Are the alternative ecosystem states produced by positive fire-flammability feedbacks reversible?

Abstract Forest communities that have a positive flammability feedback to fire can enter a ‘landscape trap’ if disturbance levels are too frequent. It is not known whether this landscape trap constitutes an alternative stable state, or whether a forest can return to its original state when disturbance levels are reduced. Here, we examine a likely landscape trap caused by the frequent burning of a 528 343 ha forest environment in Australia and previously shown to have a positive fire-flammability feedback. We ask whether the now flammable landscape can be returned to its original low-flammability state, or if the transition is irreversible in the warming climate. Using site-specific empirical models of biophysical and climatic influences on fire frequency, we predict fire frequency up to the year 2100 for three shared socioeconomic pathways (SSPs) in the context of different management approaches. A warming climate primarily increased wildfire area in our study area by increasing the frequency of synoptic changes, likely reflecting increased rates of escape from suppression firing efforts. Declining winter rainfall had the opposite effect, reducing wildfire area consistent with trends in other seasonally dry environments. The overall effect of warming was therefore a small but significant increase in wildfire area that was more severe under higher GHG emission scenarios. In contrast, removing prescribed burning and incentives for suppression firing had an effect size 2–5 times larger than did the increasing emissions scenarios, demonstrating that the landscape trap was reversible even under the worst-case emissions scenario (SSP3-7.0). Correcting fire management policies immediately reduced annual fire area by 87%, of which 77% was prescribed fire, and 43% of the remaining wildfire proportion was a by-product of the two policies. This allowed forests to escape their flammable age range, reversing a landscape trap. Our study is the first to demonstrate that such states are reversible.