The Amazon rainforest spans nine South American countries. The rainforest, fed by the Amazon River, is an ecologically diverse area of the planet, providing resources the planet needs to survive. The Amazon rainforest provides over 20 per cent of the world's oxygen, one-fifth of its fresh water and contains more than half of the world's species of animals, plants and insects. Its physical characteristics that result from proximity to the equator provide mostly moist dense tropical forests, but also include habitats such as montane, palm, bamboo, lowland and floodplain forests, grasslands and swamps.
The Amazon rainforest's tropical climate is humid and provides an average of 80 inches of annual rainfall, with half of the precipitation resulting from the forest's own evaporation. It rains more than 90 days a year with temperatures ranging between 17.7 and 25.0 degrees C (64 and 77 degrees F). Flooding can occur between June and October, but much of the rain that falls stays on trees and never reaches the forest floor. Direct sunlight hits the upper part of the Amazon rainforest and the sun shines brightly between rain showers.
The majority of plants in the Amazon rainforest are trees. Tropical rainforests have more types of trees than any place in the world; scientists have counted 100 to 300 species in a 1 hectare (2 1/2 acre) area in the Amazon rainforest. The trees form four separate areas in the rainforest, including emergent trees, the canopy, the understory and the forest floor. Emergent trees are umbrella-shaped trees with smooth bark that are 30 to 72 m (100 to 240 feet) tall. The upper canopy has 18 to 39 m (60 to 130 feet) tall trees and most of the rainforest's animals live in the upper canopy. The understory, or lower canopy, is shaded by the upper canopy and contains shrubs, plants and trees up to 18 m (60 feet) tall. The forest floor is so shaded that few shrubs can grow there; a shrub/sapling layer on grows on the forest floor, however it receives very little light that filters through the canopies, and hence, has some stunted growth.
Plants that grow in the Amazon rainforest include herbaceous, perennials and bulbous flowering plants, shrubs, vines, ferns and lilies. Many plants grow on trees in the rainforest's upper canopy, including epiphytes such as orchids and bromeliads. Edible plants from the Amazon include fruits like avocados, coconuts, figs, oranges, lemons, grapefruit, bananas, guavas, acai berries, pineapples, mangoes and tomatoes; vegetables including corn, potatoes, rice, winter squash and yams; spices like black pepper, cayenne, chocolate, cinnamon, cloves, ginger, sugar cane, turmeric, coffee and vanilla and nuts including Brazil nuts and cashews. Many medicinal plants including those with anti-cancer properties are only found in the rainforest. Amazon rainforest researchers discovered 637 new plants in 10 years. Most plants used by Amazon natives haven't yet been studied by modern science.
Insects including butterflies, mosquitoes, ants and camouflaged stick insects make up the largest group of animals that live in the Amazon rainforest. Threatened species such as harpy eagles and pink river dolphins live in the Amazon as well as jaguars, giant otters, scarlet macaws, southern two-toed sloths, pygmy marmosets, piranhas, anacondas and howler monkeys. According to the report Amazon Alive, researchers found 1,200 new species in the Amazon between 1999 and 2009, with invertebrates including insects making up most of the discoveries. Other new species included 357 fish, 216 amphibians, 55 reptiles, 39 mammals and 16 birds.