Tropical rainforests

Tropical rainforests

1. Ecological features

   • Close to equator, no large seasonal changes, high light levels, warm temps, water.
   • Stable conditions allow species to evolve, producing high biodiversity. Biotic factors and species inter-relationships increase biodiversity. Evolved to microclimates with specialised niches.
   • Each area unique, loss of one area results in loss of a unique part of the gene pool.

2. Importance

   • Biodiversity
     • Abundance and variety of life produce a more stable ecosystem able to resist change.
     • Aesthetic and educational value, ecotourism for the economy but can damage the rainforest.
   • Resources
     • Timber.
     • Fuel.
     • Plant foods.
     • Bushmeat.
     • Spices.
     • Waxes.
     • Resins.
     • Fibres.
     • Palm oil and palm leaves.
     • Traditional medicines.
   • Economic value of unexploited resources
     • Chemicals (alkaloids) of medicinal value.
     • Food suitable for domestication, gene pool of wild plants may contain characteristics for better adaptation/higher quality food.
     • Timber and fibres of great potential value.
   • Carbon sequestation
     • Biomas is a large store of carbon, in the form of carbohydrates cellulose and lignin. Carbon removed from the atmosphere in photosynthesis.
   • Rainfall
     • Trees return water via transpiration, carried further inland by winds.
   • Soil conservation
     • Hot and moist conditions, decomposition is rapid, nutrients readily absorbed by plants. Roots hold shallow soil together, foliage protects from wind and rain. If removed, soil may be eroded.

3. Threats

   • Fuelwood
     • Wood used as fuel in LEDCs, other fuels are too expensive or require expensive appliances. Wood use is unsustainable with little replanting.
     • Wood converted to charcoal, cleaner fuel and production removes water so has a higher energy content.
   • Timber
     • Only affordable material for construction in LEDCs, used for houses and furniture.
     • Most timber exported to other countries. Highly valued wood (mahogany, teak) valued for hardness, colour and texture. Lower valued wood made into plywood, used for concrete moulding, thrown away after a few uses. Some tropical timber grown in plantations, may involve destroying rainforest to clear the land.
   • Mineral extraction
     • Rich mineral deposits under rainforests. Short term needs of LEDCs to repay debts results in the destruction of forests to exploit minerals.
   • Agriculture
     • Subsistence farming,, using traditional slash and burn methods does little long term damage, clearing made large enough for food for a family, farmed for a few years until soil fertility drops and forest vegetation recolonises. New area cleared. Sustainable providing the farmland is left long enough for the forest to recolonise and for soil to regain fertility. Unsustainable when the population is too large so the land is cleared too soon, causes soil to lose its fertility sooner and become unproductive so the family clear another area of land, eventually the forest is exploited to a point where none has time to mature and species are lost.
     • Threatened by commercial agriculture, clearance for cash crops and cattle ranching is unsustainable as soils can't provide high yields for long, land is abandoned and it may be difficult for the forest to recolonise. Soils may be eroded and the scale of the forest clearance may be too large for species to recolonise.
   • Reservoirs
     • HEP can flood large areas of land and dams act as barriers to aquatic species.
     • Decaying dead organic matter produces anaerobic acidic water that may harm river life.
     • Rate at which water is released is too varied to match the demand for electricity, different from natural river flow so river life affected, water level rises flood sandbanks where lizards and river turtles lay eggs, increases turbidity so is difficult for kingfishers to see fish.
   • Global climate change
     • Higher temps increase ability of air to hold water vapour, rain less likely to form.
     • Populations of frogs/toads are declining, need humid conditions and higher temps cause clouds to form higher up, reducing the area they can survive in.
     • Small orchid species become rarer as humidity declines.
     • Complex webs of interdependant species, loss of one effects others.
     • Predictions suggest Amazon rainforest may be replaced by savannah grassland.

4. Conservation

   • Dept-for-nature swaps
     • Panama: national parks protected by donations from The Nature Conservancy. Rainforests of Panama are economically important as they include catchment areas around the canal and regulate water flow into the canal and therefore income from ships.
     • Banks in MEDCs lent money to LEDCs want debts repaid, LEDCs too poor, forced into making inappropriate development decisions to raise money (clearing rainforests for timber or farmland.) Debt-for-nature swaps involves a conservation charity in a MEDC giving money to the bank to cancel debt, LEDC protects the area using the money that would have paid to the bank.
   • Protected areas
     • Korup rainforest: money for establishment came from public donations from the UK, establishment wasn't popular with locals as villages were removed and people were relocated to the buffer zone. High biodiversity with endemic species.
     • Rio Bravo rainforest reserve: threatened with clearance for farming, managed by Programme for Belize (independant charity.) Initial land paid for by donations raised in the USA and UK. Further areas donated by Coca-Cola and electricity companies in the USA that started research into the role of rainforests in offsetting carbon emissions. Reserve protects wide range of species (jaguar, Baird's tapir, ocelot, yellow-headed parrot.) Funded by ecotourism, sustainable logging and supporters donations. Ecological and archaeological research carried out by PfB and scientists. Organised groups and independant travellers visit to study wildlife, learn about medicinal plants, sustainable forestry, sociology and history. PfB supports local population through employment, timber for souvenir and furniture industries and supporting conservation and tourism projects. Most the reserve isn't exploited for forestry, edges sustainably logged.
   • Trade controls
     • Complete ban on trade can reduce the conservation of forests rather than protect them as timber cannot be sold and so has no financial value. Limited trade from sustainably managed resources with a fair price is better.