The compounding consequences of wildfire and climate change for a high‐elevation wildflower (Saxifraga austromontana)

Abstract

AbstractAimHigh‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.LocationRocky Mountain Floristic Region, western North America.TaxonSaxifraga austromontana (Saxifragaceae), a wildflower endemic to high elevations of the Rocky Mountain Floristic Region.MethodsOur approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.ResultsOur results indicate wildfire has significantly reduced the abundance and increased the likelihood of extirpation for S. austromontana. Increased fire frequency compounded with direct climatic changes will likely reduce the range of the species by approximately 43% by 2050 compared to 38% due to climate alone, under a moderate CO2 emissions scenario. The influence of wildfire varies regionally. For instance, the Middle Rockies will likely lose 74% of its suitable habitat of which 16% may be lost due to fire, while other regions, such as the northern range, will be less negatively affected by direct and indirect effects.Main ConclusionsOur evidence that increased wildfire frequency will compound the impacts of climate change on alpine taxa in North America led to the development of a new, general hypothesis on the fundamental interaction between direct and indirect effects of climate change on species range reductions.