The Laguna Cartagena National Wildlife Refuge is a National Wildlife Refuge in Lajas, Puerto Rico. It is part of the Caribbean Islands National Wildlife Refuge Complex. The present lagoon is a remnant of what was once a large open expanse of water and one of the most important freshwater habitats for migrating waterfowl and aquatic birds in Puerto Rico. Due to agricultural practices, about 90 percent of the lagoon is covered with cattail. Intensive cattle grazing and sugar cane production have greatly altered the original landscape.