Grassification and fast-evolving fire connectivity and risk in the Sonoran Desert
In the southwestern United States, non-native grass invasions have increased wildfire occurrence in deserts and the likelihood of fire spread to and from other biomes. Wildfires were historically small and infrequent in the warm deserts of western North America, with minimal impact on the desert vegetation. In recent decades, the fire regime has shifted with the spread of non-native grasses. Fires are increasingly burning large areas in desert habitats, largely driven by grassification, the physiognomic conversion of shrublands to grassland by non-native grass invasions. This conversion is especially concentrated at the upper elevational and northern latitudinal boundaries of the Sonoran Desert, which are transition zones to adjacent fire-prone biomes.