The South American country containing the majority of the Pantanal, the world's largest tropical wetland, is Brazil.
The Pantanal is a vast seasonally flooded plain in the upper Paraguay River basin. Most of it lies in Brazil, especially across the states of Mato Grosso and Mato Grosso do Sul, while smaller portions extend into Bolivia and Paraguay. Because its boundaries vary by definition and mapping method, published estimates of its total area differ, but Brazil consistently contains the largest share.
Seasonal flooding shapes nearly every part of the ecosystem. During the rainy season, roughly 80 percent of the floodplain can be submerged, creating nurseries for fish and feeding grounds for birds, caimans, capybaras, jaguars, giant river otters, and marsh deer. The Paraguay River and its tributaries slowly drain the shallow basin.
The Pantanal is not simply a permanent swamp. It is a mosaic of grasslands, forests, lagoons, rivers, and dry-season habitats. That seasonal rhythm explains its exceptional biodiversity and also makes it vulnerable to drought, fires, altered river flows, agricultural expansion, and deforestation.