EQs

What is a decomposer? (2 marks)

(Eg.) A decomposer is an organism, such as bacteria or worms, that breaks down dead tissue/material, which is then recycled to the ecosystem.

Describe a food chain for a chosen small-scale ecosystem in the UK. (4 marks)

(Eg.) A food chain shows the direct links between the various organisms which rely on each other as a source of food. Algae eaten by tadpoles, eaten by stickleback, eaten by perch, eaten by Heron - this is a food chain for a freshwater pond. Algae are the producers, tadpoles the primary consumers, stickleback is the secondary consumer, perch is the tertiary consumer and the heron is the quaternary consumer.

Describe how animals have adapted to living in hot deserts. (6 marks)

(Eg.) Animals have adapted to living in hot deserts in the following ways. Many rodents are nocturnal, hunting during the cool nights. These animals often have large eyes to help them see in low light conditions. Animals often live in burrows, enabling them to stay cool during the daytime. Some animals, such as the jerboa, have large ears to enable heat loss to occur. Kangaroo rats obtain water from their food, live in burrows during the day and have highly efficient kidneys enabling them to produce little urine. They also do not perspire. Camels have long eyelashes and slit-like nostrils, which can close to protect them from blowing sand. They also have wide feet for walking on the sand. Desert foxes have thick fur on the soles of their feet to protect them from the hot ground. Their light coloured fur reflects the sunlight and helps to keep them cool.

What is meant by the term biodiversity? (2 marks)

(Eg.) Biodiversity refers to the variety of life, such as plants and animals, in the world, particular area, habitat or ecosystem.

How have plants in the tropical rainforest ecosystem adapted to their physical conditions? (4 marks)

(Eg.) Plants in the tropical rainforests adapt to the climate, which is hot and wet. Trees have buttress roots that help to anchor them in the shallow soil. Plants found in the shrub layer have little access to sunlight as it is blocked out by the dense vegetation of the canopy, so they have adapted to grow in low levels of light. Many plants have large leaves, which will enable them to absorb large amounts of sunlight in order to photosynthesise. The leaves also have drip tips to channel the water away from the branches and trunks to the ground to prevent waterlogging and rotting.

With reference to a case study, discuss to what extent the economic benefits of deforestation outweigh the losses. (6 marks)

(Eg.) Deforestation in the Amazon Rainforest has been happening for many years. Deforestation can be caused by different things, including mining, commercial and plantation farming, the building of hydroelectric dams and reservoirs, building new roads and logging for timber. All of these activities can contribute to the economic wellbeing of the local people as well as the country as a whole. The economic benefits can include the money gained from selling products such as timber, gold, bauxite, palm oil, rubber and beef. For example, in 2010 just over 65 million tonnes of soya beans were produced in rainforest areas in Brazil and today there are 50,000 hectares of land in the rainforests being used to mine gold. Local people benefit from an increase in jobs, which raises their income. The government gains from the increased tax revenue from both the companies and the individuals who are working. Industry will be encouraged by the availability of electricity and easy access through improved infrastructure - again providing jobs and income to both local people and the country. However, the destruction of the rainforest has negative effects as well. For example, there will be a loss of biodiversity caused by deforestation, which could impact on the tourist industry. Tourists come to see the wildlife in the rainforest and with continuing deforestation there will be less wildlife, and so the appeal to tourists will fall, causing a decline in the income earned from them. Plants that could bring medical benefits and income could be destroyed. Almost all of the activities giving economic gain to Brazil from deforestation are finite - they will eventually run out. For example, reserves of minerals will become exhausted, the soil will lose its fertility and eventually the crops grown will need large amounts of artificial fertilisers. Therefore the cost may outweigh the income gained and there will be few trees left to log. The short term economic benefits clearly outweigh the economic losses, but in the long term these activities are not sustainable and the benefits will decline.

Explain how population growth can cause desertification. (4 marks)

(Eg.) Desertification is where the land turns to desert. In the Sahel, the population has increased from 30 million people in 1950 to almost 500 million today. As the demand for food from the increased population rises, the land is put under huge pressure. Areas of marginal land may be cultivated unsuccessfully and vegetation destroyed in the process. Without vegetation the soil cannot be held together and will be eroded by the wind and rain and eventually this land will turn into desert. Over-cultivating land to meet the demand for more food can also exhaust the soils fertility.

To what extent is change a natural part of the development of an ecosystem? (6 marks)

(Eg.) Ecosystems are the result of the complex interrelationships between the different components. All ecosystems change and evolve over time - sudden change can have disastrous effects, causing the ecosystem to become imbalanced. Sudden changes caused by humans can cause ecosystems permanent damage. Changes caused by physical factors over a long period of time tend to be less damaging, and cause evolution, rather than destruction, on the ecosystem. For example, the deforestation of tropical rainforests through logging, mining and farming, has happened in a very short period of time, relative to the existence of the ecosystem. Removing the tree cover has knock-on effects on the soil, climate and animal species. The interrelationship between the components is destroyed through the removal of one major part - vegetation. The introduction of an alien species by people to an area, such as Sika Deer in the Dorset heathlands, has reduced the vegetation cover and impacted on the food supply for other species. Overall, changes to ecosystems are part of the natural process of evolution but sudden unexpected changes can have a much more dramatic effect on the ecosystem.

Explain how ecotourism can be an effective strategy in the sustainable management of tropical rainforests. (4 marks)

(Eg.) Ecotourism is a sustainable form of tourism that relies on the natural environment to attract people. It has a very low impact on the area and usually employs local people and supports communities as the profits made stay in the local area, contributing to social improvements, such as health care and education. It aims to educate visitors and increase their understanding and appreciation of nature and the local environment. If ecotourism is promoted in the tropical rainforests it can preserve the forest and support local people, therefore reducing their need to work in destructive industries, such as mining, to earn money. Ecotourism is sustainable as it causes little or no damage to the environment and uses traditional skills and knowledge. The indigenous people are in charge and use appropriate technology such as huts made from local materials and solar energy, which are cheap and easy to maintain.

What are the physical characteristics of hot deserts? (4 marks)

(Eg.) Hot desert are very dry or arid. Hot deserts have total annual rainfall below 250 millimetres per year. Summer temperatures of hot deserts rise well above 40°C. The mainly clear skies account for the very high daytime temperatures but quite cool night- time temperatures, as heat is allowed to escape to the atmosphere. In the winter, hot deserts can experience the occasional frost and even light snowfall. There is very low rainfall, meaning water is in short supply for much of the year. When rainfall does occur, it will often take the form of short torrential downpours, which can cause flash flooding. Hot desert soils are typically sandy or stony and dry and contain little organic matter due to the sparse growth of vegetation. Due to the lack of organic matter, desert soils are generally not very fertile. When rain does fall, the soils rapidly absorb the rainfall and this can lead to a sudden flush of vegetation growth and colour on the desert floor as flowering plants burst into life. The high rate of evaporation draws water to the surface, leaving behind salt deposits that form an infertile crusty surface. This process is called salinisation. Most deserts are rocky, desolate places with isolated thorny bushes and cacti.

'Water supply is the most significant challenge facing development in hot deserts.' With reference to a case study, to what extent do you agree with this statement? (6 marks)

(Eg.) In the Western Desert in the USA, water supply could become a major challenge in the future as demand increases in cities, such as Phoenix in Arizona. Until now the area has prospered due to massive water transfers from the River Colorado, but this will not be able to sustain the predicted population increase of double the current population by 2050. In addition, several states have experienced rapid population growth of more than the national average, including a rise of 35% in Nevada. There is a physical limit to how much water can be taken from the Colorado River. The region's water security is also threatened by predicted temperature rises and rainfall reduction due to climate change. The lack of surfaced roads in the Western Desert does cause limited accessibility and, combined with the extreme heat, is potentially very dangerous for tourists, but there are major highways linking the main cities and there are good direct air links. The climate is another challenge but people have used technology and learned to adapt to this. Air conditioning and the use of solar energy can keep homes cool. Plastic grass can be used instead of real grass and buildings can be painted white to reflect the sunlight and heat. Overall the issue of water supply is one which is much more difficult to deal with and is the most significant challenge facing the Western Desert.

What is overgrazing? (2 marks)

(Eg.) Overgrazing is when too many livestock animals are grazed on an area of land for too long, leaving the vegetation unable to recover.

Use a case study to describe the opportunities for developing mineral extraction and energy in hot deserts. (6 marks)

(Eg.) The Western Desert in the USA stretches across three states in the south west of the country. The desert is rich in minerals such as copper, uranium and coal. Copper is mined in the Sonoran Desert, part of the Western Desert, in the south west of Arizona. Developments have been limited due to environmental concerns and the impact on tourism. For example, a plan to mine uranium near the Grand Canyon was halted due to the risk to wildlife and endangered species. There was also concern over contamination of the water supplies. The climate in this desert area is ideal for solar power. The Sonoran Solar Project in Arizona is a solar power plant that will eventually produce energy for 100,000 homes, and provide 360 jobs for workers to build it. Hydroelectric power plants also provide energy to Western Desert communities. These are powered by water leaving Lake Mead. Oil is also found in Arizona and drilling has taken place since 1905. Today there are 25 active oil drilling sites.

Assess the importance of interdependence between abiotic and biotic components of the hot desert ecosystem. (9 marks)

(Eg.) The biotic and abiotic components of a hot desert ecosystem are the living parts (biotic), such as the animals and plants, and the non-living parts (abiotic), such as the soil, rock and water supply. The interdependence of these parts is vital for the survival of the ecosystem. The importance of interdependence is shown by the existence of links between the various parts of the food web, such as animals eating plants that have gained nutrients from the soil. Interdependence is also shown by the adaptation of plants and animals to the soil and climatic conditions. For example, the cacti store water in their tissues, and the Saguaro cactus in particular has small waxy leaves, which reduce water loss through transpiration. Additionally, people, plants and animals who co-exist successfully in these fragile ecosystems shows the importance of interdependence. Overgrazing, which reduces vegetation cover and leads to soil erosion, shows the potential damage that can be caused by the removal or damage of one component in an ecosystem. The interdependence of the components is what causes the existence of the hot desert ecosystem and the

To what extent do tropical rainforest ecosystems demonstrate interdependence between their components? (6 marks)

(Eg.) The tropical rainforest ecosystem exists due to the complex interdependence between the components. For example, nutrients are rapidly recycled from the biomass into the soil due to the warm and wet climate. From here they are taken back up into the biomass to be used again for plant growth. Different animal species contribute to the ecosystem by the spreading of seeds, leading to the continual renewal of plants and the addition to the soil nutrients through the organic waste they produce. The extent of the interdependence can be seen when one component is removed or damaged and the knock-on effect this has on the other components. For example, the removal of trees through logging, mining and farming, leaves the soil exposed. The soil can then be washed away by the heavy rainfall. The lack of leaf fall from trees reduces the nutrients entering the soil. Both these impacts of deforestation can result in a lack of fertile soil, meaning little or no plant life is able to grow. It is clear that components of the tropical rainforest ecosystem show a high level of interdependence.

'International co-operation is the only way to protect rainforests in the future.' Do you agree with this statement? (6 marks)

(Eg.) The tropical rainforests are an international resource impacting global climate and containing resources of international importance and as such should be protected. As many of the countries where the rainforests are located are LICs, they often do not have the money or resources to protect the forests and so need the help of the international community. There are a number of international agreements and strategies which could be used to protect tropical rainforests. The Forest Stewardship Council (FSC) promotes sustainable management by approving timber from sustainable sources. Suppliers are encouraged only to buy wood with the FSC stamp. This is a form of environmental quality control. The International Tropical Timber Agreement (2006) restricts the trade in hardwoods by only marking timber with a registration mark if it is from a sustainably managed forest. Most countries with tropical rainforests are less developed countries (low income countries, LICs, or newly emerging economies, NEEs). To promote development, some have taken out sizeable loans which they now find hard to repay and in order to do so are using income from mining, logging etc. Some high income countries have agreed to write off debts (debt reduction) in return for rainforests being protected. For example, in 2010 the USA agreed to convert a Brazilian debt of £13.5 million into a fund to protect areas of rainforest. This is called 'debt for nature swapping'.

Describe the value of tropical rainforests to the environment. (6 marks)

(Eg.) Tropical rainforests have a huge value to the environment. Rainforests are important sources of freshwater. About 20% of the worlds freshwater comes from the Amazon Basin. Tropical rainforests contain 50% of the world's plants and animals, including thousands of different species - many yet to be discovered, which may produce cures for illnesses in the future. Rainforests are known as the 'lungs of the world' as they contribute 28% of the world's oxygen. Moisture emitted through transpiration feeds into the water cycle and prevents the climate becoming too dry and hot. Evaporation of water from rainforests helps to cool the air (heat is extracted from the air during the process of evaporation). Rainforests absorb carbon dioxide (an important greenhouse gas) from the atmosphere, acting as a 'carbon sink'. This helps to offset global warming. Rainforests shelter and bind together the tropical soils, preventing harmful soil erosion, which can silt up rivers and reservoirs.

Evaluate the strategic options for reducing the risk of desertification. (9 marks)

There are a variety of strategies which can be used to reduce the risk of desertification. Water and soil management addresses the problem of intense rainfall events washing away loose soil and causing soil erosion. It often involves water storage and attempts to control the surface flow of water. For example, in Burkina Faso a series of low rock walls called bunds are built. These are deliberately constructed to follow the contours of the land, interrupting the downslope flow of surface water. Any soil carried by the water is deposited on the upslope side of the walls, creating a reasonable thickness of soil that can then be cultivated. Trees are very effective in preventing soil erosion and desertification. They act as an umbrella, protecting the soil from the direct impact of torrential rain and providing shade for seedlings. Their roots help to bind the soil together, preventing it being washed or blown away. In 2007, the African Union launched a project called the 'Great Green Wall', which is a plan to plant trees across the southern edge of the Sahara Desert with the aim of reducing desertification and addressing issues such as water management and food security. Some 21 African countries are involved, and already 15 million hectares of land have been restored in Ethiopia. Appropriate technology has been used in a variety of ways to address desertification. As mentioned above the use of low walls (bunds) to manage water is a good example as it makes use of local materials, basic tools and transport and is based on a simple idea. Community-led, it makes use of local people who work together for a common aim. Alternative cooking devices that use efficient stoves (often supplied by charities such as Practical Action) burn small amounts of wood or charcoal, reducing the quantity of fuelwood required. All of these strategies are small scale and are operated by local people, so have much more chance of success than large scale top-down strategies. The ownership of the projects by the local community makes them more likely to succeed, along with the simple technology and construction methods, which can easily be used by local people.