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Pondelok, 18. októbra 2021
Rainforests
Dátum pridania: 08.11.2005 Oznámkuj: 12345
Autor referátu: lucassos
 
Jazyk: Angličtina Počet slov: 690
Referát vhodný pre: Gymnázium Počet A4: 2.5
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Rainforests
1)Introduction:

The rainforests are 3,4 million square miles of tropical forest that encircle the equator. Before 1900, rainforests covered 14% of the world’s surface. Today they cover 2%. The reason is simple. They have been cut down to provide: land, paper, wood, medicines, minerals, fuel,… But it’s not only trees disappearing. Although rainforests cover less than 2% of Earth’s surface, they are home to more than half of all its living things. Land half the size of San Francisco contains 545 kinds of birds, 100 species of dragonflies, and 729 kinds of butterflies. Two hundred ond five kinds of mammals, 845 types of birds, and 10,000 different varieties of plants inhabit the Costra Rican rainforests. This animals are destroyed, too. If man continues to cut down rainforests, more than one million species of plants and animals will become extinct by the byear 2030!


2)Degree of destruction:

Originally 8 million square miles of tropical rainforest encircled planet. More than half has been burned and bulldozed. Now only 3,4 million square miles remain. Over last decade, man destroyed 113 million acres of rainforest. In 2 hours, modern machinery can clear 900 tons of rainforest. That mean, that every second humans wipe out a area of rainforest the size of two football fields. For example: since 1950, man has destroyed Costa Rica’s rainforests at the average rate of 300 to 500 square kilometres per year. Two-thirds of Central American rainforests have allready disappeared. The largest cause of rainforest destruction is commercial logging. The current rate of rainforest destruction indicates a potential loss of 5 to 15 % of the world’s animal species. Between 1990 and 2020, estimates indicate that at lest 100 animal species could be lost each day! Rainforest destruction is the single largest cause of species extinction. If these current rates of destruction continue, scientists predict that 80 to 90% of Earth’s tropical rainforests will be decimated by the year 2020.


3)Effects of deforestation:

On the Water:
Rainforests absorb nearly half of the Earth’s rainfall and gradually release it into rivers and streams. The tropical forests release rainwater into watersheds slowly and evenly. Preventing both flooding and droughts. Therefore, when rainforests are intact, the rivers run full and clear. However, when the forests are destroyed, the rivers dry up and become muddy.

Tropical rainforests provide a natural defense against hurricanes, cyclones, and typhoons. However, as rainforests are cut down, tropical storms kill at least 20,000 people each year and cause $4 bilion in damage. Flooding and soil and water degradation caused by tropical deforestation periodically disrupts the lives of approximately 1 billion people.

On the Air:
Due to the deforestation of dense, virgin rainforests, 1,4 billion tons of carbon dioxide enter the Earth’s atmosphere each year. Ten percent of it derives from the destruction of Brazilian rainforest. Burning rainforests are the source forr about 20% of carbon dioxide released each year.In single day, satellite photos have show 7,603 different fires raging in the Brazilian rainforests! The smell of smoke is not unusual in the rainforests. Because of heavy smoke in the air, local airports are sometimes closed. In 1997, the smoke from forest fires burning out of control was cause of a plane crash in Indonesia.

On the Land:
A primary or virfgin rainforest is one that reaches a state of balance and adulthood. A secondary forest is a primary forest, that has been cut down and then replanted. However the secondary forest harbors only ¼ of the plant and animal species of the original and the lifespan of the trees decreases. It takes nearly 1,000 years for a secondary forest to evolve byck into primary forest. Just 3 years after deforastation, the land loses half its organic content.


4)Reasons to save the rainforests:

The rainforests contains such a plethora of life that humans have been unable to classify and name all of it. Brazil has ane-third of the world’s remaining rainforests. Yet humans identified only 10% of the plant species that occupy them. Tropical rainforests provide between 25 to 50% of all pharmaceutical products. Three thousand plants have anti-cancer properties. Of these, 70% inhabit the rainforests. Only 1% of tropical plants have examined for possible medicinal use. But, those that have field ¼ of all prescription drugs sold in the United States.

Governments in rainforest countries need to plan and work together. they should also protect certain areas and plant new forests….
 
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