c. steven holt, stock photography © national ocean service – picutres free to public

c. Steven Holt, Stock Photography

© National Ocean Service – picutres free to public


Tropical Rainforests•Cover 2% of the earth’s surface, yet they house over half the plant and animal species on the earth.

•Oldest living ecosystems, they have existed in their present form for 70 to 100 million years.

•Are home to half of the 5 to 10 million plant and animal species on the globe

•Over ¼ of medicines available today owe their existence to rainforests plants.


Tropical Rainforests•Rainforests are defined by two main factors – location (the tropics) and the amount of rainfall that they receive.

•Temperatures are always high, typically between 25C and 30C with no seasons. There is no dry or cold seasons or time of slower growth or dropping of leaves.

•Many of the foods we eat today originated in rainforests – eg avocado, banana, brazil nuts, peppers, cashew nuts, chocolate, cinnamon, cloves, coffee, cola, corn, fig, ginger, herbal tea ingredients, lemon, orange, peanut, pineapple, rice, sugar, tomato – to mention just a few!!!!


Tropical Rainforests

•Rainforests play a critical role in the atmosphere in part because they hold vast reserves of carbon in their vegetation. When rainforests are burned, or the trees are cut and left to decay, the carbon is released into the atmosphere as carbon dioxide (CO2). This is the second largest factor contributing to the greenhouse effect.



•A typical four square mile patch of rainforest contains as many as 1500 species of flowering plants, 750 species of trees, 125 mammal species, 400 species of birds, 100 of reptiles, 60 of amphibians, and 150 different species of butterflies. In one study, one square meter of leaf litter, when analysed, turned up 50 species of ants alone. (National Academy of Sciences.)

Amazon river


Tropical Rainforests•This is an example of slash and burn where native Indians clear small areas of forest for their subsistence agriculture.

•Four-fifths of the nutrients in the rainforests are in the vegetation. This means that the soils are nutrient-poor and become eroded and unproductive within a few years after the rainforest is cleared.


Tropical Rainforests•The most valuable trees such as teak, mahogany, rosewood and ebony are cut down first. Roads are built to transport these trees and much damage is caused by this extraction.

•Extreme poverty amongst people living in the tropical rainforest countries is a major reason for their destruction. The World Bank estimates that of the 2.5 billion people now living in the tropics one billion exist in absolute poverty. (Raven, Peter H, Bulletin of Atomic Scientists, November 1984.)

Tree felled in the Amazon


Tropical Rainforests•After selective logging, whole areas are cleared for their timber. The protective canopy of the forest is removed, and all the plants and animals living their either die or are forced to leave.

•This also leaves the thin soil exposed to heavy rain which washes it away.

Forest cleared in the Amazon


Tropical Rainforests•The remaining timber may be also be burnt, either for slash and burn or to clear the land for cattle, which improves the soil for a short time.

Burning timber waste in the Amazon



•.Rainforest which has been cleared of all timber and then burnt


c. Scalloway Junior High School

•. This leaves the soil unprotected and vulnerable to erosion from the heavy rains.



•.The result can then be severe soil erosion, leaving the land useless for any further agriculture.

Gullying in the Amazon



•.Tropical timber yard with wood stored for further transportation.


Tropical Rainforests•Global rates of destruction

2.4 acres per second, equivalent to two U.S football fields

78 million acres per year – an area larger than Poland

6 - 9 million indigenous people inhabited the Brazilian rainforest in 1500 In 1992, less than 200,000 remain. •Projected economic value of one hectare:-

$6,820 per year if intact forest is sustainably harvested for fruits, latex, and timber

$1,000 if clear-cut for commercial timber (not sustainably harvested)

$148 if used as cattle pasture

Cattle ranching in the Amazon




•Uses of the rainforests

Timber – for furniture, plywood, panelling and construction

Wood pulp and wood chips to make paper and disposable cardboard packaging.

Oil – the western Amazon is being heavily damaged due to oil extraction

Beef – imported into the UK for hamburgers, luncheon meat, pet food, sausage and frozen dinners – Campbell’s Soup uses rainforest beef.

Pulp mill in Amazon

DesertificationMoreAnimals

MorePeople

MoreCrops

MoreFirewood

InsectsEat crops

Drought

Overgrazing

Deforestation

Overcultivation

BARESOILS

DESERTIFICATIONThe land provides Less food

NaturalHazards