Managing Fire-Adapted Invasive Plants in the American West

Abstract

Humans impact fire in many ways. They may reduce ignitions by implementing fire suppression protocols or increase fire incidence through accidental or prescriptive ignitions. Anthropogenic changes to climate affect wind speeds and temperature that in turn may translate to more dangerous fire behaviour. Importantly for this discussion, humans also change the species composition of plant communities either directly by moving plant propagules or indirectly by affecting climate which in turn affects the geographical distribution of plants. Largely because of human actions, Western United States have witnessed drastic increases in the geographic distribution and severity of several important fire-adapted exotic plant species including Bromus tectorum (cheatgrass), Cenchrus ciliaris (buffelgrass), Ventenata dubia (ventenata), Taeniatherum caput-medusae (medusahead), Arundo donax (giant reed), and others. A recent United Nations study finds "the management of invasive alien vegetation is crucial for the prevention of extreme wildfires". The increase of invasive plants that are fire-adapted has changed the fire regimes in the American West fundamentally leading to more frequent and intense fires. Altered fire regimes have significant human and environmental-health consequences and threaten the economic sustainability of communities broadly, especially in the wild-land-urban interface. In California, seven of the 20 deadliest fires on record and 11 of the 20 most destructive fires have occurred in the past five years. Exposure to smoke from wildfires can have severe health consequences broadly across the region. Environmental degradation and severe wildfire events associated with exotic plant invasion have had significant impacts on rare, threatened and endangered species.