The Pantanal is a natural region encompassing the world's largest tropical wetland area. It is located mostly within the Brazilian state of Mato Grosso do Sul, but it extends into Mato Grosso and portions of Bolivia and Paraguay. It sprawls over an area estimated at between 140,000 and 195,000 square kilometres (54,000 and 75,000 sq mi).
Roughly 80% of the Pantanal floodplains are submerged during the rainy seasons, nurturing an astonishing biologically diverse collection of aquatic plants and helping to support a dense array of animal species. The name "Pantanal" comes from the Portuguese word pântano, meaning wetland, bog, swamp, quagmire or marsh.
The vegetation of the Pantanal, often referred to as the "Pantanal complex", is a mixture of plant communities typical of a variety of surrounding biome regions: Brazilian cerrado savanna plants and plants of the Chaco savannas of Bolivia and Paraguay. Forests usually occur at higher altitudes of the region, while grasslands cover the seasonally inundated areas. The key limiting factors for growth are inundation and, even more importantly, water-stress during the dry season. The Pantanal ecosystem is home to 3500 known plant species.
The Pantanal ecosystem is also thought to be home to 1000 bird species, 400 fish species, 300 mammalian species, 480 reptile species and over 9000 subspecies of invertebrates.