leaves and other material, and the bacteria break this material down into the nutrients

　　that the trees need to survive。

　　One of the most remarkable things about rainforest plant life is its diversity. The

　　temperate rainforests of the Pacific Northwest are mainly composed of a dozen or so

　　tree species. A tropical rainforest, on the other hand, might have 300 distinct tree　species。

　　All Creatures, Great and Small

　　Rainforests are home to the majority of animal species in the world. And a great

　　number of species who now live in other environments, including humans, originally

　　inhabited the rainforests. Researchers estimate that in a large rainforest area, there

　　may be more than 10 million different animal species。

　　Most of these species have adapted for life in the upper levels of the rainforest,

　　where food is most plentiful. Insects, which can easily climb or fly from tree to tree,

　　make up the largest group (ants are the most abundant animal in the rainforest). Insect

　　species have a highly symbiotic relationship with the plant life in a rainforest. The

　　insects move from plant to plant, enjoying the wealth of food provided there. As they

　　travel, the insects may pick up the plants' seeds, dropping them some distance away.

　　This helps to disperse the population of the plant species over a larger area。

　　The numerous birds of the rainforest also play a major part in seed dispersal.

　　When they eat fruit from a plant, the seeds pass through their digestive system. By the

　　time they excrete (排泄) the seeds, the birds may have flown many miles away from　the fruit-bearing tree。

　　There are also a large number of reptiles and mammals in the rainforest. Since

　　the weather is so hot and humid during the day, most rainforest mammals are active

　　only at night, dusk or dawn. The many rainforest bat species are especially well

　　adapted for this lifestyle. Using their sonar, bats navigate easily through the mass of

　　trees in the rainforest, feeding on insects and fruit。

　　While most rainforest species spend their lives in the trees, there is also a lot of

　　life on the forest floor. Great apes, wild pigs, big cats and even elephants can all be

　　found in rainforests. There are a number of people who live in the rainforests, as well.

　　These tribes--which, up until recently, numbered in the thousands--are being forced

　　out of the rainforests at an alarming rate because of deforestation。　Deforestation

　　In the past hundred years, humans have begun destroying rainforests at an

　　alarming rate. Today, roughly 1.5 acres of rainforest are destroyed every second.

　　People are cutting down the rainforests in pursuit of three major resources:

　　· land for crops

　　· lumber for paper and other wood products

　　· land for livestock pastures

　　In the current economy, people obviously have a need for all of these resources.

　　But almost all experts agree that, over time, we will suffer much more from the

　　destruction of the rainforests than we will benefit。

　　The world's rainforests are an extremely valuable natural resource, to be sure, but

　　not for their lumber or their land. They are the main cradle of life on Earth, and they