Modeling Cropland Conversion Risk to Scale-Up Averted Loss of Core Sagebrush Rangelands

Abstract

Cropland conversion is anticipated to continue westward from the Great Plains into the sagebrush (Artemisia spp.) biome – the most intact biome remaining in the conterminous United States. However, relatively little is known about the extent and risk of cropland conversion to sagebrush ecosystems and the landscape scale benefits of easements in averting loss of ecological function. Therefore, our goals were to 1) quantify the cropland area of the sagebrush biome, 2) identify where the highest quality sagebrush rangelands are most at risk to future cropland conversion, and 3) estimate the ecological benefits of conservation easements to adjacent public lands. We found that croplands span 14.4 million ha in the sagebrush biome, 16.2 million ha in the historic range of the greater sage-grouse (Centrocercus urophasianus), and are clustered regionally. Our spatial risk model identified 3.7 million ha of high-quality sagebrush rangelands in need of conservation protections from cropland conversion, with higher risk areas clustered regionally (e.g., Northern Great Plains). Our estimates of previous losses to cropland conversion indicated that roughly 80% of at-risk high-quality sagebrush communities have already been tilled. Spatial data and online maps of our risk model are publicly available as planning tools for prioritizing conservation and restoration actions in support of the Sagebrush Conservation Design framework. Using a case study from north-central Montana, we demonstrated that private land easements are crucial for the preservation of Core Sagebrush Areas (CSAs). These easements were found to indirectly preserve an area of CSAs that is 3.6 times larger than the easements themselves. Notably, a significant portion of this conservation benefit—approximately 80%—occurred on public lands adjacent to the easements. Our findings establish a clear connection between investments in private land conservation and beneficial outcomes on nearby public lands, and that focused, permanent protection efforts can extend ecosystem function beyond easements.