Some Common Misconceptions
(Correcting Some Popular
rainforests are beautiful and fascinating phenomena of nature. Two basic
things are necessary for a tropical rainforest to exist: warm temperatures
and plenty of rain. These requirements are generally found on earth within a
band to either side of the equator between the Tropic of Cancer and the
Tropic of Capricorn with the most intense band being 10 degrees to either
side of the equator. Tropical rainforest conditions are not guaranteed to
occur within this band however. Local wind and climate patterns can create
deserts as well. A good example is the vast Sahara Desert in North Africa.
Tropical rainforest conditions depend to some extent on an interaction
between the atmosphere and the rainforest itself. The extent of this
interaction is not fully understood. See Deforestation.
There are many popular
misconceptions about tropical rainforests. Contrary to popular belief, the same
rainforests have not been here for "millions of years". The fossil record
demonstrates that rainforests have existed, off and on, for millions of years, but not the
same rainforests that we have today. In fact, all of today's rainforests formed after the
end of the last Ice Age which was winding down only about 15,000 years ago. 6,000 to 8,000
years ago, the Peten in Guatemala was savannah and grassland. Some scientists say that the
rainforests in Guatemala appeared as recently as 2,000 years ago and that the climate
change which caused the formation of the rainforests may have contributed to the end of
the Mayan civilization.
Another popular misconception is that the rainforest is
a dense, impenetrable, dark jungle. To many people, "rainforest" and
"jungle" are synonymous. It is true that secondary rainforest which springs up
when primary rainforest is cut down is dense and impenetrable but primary rainforest is
open and airy. Tall trees lacking low branches reach 150 feet up and the tops of the trees
form the canopy of the forest. The tops of the trees join to form a relatively solid roof
that breaks the force of heavy rain for the plants below but plenty of light still filters
through. Because the trees lack lower branches, it is easy to see relatively long
distances through the rainforest. The soil is completely covered with living plants,
mosses, lichens, etc. but walking through primary rainforest is no more difficult than
walking through a European forest. Between the ground cover and the tree tops, there's
open space with occasional vines and a few trees with low branches. Unlike in the movies,
you do not need a machete to chop your way through primary rainforest!
A third popular misconception is that the rainforest is
noisy. Tarzan movies and others like it have probably given people this impression. During
the day, the rainforest is remarkably quiet and peaceful. At sunrise and sunset, the birds
and monkeys will make noise in certain parts of the forest and at night, the crickets,
leafhoppers and cicadas make their noises. In some parts of the forest, frogs can set up a
surprisingly loud racket. But during the day, the rainforest is usually so quiet that you
can hear single leaves falling!
fourth common misconception is that the soil of the rainforest is very fertile. This is an
easy mistake to make. The lush and profuse growth of plants makes it seem obvious that the
soil is fertile. It's true that just about anything will grow in the rainforest -- and
that is the key phrase: "in the rainforest". The soil in the rainforest is very
fertile but only the top few inches and only while the rainforest is left in place. If you
take away the rainforest, the soil itself is not very good at all. The soil's fertility
derives from the intense biological activity in the rainforest. This activity is so rapid
that biomass from dead plants is recycled and the nutrients made again available in a
matter of weeks. The warmth, shade and moisture promote bacterial and fungal activity and
a fallen plant is broken down and recycled very rapidly.
Rainforest soil, however, is not good farmland. The
good topsoil in the rainforests around the Rio Dulce extends down only about 12 inches,
below which is impermeable clay. The topsoil in good farmland extends down several feet.
To illustrate the difference between rainforest soil and farmland, consider that when you
look at a crop growing on good farmland, the crop is only a small fraction of the biomass
in the system. Far more biomass lies buried in the soil down to a depth of several feet.
In contrast, when you look at a rainforest, you are looking directly at most of the
biomass. It is all up in the air and very little is in the soil. Only the top few inches
of rainforest soil is fertile. This is why deforestation is such a problem. When the
forest is clear cut or burned off in order to plant food crops, the remaining soil can
only function for a season or two before it is depleted. Rainforest soil is loaded with
bacteria and fungi that are biochemically very active but only when protected by the
rainforest canopy. When the rainforest is cleared off, the soil is exposed to the direct
sun which destroys the bacteria and fungi leaving just the meager chemicals in the top few
inches of soil.
The popular conception that is correct is about the
rainforest's diversity. A healthy rainforest is characterized by species diversity and is
home to thousands of species of life. Biologists estimate that just one hectare (about 2.5
acres) of the rainforest along the Rio Dulce contains around 250,000 species! Some of
these species are unique to just a small area. The number of different kinds of plants,
insects and birds is mind-boggling.