Amazon rainforest, Tropical rainforest in South America

The Amazon rainforest is a tropical forest that spans nine South American countries, crossed by a dense web of rivers and streams. It is organized in layers, from the high tree canopy down to the shaded forest floor where vines hang between trunks.

European explorers first crossed the region in the mid-1500s, finding established settlements along the main rivers. Those encounters set off deep changes that shaped the local populations and land use for centuries.

The name Amazon comes from a 1542 battle Francisco de Orellana fought with the Tapuyas, whose women fought alongside the men; he linked them to the Amazons of Greek myth. Today over 30 million people live in the region, including 350 ethnic groups and 60 largely isolated peoples.

Getting into the interior means traveling by river or small aircraft, since roads are rare and often impassable. Local guides are needed to navigate trails and waterways, especially because conditions change noticeably between the wet and dry seasons.

The forest floor holds very few nutrients, because almost all of them stay locked inside living plants rather than in the soil. When leaves or branches fall, fungi and insects break them down so fast that the nutrients are taken back up within days.