Only a third of Earth’s longest rivers still run free
Mapping millions of kilometers of waterways allowed scientists to make the new calculation
![Coco River in Brazil](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2019/05/050919_cg_river_feat.jpg?fit=860%2C460&ssl=1)
BRANCHES AND BRAIDS In central Brazil, the Coco River (left) empties into the Araguaia River, or “River of the Macaws,” one of the world’s remaining free-flowing long rivers.
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