Grazing management can counteract the impacts of climate change-induced sea level rise on salt marsh-dependent waterbirds.
Abstract
Climate change-induced rises in sea level threaten to drastically reduce the areal extent of important salt marsh habitats for large numbers of waterfowl and waders. Furthermore, recent changes in management practice have rendered existent salt marshes unfavourable to many birds, as lack of grazing has induced an increase in high-sward communities on former good-quality marshes. Based on a high-resolution digital elevation model and two scenarios for projected rise in near-future sea levels, we employ an ArcMap allocation model to foresee the areal loss in salt marsh associated with these changes. In addition, we quantify the areal extent of inadequate salt marsh management in four EU Special Protection Areas for Birds, and demonstrate concurrent population dynamics in four species relying on managed habitats. We conclude by investigating potential compensation for climate change-induced salt marsh losses by means of more efficient management. Our models indicate that by the end of this century 15.3-43.6% of existent salt marshes will be flooded due to rising sea levels, and that inadequate managed salt marsh presently makes up around 51.1% of total marshes. Thus, re-establishing extensive areas of well-managed marshes might counterbalance the loss expected from rising sea levels during the next century. In addition to positive effects on plant diversity, this will benefit energetically challenged herbivorous waterfowl such as light-bellied brent geese Branta bernicla hrota L. and increase potential recovery of wader populations with unfavourable conservation status such as black-tailed godwit Limosa limosa L., dunlin Calidris alpina L. and ruff Philomachus pugnax L. Synthesis and applications. Implementing environmentally friendly management schemes based on extensive grazing (around 1 cow per hectare) is an important initiative to counteract the accelerating climate change-induced habitat loss in near-coastal areas across the globe, and to secure priority salt marsh habitats that support internationally important populations of breeding, wintering and staging waterfowl. However, this may only be a temporary solution that will have to be supplemented by increased reintegration with the sea and managed retreat of seawalls or near-coastal agricultural areas to effectively safeguard the future salt marsh biome.