XXX Background information

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1 XXX Background information Tropical rainforests Tropical rainforests are dense, wet, warm places that sustain an abundance of plant and animal life. Although they cover about 2.5 per cent of the Earth s surface, it is estimated that they are home to as many as 30 million animal and plant species 50 per cent of the world s total. Many forests are thought to be million years old. Climate and weather On most days the temperature is at least 20 degrees Celsius and often reaches 30. The weather remains the same for most days of the year, with clear skies in the morning and rain in the afternoon. Humidity can be as high as 100 per cent. Most rainforests get at least 2000 millimetres of rain each year (average rainfall for South East England is millimetres per year). During some months of the year the rainfall is extremely heavy, while in other months it rains less. There are two seasons: the wet season and the dry season. Location Tropical rainforests can be found in a 4800 kilometre wide band round the equator, extending north to the tropic of Cancer (latitude 23.5 N) and south to the tropic of Capricorn (latitude 23.5 S). This band is known as the tropics. The largest rainforests are in South America (surrounding the Amazon River), West Africa (surrounding the Congo River) and through much of South-East Asia, stretching from Thailand right across Indonesia, and including Borneo and New Guinea. Smaller rainforests can be found in Central America, Madagascar, India and Australia. The largest is the Amazon rainforest, which spans eight countries and covers around 3, 218, 688 square kilometres (2 million square miles). Layers of the forest The rainforest can be divided into four layers, each with different conditions, plants and animals: Forest floor Conditions: Quiet, damp, warm with little light. Can get flooded during times of high rainfall. Covered in a thin layer of dead leaves. Plants: Small trees, ferns, palms and fungi (important decomposers). Animals: Teeming with small creatures including termites, earthworms and spiders. Home to the larger animals of the rainforest, including the jaguar. Understory Conditions: Limited light and cooler than the canopy (the layer above). Plants: Young trees waiting for the larger trees above to die, so that they can grow up into the canopy. Lianas (woody climbers) grow up from the forest floor towards the light above. Epiphytes and orchids grow from tree branches. Animals: Variety of animals including insects, birds, reptiles and mammals. Canopy Conditions: This is the roof of the forest formed by the tops of the trees. The leaves of these trees make the canopy that shades the ground below. Plants: Fully grown trees (about metres tall) with their nuts and fruits. Animals: Huge variety of animals including birds, monkeys and other mammals, including the sloth. This is the noisiest layer of the rainforest. Emergents Conditions: Full sunlight. Plants: A few fully grown trees rising to a height of 50 metres, which are above the canopy. Animals: Monkeys and birds, including eagles. Animals The rainforest is a complex ecosystem in which animals and plants all depend on each other. The animals living there have adapted to the environment in many ways. Some use camouflage to hide from predators while others are brightly coloured to warn them off. The sloth has developed claws that allow it to cling between branches high in the canopy; the flying lizard and flying fox have developed wing-like flaps of skin at the sides of their bodies, allowing them to glide between the trees. Birds, too, have adapted to their environment, with beaks that can open hard nuts and seeds. Most animals in the rainforest are insects. Millipedes and others living on the forest floor eat the dead leaves from the trees above. Most animals rest in the middle of the day and for most of the night, so at these times the rainforest is less noisy. At dawn and dusk it comes alive with the sounds of monkeys, birds, frogs, cicadas, crickets, flies, bees and other animals. 6

2 Plants Like animals, plants have adapted to the conditions of the rainforest. Trees: Some of the world s tallest, heaviest and fastest growing can be found in the rainforest, reaching up to the sunlight above the canopy. The smaller trees of the understory often have larger leaves as they are trying to gather as much light as possible in the dim conditions below. Once these smaller trees find a gap they grow in height towards the sunlight and often replace their big leaves with smaller ones. On average, there are between twenty and eighty different species of tree per acre. Buttress roots anchor tall trees into the ground. They grow out from the bottom of the trunk and can reach as high as 2 metres from the ground. Leaves: Many rainforest plants and trees have shiny leaves with pointed tips. Rainwater easily drips from these leaves rather than remaining on the surface and encouraging mould to grow. Orchids grow on the branches of trees where there is more sunlight. Their long roots can absorb water from the air. Bromeliads also grow on tree branches. They catch rainwater in their circle of thick, prickly leaves and provide a home for frogs and tadpoles. Mosses grow on the branches and trunks of trees and on rocks. They form soft, green carpets. Woody climbers (lianas) use trees to support them as they climb up to the sunlight of the canopy. Some reach a length of more than 60 metres. Pitcher plants get their nutrients from insects and other small animals that fall into the liquid contained in the pitcher. Fan palms have large fan-shaped leaves for trapping as much sunlight as possible. Soil Soil in the rainforest is old and poor. The decaying plants and leaves on the forest floor provide nutrients for the top 8 10 centimetres of soil; below that, there are few nutrients. As a result, tree roots rarely go deeper than 50 centimetres. Many trees have developed buttress roots which stretch from the ground to a height of 2 metres or more up the trunk of the tree. These help to anchor the tree firmly in the ground. Plants for food Many of the foods we eat every day such as nuts, bananas, pineapple, avocados, oranges, sweet potato, coffee and chocolate originally came from tropical rainforests. Scientists believe that the rainforests house many more undiscovered food sources that are still waiting to be found. Medicine As many as 25 per cent of modern medicines have been developed from tropical rainforest plants. This includes quinine, made from the bark of the cinchona tree, used to treat malaria, and a treatment for childhood leukaemia made from rosy periwinkle, a plant only found in the rainforests of Madagascar. Scientists believe that around only 4 per cent of rainforest plants have been tested for their medicinal properties and that in the future the rainforest could provide cures for many other diseases, including cancer and AIDS. People It is estimated that as many as 50 million indigenous people live in the rainforests of the world. Many tribes have lived there for thousands of years hunting and gathering food and medicines and using materials from the forest for clothes and shelter, none of which causes harm to the forest. Rainforest tribes have developed a system of farming in which they clear small areas of forest to make gardens in which to grow crops, fruit trees and plants for medicine. These gardens are known as chakras. After a few years, when the soil is no longer fertile, a new garden is created, leaving the old garden to become forest again. The people still return to the older garden to collect the fruit that continues to grow on the established trees. Rainforest water cycle The rain falling on the forest is gathered up by the plants and trees through their roots. Each day some of this water evaporates from the surface of the leaves and is released as water vapour into the atmosphere. The vapour then condenses to form mists and clouds. Each day, the water in the clouds falls back down onto the forest as rain and the cycle begins again. Some of the rain is not gathered up by the plants and trees but drains into streams and rivers. 7

3 XXX Deforestation the causes In the past one hundred years it is estimated that humans have destroyed almost half of the world s rainforests, and that destruction continues with 1 per cent (an area the size of England) being cut down every year. The main reasons for this destruction are: Logging: Tropical hardwood is highly valued for building and making furniture. Timber companies build roads deep into the forest so that they can move machinery in and transport logs out. Many governments now try to control the amount of logging that occurs, but many loggers continue to cut down the forest illegally. Agriculture: Large companies clear and then burn huge areas of rainforest so that cash crops can be grown and cattle can be raised. The soya bean and beef industries are responsible for the destruction of thousands of acres of the Amazon rainforest every year, while in Borneo the palm oil industry is to blame. The land is very soon over farmed and the soil becomes exhausted. Mining: The rainforests of the world are rich sources of precious minerals such as gold. The mercury used in gold extraction can pollute both the atmosphere and rivers, killing fish and poisoning the water supply. Dams: The creation of dams can lead to the destruction of large areas of rainforest through the initial building programme and subsequent flooding of huge areas of land. Deforestation the effects Deforestation has both local and global effects: Soil erosion: When the trees are cleared away there are no roots to hold the soil in place. Heavy tropical rains wash the fertile topsoil away into rivers and streams. This causes aquatic animals and plants to die, as they need clean and clear water to survive. Reduced rainfall: With fewer trees to take up the rain, more rainwater drains into the streams and rivers and less water evaporates into the atmosphere. Fewer rain clouds form and less rain falls. The rainforest climate can change to one of drought. The drought can affect countries throughout the tropics. Flooding: With more rain flowing into the streams and rivers, valleys below the deforested areas can suffer from frequent flooding. Loss of tribal land and effects of disease: Local tribes have had their homes and land taken away from them. Some tribes have been decimated by diseases brought in by the outside world, against which they have no immunity. Destruction of plants: Scientists estimate that numerous plant species are being destroyed every day. Their medicinal properties and possible use to us as food are then lost forever. Animal species endangered or extinct: Scientists estimate that as many as fifty animal species, most of which are insects and spiders, become extinct each day. Many species are found in just one small area of rainforest in the world and destruction of that forest has resulted in them becoming endangered and in some cases near extinction. Global warming: Like other plants, rainforest plants and trees take in and use carbon dioxide to make sugars (their food) through the process of photosynthesis. They release oxygen as a result of this process and, because of this, the rainforests are often referred to as the lungs of the world. Carbon dioxide gas is produced by humans all over the world when we burn coal, oil, gas or wood. As it remains in the Earth s atmosphere and traps the heat of the sun it is know as a greenhouse gas. Scientists believe that carbon dioxide is the most important gas affecting global warming and climate change. If rainforests are cleared, there are fewer trees to take up the carbon dioxide, and as a result, deforestation is considered to be an important contributory factor to global warming. The slash-and-burn process, in which rainforest trees are cut down and then burnt, results in even more carbon dioxide being produced, adding further to the problems of global warming. Scientists have recently estimated that 85 per cent of rainforest trees would die if the global temperature rose (as a result of global warming) by a modest rise of just 4 degrees Celsius. Rainforest conservation Many people recognise the need to conserve the rainforests. The following are examples of action being taken around the world: Controlled logging: Timber companies are policed to ensure that the agreed amount of forest is cut down. Replanting schemes: Deforested land is replanted with new trees to create sustainable forests. However, the rate of replanting is still only 10 per cent of the rate of deforestation. 8

4 XXX Forest Stewardship Council: This was set up in 1993, to check that timber companies in rainforests work in an environmentally friendly way. Timber companies who follow council guidelines are entitled to use the FSC logo on their wood. Local education programmes: Charities and other organisations provide local education programmes about soil conservation and the advantages of using traditional and sustainable methods. Rainforest charitable organisations: Many organisations work to educate others about the importance of conserving the rainforest. Some endorse and recommend sustainable products while others raise money to purchase areas of rainforest before they are destroyed. National parks: The creation of national parks protects the local tribes, animals and plants and encourages ecotourism. Wildlife corridors: These allow threatened animals to move between isolated areas, rather than becoming trapped in islands of rainforest between vast areas of deforestation. Animal sanctuaries: Sanctuaries for endangered animals have been set up all over the world. Many aim to return the animals to their natural habitat in the future. Global conferences: Meetings and conferences, like the Earth Summit, are forums for discussing and agreeing long-term actions that will lead to sustainable development and the conservation of the world s rainforests. The future Many people fear that, despite all of this effort, the only thing that will save the world s rainforests is an immediate halt to deforestation. The future of the rainforests lies in finding a balance between the way in which people live in them, find food in them, earn a living from them and conserve them. 9

5 XXX Find out more Use the following websites for more information: Guided tour through the rainforest This interactive leaflet from Rainforest Concern gives background information about the rainforests, why they are important, the animals and plants that live there and why they are disappearing. Photographs of the world s rainforests A large bank of high-quality rainforest photographs from The Nature Conservancy a leading conservation organisation. Rainforest sounds html#christian%20answers%20sounds A large selection of ambient rainforest sounds, as well as animal sounds. Jewels of the Earth jewelsoftheearth/index.html Use this interactive site from the Rainforest Alliance to match animals and plants to the layers of the rainforest. ARKive A huge collection of thousands of videos, images and fact files illustrating the world s plant and animal species. Tropical plant database A database of plants that grow in the Amazon rainforest. Just click on the name of a plant to see an image and to find out what it is used for. Track it back trackitback/index.html Track the journeys that coffee, bananas and chocolate make, from where they grow to the supermarket shelf. Another interactive site from the Rainforest Alliance. My world myworld/index.html Find out about the lives of children who live in the rainforest of North Guatemala with this series of photographs and accompanying text from the Rainforest Alliance. Rainforest stories cfm?id=rainforest_stories Fully illustrated fictional stories set in the rainforest and personal accounts by children who live there. Eco-Schools Find out about this international award programme that guides schools on their sustainable journey. Sustainable Schools Use this site to find out how sustainable development can be embedded into whole school practices and for practical guidance on how to operate your school in a more sustainable way. N.B. BBC Active accept no responsibility for the content and availability of any websites to which we provide a link. Tropical rainforest animals animals/rfbiomeanimals.shtml Find out about the many different animals found in the world s rainforests on this Enchanted Learning site. 10

6 XXX Rainforests of the world AS1 Arctic Ocean Atlantic Ocean Indian Ocean Pacific Ocean Colour the rainforests green. Label the following and colour them red: Tropic of Cancer, Tropic of Capricorn, Equator. Label the areas where rainforests are found: South America, Central America, Africa, Madagascar, India, South-East Asia, Australia. What is the South American rainforest called? BBC Active iposter Rainforests

7 XXX Comparing rainfall AS1 AS2 London Manaus Compare the annual rainfall in Manaus, Brazil, with the annual rainfall in London, England. Manaus Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total mm London Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total mm Construct graphs using this data. Questions 1 In which months do Manaus and London have the most rain? 2 In which months do they have the least rain? 3 Manaus has a dry season. Which months do you think are in the dry season? 4 Make a list of other questions that can be answered using this data. 5 What patterns do you notice? Go to and type in your nearest city. Record its rainfall in the table below: mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Is its annual rainfall higher or lower than that of London? Construct a graph using this data. BBC Active iposter Rainforests

8 The rain cycle AS3 Label the diagram with the correct letters. A B C D E Every day throughout the year the sun heats the rainforest. Water vapour cools as it rises above the forest and condenses to form clouds. Rain falls from the clouds onto the forest. Trees and plants take up the water through their roots. Trees and plants lose water vapour from their leaves through evaporation and transpiration. Draw lines to match each word to its definition. water vapour evaporation transpiration condense when a liquid turns into a gas when plants lose water through tiny holes in their leaves when a gas turns into a liquid water when it is a gas BBC Active iposter Rainforests

9 Animal fact file AS4 Name of animal: Illustration: Habitat: Food: Eaten by: Fact 1: Fact 2: Nocturnal (yes/no) Endangered (yes/no) Other information: BBC Active iposter Rainforests

10 Why protect the rainforest? AS5 Cut out the statements below. Put them in order of importance. Around a third of the plant and animal species living on our planet live in the rainforest. If we destroy the forests, many will become extinct. Scientists believe that many medicines, foods and other useful resources remain undiscovered in the forests. The rainforest trees make oxygen. We breathe in oxygen and need it to stay alive. When we burn coal, gas and oil it produces carbon dioxide a greenhouse gas. Carbon dioxide is taken in by rainforest trees and plants Burning the trees in the rainforest produces carbon dioxide a greenhouse gas contributing to global warming and climate change. We must respect the indigenous people who live in the rainforest and leave their land alone. The loss of trees can cause soil erosion which means that the land cannot offer a sustainable future. BBC Active iposter Rainforests