the region is home to ~2.5 million insect species, tens of thousands of species of plants, and some 2000 species of birds and mammals and a similar number of fish. the diversity of plant species is the highest on earth with some experts estimating that one square kilometre may contain over 75,000 types of trees and 150,000 species of higher plants. one square kilometre of amazon rainforest can have about 90,000 tons of living plants. this is the largest collection of living plants and animal species in the world. one in five of all the birds in the world live here. to date, an estimated 438,000 species of plants of economic and social interest have been registered in the region with many more remaining to be discovered or cataloged.