The Amazon River: Lifeblood of a Continent

Introduction

Few places on Earth inspire the imagination quite like the Amazon River. Flowing more than six thousand kilometers across the width of South America, from its headwaters high in the Andes mountains of Peru to its vast delta on the Atlantic coast of Brazil, the Amazon is not merely one of the world's great rivers but an entire world unto itself. It carries more water than any other river on the planet, discharging roughly one-fifth of all the fresh water that flows into the world's oceans. It drains a basin of some seven million square kilometers, an area larger than the continental United States, and this basin is home to the Amazon rainforest, the largest tropical forest on Earth and one of the most biologically diverse ecosystems in the history of life on this planet.

The Amazon is a river of superlatives. Its drainage basin is the largest of any river in the world. Its water discharge exceeds that of the next seven largest rivers combined. Its fish fauna, with more than two thousand two hundred known species, is the most diverse of any river system on Earth and represents a greater variety of freshwater fish than is found on the entire African continent. Its surrounding forest contains an estimated ten percent of all species of plants and animals on Earth, including more than forty thousand plant species, fourteen hundred mammal species, fifteen hundred bird species, and untold millions of insect species, many of which have never been described by science.

Yet the Amazon is also a river under extraordinary pressure. In the decades since the second half of the twentieth century, the Amazon basin has been transformed by human activity at a rate and scale that has few parallels in the history of land use. Deforestation, agricultural expansion, cattle ranching, mining, dam construction, and urban growth have together converted enormous areas of the original forest cover into degraded landscapes, releasing vast quantities of carbon into the atmosphere, destroying habitat for millions of species, and fundamentally altering the hydrological and ecological systems that sustain both the forest and the communities that depend on it. Scientists and conservationists have warned for decades that the Amazon is approaching a tipping point beyond which large areas of the forest could convert from humid tropical rainforest to a drier savanna-like ecosystem, with catastrophic consequences for biodiversity, climate, and the hundreds of millions of people who depend on the Amazon basin's ecological services.

This article traces the full story of the Amazon River: its geography and hydrology, its extraordinary biodiversity, the history of human presence in the basin from the first indigenous settlements to the European conquest and the modern era, the environmental threats facing the river and its forest, the economic importance of the basin, the role of the Amazon as a global carbon sink, and the conservation efforts that aim to protect one of the world's most irreplaceable natural treasures.

Geography and Hydrology

The Amazon River begins its journey to the sea in the high Andes of southern Peru, where glaciers and snowfields feed the streams and rivulets that merge to form the Apurimac River, itself a tributary of the Ucayali, which in turn joins the Maranon to form the mainstream of the Amazon. The precise identification of the Amazon's most distant source has long been debated by geographers, with different investigations identifying different Andean streams as the true headwaters. A study conducted by Brazilian scientists in 2007 identified a glacial stream high on the slopes of Nevado Mismi in southern Peru as the farthest source point, giving the Amazon a total length of approximately six thousand nine hundred and ninety-two kilometers, which would make it longer than the Nile and thus the world's longest river. However, this conclusion remains disputed, and many geographers still cite the Nile as the longest, depending on exactly how the source and mouth of each river are defined.