Crossing the Amazon River Bar, Brazil

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After traveling some 6,400 kilometers (4,000 miles), the Amazon River finally arrives at the Atlantic Ocean. (The word some may sound unnecessarily imprecise, but geographers measure the length of the river from different points.) This section of the world’s largest river measured by volume is often referred to as its “bar,” a name used to describe the mouths of other rivers as well. The delta here is a maze of islands, formed by the sediment that accumulates when the Amazon enters the ocean.  The largest island in this area is Ilha de Marajó, which measures 40,100 square kilometers (15,500 square miles). That’s roughly equivalent to three Connecticuts or one Switzerland. The region is fascinating to naturalists, though much of what is of interest is impossible to see from a ship, namely, the variety of aquatic life that can exist where freshwater and ocean water meet. What is visible, though, is the remarkable diversity of birds above the water’s surface—around 540 different species, including a profusion of egrets and herons—and the palm trees that cover many of the islands. You are also likely to see cattle and water buffalo, a cause of concern, as ranching has threatened the habitats of many native species, both plants and animals.