Shrub Control to Restore a Coastal Prairie Ecosystem

The coastal prairie in Laguna Atascosa National Wildlife Refuge-Bahia Grande Unit in South Texas protects inland areas from storm surges and erosion while also serving as habitat for grassland-dependent species, such as the federally Endangered northern aplomado falcon (Falco femoralis septentrionalis). Past research indicates that each falcon breeding pair requires at least two thousand acres of open prairie with low woody plant densities to establish and occupy a territory. Records from the early 1900s indicate the Bahia Grande Unit was once an expansive coastal prairie and home to a healthy northern aplomado falcon population. 

However, historic land management practices, such as overgrazing and fire suppression, have resulted in an increase in the density of native woody plant species in the coastal prairie. For example, prior to U.S. Fish and Wildlife Service (USFWS) acquisition in 2000, the area supported private ranching operations during much of the twentieth century. While valuable for thornscrub-dependent species, honey mesquite (Prosopis glandulosa) and huisache (Acacia farnesiana) shrubs are encroaching into the grassland, reducing the cover of gulf cordgrass (Spartina spartinae), a critical component of the northern aplomado falcon’s habitat in the Bahia Grande Unit. Scientists from The Peregrine Fund previously reintroduced the falcons to Coastal Texas. Without these reintroduction efforts, the northern aplomado falcon might have become extinct. 

Researchers from the University of Texas at Brownsville (now University of Texas Rio Grande Valley) partnered with The Peregrine Fund and USFWS to evaluate several grassland management strategies to address honey mesquite and huisache shrub encroachment in the Bahia Grande coastal prairie. The team measured the effectiveness and financial cost of various combinations of mechanical treatments, herbicide applications, and prescribed fire at reducing cover of woody plants.