Tropical rainforests

Basic facts

• Found in central and South America, Africa, Asia, and Australia

• Amazon rainforest is the largest rainforest in the world

• It is the most biodiversity ecosystem:

  • 50% of all terrestrial species

  • 10% of earth’s land area

Ecological features: warm and high precipitation

• Allows plants to grow all year

  • Provides reliable food supplies and animals- populations remain stable

Ecological features: high light levels

Allows photosynthesis rates to be high:

• Tall plants have more access to light but invest a ,to of energy to produce wood for the trunk

• Smaller plants may need top utilise lower light levels, such as having denser chlorophyll or more pigments to absorb wavelengths that pass through taller plants

• Epiphytes have greater access to light but may have lower water and nutrient supplies

Ecological features: interspecies relationships

• There are no distinct seasons

• This decreases competition

• Near the equator, day and night is the same all year so temperatures don’t change

• Impacts:

  • Plant species don’t have to flower or produce seeds at the same time

  • Nectar, seeds, or fruit are available all year- increases animals survival

Importance: high biodiversity

• Increases chances of finding species that are useful to humans

  • New food species

  • Medicinal discoveries

  • Biomimetic applications

• High ecological stability and no dominant species

  • Plants produce toxins to protect themselves, e.g. alkaloids which have medicinal value

Importance: forest resources

Important to those that live in or near the forest. Long distance transport has became easier, forest resources became important in other areas such as Europe.

• Timber- construction, furniture, tools

• Fibres- cotton, hemp, raffia, wood cellulose

• Resins, oils and waxes- rubber (gloves and tyres), carnuba wax (polish and coating), palm oil (cooking oils, biofuel, processed food)

• Food- cacao, spices, bushmeat, nuts, fruit

• Medicines- cinchona trees (quinine to treat malaria), Mexican wild yams (diosgenin- cortisone to treat asthma and arthritis)

Importance: climate maintenance

• Important for increasing downward rainfall, over 50% of Amazon rainforest rainfall isn’t from evaporation

• Carbon sequestration- stores large amounts of carbon- reduce natural greenhouse effect

Importance: soil maintenance

• Warm, moist conditions make dead vegetation decay fast so nutrients is re-absorbed quickly by trees- so soils in tropical rainforests are often very shallow

• Vegetation cover sand tree roots are important in preventing soil that is present form being eroded, as the foliage protects soil from heavy rain and roots hold it together

Threats

• Unsustainable exploitation of resources

• Removal for alternative land use

• Indirect threats from other human activities

Threats: fuelwood collection

Cause:

• Used by people in low economically developed countries especially in rural areas as use of gas or income

• May be converted to charcoal or transported to cities

Consequence:

• Unsustainable and no replanting

  • Soil degradation

  • Reduced biodiversity leads to less food and shelter

Threats: Timber harvesting

Cause:

• Used for furniture and construction in the country of origin

• Exported to MEDCs for furniture, doors, windows, decking and plywood

Consequence:

• Can cause habitat loss and fragmentation

• Increased soil erosion and surface runoff = flooding = lower climate maintenance

Threats: subsistence agriculture

Cause:

• Slash and burn clears areas

• Clearing made with enough space to cultivate to feed family

• Family move to new area when soil becomes infertile

Consequences:

• Soil erosion and river siltation

• Decreased carbon sequestration- less stored = atmospheric pollution

• River contamination with fertilisers and pesticides

Threats: commercial agriculture

Cause:

• Uses large areas e.g. palm oil plantations

• Cleared for cash crops and cattle ranching (livestock)

Consequences:

• Poor soils can’t provide high yield for long = infertile = difficult for forest to recolonise

Threats: mineral extraction

Cause:

• Mineral rich deposits; iron, gold, silver, copper and aluminium

• Low economically developed country may use it to pay debts to higher income developed countries

• E.g. oil and gas

• Cleared for roads to increase access to mines

Consequences:

• Habitat loss reduces biodiversity marking the habitat less ecologically stable

• Water pollution

Threats: reservoirs

Cause:

• Flood large areas in valleys

• Decaying matter = anaerobic conditions

Consequences:

• Migration barrier to species such as dolphins

• Deoxygenating

• Downstream species effected due to rate of water release

Threats: climate change

Cause:

• Higher temperatures hold moire water vapour = less rain

• Droughts = forest fires

Consequences:

• Less humid impacts frogs and toads, if they die it impacts the food chain

• Orchid species effected

• Interdependence suffers

Threats: tourism

Cause:

• Increased tourism = habitat threat

• Land is cleared for hotels and entertainment

Consequence:

• Causes fragmentation and increased edge

Solution:

• Sustainable ecotourism

What is an MEDC?

More economically developed countries

• High standard of living and large GDP

What is an LEDC?

Less economically developed countries

• Low standard of living and lower GDP

Conservation: debt for nature swaps

• Financial tool that allows developing counties to reduce their debt in exchange for using the funds to protect the environment

• LEDCs have a huge amount of debt to MEDCs

• This can lead to inappropriate development decisions

• Conservation charities give money to pay off loans in return the LEDC protects areas of rainforests

• E.g. US and Costa Rica

  • Signed agreement to swap US $26 million of Costa Rican debt for funds to protect moire than 1000 acres of tropical rainforests

  • Negotiated by WWF

Conservation: protected areas

Brazil:

• In 2014, the new Alto Maues reserve was established to protect 6680 square km of rainforest

• It is home to over 600 bird species and B species primates

• In 2002, the Tumucumaque national park was established to protect 39,000 square km of rainforest, this makes it the largest rainforest reserve in the world, it is next to a rainforest reserve in French Guiana, giving a total protected area of 59,000 square km