Transcript Rainforest

Rainforests
Rainforests have been called the womb of life
because they are home to 50-90% of the species on
Earth. It’s vegetation helps clean the earth’s
atmosphere and regulate the climate.
Several hundred million people live in or depend on
rainforests. Many of the world’s important food crops and
domestic animals have been developed from rainforest
species.
Tropical rainforests are the result of the unique climatic
conditions found between the Tropics of Cancer and
Capricorn. Constant heat and humidity allow trees and plants
to grow year round. Columns of hot air rise and condense out
as rain, resulting in annual rainfall of 80 to 400 inches:
temperatures average over 80 degrees Fahrenheit.
Structure
of the
Rainforest
Emergent trees
Above the upper canopy,
tower a few emergent trees,
sometimes as tall as 130 feet.
In all the forest, they alone
enjoy unobstructed access to
the sun and sky.
The Canopy
The vast carpet of green
comprises the canopy that
hovers over the forest below. It
absorbs as much as 90% of
the sunlight falling on the
forest, darkening the lower
regions. Here65-100 feet up
live butterflies and mammals.
Temperatures here reach 96 F
but the humidity is only 60%,
compared to 90% down below.
The Understory
In the undeveloped
forest, the understory is
not the jungle of tangled
vines seen in old movies.
Undisturbed rainforest is
clear of vegetation close
to the ground because so
little light filters down
through the canopy,
sometimes only 1 to 2
per cent. Temperatures
are cooler, averaging
about 82 F with humidity
at about 90%.
By most estimates, the world’s forests are
disappearing at an alarming rate. Logging,
fires, and land-clearing for agriculture and
grazing account for most of the loss. More
than 80 percent of the Earth’s natural
forests already have been destroyed.
Among the obvious
consequences of
deforestation is the loss of
living space. Seventy
percent of the Earth’s land
animals and plants reside
in forests.
It has been estimated that at
least 40 species are
perishing every day. This is
a rate hundreds of times
faster than at any period in
recent geological time.
Rainforests are also a vital source of medicines. Today, less
than 1% of the world's tropical forest plants have been
tested for pharmaceutical properties, yet at least 25% of all
modern drugs came originally from rainforests.
70% of all plants known to have anti-tumor properties come
from tropical rainforests. Any one of these could lead to
breakthroughs in the treatment of cancer. The potential of
this living pharmaceutical factory remains almost
completely untapped.
The potential and fragility of the rainforests as an invaluable
source of medicine is illustrated in the following account from
the World Rainforest Report no.26:
"Starting with twigs from a Malaysian gum tree, researchers in
1991 isolated a compound that blocked the spread of the AIDS
virus in human cells. The team sent biologists racing back to
Malaysia for more samples from the tree. But when they got to
the swamp, the tree was gone, it had been cut down. And no tree
found since has produced the same compound. "
But the harm doesn’t stop there. Rain forests help
generate rainfall in drought-prone countries elsewhere.
Deforestation may have catastrophic global effects as
well. Trees are natural consumers of carbon dioxide—
one of the greenhouse gases whose buildup in the
atmosphere contributes to global warming.
No one knows just how the rest of the
global ecosystem depends on
rainforests, but we may find out in the
next 30 to 50 years. That is how long it
is estimated that it will take for
tropical forests to disappear
altogether if current trends continue.
The Amazon
The Amazon is the world's
largest tropical rainforest,
spanning Brazil,
Colombia, Ecuador, Peru,
Bolivia, and Venezuela .
Within the 2.5 million
square miles of the
Amazon Basin resides a
wealth of life richer than
anyplace else on earth,
including 500 mammals,
175 different lizards, 300
other reptile species, tree
climbers of every kind,
and a third of the world's
birds. Millions of species
still remain undiscovered.
The basin also has huge reserves of bauxite, nickel, copper, tin
and timber. Trees and vegetation in the basin help to balance
carbon dioxide and oxygen.
The basin holds 20% of the earth’s fresh water, more than the
next six largest rivers combined. The flow of the Amazon is so
powerful that it dilutes the saltwater more than one hundred
miles beyond the coastline.
Most of the people living in South
America today have both
European and indigenous
ancestors. Until recently,
however, few of them lived in
the Amazon. They preferred to
live in established cities along
the coasts and in the Andes
mountains.
But in the past few decades, more
and more mestizos have moved
to the Amazon. They were
having trouble finding work in
their hometowns and saw
opportunity in the Amazon.
Many went looking for
agricultural land. Others took
jobs in oil fields or other
industries.
Settlement in the Ecuadorian
Amazon 1960 to 1990
About a third of Ecuador
lies within the Amazon.
Since the 1950s,
Ecuadorians (mostly
mestizos) from the
Andean highlands and
the western coastal
plain have been
migrating to the
Amazon.
The population of the
Ecuadorian Amazon
has increased from
about 60,000 people in
the 1950s to 350,000
people now. By clearing
forest to build homes,
plant crops, and extract
petroleum, these people
have had a dramatic
impact on the rainforest.
The deforestation of the Amazon basin may have long
reaching effects. When the trees are removed, we
reduce the amount of carbon dioxide taken from the
air. Some scientists predict that the buildup of carbon
dioxide will cause global warming. If the temperature
of the earth rises, polar ice will melt, raising the level of
the ocean.
Plants and animals are also in danger of extinction and
medical advances may be delayed or negated as a
result of deforestation.
What is lost as the rain forests disappear is more than
biodiversity and a stable environment. The rain forests
also hold secrets of nature that might improve and
extend the quality of people’s lives.
Endangered Species of
South America
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http://www.eduweb.com/amazon.html
http://www.rainforestinfo.org.au/
http://passporttoknowledge.com/rainforest/main.html
http://www.nationalgeographic.com/eye/deforestation/deforestat
ion.html
 http://www.junglephotos.com/
 http://www.mrdowling.com/712-amazon.html
Rainforest Quiz!
 1. Where are rainforests found around the
world?
 2. What is the world’s largest tropical
rainforest?
 3. What country’s population in the
rainforest increase from 60,000 to 350,000?
 4. Name two causes of deforestation.
 5. Name two effects of deforestation.
 BONUS: Name the three layers of the
rainforest.
 1. What are Costa Rica’s major exports,
and what do they mean to its economy?
 2. What is ecotourism, and why is it
important to Costa Rica?
 3. What is the real condition of the tropical
rainforests in Costa Rica and throughout the
world?
 4. What is being done to preserve rain
forest ecosystems?
 5. Can people and natural ecosystems
coexist? Explain.