Tropical Rain Forests
Areas in Africa, Central and South America, and Southeast Asia are dense with
green growth, unusual insects, colorful birds, and exotic animals. Life is everywhere:
beginning, thriving, dying, and beginning again. From these rain forests people
harvest beautiful wood, delicious fruits and nuts, and powerful medicines. The lush
vegetation of the tropical rain forest holds the greatest variety of species on Earth. A
single hectare of Amazon rain forest in Brazil, for example, might support as many as
three hundred different types of woody plants, a great range of biodiversity. In
contrast, forested land in France normally supports only twelve different woody
species—not much variety at all.
Rain forests have so much rich growth that people have long thought that they
were indestructible: cut down one tree and two would grow in its place. The
resources in these dense rain forests could surely be used freely. Governments, too,
have assumed that the rain forests could be easily turned into profits. The growth
seems so abundant; it seems to be easily renewable. To owners of large agricultural
businesses, the rain forest is an enemy; it covers land that they need for fields. Surely,
these businesspeople think, there are plenty of trees. It will not matter if we cut some
down to make a large field. They may even believe that the rain forest will take over
the land again when they stop farming. Such is not the case, however. Although the
ecosystems of tropical rain forests include many plant and animal species, the
ecosystems are fragile. The balance is easily upset.
All rain forests share certain characteristics. They grow in very wet, humid places
where the annual rainfall exceeds 1,000 millimeters (40 inches). The tallest trees
form an umbrellalike ceiling called a closed canopy. Such a top layer of vegetation
forms when a large number of trees branch out horizontally at approximately the
same height. Their branches hold vines; the leaves of the trees and the vines make a
forest ceiling. Under a closed canopy, young plants grow in the shade. Only the plants
with leaves at the top of the canopy get direct sunlight. In fact, the forest floor is quite
dark. Because of the closed canopy in a rain forest, as little as one or two percent of
the sunlight reaches the floor.
Another characteristic of most tropical rain forests is poor, thin soil. Only rain
forests in volcanic areas might have somewhat better soil. People who wish to farm
must move their fields frequently because of the nutrient-poor soil. Most rain forest
land is exhausted after only two years of farming. That is why the farmers cut more
trees and move to new land.
Many people want to understand: rain forests have so much biodiversity (many
different kinds of plants). Yet, the soil is nutrient-poor. The answer is that the rain
forest ecosystem depends on a long string fungus, mycorrhiza (MEE-ko-REE-uh). The
strings of the fungus are the thickness of a spider’s web. These strings connect fallen
leaves with the roots of trees. Like tiny pipes, they carry nutrients from the rotting
vegetation to the roots of the trees. The fungus makes it possible for plants to get food
without taking it from the soil.
Rainwater washes nutrients from the leaves as it falls. This water goes straight to
the trees. It is not surprising that a thick web of roots lies below the surface of the
forest floor. The ecosystem of the rain forest does not depend on rich soil at all. When
the trees are removed, the richness of the forest disappears. Rain forest ecosystems are
really simple. Ignoring how the system works results in a wasteland.
TIMED READING
There Is No More “Away”
Everyone is talking about, practicing, and discovering new ways to be
environmentally responsible. The word recycle tells the story: re- means “(to do
something) again,” and cycle is “a full circle, a return to the beginning.” Therefore,
recycling means recovering and reusing spent (used up) products—finding ways to
use products a second time. The motto of the recycling movement is “Reduce, Reuse,
Recycle”; the term recycling covers the whole program.
The first step is to reduce garbage. Supermarkets sell products in expensive
wrappings. A fast-food hamburger often comes wrapped in paper in a box in a bag.
What a waste of resources! Every day, millions of plastic cups are used for coffee and
tea. Each time someone buys a hamburger or uses one of those cups, energy and
resources are wasted. To reduce garbage, the throwaway trend must stop.
The second step in the general recycling program is to reuse. If customers buy
juices and soft drinks in returnable bottles, they can return them to the store.
Manufacturers of drinks collect the bottles, wash them, and then fill them again. The
energy for making new bottles is saved. Where returning bottles for money is
common, garbage dumps have relatively little glass and plastic throwaway bottles.
The third step in being environmentally sensitive is to recycle. Used motor oil
can be cleaned and used again. Aluminum cans are easily recycled. When people
collect and recycle aluminum (for new cans), they help save one of the world’s
precious resources. The problem of garbage has other aspects. People cannot throw
things away because there is no more space for dumps. Furthermore, liquids from
garbage contaminate groundwater.
Recycling is a challenge because it requires a basic change in everyday life. For
recycling to be successful, ordinary people must be aware of what they buy. They
must also sort their trash and garbage into organic garbage, newspapers, steel cans,
glass containers, and plastic. Waste materials of the same kind are compacted
(crushed into blocks). A manufacturer buys the sorted, compacted blocks of material
to make into something new. Once a customer buys and uses the product, the same
materials follow the same cycle—being sorted, collected, and used again. Hence the
word recycled. In the end, the real meaning of recycling is keeping Earth safe and
clean for future generations. It is one way for everyone to contribute to a better
world.