Fighting Fire With Fires: The Fire-Fuel Feedback Effect in Canadian Forests

Aim

Climate-driven fire increases could be modified by fire-fuel feedback, as recent fires reduce burnable fuels for future fires. Knowing the effects of fire-fuel feedback is essential for more accurate projection of fire activity, which, however, has often been overlooked due to the challenge in its quantification. This study aims to project future fire activity under the changing climates with consideration for fire-fuel feedback effects across Canada.

Location

Canadian forests.

Time Period

1981–2100.

Major Taxa Studied

Trees.

Methods

We projected future changes in a full set of fire activity variables, including annual area burned (AAB), annual number of fires (ANF) and annual maximum fire size (MFS), based on extreme fire weather in Canada. We then incorporated fire-fuel feedback into the projections to quantify its effects in Canadian forests and consequently answered the question of whether the unprecedented 2023 fire season would become a common occurrence in the future.

Results

The feedback from fires within 6–11 years prior showed the strongest power in rectifying fire activity projections, and the feedback effects strengthened as climate change became more severe. By century's end (2080s), under the extreme climate change scenario (RCP8.5), fire-fuel feedback could reduce weather-based AAB, ANF and MFS projections by 21%, 21% and 16%, respectively. Spatially, eastern and northwestern regions may see the greatest fire activity increases, while the strongest feedback effects appear in the south and northwest. In the 2080s, under RCP8.5, years with more extensive fires than 2023 may occur once every 9 years in regions most affected by the unprecedented 2023 fire season.

Main Conclusions

The results indicate that fire-fuel feedback could modestly mitigate climate-driven increases in future fire activity in Canadian forests. With more accurate projections that account for such feedback effects, the extraordinary 2023 fire season could be considered a low-frequency but more plausible occurrence in the future.