This study examines the drought ﬁre relationship, speciﬁcally the correlations between water balance deﬁcit and annual area burned, across the full gradient of deﬁcit in the western USA, from temperate rainforest to desert. In the middle of this gradient, conditional on vegetation (fuels), correlations are strong, but outside this range the equivalence hotter and drier equals more ﬁre either breaks down or is contingent on other factors such as previous year climate. This suggests that the regional drought ﬁre dynamic will not be stationary in future climate, nor will other more complex contingencies associated with the variation in ﬁre extent. Predictions of future wildﬁre area therefore need to consider not only vegetation changes, as some dynamic vegetation models now do, but also potential changes in the drought ﬁre dynamic that will ensue in a warming climate.
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