Historical burn area in western Canadian peatlands and its relationship to fire weather indices

Abstract

Peatlands store the majority of soil carbon in many northern regions, yet their vulnerability to fire remains poorly understood. We used large‐scale mapping of fire and peatland distributions to explore patterns of burning at two spatial scales. On a landscape scale in central Alberta, we used spatially explicit distributions of peatlands and 50 years of fire perimeter maps to determine whether uplands burn more preferentially than peatlands. Burn area and ignition localities in central Alberta did not occur preferentially in uplands relative to bogs and fens. Extrapolating this result at a regional scale, we used the Peatlands of Canada database and 20 years of historical fire records to estimate annual burn areas for Alberta, British Columbia, Northwest Territories, and Saskatchewan peatlands. Peatland burn areas varied tremendously over time, with high fire activity in the early 1980s and mid‐1990s. On average, fires impacted 1850 km2 of peatland annually across this region of western Canada. Positive relationships between the area of peatland burned and weather variables calculated for each fire event using the Canadian Fire Weather Index, including maximum air temperatures and the duff moisture code, suggest that drier and/or warmer conditions likely would increase the burning of peatlands in western Canada.

Temperature sensitivity of soil carbon decomposition and feedbacks to climate change

“…On the other hand, carbon in desiccated peat is also subject to natural and human fires, rapidly releasing huge amounts of carbon to the atmosphere. Siberian and Canadian peatlands are already subject to important peat losses during fire-prone dry years 70 and the combination of higher temperatures and peat drying may increase fire frequency and severity 71 . During the 1997 El Niño, 0.6-0.8 Pg of C (10% of anthropogenic emissions) was lost owing to peat fires in Indonesia alone 72 .…”

The changing radiative forcing of fires: global model estimates for past, present and future

“…These fires are not predicted in our CLM3 simulations. According to one estimate, in Canada alone peatland fires emit about 6 Tg C yr −1 (Turetsky et al, 2004). Flannigan et al (2009) note that peatland fire emissions are more sensitive to climate changes since they are not fuel-limited.…”

Experimental drying intensifies burning and carbon losses in a northern peatland

“…Land use change in tropical peatlands has lowered water table position and increased fire severity, leading to carbon losses equivalent to as much as 40% of global fossil fuel combustion in some years 1 . More than 90% of the world's peatlands, however, are found in high-latitude regions 4 , where they also are vulnerable to large wildfires 5 . Burning of disturbed peatlands is thought to have been a major contributor to the large wildfires that affected Russia in 2010, causing as much as US$15 billion in damages, and reduced industrial output 6,7 .…”

“…Summer daily mean temperatures in Canada's boreal region are predicted to warm by 1.5-2.5 °C. Whereas precipitation is expected to increase by ~20% in eastern Canada, precipitation is not expected to increase in western regions 18,21 where peatlands are most likely to burn 5,22 . Across Canada's boreal region, warming is widely expected to result in declining soil moisture and a significant increase in the frequency of large fires 21 .…”