Fire Effects and Management in Riparian Ecosystems of the Southwestern United States and Mexico

Lowland riparian ecosystems constitute a tiny fraction of total land area in the southwestern United States and northern Mexico, yet they are extremely important to human livelihoods and biotic communities. Facing ongoing projected climate change toward hotter and drier conditions, riparian ecosystems are both vulnerable to changes in climate and increasingly critical to the well-being of humans and wildlife. Due to the dynamic nature of these ecosystems and their abundance of resources, riparian areas have been modified in various ways and to a large extent through human endeavor. These alterations often interfere with multiple and complex ecological processes, making riparian areas more vulnerable to disturbance and change. Few naturally functioning riparian areas remain, and those that do are imperiled by climate change, groundwater pumping, land use, and other factors. A small but growing body of literature suggests that wildfires may be increasing in frequency and severity in southwestern riparian zones. This literature review summarizes and synthesizes the state of the knowledge of wildfire and prescribed fire effects on abiotic processes and vegetation, and post-fire rehabilitation. Results suggest that in lowland riparian ecosystems, fire regimes and fire effects are influenced primarily by streamflow and groundwater regimes. Thus, increasing fire frequency and severity may be attributed to drought, land use, water use, and their subsequent effects on the spread of non-native plant species, as well as a history of fire suppression and increasing anthropogenic ignitions in areas with a growing human presence. Changing fire regimes are likely to have drastic and potentially irreversible effects on regional biodiversity and ecosystem function. However, there are options for managing riparian ecosystems that will be more resilient to fire and climate change, such as implementing environmental flows, prescribed fire, fuel reduction treatments, floodplain restoration, and promoting gene flow. This study is intended to inform management decisions, and identify gaps in systematically reviewed literature