Tropical Rainforests

The climate is the same all year round without any definite seasons
- It is warm with average temperatures of 27°C because they are near the equator where the sun is overhead all year round
- Rainfall is very high, around 2000mm per year with daily showers
- Rainforests also have microclimates
The nutrient cycle is the way that nutrients move through an ecosystem
- Trees are evergreen, so dead leaves fall all year round
- The warm, moist climate means that fungi and bacteria decompose quickly, releasing nutrients into the soil
- Rainwater soaks into the soil and the nutrients are dissolved in the water
- Dense vegetation and rapid plant growth mean that the nutrient-rich water is rapidly taken up by plant roots
- Most of the nutrients are stored in the biomass
Soils are often very deep but only have a thin fertile layer and are generally nutrient poor due to the high temperatures and high rainfall
- The constant supply of dead leaves and twigs falling onto the soil surface form a thick leaf layer
- This is broken down to form humus which then mixes with the soil
- The humus layer is thin because the nutrients in it are quickly absorbed by the high density, fast-growing plants
- Heavy rainfall leaches the nutrients towards the bedrock, making the soil nutrient poor
- Vegetation has roots close to the surface where the nutrients are
- The sub-soil is deep due to weathering of rocks below by the high temperatures
  - There is usually a deep layer of soil with bedrock up to 30m below surface
The water cycle is made up of the bodies of water, land and atmosphere
- - - - Evaporation occurs from the water bodies and land, and transpiration occurs
- Water vapour is moved by winds
- The water vapour condenses to form clouds and then falls as rain
- Water flows from one place to another
  - Runs off surface
  - Flows in small channels
  - Soaks into ground
  - Flows through soil and rock
- Water is stored on the land
  - Stored in small channels, ponds and lakes
  - Intercepted and stored by plants
  - Stored as groundwater
- Water eventually ends up back in the river or sea, and the cycle begins again
Climate, soil, water, plants, animals and human activity are interdependent
- The warm and wet climate means that plants grow quickly; the dense leaf cover protects the forest floor from wind and heavy rainfall while the root systems prevent soil erosion
- The lack of wind on the forest floor means that many plants need to rely on animals for pollination
  - Symbiotic relationships between plants and animals are very common
- Epiphytes are common in rainforests; they get access to light by growing high up on other plants, but they are dependent on rainfall for water and nutrients as they have no access to the soil
- Deforestation reduces the amount of carbon dioxide absorbed from the atmosphere which adds to the greenhouse effect and changes the climate

Valuable Goods and Services

High biodiversity means rainforests are a rich source of goods
- Raw materials such as timber, rubber, oils and fibres were commonly used by indigenous people for survival and have now made their way around the world
- 25% of modern medicines are made from rainforest ingredients
  - Such as Vincristine, which has dramatically improved survival rates from childhood cancers
- Many foods used by indigenous people have found their way into diets all around the world such as bananas, pineapples, avocados, cocoa, coffee, nuts and spices
- Undiscovered species may hold new medicine or other products
- Hardwoods are widely used for furniture and building
Rainforests provide services through their impact on the global climate and local environment
- They are home to the highest biodiversity on the planet
- Rainforest plants absorb 0.7 billion tonnes of carbon dioxide each year, reducing climate change
  - They act as carbon sinks, storing 15% of our carbon dioxide emissions
- Huge volumes of water evaporate from them, which helps to cool Earth’s surface, and create clouds that reflect the Sun’s heat back into outer space
- Rainfall is intercepted by the high density of vegetation, reducing the risk of local flooding because the movement of water into rivers is slowed down
- Water is purified through rainforests acting like huge filters
- Rainforests help regulate the global water cycle by storing water and releasing it into the atmosphere slowly, helping to reduce the risk of drought and flooding elsewhere
- Hydroelectric power can be generated by dams built on rivers in rainforests
- Job opportunities in farming and mining sectors are provided if vegetation is cleared

Human Impacts

Logging involves felling trees for timber
- Indigenous people have done this on a small scale for thousands of years but now it is done on an industrial scale for building roads in rainforests
- The timber is often exported to the USA or Europe for furniture and construction
- Tropical hardwood trees, like teak, are very popular
- With no trees to hold the soil together, heavy rain erodes the soil which can then enter rivers, silting up the habitats that fish use for breeding
- The removal of trees interrupts the water cycle, leading to some areas becoming dry, with an increased risk of wildfires, and others becoming more likely to flood
- Logging requires the building of new roads, which opens the rainforest to further development
- Clearing trees can also make an area less appealing to tourists, so tourism decreases
Mineral extraction takes place in rainforests especially for gold, copper and diamonds
- The forest and soil are removed from large areas for open-cast mining
- Toxic chemicals used to extract and purify the metals are washed into streams and rivers, killing wildlife and polluting drinking water
- Oil and gas are also found deep below the ground and drilling for them can lead to air and water pollution
- Building roads or pipelines leads to further destruction of the rainforests
- There can be conflicts with local people over rights to the land
Agriculture in rainforests first involved clearing trees in order to use the land
- Poor farmers clear small areas of forest to feed their families
- When the soil loses fertility, they move on to clear a new patch of forest, rather like shifting cultivators
- In the Amazon, most farming is carried out by big companies that clear vast areas of land to grow soya beans or graze cattle
  - Brazil is one of the world’s largest producers of beef and soya
- Land is often cleared using slash-and-burn techniques
  - Burning vegetation produces carbon dioxide, contributing to the greenhouse effect
- Without trees to intercept rainfall, more water reaches the soil and nutrients are washed away, reducing soil fertility
- Artificial fertilisers added to improve soil fertility are washed into streams, threatening wildlife
- Clearing trees can also make an area less appealing to tourists, so tourism decreases
Tourism is an alternative way to use rainforests without chopping the trees down
- Some countries have created protected areas of forest where deforestation is banned
- Indigenous people can be involved in protecting the forest and can continue to lead their traditional way of life
- Foreign tourists like to visit rainforests, and this can help the local economy
- Tourists may scare wildlife, causing nesting birds to abandon their young
- They may damage vegetation and leave litter
- If tourism is unregulated, a lack of infrastructure can lead to pollution and in order to build infrastructure, vegetation must be cleared

Case Study: Tropical Rainforest, The Amazon

The Amazon rainforest is in northern South America and covers around 8 million km² and includes parts of Brazil, Peru, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana
Some management strategies, including ecotourism, community programmes, biosphere reserves and sustainable forestry, aim to use the rainforest sustainably
Ecotourism is tourism that minimises damage to the environment and benefits the local people
- Yachana Lodge is an ecotourism project in Ecuador, in a remote area of the Amazon rainforest where local people rely on subsistence farming
- It employs locals, giving them a more reliable income and better quality of life
- It encourages the conservation of the rainforest so that visitors continue to want to visit
- Tourists visit in small groups so that harm to the environment is minimised
- Tourists take part in activities to raise awareness of conservation issues
- Tourists must pay entrance fees for conservation and the profits are invested in education projects to promote conservation in the local community
Natütama is an organisation in Puerto Nariño, Columbia that is running a community project to protect river species
- It employs local people to teach others how they can protect endangered river animals and their habitats
- Local fishermen collect information about the number and distribution of species, and report illegal hunting or fishing in the area
- The team organise clean-up days to remove litter from local rivers
A biosphere reserve is an internationally recognised protected area that aims to combine conservation and sustainable use
- The Central Amazon Conservation Complex (CACC) in Brazil is the largest protected area in the rainforest, covering around 60 000km²
- It is home to many different species of flora and fauna
- Access to CACC is restricted, and hunting, logging and fishing are limited
- Scientific research projects and environmental education activities are encouraged to make people more aware of conservation issues
Sustainable forestry balances the removal of trees to sell with the conservation of the forest as a whole
- It can involve selective logging, where only some trees are felled so that the forest is able to regenerate or, planting new trees to replace the ones that were cut down
- International agreements try to reduce illegal logging and promote wood from sustainably managed forests
  - The Forest Stewardship Council (FSC) is an organisation that marks sustainably sourced timber products with its logo so that consumers can choose sustainable products
- Precious Woods Amazon is a logging company operating in Brazil that limits the number of trees cut down, so that they can regenerate
  - They use a variety of species so that none are over-exploited
  - They are FSC-certified