When people think of animals that live in forests, creatures such as bears, eagles, gorillas, tigers are usually what come to mind. Forest plants, other than trees, are often ignored. And many people are unaware of the fact that organisms such as bacteria and fungi are just as important to the forest as the trees themselves.

Inorganic materials are also crucial to the living organisms. Green plants--everything from trees to the most delicate ferns--form the base of all forest ecosystems. These plants require clean air, soil, water, and sun to grow and support the fragile network of life in a forest.

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Tropical rainforest, Maui. Photo by Maya Walters.

Forests are some of the most diverse habitats on the planet. Biodiversity* is not simply something that's "nice" to have. All species, including humans, are dependent on all other species for survival. The extinction of even one organism--a monkey, a flowering plant, a water flea--will have unpredictable and often disastrous consequences. Tropical rainforests are the richest ecosystems in the world. Because of the great diversity of plants and animals, there are actually relatively few individuals of most species. This makes them especially susceptible to habitat loss and other stresses.

While many temperate species have tropical equivalents, there is a greater range of habitats in tropical forests. The warm, moist climate also contributes to the great numbers of species. There are complete groups of tropical rainforest organisms that are absent from areas with cooler climates. One example are the epiphytes -- smaller plants that actually grow in the branches of larger trees.

Epiphytes and vines growing in the forest canopy, Costa Rica. Photo courtesy Naomi Woods.

If you're soft and defenceless, you are likely to be eaten--unless you look like something else. With close examination, tree bark may turn into a beetle, dead leaves into a moth, twigs and foliage into other well disguised insects. But confusing colors, shapes, and patterns are used for more than defense: predators also take advantage of camouflage. Sometimes hiding is not enough, and seemingly harmless creatures defend themselves with poisonous chemicals. find out more...

A recently burned clear-cut: not a very hospitable habitat. Photo by Maya Walters. When a temperate forest is clear-cut, more deer begin to move into the open areas where they find food. Then the number of predators increases--coyotes, cougars, even bears. This affects the amount of food available for birds such as ravens and other scavengers. The soil which is no longer held in place by the trees washes into streams and destroys fish habitat. If the network of plants is changed, the network of animals is also disrupted.

There is another animal besides humans which can change the forest landscape in powerful and dramatic ways. This animal is a rodent--the . Beavers build dams using trees which they cut down. The dams slow the flow of the streams, creating wetlands and ponds. The wetlands and ponds help prevent flooding and collect rich sediment and organic matter. Beavers favor certain types of trees for their dams, and eventually their less preferred types of trees dominate the forest at the edge of the stream.

In many areas, people try not only to change forests, but to create forests for economic reasons--tidy plantations of one tree species, all the same age. Biodiversity suffers.

Forests need trees of all ages for different purposes, and a healthy forest will actually include a lot of dead trees--both those that are still standing, and those that have fallen to the forest floor. When trees die they still play an incredibly important role in the life of the forest. Insect larva work their way into fallen trees, hollowing out tunnels in the spongy wood, which helps the forest floor store moisture.

Trees that are dead but still standing are often referred to as "snags", or, more appropriately, as "wildlife trees". These trees are more than a convenient place for woodpeckers to take out their aggressions. When trees die and remain standing, insects such as carpenter ants move in and build nests. Woodpeckers create hollows and cavities in the wood as they search for and eat the insects. These holes are perfect nesting sites for songbirds, which consume pests that are harmful to the forest.

Insects and fungi move into rotting tree trunks, helping to break them down into new soil. Photo by Maya Walters.

Remove any of these organisms, and the entire ecosystem would collapse. Everything is essential--the snags, the ants, the woodpeckers, the songbirds, even the pests, for without the pests, there would be no snags.

Fruit grows at the ends of branches. The ends of branches are hard to reach, and often too thin to support the weight of an animal such as a monkey. Some animals have come up with a solution: the prehensile tail, which works like an extra arm. Others have taken to gliding through tree tops. These are two adaptations which have evolved in response to the particular characteristics of the animals' forest habitat. find out more...