Tracking invasive cheatgrass role in larger, more frequent Western fires

PhysOrg: New research that relied in part on satellite images suggests that cheatgrass, an invasive species brought west by settlers in the 1800s, is one cause for the larger, hotter and more frequent range fires experienced recently in the Great Basin of the American West. The arid region covers about 230,000 square miles (600,000 km) over much of Nevada and parts of Utah, Colorado, Idaho, California and Oregon.

Bethany Bradley, a biogeographer at the University of Massachusetts Amherst, brought her expertise in remote sensing and spatial analysis to the study, which was led by fire expert Jennifer Balch of Penn State University.

Bradley used data from NASA's Moderate Resolution Imaging Spectoradiometer from 2000 to 2009 to detect burned areas to create the first land cover map for the Great Basin area. With it, the two researchers and their colleagues combined data sets, matched fire dates and perimeters with land cover data to reach their conclusions, reported in the current online edition of Global Change Biology.

Bradley, Balch and colleagues say that over the past 10 years, cheatgrass fueled most of the largest fires, influencing 39 of the largest 50. Also, fires in grass-covered lands were on average significantly larger than the average fire size on lands dominated by other types of vegetation such as pinyon-juniper, montane shrubland and cultivated areas. Data also suggest that cheatgrass plays a role in more frequent fires.

"From 2000 to 2009, cheatgrass burned twice as much as any other vegetation," Balch says. "Although this result has been suspected by managers for decades," the authors note, "this study is the first to document recent cheatgrass-driven fire regimes at a regional scale."...

A 2007 fire outside San Diego, US Navy photograph