Home for the Winter
The mangroves of Sinaloa and Nayarit in Mexico are the largest area of mangroves in the Mexican Pacific. Forty percent of the more than 250 species of birds in this region are winter visitors, giving this region one of the highest concentrations of migratory birds in Mexico. The diverse bird communities feast on the many different invertebrates in the mangrove’s waters and in the trees. These mangroves are also a feeding area for a variety of other species that live here, including marine fish and crustaceans. Over 50 species of vertebrates have been recorded in these mangroves, including four endangered turtles that use the coastal beaches of Nayarit as a nesting site. Mangroves filter nutrients, stabilize lagoon shores, help in forming soil, and prevent erosion of the coast. Because of its rich biodiversity, the site is considered to be among the most important wetland areas in the northern Neotropics.
The mangroves of this ecoregion are near a vast plateau with various beaches that isolate the coastal waters and shape them into lagoons. Mangroves grow on mud flats and around the mouths of rivers that descend from the numerous mountains in the area.
Birds such as American kestrels and blue-winged teals travel from as far away as Alaska and northern Canada to spend the winter in this habitat that’s rich with fish, shrimp, crabs, and snails. Great blue herons, snowy egrets, and roseate spoonbills wade in the waters feeding on fish and crabs. Black-bellied tree-ducks flock to the nearby shallow lagoons. Rare leatherback turtles lay eggs on the sandy beaches. And endangered Morelet’s crocodiles catch fish.
Cause for Concern
The Marismas Nacionales-San Blas Mangroves ecoregion faces many threats from humans. Clearing for shrimp farms is one major threat to these mangroves. Logging is extensive in the area and is destroying critical habitat for many species. Water pollution caused by humans dumping waste in Mexico’s rivers threatens the survival of many aquatic species. Pesticide run-off from agricultural fields eventually ends up in mangrove communities. Draining of mangroves to create farms and highways, and dam construction that alters the flow of fresh water are also destroying vast areas of critical habitat. Mangrove destruction has already led to severe consequences for the fishing industry in other countries.
For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.All text by World Wildlife Fund © 2001