The Biological Richness of Rainforests

Rainforest are amazingly rich in species. Whereas a New England forest may have 20 or 30 species of trees at most and a coniferous forest may have only one or two tree species, a 25 hectare plot near Camp 41 in the Amazon has 295 species of trees. A single tree in Peru has more ant species than all of the United Kingdom. And the Amazon River system has 3000 species of fish -- more than the entire North Atlantic.

Life builds on life in these forests. Lianas loop around more than one tree at a time. Epiphytes like bromeliads and philodendrons cling to the tree trunks. Within each bromeliad there is a tiny microcosm of species living in the water trapped by the whorl of leaves: microbes, invertebrates, insect larvae and some frog species use them as a place to lay their eggs.

The richness in species in rain forests is part of a general pattern of ever more species from the poles to the equator. At the tip of South America in Tierra del Fuego there are only two species of ants. At the very edge of the tropics in Sao Paulo Brazil there are 222 species of ants, with the equator still a very long distance away. This pattern is not universal for all groups of organisms. For example, there are very few species of bumblebees in the Amazon and almost no bears in any rainforest.

Rainforest Birds

There are literally thousands of species of rainforest bird species from hummingbirds to hornbills. Typically those that live in the canopy and near the top of the forest tend to be brightly colored like tanagers, pompadour cotingas or parrots, whereas those that live lower down and in the forest interior tend to more camouflaged. If they have brightly colored for mating displays, they often keep them out of sight except for times of display. Many species eat fruit like toucans or trogons, or nectar like hummingbirds and honey-eaters. Some have very elaborate displays like manakins, bowerbirds or birds of paradise. Most rainforests have mixed species flocks in which many unrelated bird species will participate to achieve more efficient foraging or vigilance against predators.


Rainforest Animals

Rainforests have some big animals, like the Indian elephant or the African forest elephant, gorillas or orangutans, and tapirs. Almost all have many smaller species like marmosets in the new world tropics. Monkey species occur in almost all tropical forests.  Some specialize on ants and termites which occur in untold numbers in these forests like anteaters and pangolins. There is a multitude of rainbow hued butterflies, some of which are brightly colored to send the message “Don’t eat me, I am poisonous”. Yet others are look alikes which mimic the toxic ones so birds that otherwise would eat them leave them alone. The greatest animal biomass in the rainforests is made up of ants and termites (and contributes to decomposition).