Use of remote sensing to assess changes in wetland plant communities over an 18-year period: a case study from the Bear River Migratory Bird Refuge, Great Salt Lake, Utah

Successfully managing wetlands requires monitoring changes in plant community composition. We used remote sensing techniques to document the replacement of desirable native wetland vegetation with invasive species in response to catastrophic flood disturbance in the 1980s and to evaluate wetland vegetation management between 1998 and 2010. We conducted our study at the Bear River Migratory Bird Refuge wetlands, which are located on the northeastern arm of the Great Salt Lake in northern Utah. We acquired high-resolution airborne multispectral imagery of the refuge in 1992 and 2010 to quantify changes in vegetation cover over time. We produced classified vegetation maps for the years 1992 and 2010 to calculate vegetation and water cover in management units. Classification results indicate that invasive vegetation is fast replacing native species in areas adjacent to the water delivery canals. We also compared vege tation changes to historical data provided by refuge managers, and these data contained information about the management activities undertaken in the wetland units over the study period. We found that the managers’ efforts to control the expansion of invasive species—such as keeping the units full of water throughout the year, adjusting water depth to manage salinity levels and aquatic vegetation, and undertaking burning or mechanical disturbance when needed—were successful in most of the units, although some units were still invaded by undesirable plants. Here we demonstrate how wetland managers can use remote sensing and historical data of vegetation cover to understand which native plant species are most susceptible to replacement by invasive species, how vegetation responds to management actions, and ultimately how managers can promote diverse plant communities with high wildlife value