The Mesoamerican Reef System (MAR) is home to the largest barrier reef in the Atlantic and is the world’s largest transboundary reef. 

Threats to this reef include: climate change, which can lead to more hurricanes, acidification, and bleaching; coral diseases; overfishing, especially of large species; water pollution from sewage and agricultural runoff; and the proliferation of macroalgae and sargassum. These threats have contributed to the reduction of the regional average of living coral cover from 19% to 17%.