Background

Catastrophic wildfire has escalated across the globe in recent decades with devastating consequences for human communities and native ecosystems. Global change processes, including climate warming and land use practices, are altering fuels, fire risk, and ecosystem recovery. Managing ecosystems to reduce fire risk and prevent conversion to undesirable alternative states requires knowledge of the ecological conditions of ecosystems, trajectories of change, and drivers of those changes. We developed an approach for evaluating ongoing changes in climate and vegetation and using that information to determine appropriate fuels and other vegetation management strategies for southwest US dryland shrubland and woodland landscapes. We illustrated the approach at a management appropriate scale—a USDA Forest Service Wildfire Crisis Strategy landscape.

Results

We developed an understanding of ecological types, current climatic regimes, ecological resilience to disturbance, and resistance to invasive annual grass (R&R). We then evaluated changes in plant functional type cover, historical fires, and R&R using long-term data. In unburned areas, changes in plant functional type cover included decreases in perennial forbs and grasses but increases in annual forbs and grasses, shrubs, and especially pinyon and juniper trees. In burned areas, tree cover was reduced and both perennial forb and grass and annual forb and grass cover increased. Most ecological types had moderate wildfire risk based on modeled annual burn probabilities and large areas burned since 1998 (16% of study area). These types were likely burning within expected fire return intervals, but areas burned during a single event may have exceeded historical extents and post-fire outcomes had changed. Transitions to warmer temperature regimes occurred between 1980–1999 and 2000–2019 resulting in an 11% decrease in R&R with the greatest impacts in cooler and moister ecological types.

Conclusions

We showed that climate warming in southwest drylands has been associated with concurrent changes in vegetation and fuels and decreases in R&R. We provide an approach that allows managers to quantify the ongoing changes at management appropriate scales. We suggest climate smart management strategies to help direct ecosystems into conditions that can decrease fire risk, increase resistance to plant invasions, and reduce vulnerability to climate change.