Tropical Rainforests

Ecology

What is a rainforest?

• In ecological terms- “ multi-storied closed, broad-leafed vegetation with a continuous tree canopy of variable height and with characteristic diversity of species and life forms”.

• Home to over 50% of all species on Earth

Location

Forest Climate• Global heat and water pumps• Rainforests are dark, - they absorb

heat. • Above a rainforest the air is cooler so

it is more likely to rain. • Inside rainforest, below canopy,

humidity stays high. • The forests stay wet and evaporate

vast quantities of water through their foliage and into the air above, forming clouds.

• Some falls again as rain in the tropics but often clouds are carried great distances to fall as rain in the mid latitudes

http://www.bbc.co.uk/weather/world/south_america/

Climate ComparedManaos(Brazil) London (England)

The Forest Structure

• Notes:

Adaptations

Fertile & Fragile

• Soil in r/forests very thin - trees have shallow roots

• Depends on rapid recycling of nutrients

• Removal of trees devastates this nutrient cycle

Rainforest Nutrient Cycle

Abundant trees

Numerous fallen leaves

Rapid decay to form humus

Nutrients added to soil

Rich soil

Rich tree growth

Rainforest Nutrient Cycle

Trees removed

No leaves falling

No decaying leaves to form

humus

Remaining Nutrients

leached from soil

Soil deteriorates

V.difficult for new trees to

recover

Deforestation - the destruction of rainforests

Forest Fires and Deforestation in Mato Grosso, Brazil

The Amazon River Basin

• Clear-cutting– Starting point for other activities - logging, mining,

agriculture, roads, settlements

– mongobay

Causes of Deforestation

• Agriculture• Clearing forest for

cattle ranching, plantations (palm oil) or crops - eg. soybeans

Causes of Deforestation

• Logging• Removal of trees for

valuable hardwoods • (e.g. mahogany, teak)• Often illegal or

uncontrolled

Causes of Deforestation

• Mineral Extraction(Mining)

• Mining trucks, equipment, open pits and roads at the Rio Huaypetue gold mine in southeastern Peru Location: Southeastern Peru; from Cuzco to Boca Manu

• mongobay

Rates of Deforestation in South America

% loss per year

http://www.mongabay.com/deforestation_rate_tables.htm

Rates of Deforestation Worldwide

Hectares per year

http://news.mongabay.com/2005/1115-forests.html

What else is causing loss of rainforest?

• Look up the following websites and see what you can find.

• http://www.rainforestinfo.org.au/background/causes.htm

• http://www.greenpeace.org/international/ • http://www.sfu.ca/~ftcheng/educ260/

resources.html• http://www.bbc.co.uk/nature/animals/features/

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