tropical rainforests

What is the climate of a tropical rainforest like?

• High, constant temperatures (approx. 27°) throughout the year → Sun is directly overhead equator all year round, causing its energy to be more intense

• High precipitation (up to 2000mm a year) → belt of low pressure by the equator

What is the soil in a tropical rainforest like?

• Infertile as heavy rain washes nutrients away

• Thin layer of surface nutrients due to the fast decay of fallen leaves in the hot and humid conditions

What are the plants in tropical rainforests like?

• Most trees are evergreen to take advantage of the continual growing season

• Many trees are tall, and the vegetation cover is dense → thus, little light reaches the forest floor

• Many epiphytes (plants that grow on other plants but take nutrients + moisture from the air) like orchids

How are tropical rainforests interdependent?

All components of the rainforest rely on each other - if one component changes, so will many others.

EX:

The warm, wet climate increases the rate at which decomposers are able to decompose dead plant material.

This make the surface soil high in nutrients, meaning plants can grow more easily.

How are plants adapted to the physical conditions in tropical rainforests?

• Trees grow tall to compete for sunlight

• Plants have thick, waxy leaves with pointed drip-tips which repels and channels rainwater to the point

  • encourages runoff so that the weight of the water doesn’t damage the plant

  • means there’s no standing water for bacteria/fungi to grow in

• Climbing plants, such as lianas, grow around tree trunks to reach the sunlight

• Many trees have smooth, thin bark as:

  • they do not need protection from the cold

  • it allows water to run off easily

• Buttress roots are large and stable to support tall trees’ trunks

• Plants drop their leaves gradually throughout the year to continue growing all year round

How are animals adapted to the physical conditions in tropical rainforests?

• Many animals living in the canopy have strong limbs so that they can move around their habitat more easily

• Many animals are nocturnal - they feed at night when it is cooler, helping them save energy (e.g. sloths)

• Many animals can swim (e.g. jaguars) to help them cross river channels

• Some birds have short, pointed wings so that they manoeuvre between the dense tangle of trees

• Some animals are adapted to the low light levels by having a sharp sense of smell to detect predators, e.g. anteaters

What is an example of a tropical rainforest being impacted by deforestation?

The Malaysian rainforest, located in Malaysia in south-east Asia.

What are the causes of deforestation in that tropical rainforest?

• Subsistence and commercial farming

• Logging

• Road building

• Mineral extraction

• Energy development

• Population pressure

How does subsistence and commercial farming cause deforestation?

Forest is cleared to make space for cattle grazing or for plantations, such as palm oil plantations.

Malaysia is the second-largest palm oil producer.

Commercial farming causes a significantly larger proportion of deforestation because the food produced is sold for profit, so must be produced on a larger scale.

Subsistence farming produces food on a smaller scale because it is grown only to feed the farmer and their family.

How does logging cause deforestation?

Trees are cut down for wood so that it can be sold.

During the 1980s, Malaysia was the world's largest exporter of tropical wood.

Before, trees were clear felled (all the trees in an area were chopped down) but now this has been replaced with selective logging.

How does road building cause deforestation?

Trees are cut down to make way for new roads which provide access to mining areas, new settlements and energy projects.

The building of roads also enables logging to continue by allowing machinery to travel into the rainforest and take away the timber.

This causes even more trees to be felled.

How does mineral extraction cause deforestation?

Rainforest is cleared for mining, particularly the mining of Bauxite in Peninsular Malaysia.

How does energy development cause deforestation?

Large areas of rainforest must be flooded to make a reservoir for generating HEP.

EX: Bakun dam in Sarawak began generating HEP in 2011 - its reservoir flooded over 700km² of forest and farmland.

How does population pressure cause deforestation?

As the population grows, more housing is needed - this requires the felling of trees to make space.

Between 1956 and 1980, Malaysia’s government encouraged the urban poor to migrate to rural areas to reduce overcrowding in the country’s rapidly growing cities.

This resulted in 15,000 hectares of forest being felled for the settlers.

What are the impacts of deforestation in that tropical rainforest?

• Economic development

• Soil erosion

• Contribution to climate change

How is economic development an impact of deforestation?

• Development of land for mining, farming and energy development will lead to more job opportunities

• Companies behind these industries in Malaysia will pay more taxes to the government → these can be used to improve public services

• Improved transport infrastructure (from road building) provides access to new areas for industrial development and tourism

How is soil erosion an impact of deforestation?

The roots of trees and other plants bind soil together, so when vegetation is removed, it becomes loose and easily eroded.

How is contribution to climate change an impact of deforestation?

Trees take in CO₂ from the atmosphere for photosynthesis, helping reduce the rate of global warming.

By removing trees, there are less trees available to absorb the CO₂ from the atmosphere which enhances global warming.

How are tropical rainforests valuable to people?

• 25% of medicine is sourced from rainforest plants

• They provide valuable hardwoods, rubber, coffee and chocolate

• Indigenous people depend on rainforests for food, building materials and fuel

• Tropical rainforests offer job opportunities in industries such as ecotourism

How are tropical rainforests valuable to the environment?

• Rainforests reduce the greenhouse effect by taking in CO₂ from the atmosphere

• They are the most biodiverse ecosystem, containing 50% of the world’s known plant and animal species

• They are an important source of clean water → 20% of the world’s fresh water comes from the Amazon Basin

• The transpiration of rainforest plants ensures the climate does not become too hot/dry

How can tropical rainforests be managed sustainably?

• Selective logging

• Replanting

• Conservation and education

• Ecotourism

• International agreements about the use of tropical hardwoods

• Debt reduction

How does selective logging help manage rainforests sustainably?

In selective logging, only a few particular trees (e.g. old ones) are felled in an area.

Most trees in the area are left standing, maintaining the overall forest structure - the canopy remains to cover the soil.

This protects the nutrient cycle as it prevents the leaching of nutrients from heavy rain, allowing the forest to regenerate.

How does replanting help manage rainforests sustainably?

It involves planting new trees to replace those that have been felled, helping regenerate the rainforest for future generations.

How does conservation help manage rainforests sustainably?

It involves setting up national parks and nature reserves within tropical rainforests in order to restrict damaging activities (such as logging) in these areas.

This ensures that parts of the rainforest are preserved for future generations.

How does education help manage rainforests sustainably?

Educating people about the impacts of deforestation can reduce the deforestation by:

• making locals realise the long-term effects of their actions

• encouraging people around the world to buy products from sustainable sources

Locals can also be taught about alternative ways of earning income that are more sustainable, such as ecotourism.

How does ecotourism help manage rainforests sustainably?

It involves introducing people to rainforests and minimising the environmental impact of doing so.

Ecotourism reduces deforestation by:

• providing local people with a more sustainable source of income - they no longer have to farm/log to make money

• encouraging the government to conserve the environment if the country’s economy begins relying on ecotourism

EX: Ecotourism is the largest source of income for Costa Rica

How do international agreements about the use of tropical hardwoods help manage rainforests sustainably?

Tropical hardwood is in high demand from consumers in HICs, making hardwood trees increasingly rare as more are cut down.

International agreements prevent illegal logging and promote the use of hardwood from sustainably managed forests.

This reduces the demand for valuable and rare hardwoods.

EX: FSC (Forest Stewardship Council) source and mark sustainably-sourced timber with their logo so that the people buying the wood know that it is sustainably-sourced.

How does debt reduction help manage rainforests sustainably?

It involves reducing a country’s debt so that they don’t have to exploit their rainforest in order to pay it back.

A conservation swap guarantees that the money from the debt reduction will be spent on conserving the tropical rainforest.