fires, more frequent extreme fire weather.
Key insights
2023 was the worst Canadian fire year on record
Canada burned ~18 million hectares in 2023 — more than the previous 5 years combined. Smoke reached US East Coast and Europe. Carbon emissions roughly equivalent to all Canadian fossil-fuel emissions. Boreal fires release particularly carbon-dense smoke from peat soils, with potential to remain smoldering through winter and into following year. 2024 was again severe.
Australia's Black Summer (2019-20) was unprecedented
Australia's 2019-20 bushfires burned 24 million hectares, killed 33+ people directly, killed an estimated 1+ billion animals. Smoke covered eastern Australian cities for weeks; reached South America. Australia's average fire weather index rose ~20% from 1979-2019; Black Summer represented a multiple-standard-deviation extreme. Climate attribution studies linked the event to warming-induced increases in fire weather.
Fire-climate feedback is establishing
Larger fires release more CO₂, contributing to warming, which extends fire seasons and creates more fire weather, leading to larger fires. The feedback is small in current global carbon balance but growing. Wildfires also release particulate matter (PM2.5) causing significant health impacts — wildfire smoke is now the largest source of fine particulate pollution in some California counties. Indigenous fire management and prescribed burns can reduce extreme fire risk; widespread adoption has been politically/practically difficult.
Global wildfire area burned — annual
Million hectares per year, satellite-derived
Key Finding: Year-on-year variability is high; the 2023 Canadian fire season pushed global total to ~430Mha — the highest recorded.
Wildfire emissions by country — 2023
Mt CO₂ from wildfires in selected countries
Key Finding: Canadian 2023 emissions exceeded most major fire countries' historical typical years.
Methodology & caveats
Fire emissions calculation
Satellites detect fires (MODIS, VIIRS) and estimate area burned. Combined with fuel loading data (vegetation type, biomass density) and combustion completeness factors, this yields CO₂ emissions. Multiple inventories (GFED, GFAS, FINN) use slightly different methods; agreement on global total is moderate, country-level variability is wider.
Why some fires are unusual
Boreal forest peat fires can smolder underground for months, releasing carbon long after surface fire ends. Tropical peat fires (Indonesia 2015, 2019) similarly burn slowly underground. Surface savanna fires are typically the dominant area-burned but lower carbon-density. Each fire type has different climate, smoke, and recovery implications.
Climate vs management
Fire regimes are shaped by: climate (temperature, humidity, wind, lightning), vegetation (fuel type, fuel load, fuel moisture), ignition source (lightning, human), management (prescribed burn, suppression). Climate change shifts fire weather, but accumulated fuel from decades of suppression also drives extreme fires. Mixed-attribution studies find both factors important; the relative weights vary by region.