Study warns that rising sea levels threaten migratory waders
Rising sea levels are reducing the availability of habitat for migratory waders on the Amazon coast, a new MARE study reveals. The research warns of the gradual transformation of the tidal flats that serve as feeding grounds for waders during their long migrations. This phenomenon may be underway in several regions of the world, putting a large number of bird species dependent on coastal wetlands at risk.
Not even remote and pristine regions, such as the coast of the Amazon, are safe from human impact. Led by MARE researcher Carlos David Santos, a new study published in the scientific journal Environmental Research Letters reveals that rising sea levels are profoundly transforming the coastal wetlands of the Brazilian Amazon, reducing the feeding areas of migratory waders. These birds, which travel between North and South America, depend on the extensive tidal flats to feed along their routes.
The authors of the study found that the tidal flats are gradually being occupied by areas resulting from recent marine transgression. Marine transgression is a phenomenon caused by the rise in mean sea level that leads to the migration of coastal wetlands inland. The tidal flats that result from marine transgression have sediments that are too compact to be colonized by invertebrate animals that serve as food for waders. The team of scientists, made up of researchers from Portugal and Brazil, used satellite images to map the distribution of the tidal flats over 40 years and carried out aerial surveys to count the birds along 630 km of the Amazon coastline.
The results show that birds avoid tidal flats resulting from marine transgression, where the availability of prey - such as small crustaceans - is significantly lower. The semipalmated sandpiper (Calidris pusilla), the dominant species in the region, showed densities ten times lower in these areas than on the older tidal flats, indicating a direct impact on its diet.
“Although the migration of wetlands inland is a positive adaptation to sea level rise, the tidal flats generated by marine transgression do not provide the necessary conditions for feeding waders, at least within four decades,” explains Carlos David Santos, also a researcher at the ARNET Associated Laboratory and the Max Planck Institute, and a professor at the Faculty of Science and Technology at NOVA University Lisbon | NOVA FCT. He adds that sea level rise is a global phenomenon and that this type of habitat loss may be underway in several regions of the world, putting many species of water birds dependent on coastal wetlands at risk.
Text obtained by press release.
Photographs by José Onofre Monteiro