The Amazon rainforest occupies the drainage basin of the Amazon River, bounded to the west by the Andes Mountains, to the north by the Guiana Shield, and to the south by the Brazilian Shield. The forest extends across nine political jurisdictions.⁹ Brazil holds the largest share, containing approximately 60 percent of the rainforest within its borders, followed by Peru with 13 percent and Colombia with 10 percent. Smaller portions lie within Bolivia, Ecuador, Venezuela, Guyana, Suriname, and French Guiana. Four countries—Brazil, Colombia, Peru, and Venezuela—designate one of their primary administrative divisions as "Amazonas," while France administers much of its territory's interior as the Guiana Amazonian Park.

At the center of the biome's geography is the Amazon River, which stretches more than 6,400 kilometers from its Andean headwaters to the Atlantic Ocean and is fed by over 1,100 tributaries. The river system accounts for 16 to 22 percent of the world's total river discharge into the oceans, releasing roughly 200,000 cubic meters of water per second.¹⁰ Because of the basin's flat topography and the sheer volume of water, oceanic tidal effects can be detected up to 800 kilometers upstream, and during strong tides, the collision of river water with the Atlantic produces a powerful tidal bore known locally as the pororoca. Over 3,700 kilometers of the river network are navigable by ocean-going vessels, connecting major interior ports such as Iquitos in Peru and Manaus and Belém in Brazil.

Geological history has shaped the modern basin over tens of millions of years.¹¹ Following the breakup of the supercontinent Gondwana roughly 184 million years ago, South America drifted westward, colliding with the Nazca tectonic plate. This collision initiated the uplift of the Andes Mountains around 25 million years ago, blocking the westward drainage of the continent's rivers. Approximately 15 million years ago, the central basin was covered by a massive freshwater lake and wetland system. During subsequent glacial cycles, falling sea levels and ongoing erosion from the rising Andes caused the lake to breach the eastern rim of the basin, establishing the modern eastward flow of the Amazon River and depositing nutrient-rich Andean sediments across the western floodplains.

Rather than a uniform wilderness, the Amazon biome consists of a mosaic of more than 50 interconnected terrestrial and aquatic ecosystems shaped by soil chemistry, topography, and seasonal water levels.¹² Ecologists classify the forested landscape into three primary regimes alongside smaller specialized habitats such as white-sand podzol forests and permanent swamps.¹³ The dominant regime is terra firme, or upland forest, which grows on higher ground consisting of clay or brown sandy soils that do not experience seasonal flooding.¹⁴ Terra firme forests are characterized by a dense, multi-tiered structure of towering canopy trees, lianas, epiphytes, ferns, and mosses growing on ancient, highly acidic, and nutrient-poor soils where organic matter is rapidly recycled at the surface.¹⁵¹⁶

Along the river networks, seasonal fluctuations in water levels create two distinct types of floodplain forests: várzea and igapó. Várzea forests develop on eutrophic terrains periodically inundated by "whitewater" rivers, such as the main stem of the Amazon and the Madeira, which carry heavy loads of mineral-rich sediment eroded from the Andes. The high nutrient availability in várzea environments supports rapid plant growth and high regeneration rates.¹⁷ In contrast, igapó forests grow on oligotrophic terrains flooded by "blackwater" or clearwater rivers, such as the Rio Negro, which drain the ancient, weathered soils of the Guiana and Brazilian shields. Stained dark by tannins leached from decaying vegetation, blackwater rivers are acidic and low in nutrients, selecting for tree species with slower growth rates and higher wood density. Near Manaus, the sediment-laden, ocher waters of the Amazon main stem (known there as the Solimões) and the dark waters of the Rio Negro flow side by side for dozens of kilometers without mixing due to differences in temperature, speed, and water density.

Despite the vast diversity of the canopy, botanical surveys indicate that half of the Amazon's roughly 390 billion trees belong to just 227 to 299 "hyperdominant" species. Many of these abundant trees—such as the Brazil nut, açaí palm, rubber tree, and cacao—are species useful to humans, a distribution pattern that researchers link to thousands of years of forest management by pre-Columbian Indigenous societies alongside natural evolutionary adaptations to specific soil and flooding regimes.

The Amazon rainforest supports the highest concentration of living species on the planet, housing an estimated one in ten of all known species globally. Botanists have cataloged between 40,000 and 50,000 plant species within the basin, including roughly 16,000 tree species, alongside thousands of shrubs, vines, and vascular epiphytes.³ Plant and animal communities in the forest are tightly interdependent; the majority of Amazonian trees rely on mammals, birds, and fish to consume their fruits and disperse their seeds, while insects, bats, and hummingbirds drive pollination across the canopy and understory.¹⁸

Vertebrate diversity in the basin is unmatched by any other terrestrial biome. The rainforest is home to approximately 1,300 bird species—representing about 15 to 20 percent of the world's total avian diversity—including the harpy eagle, scarlet macaw, and hoatzin.¹⁹ Around 427 mammal species inhabit the forest, roughly 34 percent of which are endemic to the region. Prominent terrestrial and arboreal mammals include apex predators such as the jaguar and puma, herbivores like the tapir and capybara, and dozens of primate species ranging from howler and spider monkeys to pygmy marmosets, emperor tamarins, and Goeldi's monkeys, alongside two-toed and three-toed sloths.

Aquatic and herpetological life is similarly varied. The river systems contain between 2,400 and 3,000 known species of freshwater fish, the largest number in the world, including the carnivorous piranha, freshwater electric eels, and the giant pirarucu (arapaima), as well as aquatic mammals like the Amazonian manatee, the giant river otter, and the pink river dolphin (Inia geoffrensis).²⁰ Over 370 to 378 species of reptiles—such as the green anaconda, black caiman, and boa constrictor—and more than 400 species of amphibians, including numerous poison dart frogs, occupy the basin's wetlands and forest floors. Invertebrates make up the vast majority of the biome's animal biomass and species richness, with estimates suggesting at least 2.5 million insect species live in the canopy and leaf litter, and thousands of new beetle and arachnid species are described by taxonomists each decade.

The Amazon rainforest functions as a giant hydrological pump and carbon reservoir that stabilizes both regional weather and the global climate. Its vegetation and soils hold an estimated 150 billion to 200 billion metric tons of carbon. Through photosynthesis, the intact forest historically absorbed vast quantities of anthropogenic carbon dioxide from the atmosphere, acting as a vital terrestrial carbon sink.²⁷

Equally critical is the forest's role in moisture recycling.²⁸ Trade winds carry warm, moist air from the tropical Atlantic Ocean westward into the basin, falling as rain over the eastern forest. Amazonian trees absorb this groundwater through deep root systems and release it back into the atmosphere via evapotranspiration. Through this process, the forest generates up to half of its own rainfall. The resulting water vapor forms massive aerial streams of moisture—often called "flying rivers"—that flow westward to the Andes and are deflected southward, supplying essential precipitation to the agricultural heartlands and urban reservoirs of southern Brazil, Paraguay, Uruguay, and northern Argentina.

Since the early 2000s, earth system scientists—most notably Thomas Lovejoy and Carlos Nobre—have warned that the interactions between deforestation, fire, and global warming could push the hydrological cycle past an ecological "tipping point". If tree cover drops below a critical threshold, reduced evapotranspiration can lengthen the dry season and decrease regional rainfall to the point where moist tropical trees can no longer survive, triggering a self-reinforcing dieback that would convert large portions of the southern and eastern Amazon into degraded savanna. Early models estimated this threshold at 20 to 25 percent total deforestation across the basin. A February 2024 study published in Nature by Bernardo Flores and colleagues analyzed compounding water-stress drivers and projected that by 2050, between 10 percent and 47 percent of Amazonian forests will face combined disturbances severe enough to trigger ecosystem transitions, recommending a safe planetary boundary of no more than 10 percent total deforestation alongside limiting global warming to 1.5 degrees Celsius.

Field and satellite measurements from the 2020s indicate that the Amazon's carbon sink is weakening under the strain of elevated temperatures and moisture stress, with heavily deforested and drought-stricken regions in the southeastern basin already functioning as net sources of carbon emissions. In late 2025, the European Space Agency and Brazilian research institutions launched an intensive field and airborne campaign across undisturbed and degraded sites to measure land-atmosphere gas exchanges and clarify how close the wider biome is to saturation.²⁹

Between 1990 and 2025, the Pan-Amazon lost approximately 976,251 square kilometers of intact humid forest—representing roughly 17 percent of its original forest cover—while an additional one-third of the remaining biome experienced measurable degradation from selective logging, understory fires, and edge effects. The primary economic driver of forest clearance is the expansion of pasture for cattle ranching, followed by industrial agriculture (particularly soybean cultivation), land grabbing, illegal gold and mineral mining, and the construction of roads and hydroelectric dams.³⁰

Forest loss fluctuates in response to both national political enforcement and extreme climatic events.³¹ In Brazil, deforestation spiked beginning in 2019 under the administration of President Jair Bolsonaro before entering a sustained decline following the return of President Luiz Inácio Lula da Silva and Environment Minister Marina Silva, who revitalized the Action Plan for the Prevention and Control of Deforestation in the Legal Amazon and strengthened enforcement operations by the environmental agency Ibama.³² However, in 2024, a severe drought driven by El Niño and anomalous warming of the North Atlantic Ocean dried out the forest understory, causing a massive surge in wildfires. According to the Amazon Regional Observatory (ARO) of the Amazon Cooperation Treaty Organization (ACTO), total area affected by deforestation and degradation across the eight Amazonian member states jumped to approximately 64,000 square kilometers in 2024—with deforestation rising 256 percent to 37,033 square kilometers and degradation reaching 27,349 square kilometers—as fires accounted for roughly 60 percent of primary forest loss in Brazil.

As extreme drought conditions eased and law enforcement intensified in 2025, total forest area impacted across the ACTO nations fell by roughly 60 percent to just over 25,000 square kilometers. This downward trend continued into the first half of 2026: satellite data from Brazil's National Institute for Space Research (INPE) recorded 1,295 square kilometers of deforestation in the Brazilian Amazon between January and June 2026, a 38 percent drop compared to the 2,090 square kilometers cleared during the same period in 2025 and the lowest level in a decade. Burned area in the Brazilian Amazon during the first six months of 2026 was also nearly 40 percent below the 2013–2025 historical average, though localized deforestation rose by 21 percent in the northern state of Roraima due to persistent dry conditions and agricultural fires. Conservation authorities remained on high alert through late 2026 amid meteorological forecasts of a developing El Niño event.

Efforts to permanently halt forest loss center on expanding Indigenous land rights, strengthening regional cooperation through ACTO, and restructuring global conservation finance.³³ Studies consistently show that legally demarcated Indigenous territories act as the most effective barrier against deforestation and fire. On the international stage, the city of Belém—located at the mouth of the Amazon River in Pará, Brazil—hosted the 30th United Nations Climate Change Conference (COP30) in November 2025.³⁴ During the summit, the Brazilian presidency and the World Bank officially launched the Tropical Forests Forever Facility (TFFF), a multilateral endowment fund designed to raise 125 billion US dollars from sovereign governments and private institutional investors.³⁵ Supported by nearly 50 nations with initial financial pledges from Brazil, Indonesia, Norway, and Portugal, the TFFF invests capital in bond markets and uses the returns to issue fixed, annual payments per hectare to tropical forest nations and local communities that keep their standing forests intact.