Agusan Marsh Wildlife Sanctuary, protected by law, covers an area of 57.2 miles. The area was given Ramsar site status in 1999. It is a vast complex of freshwater marshes and watercourses with numerous small shallow lakes and ponds in the upper basin of the Agusan River and its tributaries which rise in the hills of eastern Mindanao. Some parts of the marsh are used for traditional fish ponds and rice paddies. The site acts as storage for rain water and reduces the immediate downstream flow of flood water into Butuan City. Agusan Marsh is one of the largest and the most contained freshwater catch basin wetland in the Philippines. The main habitats of the marsh include freshwater swamp forest (49%), secondary scrub (14%), herbaceous swamp (7%), lakes, pools and rivers (10%), rice paddies and other agricultural land (6%), and small settlements (6%).
The Marsh is a valuable habitat for water birds such as species of wild ducks, herons and egrets. It is also the refuge of the rare Oriental Darter (Anhinga melanogaster) and Purple Swamp Hen (Porphyrio porphyrio) and the threatened Philippine Hawk Eagle, Spotted Imperial Pigeon and Rufous-lored Kingfisher.
The Agusan Marsh Wildlife Sanctuary is currently listed on the tentative lists of UNESCO’s World Heritage List.