- Created by: mbull
- Created on: 01-04-18 16:10
Location of tropical rainforests
Tropical rainforests are found in a broad band through the Tropics in:
- Central and South America.
- Central Africa.
- South East Asia.
- Northern Australia.
Features of tropical rainforests
- Same climate all year round.
- Hot because it is near the equator, the sun is overhead all year round.
- Rainfall is very high, it rains every day.
- Temperature high and constant throughout the year.
- Rainfall varies throughout the year.
- Soil isn't very fertile as heavy rain washes nutrients away.
- There are nutrients at the surface due to decayed leaf fall, but this layer is very thin as decay is fast in the warm, moist conditions.
- Leaching - heavy rainfall can quickly dissolve and carry away nutrients.
- Most trees are evergreen to take advantage of the continual growing season.
- Many trees are very tall and the vegetation cover is dense - very little light reaches the forest floor.
- There are lots of epiphytes (plants that grow on other living plants.)
More features of tropical rainforests
- Rainforests contain more animal species than any other ecosystem.
- Gorillas, jaguars, anacondas, tree frogs and sloths are examples of rainforest animals.
- There are many species of insects and birds.
- Many animals are brightly coloured and make a lot of noise.
- Rainforests are home to many people who have adapted to live there over many generations.
- They make a living by hunting and fishing, gathering nuts and berries and growing vegetables.
All the parts of the rainforest are dependent on one another - if one changes, they are all affected.
- The warm and wet climate means that dead plant material is decomposed quickly by fungi and bacteria on the forest floor. This makes the soil high in nutrients, meaning plants grow quickly and easily.
- Plants pass on their nutrients when they are eaten by animals. The dense vegetation provides lots of food so animal populations are high. Many plant and animal species have formed symbiotic relationships.
- Changes to the rainforest ecosystem can have knock-on effects on the whole ecosystem.
- Trees also intercept and take up lots of water, and release it back into the atmosphere, providing moisture for further rainfall.
Biodiversity - the variety of organisms living in a particular area - both plants and animals.
- Rainforests have high biodiversity, they contain 50% of the world's plant, animal and insect species.
- Rainforests are stable and productive environments because it is hot and wet all year round.
- Plants and animals don't have to cope with changing conditions as there is always plenty to eat.
- Many organisms have evolved to depend on just a few species for survival.
- Deforestation and uncontrolled development of the rainforest are likely to lead to the extinction of many species and loss of biodiversity.
- Buttress roots- tall trees competing for sunlight have big roots called buttress roots to support their trunks. May also help oxygen/carbon dioxide exchange by increasing the surface area.
- Many trees have smooth, thick bark, as there is no need to protect the trunk from cold temperatures. The smooth surface also allows water to run off easily.
- The rainforest has four distinct layers of plants with different adaptations.
- Kapok - fast growing trees - out-compete other trees to reach sunlight.
- Plants have thick, waxy leaves with pointed tips called drip-tips. Drip-tips channel the water to a point so it runs off - that way the weight of the water doesn't damage the plant, and there's no standing water for fungi and bacteria to grow in. The waxy coating also helps repel the rain.
- Lianas - climbing plants - use the tree trunks to climb up to the sunlight.
- Plants drop their leaves gradually throughout the year, meaning they can grow all year round.
- Many leaves have flexible bases so that they can turn to face the Sun.
- Epiphytes - live on branches high in the canopy to seek sunlight, they obtain nutrients from water and air rather than soil.
The majority of plant and animal species are found in the canopy where there is most light. The forest floor is dark which is where plants and animals along with fungi and bacteria live. Small changes to biotic or abiotic factors can have serious knock on effects on the entire ecosystem.
- Some animals spend their entire lives high up in the canopy. They have strong limbs so they can climb and leap from tree to tree.
- Some animals have flaps of skin - enables them to glide between trees. Others have suction cups for climbing.
- Some birds have short, pointy wings so that they can easily manoeuvre between the dense tangle of branches in the trees.
- Many animals are nocturnal - they sleep through the day and feed at night when it's cooler - this helps them to save energy.
- Some animals are adapted to the low light levels on the rainforest floor.
- Many rainforest animals can swim - allows them to cross river channels.
Interdependence in the rainforest
- Tropical rainforests have competition for resources and sunlight.
- Many of the plants and animals are in competition with one another and in many cases they are also reliant on one another.
- Changes in one part of the ecosystem, either the living or non-living, could be very damaging for this ecosystem.
- The loss of some tree cover to deforestation or fire would affect both the water and nutrient cycles for example, and cause soil erosion, increased loss of nutrients from the soils via leaching and extra flooding.
- If one of the elements of the tropical forest food web were to change, there would be knock on impacts throughout that food web.
Structure of a rainforest
Deforestation - the cutting down of trees, often on a very large scale.
Reasons for deforestation:
- Population pressure - trees are cleared to make land for settlements.
- Mineral extraction - minerals (e.g, gold and iron ore) are mined and sold to make money.
- Energy development - building dams to generate hydro-electric power.
- Commercial logging - trees are felled to make money.
- Commerical farming - forest is cleared to make space for grazing cattle or for plantations.
- Subsistence farming - forest is cleared so farmers can grow food for themselves and their families.
- With no trees to hold soil together, heavy rain washes away the soil - soil erosion. This can lead to landslides and flooding.
- Without a tree canopy to intercept rainfall and tree roots to absorb it, more water reaches the soil. This reduces soil fertility as nutrients are washed away, out of reach from plants.
- Trees remove CO2 from the atmosphere.
- Burning vegetation to clear forest produces CO2, so deforestation means more CO2 in the atmosphere which adds to the greenhouse effect.
More impacts of deforestation
- Logging, farming and mining creates jobs.
- A lot of money is made from selling timber, mining and commerical farming.
- In the long term, deforestation can destroy the resources that countries depend on - e.g, timber reduces the attractiveness of the area to tourists.
- The livelihoods of some local people are destroyed - deforestation can cause the loss of the animals and plants that they rely on to make a living.
The rate of deforestation
- The rate of rainforest deforestation is very high.
- Globally the rate seems to be slowing down however there are still hotspots where the rate of deforestation is increasing - e.g, Boreno and Nigeria.
Case study - Amazon Rainforest
- The Amazon is the largest rainforest on Earth, covering an area of 8 million km^2.
- The rainforest is shrinking fast due to deforestation.
- Since 1978, an area three times the size of the UK has been destroyed by deforestation.
Causes between 2000 and 2005:
- Commerical (cattle) ranching: 65-70%.
- Small - scale subsistence farming : 20-25%.
- Commerical farming: 5-10%.
- Logging - including illegal logging. New roads have opened up areas of forest that were previosuly too hard to get to: 2-3%.
- Mineral extraction: 1-2%.
- Population growth and migration - Brazilian government offers land in the rainforest to poor people from overcrowded cities.
- Energy development.
Impacts of deforestation in the Amazon
- The Amazon stores around 100 billion tonnes of carbon - deforestation will release some of this as carbon dioxide which causes global warming.
- Brazil is losing 55 millions tons of topsoil every year because of soil erosion caused by soy farming.
- Economic development has brought wealth to countries that were very poor.
- Farming makes a lot of money for countries in the rainforest - e.g, for trading cattle and Brazil is the world's second biggest exporter of soy beans.
- The mining industry creates jobs for loads of people.
- Logging contributes a huge amount to Brazil's economy.
- Local Brazilian rubber tappers who extract natural rubber from rubber trees have lost their livelihoods as trees have been cut down.
Importance of protecting rainforests
- It is important to protect rainforests to preserve its biodiversity - maintaining the high diversity of plants and animals is valuable to both people and the environment.
- Many products including rubber, coffee, chocolate and medicines are sourced from the rainforest.
- If species become extinct, the chance to discover new medicines and develop new products is reduced.
- Sustainable development also allows for long-term economic benefits -e.g, through developing ecotourism.
- Protecting the rainforests may also help reduce the greenhouse effect by reducing CO2 emissions and allowing trees to continue absorbing CO2.
- Some of the impacts of rainforest destruction, e.g, climate change, could affect all countries, not just countries where the deforestation is happening.
- Rainforests help to regulate the climate and water cycle - without them the risks of drought and flooding in certain areas can increase.
Sustainable management strategies
1. Selective logging
- Only some trees (e.g, just the older or inferior ones) are felled - most trees are left standing.
- This is less damaging to the forest than felling all the trees in one area.
- If only a few trees are taken from each area the overall forest structure is kept - the forest will be able to regenerate so it can be used in the future.
- The least damaging forms are horse logging and helicopter logging - dragging felled trees out of the forest using horses or removing them with helicopters instead of huge trucks.
- EG, Helicopter logging is used in the Malaysian state of Sarawak.
- When new trees are planted to replace the ones that are cut down.
- Means there will be trees for people to use in the future.
- It is important that the same types of tree are planted that were cut down, so that the variety of trees is kept for the future.
- In some countries, there are laws to make logging companies replant trees when they clear an area.
More management strategies
- Tourism that minimises damage to the environment and benefits the local people.
- Only a small number of visitors are allowed into an area at a time.
- Enviromental impacts are minimised, e.g, by making sure waste and litter are disposed of properly to prevent land and water contamination.
- Provides a source of income for local people - e.g, act as guides or provide accommodation and transport. It can also raise awareness of conservation issues and bring in more money for rainforest conservation.
- If local people are employed in tourism, they don't have to log or farm to make money, meaning fewer trees are cut down.
- Ecotourism has been very successful in Costa Rica as it is their largest source of income.
4. International Hardwood Agreements
- Hardwood means wood from certain tree species - e.g, mahogany and teak. It tends to be fairly dense and hard - used for furniture.
- High demand for hardwood from consumers in richer countries means some tropical hardwood trees are becoming rarer as people are chopping them down and selling them.
- There are international agreements to reduce illegal logging and promote hardwood from sustainably managed forests.
Education and Reducing Debt
- Education of the international community about the impacts of deforestation can encourage people to buy products that are certified from sustainably managed sources.
- Some local people don't know what the environmental impacts of deforestation are. Local people try to make money in the short-term to overcome their own poverty.
- Educating local people about the impacts of deforestation and ways to reduce the impacts decreases damage to the rainforest environment.
- Educating local people about alternative ways to make money that do not damage the environment.
- Lower income countries often borrow money from wealthier countries or organisations to fund developmen schemes or cope with emergencies like floods.
- This money has to be paid back with interest.
- These countries often allow logging, farming and mining in rainforests to make money to pay back the debt.
- Reducing debt means countries don't have to do this and the rainforests can be conserved for the future.
- Debt can be cancelled or a conservation swap where part of a country's debt is paid off in exchange for a guarantee that the money is spent on conservation. EG, in 2008 the USA reduced Peru's debt for rainforest conservation.
- Many countries have set up national parks and nature reserves within rainforests.
- In these areas, damaging activities such as logging are restricted.
- However, a lack of funds can make it difficult to police the restrictions.
- Some countries have set up funds which overseas governments and businesses can invest in.
- The countries get the money in exchange for rainforest conservation.
- The money can be used to enforce restrictions on damaging activities and to promote sustainable use of the rainforests.
- EG, Norway has paid $1 billion into Brazil's Amazon Fund to be used for conservation.