The Pantanal: A Brief Review of Its Ecology, Biodiversity, and Protection Status

Abstract

The Pantanal is a large wetland of ∼150,000 km² located in the center of the South-American subcontinent. Dry and wet periods during the Upper Pliocene and Lower Pleistocene formed a geomorphically complex landscape in the Upper Paraguay Basin, covered by the Pantanal. The actual hydrological cycle of the Pantanal is characterized by a monomodal, predictable, annual flood pulse, however also with multiannual wet and dry periods. During high floods, ∼110,000 km² of the Pantanal are flooded, but during very dry periods only ∼5,500 km² are covered by water. The hydrological dynamics in combination with geomorphological heterogeneity have given rise to a very large macrohabitat diversity that provides the basis for a large biodiversity. This diversity, which includes aquatic, wetland, and many terrestrial species, is evidence of the important interactions among aquatic, terrestrial, and intermittent macrohabitats. Flora and fauna are dominated by species from the surrounding savanna (cerrado biome), but there are also species from the Amazon, chaco, and dry forest biomes. However, in the Pantanal, there are very few endemic species, because paleoclimatic and hydrologic instability hindered speciation. Cattle ranchers, who actually own 90% of the land in the Pantanal have slowly modified its vegetation cover for the last 200 years. Nonetheless, habitat and species diversity have been maintained because of low-density cattle herds. In recent years, economic pressure on the ranches has increased, forcing ranchers to augment cattle production. This has resulted in accelerated deforestation, the planting of artificial pastures, the draining of swamps, and the construction of dikes. Additional, external stress factors have also affected the Pantanal. These factors include the construction of hydroelectric dams along the headwaters, changing the natural flood regime, increased sediment input from upland agroindustries into the rivers, pollution by agrochemicals, mercury input from gold mining, and liquid and solid wastes from cities along the rivers entering the Pantanal. The recently established New Forest Code (Federal Law no. 12.561/12) left large stretches of riverine wetlands along the headwaters and along the Pantanal itself unprotected. While a new law regulating the use and protection of the Pantanal is under discussion, scientists are under intense pressure by groups with economic interest in the region, who seek to undermine existing environmental laws and inhibit the implementation of further protection measures needed to confront new environmental threats.