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View the FRAMES recordClimate change in western US deserts: potential for increased wildfire and invasive annual grasses
The authors looked at the effects of climate change on invasive species establishment in western deserts. Specifically, they examined the effects of the interannual variation of temperature- and precipitation-related indicators associated with the National Fire Danger Rating System (NFDRS). Furthermore, they projected the future influence of large fire potential into the mid-21st century using downscaled CGM models.
Reduced winter moisture either in the form of reduced snowpack or cool season rain likely increase extreme fire activity earlier in the spring (May and June) through impacts to fuel conditions. Longer freeze-free seasons favor cold-intolerant annual grasses, including cheatgrass (Bromus tectorum) red brome (Bromus rubens) and buffelgrass (Pennisetum ciliare) allowing them to germinate during warmer temperatures and expand their range creating highly flammable ecosystems.
The authors found that recent declines in cool season precipitation appear to have advanced the timing of the fire season across the Sonoran, Mojave deserts in the Southwest as well as the Colorado and the Great Basin desert. CGM models in this study project winter precipitation to continue to decrease across the warm deserts in the study area and an increase in the annual mean temperature by 2.5-3°C by the middle of the 21st century. This future climate change is likely to increase the potential for megafires across the Southwest by increasing the frequency of weather conditions conducive to extreme fire activity, especially an increase in temperature and decrease in corresponding precipitation and humidity indicators. Along with the predicted changes in temperature and precipitation, periods of extreme fire danger are expected to increase by one to three weeks across these areas leading to the occurrence of active fire seasons every fifth year to every other year. Furthermore, in these ecosystems, climate change may result in a fire-invasive feedback loop in deserts where increases in the amount and continuity of annual grasses lead to more extensive and frequent wildfire, thereby increasing the potential for invasive species to proliferate while decreasing the ability of slower-regenerating, native shrub species.
Climate and Fire Linkages
Reduced winter moisture either in the form of reduced snowpack or cool season rain likely increase extreme fire activity earlier in the spring (May and June) through impacts to fuel conditions. Longer freeze-free seasons favor cold-intolerant annual grasses, including cheatgrass (Bromus tectorum) red brome (Bromus rubens) and buffelgrass (Pennisetum ciliare) allowing them to germinate during warmer temperatures and expand their range creating highly flammable ecosystems.
The authors found that already declines in cool season precipitation appear to have advanced the timing of the fire season across the Sonoran, Mojave deserts in the Southwest as well as the Colorado and the Great Basin desert.
CGM models in this study project winter precipitation to continue to decreases across the warm deserts in the study area and an increase in the annual mean temperature by 2.5-3°C by the middle of the 21st century. This future climate change is likely to increase the potential for megafires across the Southwest by increasing the frequency of weather conditions conducive to extreme fire activity, especially an increase in temperature and decrease in corresponding precipitation and humidity indicators. Along with the predicted changes in temperature and precipitation, periods of extreme fire danger are expected to increase by one to three weeks across these areas leading to the occurrence of chronic fire seasons every fifth year to every other year.
CGM models in this study project winter precipitation to continue to decrease across the warm deserts in the study area and an increase in the annual mean temperature by 2.5-3°C by the middle of the 21st century. This future climate change is likely to increase the potential for megafires across the Southwest by increasing the frequency of weather conditions conducive to extreme fire activity, especially an increase in temperature and decrease in corresponding precipitation and humidity indicators. Along with the predicted changes in temperature and precipitation, periods of extreme fire danger are expected to increase by one to three weeks across these areas leading to the occurrence of active fire seasons every fifth year to every other year.
Fire and Ecosystem Effects Linkages
Longer freeze-free seasons favor cold-intolerant annual grasses, including cheatgrass (Bromus tectorum) red brome (Bromus rubens) and buffelgrass (Pennisetum ciliare) allowing them to germinate during warmer temperatures and expand their range creating highly flammable ecosystems. In these ecosystems, climate change may result in a fire-invasive feedback loop in deserts where increases in the amount and continuity of annual grasses lead to more extensive and frequent wildfire, thereby increasing the potential for invasive species to proliferate while decreasing the ability of slower-regenerating, native shrub species.