Predicting impacts of sea level rise on wintering redhead ducks along the lower Texas Coast

Abstract

The potential impacts of sea level rise to wildlife populations and their habitats are of concern. Localized relative sea levels have been rising at elevated rates compared to global sea levels, and this trend will impact coastal plant communities, particularly wetlands. The Laguna Madre, a hypersaline lagoon, is home to nearly 80% of North America's redheads (Aythya americana) during winter. The large, shallow lagoon provides optimal growing conditions for seagrasses, including shoalgrass (Halodule wrightii), the redhead's primary winter food. Adjacent to the Laguna Madre are coastal ponds, on which redheads rely for fresh water. The close proximity of these freshwater sources to the coast makes them vulnerable to saltwater intrusion due to sea level rise. Using Sea Level Affecting Marshes Model (SLAMM), we modeled the impacts of sea level rise on coastal ponds and foraging areas along the lower Texas coast through the year 2100. We also determined which coastal habitat types would be most affected by rising sea levels. The SLAMM model indicated that 9 land cover types had a ≥50% change in occurrence from the initial 1999 time period to 2100. The model also predicted that 93 of the known 156 coastal ponds would become inundated with salt water. The predicted loss of foraging habitat and its typical proximity to coastal ponds creates a need to identify where conservation and enhancement of wintering redhead habitat should be placed to mitigate the effects of sea level rise.