No abstract

The increase in wildfire risk in the United States in recent decades has been linked to rapid growth of the wildland-urban interface and to changing climate. While there have been numerous studies on wildfires and climate change, few have separately assessed the impact of climate response to land-use-land-cover change (LULCC) on wildfires. In this study, we analyse two 10-year regional climate simulations driven by the current (2011) and future (2100) land-use-land-cover patterns to assess modifications by the projected LULCC to the frequency and severity of fire-prone atmospheric conditions described by two fire weather indices, the Canadian Forest Fire Weather Index and the Hot-Dry-Windy Index. The simulation corresponding to future land-use-land-cover pattern yields higher surface temperature and vapour pressure deficit and lower precipitation compared to the simulation with the current pattern in areas where urbanized landscapes replace forests and grasslands, such as along the Piedmont and outside the Chicagoland region, while in areas where croplands replace forests, such as the southeast Coastal Plains, the results are reversed. These changes to local and regional atmospheric conditions lead to longer fire seasons and more extreme fire-weather conditions in much of the eastern United States, specifically in the Southeast and Ohio River Valley where significant urban expansion is projected by the end of the century. Whereas in Southern California where some highly flammable shrublands will be replaced by urban or crop lands, fire-prone atmospheric conditions are likely to be less frequent and less extreme in the future. However, much of California moves towards a yearround fire season under the projected LULCC. The results suggest that by altering atmospheric conditions, LULCC may play an important role in determining fire regime, but the effects are highly heterogeneous and regionalized.