· On a Clear Course
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
· Looking Ahead

Global 200 Snapshot

The Brazilian Shield Amazonian Rivers and Streams ecoregion makes up the largest area of "clearwater" rivers in South America. These rivers are characterized by vast numbers of fish that migrate through the ecoregion and high diversity among fish species.  

On a Clear Course

Shields aren't just devices used for protection. They are also some of the oldest land formations on Earth. The ancient sedimentary rocks of the Brazilian Shield are well weathered, and the tributaries draining them tend to be nutrient-poor "clearwater" rivers, named for their transparency. Hundreds of rivers and streams flow through this area on their way to the Amazon River.

Special Features

If you could see the Brazilian Shield Amazonian Rivers and Streams ecoregion from above, it would look like a huge tree, with many smaller rivers and streams branching out from the larger ones. Some of the biggest ones, like the Araguaia, Tapajós, and Xingu, begin their journey on the Mato Grosso Plateau, a vast elevated area of thick forest and open plains. As they near the Amazon, they swell and pick up speed. At one point, the mighty Madeira River rushes through 200 miles (320 km) of deep, swirling rapids.

	The dourada zebra is a large catfish that has zebra-like stripes. It is rarely caught and is found only in the upper Rio Madeira and the Caquetá region of Columbia.

Wild Side

The fish families that inhabit most of South America have members here, too, including the tropical characins (tetras, piranhas, pacus), catfishes (doradids, loricariids, pimelodids), gymnotoids ("electric eels"), osteoglossids (relict "bony-tongues"), and cichlids. Other kinds of aquatic animals are expected to show high levels of diversity as well. Many of the characin species are migratory, as are many of the large catfishes.

Cause for Concern

This ecoregion comprises the most altered part of the Amazon basin. The Trans-Amazon Highway cuts across this ecoregion, and numerous other roads connect the ecoregion with areas to the south. Oil and mineral exploration are widespread, as are large amounts of deforestation. Several dams are in operation or under construction, and dozens of sites have been proposed for new dams, particularly in the basins of the Tocantins/Araguaia, Xingu, Trombetas, and Tapajos rivers. Agricultural expansion, pasture development, and over-fishing and hunting of aquatic mammals, like the giant river otter, pose additional threats.

Looking Ahead

Check back soon for more about the conservation of this ecoregion.