Lower Amazon

Lower Amazon

The Lower Amazon begins at the point where the dark-colored waters of the Rio Negro meet the sandy Rio Solimóes, and for more than 6 km these waters flow side by side without mixing. The Lower Amazon region refers to the northwestern quarter of the state of Pará and contains 13 municipalities, most of them located along the Amazon River. At Óbidos, low hills rise above the river behind a 17-metre-high cliff face, making it appear that the lower Amazon was once a bay of the Atlantic Ocean, whose waters washed the rocks near Óbidos. Only around 10% of the Amazon's water flows through Óbidos, and only a very small proportion of this comes from the northern slope of the valley. The catchment area of the Amazon basin is about 5 000 000 km2 above the city of Óbidos, and only about 1 000 000 km2 below. The area has a tropical rainforest climate, with no dry seasons, and an average rainfall of at least 60 millimeters every month. The Amazon accounts for more than half of the planet's remaining rainforests and contains the largest and richest tropical rainforest in the world. Humid tropical forests are the richest biosphere, and the tropical forests of the Americas are consistently more species-rich than the humid forests of Africa and Asia. As the biggest area of tropical rainforest in the Americas, the Amazon rainforest has unrivalled biodiversity. Over a third of all species in the world live in the Amazon rainforest. The state of Pará has the highest biodiversity on the planet.