AQA GCSE Geography Paper 1 PDF

4.3 Paper 1: Living with the Physical Environment J KEY LEARNING Climate change: our fault? ➤ How the greenhouse effect works What is the greenhouse effect? ➤ How humans have...

4.3 Paper 1: Living with the Physical Environment J KEY LEARNING Climate change: our fault? ➤ How the greenhouse effect works What is the greenhouse effect? ➤ How humans have The greenhouse effect is a naturally occurring phenomenon that keeps the contributed to climate Earth warm enough for life to exist. It is thought that without the greenhouse change effect, the Earth would be approximately 33 °C colder and therefore life would not exist as we know it today. The Sun’s infrared heat rays enter the Earth’s atmosphere. The heat is reflected from the Earth’s surface. The natural layer of greenhouse gases allows some heat to be reflected out of the Earth’s atmosphere, but some of the Sun’s infrared heat is trapped, which keeps the Earth warm enough. Infrared heat Less heat able to escape Natural Enhanced from the Sun the Earth’s atmosphere due to the thicker layer of greenhouse gases er of r lay gases due cke Thi nhouse ctivity e a gre human Some heat is reflected from to the Earth’s surface and escapes the Earth’s atmosphere lly ra Some examples o atu es f n gas human causes o g se greenhouse g f gr cur of ou ases ee rin oc yer nh La Some of the heat is trapped and keeps Earth Infrared heat warm enough from the Sun The Earth’s for life temperature increases as more heat is Earth reflected back, increasing the greenhouse effect Global warming as a natural phenomenon Human-induced global warming Figure 4.9 The greenhouse effect: natural and enhanced However, there is an enhanced greenhouse effect global temperatures can be seen in Figure 4.10. whereby human activity has increased the layer of Carbon dioxide emissions have increased since the greenhouse gases which naturally exists. Activities Industrial Revolution, and especially since the 1970s. which generate more greenhouse gases include burning The Intergovernmental Panel on Climate Change (IPCC) fossil fuels in industry, agriculture, transport, heating reports that it is very likely that rising levels of carbon and deforestation. Less heat escapes from the Earth dioxide are the main cause of climate change. and more is trapped by the thicker layer of greenhouse Despite volcanoes naturally releasing carbon dioxide, it is gases, which means the Earth warms up even more. thought that humans generate more than 130 times the volume of carbon dioxide than volcanoes. Greenhouse Are humans causing gases consist of 77 per cent carbon dioxide, 14 per climate change? cent methane, 8 per cent nitrous oxide and 1 per cent chlorofluorocarbons (CFCs). Although carbon dioxide Scientists have measured and proved that natural makes up the majority of greenhouse gases, each causes are responsible for climate change, yet natural molecule of methane has 25 times and each molecule of causes cannot account for the increases in temperature nitrous oxide has 125 times the global warming potential since the 1970s (see Figure 3.29 in Section 3.11). The link over 100 years, when compared to carbon dioxide. between increasing carbon dioxide levels and increasing 48  Section A: 4 Climate change How do humans cause climate change? Fossil fuels 390 14.5 Fossil fuels account for the majority of global 370 Carbon dioxide (parts per million) greenhouse gas emissions – over 50 per cent. Burning 14.3 these releases carbon dioxide into the atmosphere. Fossil 350 fuels are used in transportation, building, heating homes, Temperature (ºC) and the manufacturing industry. Additionally, they are 14.1 330 burnt in power stations to generate electricity. As the world’s population grows and wealth increases, people 310 13.9 are demanding more and more energy, which increases the level of fossil fuels and carbon dioxide. 290 13.7 270 Agriculture Agriculture contributes to approximately 20 per cent of 250 13.5 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 global greenhouse gas emissions. It also produces large Time volumes of methane: cattle produce it during digestion, Key and microbes produce it as they decay organic matter Carbon dioxide Temperature under the water of flooded rice paddy fields. Figure 4.10 Carbon dioxide and global temperature change As the world’s population increases, more food is required, especially in areas such as Asia where rice is Figure 4.11 World agriculture emissions the staple diet. When countries increase their standard Continent % of world emissions from agriculture of life, there is almost always an increasing demand for Africa 15% meat (Section 23.1). If current population rates continue, Americas 25% it is inevitable that large-scale agriculture’s contribution Asia 44% to climate change will continue to grow. Europe 12% Oceania 4% Deforestation Deforestation is the clearing of forests on a huge scale. During the process of photosynthesis, trees absorb If deforestation continues at the current rate, the world’s carbon dioxide, which reduces the amount of carbon forests could disappear completely within a hundred dioxide in the atmosphere. The process of deforestation years. leaves fewer trees to absorb carbon dioxide. Therefore the enhanced greenhouse gases contribute to rapid There are several reasons why forests are cut down: climate change. When trees are burnt to clear an area, n clearing land for agriculture so that farmers have such as with slash and burn, the carbon dioxide that has space to plant crops and graze livestock been stored is also released, which again contributes to n logging for wood and paper products climate change. n building roads to access remote areas n making room for the expansion of urban areas. Activities 1 Describe the relationship between temperature and 3 How do (a) fossil fuels, (b) agriculture and atmospheric carbon dioxide in Figure 4.10. (c) deforestation each contribute to climate change? 2 Write a sequence of numbered statements to 4 ‘Humans are to blame for climate change.’ To what explain the greenhouse effect. extent do you think this statement is true? 49 4.4 Paper 1: Living with the Physical Environment J KEY LEARNING The effects of climate change ➤ The likely effects of climate change What are the likely effects of climate change? ➤ How people and the The IPCC states that the cost of damage caused by climate change is likely environment may be to be ‘significant and to increase over time’. The effects of climate change are affected by global not certain. The likely effects will vary and be uneven globally and regionally. climate change Skiing tourist Less heating The Flood risk from heavy rain is one of resorts such as in required means Mediterranean the main threats to the UK. The the Alps may close increased crops region may see estimated cost of damage from or have shorter and forest increased flooding could rise from £2.1 billion seasons as there growth in drought. currently to £12 billion by the 2080s. may be less snow. northern Europe. The UK may be affected by sea level rise in Europe, putting the UK’s coastal defences under increased strain. In the UK, average temperatures are likely to increase, as will the risk of diseases such as skin cancers EUROPE ASIA and heat strokes. Milder winters might lead to a decline in winter-related deaths. Extreme weather (drought, heat waves, and flooding) AFRICA is expected to increase across the UK, as are water shortages in the south and south east. Health: in Europe, more heat waves can increase deaths, but deaths related to AUSTRA Activities colder weather may decrease. 1 State two positive and two Crop yields in Europe are negative effects of climate expected to increase but change, using Figure 4.12. require more irrigation. 2 Complete the following table Drought is likely to put (notice the impacts are plural): pressure on food and water supplies in sub-Saharan Social impacts Africa due to higher Environmental impacts temperatures and less rainfall. 3 Rank in order which parts of Health in southern and Agriculture may be Warmer rivers affect marine the world you think may be wildlife. The change in eastern Africa may decline affected in South Asia. affected, most to least. as malaria would increase in A decrease in wheat food supply may decrease hot humid regions that and maize and a small the Ganges river dolphin 4 How might the effects in one population in Nepal, India remain hotter for longer in increase in rice are part of the world impact on the year. expected. and Bangladesh. another? Give at least one example. Figure 4.12 Global effects of climate change 50  Section A: 4 Climate change How might people and the environment be affected by climate change around the world? Expected global effects of climate change can be seen on the map in Figure 4.12, which is centred on the Pacific Ocean. Around 70 per The fishing Wildlife declines Less ice in the The tree line of cent of Asia may industry in East as polar bears and Arctic Ocean the Sub-Arctic be at increased Asia is expected to seals disappear would allow more boreal forests is risk of flooding. decline due to with the loss of shipping and expected to higher temperature habitat as ice extraction of gas retreat north as and more acidic melts. and oil reserves. temperatures rise. sea. It is likely that agriculture may yield more wheat soybean and rice but see a decrease in maize yields in North America. Forests in North America may be affected more by pests, disease and forest NORTH fires. AMERICA In Central America, maize crop yields may fall by up to 12 per cent. In the Amazon rainforests a modest level of climate change can cause high levels of extinction. Eastern SOUTH Amazonia may become a AMERICA savannah with warmer temperatures and less soil moisture. AUSTRALIA South America is expected to decrease in maize, soybeans and wheat crop yields. Key Predicted air surface temperature by end of the 21st century 183mm 10 9 ANTARCTICA 8 7 6 Fishing in the Lower Less rainfall may affect Coral reefs such as the Wildlife such as Adélie 5 Mekong delta would wildlife, causing food Great Barrier reef could penguins on the Antarctic 4 decline, affecting 40 million shortages for orangutans see biodiversity lost, and Peninsula may continue to 3 2 people, due to reduced in Borneo and Indonesia. warmer, more acidic (due decline as ice retreats. 1 water flow and sea level to CO2 in the atmosphere) 0 rise changing the quality of water would cause coral the water. bleaching. °C 51 4.5 Paper 1: Living with the Physical Environment J KEY LEARNING Managing climate change: ➤ What mitigation is ➤ Reducing the causes of mitigation climate change What is mitigation? ➤ The costs and benefits of The challenge of reducing the impact of climate change can be managed by two methods of mitigation main approaches: mitigation and adaptation. (See Section 4.6 for information about adaptation.) Mitigation strategies, whether local or global, deal with the cause of the problem. They reduce or prevent the greenhouse gases which cause climate change and protect carbon sinks, such as forests and oceans. How can the causes of climate Carbon capture change be reduced? Technological advances can replicate the way the Earth stores carbon dioxide (underground in rock formations and the oceans) in a process known as carbon capture Alternative energy production and storage (CCS). CCS can be used with existing and As world population and incomes grow, the demand new power plants. The IPCC (page 42) estimates that for energy also increases. The energy needed to power CCS could provide 10 to 55 per cent of the world’s total more consumer goods, such as refrigeration, computers carbon mitigation until 2100. It works by capturing CO2 and car, to travel around the world and, to produce food, from emission sources (Figure 4.13) and safely storing it. especially meat, causes a huge challenge in mitigating CCS can also remove CO2 from the open atmosphere by climate change. Renewable energy sources (such as converting it into a liquid ‘supercritical CO2’ which is then wind, solar, geothermal, wave and tidal, and biomass) injected into sedimentary rock. An impermeable ‘cap offer a solution to reduce the volume of greenhouse rock’ prevents it from escaping. gases contributing to climate change. The UK is a world leader in CCS. The Department of Energy The United Nations Environment Programme states: ‘In & Climate Change reports that: ‘By 2050, CCS could provide 2010, new investments in renewable energies reached a more than 20 per cent of the UK’s electricity and save the record high of US$211 billion, with noticeable growth in UK more than £30 billion a year in meeting our climate emerging economies’. Renewable energy sources such as targets’. Unfortunately, the process of CCS is expensive, solar energy are more expensive than fossil fuels, but are and it is unclear whether the CO2 would remain trapped in becoming cheaper and more competitive, especially as the long term. Additionally, it does not promote renewable they do not produce CO2 (Chapter 25.4). energy, which prevents CO2 emissions in the first place. Solar energy Emission source Capture Power plant, refinery, Liquefied/compressed In 2013, 14.9 per cent of the UK’s electricity industrial factory Ocean was generated by renewable energy sources. CO2 storage platform facilities Photovoltaic solar energy generated 3.8 per Transportation cent of renewable energy sources. When light shines on solar panels it creates an electrical field. The stronger the sunshine on solar panels, Drilling pipe the more electricity that is produced. A typical home saves over a tonne of CO2 per year as there Impermeable cap rock are no greenhouse gas emissions to contribute Aquifer Stored CO2 to climate change (Energy Saving Trust, 2014). Stored CO2 However, at times when there is no sunshine, such as night, solar energy cannot be relied on to generate electricity. Figure 4.13 Carbon capture and storage 52  Section A: 4 Climate change Planting trees Deforestation is a global problem as it is a major driver of climate change (see Chapter 6). According to the United Nations Environment Programme, deforestation and forest degradation occurs at a rate of 13 million hectares per year. A US$40 billion investment in reforestation, and payments to landholders for conservation each year from 2010 to 2050, could increase forest carbon storage by 28 per cent. The UK has a £24.9 million project (funded by the Department for Environment, Food and Rural Affairs) to reduce deforestation and increase forest and land restoration in Brazil (see Chapter 6). It aims to tackle climate change by reducing 10.71 million tonnes of CO2 emissions over 20 years by recovering 41,560 hectares of degraded forests. International agreements The UN negotiated a new international climate change agreement for all countries at the 2015 Paris climate conference. It will be implemented from 2020. The European Commission has set the EU’s vision for a new Figure 4.14 ‘Wind farm where a forest once stood.’ agreement that will reduce global emissions by at least 40 per cent below 2010 levels by 2030, and by 60 per cent by 2050. It was a challenge for countries to agree on targets that will go far enough to manage climate change. Some countries can afford to mitigate climate change more than others, and some are considered more responsible for causing climate change than others. Activities 1 Define mitigation. 2 Use Figure 4.13 to describe the process of carbon capture and storage. 3 Complete the following table: Mitigating climate change Method How does it reduce Advantage of the Disadvantage of the CO2? method method Alternative energy production Carbon capture and storage Planting trees International agreements 4 Explain the message in the cartoon (Figure 4.14). Include the following words in your answer: wind farm, renewable energy, deforestation, carbon dioxide. 53 4.6 Paper 1: Living with the Physical Environment J KEY LEARNING Managing climate change: ➤ What adaptation is ➤ Managing climate change adaptation through adaptation What is adaptation? ➤ The costs and benefits of Section 4.5 considered how mitigation can manage the challenges of climate methods of adaptation change. Another approach, adaptation, responds to the impacts of climate change and tries to make populations less vulnerable. Adaptation strategies are local rather than global, to respond to localised impacts. If mitigation stopped all carbon emissions from human activity, adaptation would still be required to manage the impacts of climate change that are naturally occurring and those that have already occurred. How can climate change be managed through adaptation? Change in agricultural Potato Park in Peru systems Peru’s Potato Park Although the effects of climate is a 12,000 hectare change are uncertain, agriculture will reserve high in the need to adapt to them. Some ways Andes, near Cusco. It was established to of adapting include: conserve the region’s moving production to another potato biodiversity location due to changing (more than 1,345 temperatures and extreme varieties).Warmer weather climates have altered the growing patterns increasing irrigation in areas due of some local to changing precipitation potato varieties. changing the crops and varieties grown and the time of year they The 8,000 residents, from six indigenous Quechua communities, own the land are planted, such as drought- and control access to local resources. The organisation Papa Arariwa Collective resistant crops or switching to (‘guardian of native potatoes’) helps manage all the land so everyone can benefit. livestock production which tends A typical family farm grows 20 to 80 varieties of potato. Most are grown to have more guaranteed returns. for local consumption. As the climate becomes warmer farmers have begun experimenting with different varieties at higher altitudes where temperatures The cost of adapting to climate are lower. change is more difficult for poorer Varieties which are disappearing have been conserved in the gene bank of the subsistence farmers. International Potato Centre. The disease-free varieties have helped increase The United Nation’s Food and crop yields. Agriculture Organization states that Conservation of potato varieties will provide invaluable help to local agriculture needs to be ‘climate- communities adapting to climate change. smart’ if it is to feed the world (Figure 4.15). Figure 4.15 An example of climate-smart agriculture 54  Section A: 4 Climate change Managing water supply Reducing risk from rising sea levels In the UK, Londoners consume 167 litres of water each London is currently well protected against rising sea day compared to the national average of 146 litres. It is levels. The Thames Barrier has been closed over 100 the driest part of England, contains 13 per cent of the times since it was built, in 1982, to stop tidal surges population of the UK and faces the challenge of climate entering central London. The Barrier was designed with change: summers will get drier and winters will get an expectation it would be breached once every 1,000 wetter (Chapter 15). years, but a 50 centimetre rise in sea level would increase the risk to once every 100 years. There are two ways water can be managed: Reducing demand. As Mayor of London, Boris Fieldwork: Get out there! Johnson developed a Water Strategy to reduce London’s water demand. By 2030, all London homes Investigate the impact that mitigation (such should have been offered a free retrofit package as alternative energy) and adaptation (such as of water-efficient devices (Figure 4.16), including flood prevention) strategies have on the physical aerators. environment in your local area. Increasing supply. Thames Water opened a a) Decide what evidence of mitigation and/or desalination plant in Beckton in 2010 to increase adaptation you could survey. water supply. Water is taken from the River Thames b) Suggest where you could carry out your fieldwork. at low tide (when it is least salty). A process called c) i) Devise an environmental survey to assess its reverse osmosis is used to produce drinking water for impact on the physical environment. 400,000 homes. The plant requires a lot of energy ii) Explain why an environmental survey is (enough to power 8,000 homes), so carbon emissions qualitative data. need to be offset by a biodiesel electricity plant. Figure 4.16 Impact of water-efficient devices installed in London homes Product Energy Water saved CO2 saved/ Water bill Energy bill Geographical skills saved/year (L/year) year savings savings (£/year) (£/year) What type of graph would be Tap aerators (saving 199.67 6,570 42.35 11.12 8.84 appropriate to show ‘water bill for whole house) savings’ in Figure 4.16? Construct Dual flush 0 17,155 0 29 N/A your chosen graph. Shower timers 46 12,78 14.1 2.16 2.04 Aerator 440.36 10,950 93.41 18.53 19.5 showerheads Total 686.03 35,953 149.86 60.81 30.38 Activities 1 Distinguish between mitigation and adaptation. 6 Describe how water supply can be managed to 2 Why will agricultural systems need to adapt in the cope with changes caused by climate change. future? 7 Which water efficiency measure in Figure 4.16 has 3 Use Figure 4.15 to describe how agricultural systems the greatest impact on London’s water supply? can change to cope with climate change. Explain your choice. 4 Why has the ‘Water Strategy’ been established in 8 Suggest how existing flood defence schemes such London? as the Thames Barrier may need to change due to climate change. 5 Suggest at least three other ways in which water consumption in the home can be reduced. 9 ‘The best of both worlds’. Explain why both mitigation and adaptation are needed to manage climate change. 55 5.1 5 Ecosystems J KEY LEARNING How ecosystems operate ➤ How the different parts of an ecosystem are How are the different parts of an linked together ecosystem linked? ➤ How food chains and nutrient cycles work Sunshine and rain are needed for photosynthesis, so they are essential to the ecosystem. Other climatic elements such as Animals found in a woodland wind and frost are also important. include many species of insects and birds, and mammals such as rabbits, squirrels and foxes. Micro-organisms such as fungi and Plants include trees, wild bacteria are decomposers. They help flowers, grasses, mosses and to break down dead plants and algae. They provide food and animals, releasing nutrients into the shelter for many animals. ecosystem so they can be recycled. Rocks help in the formation of soils Soils store water and contain Living (biotic) components of ecosystem and rock type is important. nutrients which plants can use. Non-living (abiotic) components of Weathering releases nutrients Soils are home to insects and ecosystem stored in rocks into the ecosystem. decomposers. Figure 5.1 The biotic and abiotic components of an ecosystem An ecosystem is made up of plants, animals and their Sunlight surrounding physical environment, including soil, rainwater and sunlight (Figure 5.1). Important interrelationships link together the biotic (living) and abiotic (non-living) parts Green plants, e.g. pondweed, Primary of the ecosystem. These interrelationships consist of: producers flag, iris n physical linkages between different parts of the Algae ecosystem (animals eating the plants, for example) n chemical linkages (mild acids in rainwater speed up the decay of dead leaves, for example). Primary Water fleas Tadpoles consumers In ecosystems, plants and animals can migrate from one place to another, bringing change. There are also inputs and outputs from the ecosystem to other places (Figure 5.2). Most importantly of all, ecosystems depend on a Dragonfly Diving Secondary constant input of light from the Sun, as well as rain from larvae beetles consumers the atmosphere. In turn, rainwater leaves the ecosystem when it evaporates and returns to the atmosphere, or runs into a river. Tertiary Frogs Goldfish consumers Ecosystems can be any size: n local (a small-scale ecosystem is also called a habitat) Quaternary n regional (England’s Lake District moorland) Grey heron consumers n global biomes (South America’s tropical rainforest) n Earth (some scientists argue that all of the planet’s organisms are linked together). Figure 5.2 Linkages, inputs and outputs for a garden pond ecosystem 58  Section B: 5 Ecosystems How do food chains and nutrient Example Number Decomposers Trophic level Tertiary consumers cycles work? Sparrowhawk 1 (top predators) 300 Secondary consumers Blue tits The biotic community of an ecosystem consists of (carnivores) different species of plants and animals in different Tortrix moth larvae 12,000 Primary consumers (herbivores) feeding groups: Primary producers Plant material 100,000 (oak leaves) (plants) n plants or primary producers: green plants that use photosynthesis and take nutrients from the soil using Figure 5.3 An ecosystem food chain their roots n Many parts of plants are simply not eaten by animals, n herbivores or primary consumers: plant-eating and carnivores do not eat all of their prey (such as animals (cows, or rabbits) the bones). Also, much of what the animals do eat is n carnivores or secondary consumers: these animals excreted. feed on herbivores (foxes, or cats) n Energy is last at each level. Hunters use a lot of kinetic n top carnivores: these animals will hunt and eat other energy: chasing prey can be time-consuming and carnivores in the ecosystem, as well as the herbivores. exhausting. Some herbivores search around a lot for They include the largest and fastest hunters, like lions plants to eat. In addition, energy is constantly being and wolves. used up in respiration. Much of an animal’s daily The interrelationships between these feeding groups calorie intake is used simply to stay alive, rather than are shown in the food chain in Figure 5.3. This diagram to build new biomass. shows the weight of biomass getting smaller at each The decomposers in Figure 5.3 are the organisms that, level. For instance, in the tropical rainforests of Brazil over time, break down dead organic matter and animal (see Chapter 6), there are only five kilograms of animal excretions. They include a mixture of: scavengers (such biomass per 40 kilograms of plant biomass. There are as insects that eat dead wood) and detritivores (such as two important reasons for this reduction: bacteria). Decomposers help to return nutrients to the soil in the form of an organic substance called humus. The importance of nutrient cycling All plants and animals depend on nutrients in food for their health and vitality. Nutrients occur naturally in the environment and are constantly recycled in every ecosystem. Figure 5.4 shows these important pathways. Activities Input dissolved in rainfall (from atmosphere) Biomass 1 Look at Figure 5.1. Identify three Fallout as interrelationships between the biotic and tissues die abiotic components of the ecosystem. Uptake 2 Look at Figure 5.2. Litter by plants a) Identify plant and animal species that are part of the pond ecosystem. Loss in Release as litter b) Suggest why the input shown is important runoff decomposes Soil for the health of the ecosystem. 3 Look at Figure 5.3. Use the information Loss by leaching provided to help you describe and explain Nutrient stores Input the difference in size between the primary Nutrient transfers weathered from rock producers and the top predators. Figure 5.4 The nutrient cycle 59 5.2 Paper 1: Living with the Physical Environment J KEY LEARNING Epping Forest ecosystem, UK Example ➤ The characteristics of Epping Forest’s food web ➤ The interdependence of the ecosystem ➤ The characteristics of Epping Forest’s nutrient cycle Ipswich Key facts M11 ESSEX n Located east of London (Figure 5.5), Epping Colchester Forest is all that remains of a larger forest that Epping Forest colonised England at the end of the last Ice Age. District Chelmsford N n Bogs and ponds in the forest have their own M2 5 unique species, including 20 kinds of dragonfly. 0 25 n For 1,000 years, Epping Forest has been managed LONDON km in a variety of ways: as hunting grounds for royalty, a timber resource and, nowadays, recreation (as Figure 5.5 shows, it is easily accessible). What are the characteristics of Figure 5.5 The location of Epping Forest Epping Forest’s food web? Biodiversity in the forest has remained naturally high, thanks to careful management, so there is a complex food web composed of thousands of species (Figure 5.6 shows this in a simplified form). Epping Forest is home to: n a large number of native tree species, including oak, elm, ash and beech   n a lower shrub layer of holly and  Fox Owl Sparrowhawk hazel at five metres, overlying a  field layer of grasses, brambles,  bracken, fern and flowering  plants; 177 species of moss and  Rabbit Mouse Small birds Badger Consumers  lichen grow here. Altogether,  there is great diversity of  producer species (Figure 5.7)  n many insect, mammal and bird  Insects, beetles, worms, caterpillars consumer species are supported,  including nine amphibian and  reptile species and 38 bird species  Mosses, grasses, Deciduous n studies have found 700 species Producers  herbs, ferns trees Shrubs of fungi, which are important decomposers. Figure 5.6 Epping Forest’s food web 60  5 Ecosystems How is the ecosystem interdependent? The forest’s producers, consumers and decomposers are all interdependent. This is most clearly shown by the annual life cycle of the trees. Most of the trees are deciduous, meaning that they lose their leaves in winter. This is an adaptation to the UK’s seasonal climate. Winters are darker and cooler than summers (the mean monthly temperature is 18 °C in July but just 5 °C in January). As a result, the trees grow broad green leaves in spring. This allows them to maximise photosynthesis during the summer. They shed their leaves in the autumn, and so conserve their energy during winter. By mid-autumn, the forest floor is covered with a thick Figure 5.7 Leaves on the forest floor and Epping Forest’s tree layer of leaves. Remarkably, by spring, the leaf litter has canopy, which In places reaches 30 metres all but disappeared: the decomposers and detritivores’ work (page 59) is now complete. Nutrients stored in What explains the characteristics the leaves are converted to humus in the soil, ready to support the new season’s plant growth. This will of Epping Forest’s nutrient cycle? ultimately include the fruits and berries that, in turn, In Figure 5.8, which reflects Epping Forest, the biomass support many primary consumers. store is large because of the great height of the trees, and the dense undergrowth beneath them. The soil store Nutrient cycling demonstrates clearly the is large too because there is always plenty of humus. interdependence of plants, animals and soil. People and ecosystem components are interdependent too. In the The high flow rates between the litter, soil and biomass past, coppicing was common (cutting back trees to stores reflect the vigorous cycle of new growth that encourage new growth of wood). Today, visitors pick takes place each year. The forest also loses a lot of berries and flowers. In turn, this helps spread the seeds, nutrients each year, via leaching, during episodes of which stick to their clothing. heavy rainfall. Balance between stores Moderate transfers B Activities P between stores 1 Look at Figure 5.6. Suggest how the populations of the different food web species might be affected by the removal of foxes from the ecosystem. 2 Birds, mammals, insects, amphibians and reptiles are all present in Epping Forest. Some are herbivores (primary consumers), whereas L others are carnivores (secondary consumers and top carnivores). Draw S a table with two columns and add as many named examples as you can of both categories (for instance, the tawny owl is a carnivore). 3 Study Figure 5.7. Describe as many characteristics as you can of the Le plants shown. What kinds of processes are taking place? R 4 Using all the information, explain two ways in which studying Epping W Forest has helped you understand the term ‘interdependence’. Figure 5.8 The nutrient cycle of a deciduous forest 61 5.3 Paper 1: Living with the Physical Environment J KEY LEARNING Changes affecting ecosystem ➤ How physical and human forces disturb ecosystem balance balance How do physical and human forces disturb ➤ How the loss or gain of one species affects a ecosystem balance? food web Periods of extreme weather or climate change can disturb the balance of ➤ How ecosystem balance ecosystems. In the years 1976–77, southern England experienced an 18-month can be restored through drought that killed many trees. A further 15 million English trees were felled management by a great storm in 1987. As a result, population numbers declined for many consumer species in the food chain. Secondary forest growth has since taken place, however, and consumer species have migrated back. The recent recovery of English woodland is an example of ecosystem resilience. Ecosystems are sometimes damaged in permanent ways, especially when human forces are involved, for instance by deforestation (page 49). The Hawks Owls removal of the forest exposes the soil beneath to rainfall, and so it can be washed away, making it impossible for the ecosystem to recover. This is especially true in tropical rainforest regions, where heavy rain falls most days Sparrows Woodpeckers Blue tits (Chapter 6). In the longer-term, human-induced climate Spiders change could threaten the ecosystem balance of many Flies places. For instance, changes in temperature and precipitation Aphids and Moth caterpillars Beetles patterns for southern England might make it harder for capsids ecosystems like Epping Forest to survive in their current form. In some places, grass (rather than trees) may dominate in the Common oak future, if climate change predictions are correct. Figure 5.9 A food web supported by an oak tree How does the loss or gain of one How can ecosystem balance be species affect a food web? restored through management? Figure 5.9 shows a food web supported by oak Many species have been hunted to extinction, without woodland. Suppose that the population of beetles is a full understanding of how this could affect ecosystem reduced by disease. This would directly impact on the balance. In Europe and the USA, killing wolves and bears numbers of woodpeckers. With fewer beetles to eat, removed danger to people and their cattle. But fewer their numbers may decline. In contrast, we may expect to carnivores meant that rabbit and deer populations see more oak tree growth now fewer beetles are feeding quickly multiplied and began to eat all available on them. In addition to these direct impacts, there are vegetation, stripping the land bare, leading to soil indirect impacts to consider: erosion. The ecosystem lacks balance. n Owl and hawk numbers may also fall because they Many scientists believe that ‘rewilding’ or ‘ecosystem eat woodpeckers. restoration’ is the best way to restore ecosystem balance. n Woodpeckers are carnivorous and have multiple food Grey wolves were recently reintroduced into Yellowstone sources. They may just eat more caterpillars instead. National Park in the USA, which has resulted in numerous However, this could now impact on blue tit numbers. impacts (Figures 5.11 and 5.12). The wolves have restored How would this happen? Can you identify more balance to the ecosystem and landscape (Figure 5.10). possible food web impacts that could follow? 62  Section B: 5 Ecosystems Figure 5.10 Yellowstone National Park Figure 5.11 A grey wolf Reintroduction of the grey wolf. There are 16 packs of around 10 animals. Each pack kills one elk per day Elk population falls from Competition from the wolves results More kills made by wolves 20,000 to 10,000 in 8 years in a decrease in coyote populations. provide more food for Male coyotes are smaller scavengers Reduction in grazing pressure on vegetation. Aspen and Reduction in predation from coyotes Increases in cottonwood start to regenerate. leads to an increase in voles, mice populations of grizzly There is more tree cover and other rodents bears, cougars, ravens, magpies, eagles Increase in bank-side Beavers create Regeneration of Increased Populations of predators trees stabilises river banks ponds and aspen attracts tree cover of small rodents, e.g. red — there is less erosion. flooded areas, beavers, which provides foxes and birds of prey, More woody debris in which promote begin to habitats for increase rivers creates pools and the growth of recolonise songbirds provides trout habitat aspen Yellowstone Figure 5.12 Impacts of the reintroduction of the grey wolf to Activities the Yellowstone ecosystem since 1995 1 Look at Figure 5.9. a) How many levels are there in the food web? ➔ Going further b) Name four primary consumers and three secondary consumers. Discuss whether potentially dangerous wild animals 2 State one human and one physical cause of like wolves and bears really can be brought back to ecosystem disturbance. Compare their impacts. the countryside in the UK. How might such a move cause conflict with other uses of the countryside like 3 Humans have deliberately or accidentally helped tourism? plant and animal species to migrate to new places. What examples can you think of, other than the ones included on these pages? Did any of these movements impact negatively on ecosystems? Fieldwork: Get out there! 4 Look at Figure 5.12. Make a list of (a) species whose numbers increased and (b) species whose Look at Figure 5.9. Plan a fieldwork investigation numbers were reduced, after the reintroduction of this small-scale ecosystem. Possible themes of wolves. to investigate could include the number of different plant and animal species, or evidence of 5 Explain how changes to the ecosystem in turn interrelationships and nutrient cycling. changed the physical environment of Yellowstone. 63 5.4 Paper 1: Living with the Physical Environment J KEY LEARNING The distribution and characteristics ➤ How climate explains the distribution and of global ecosystems characteristics of global ecosystems How does climate explain the distribution and ➤ Altitude, relief and ocean characteristics of global ecosystems? currents Figure 5.13 shows the distribution of the world’s large-scale global ecosystem in biomes. Figure 5.13 and the this page explain how global-scale variations influence the distribution of ecosystems. Tropical rainforests Coniferous forests These lie along the Equator in Asia, Africa and South Found at 60° north, where winter temperatures are America. The Sun’s rays are concentrated at this latitude, extremely cold due to lack of insolation (page 22). heating moist air which rises and leads to heavy rainfall, Due to the Earth’s tilt, there is no sunlight for some with little seasonal variation. This creates the perfect months of the year. Coniferous trees have evolved needle conditions for evergreen rainforest. leaves that reduce moisture and heat loss during the cold, dark winter months. Deserts Found close to the Tropics of Cancer and Capricorn. The air Tundra (or ‘cold desert’) that rises over the Equator heads polewards after shedding These areas are found at the Arctic Circle, where the its moisture as rain. The Sun’s rays are still highly concentrated Sun’s rays have little strength. Temperatures are below at this low latitude. Combined with the dry air, this brings arid freezing for most of the year. Only tough, short grasses desert conditions to places like the Sahara and Australia. can survive, often in waterlogged conditions (due to surface ice thawing). Tropical grasslands Why are altitude, relief and ocean Sandwiched between the two extremes of tropical rainforest and desert. Conditions are dry for half of the year, currents also important? due to the seasonal movement of the Hadley cell (page 23). Although latitude and distance from the sea are the main factors affecting distribution, the following are also Temperate grasslands important: Short tussock and feather grasses dominate the n altitude: temperatures fall by about half a degree for landscape between 40° and 60° north of the equator, every 100-metre increase in altitude, and tough grasses but only in the centre of continents away from the sea. replace trees on steep mountainsides n mountain ranges: in the USA and Asia, inland areas Mediterranean isolated from the sea suffer from low rainfall. This is because winds blowing off the oceans quickly lose Drought-resistant small trees and evergreen shrubs grow their moisture when air is forced to rise upwards over a between 30° and 40° north and south of the equator, high mountain range. The drier lands found east of the but only on the west coasts of continents. USA’s Rocky Mountains are said to be in a rain shadow n ocean currents: a cold ocean current flowing along Deciduous forests South America’s coast helps to create arid conditions These grow in many places at higher latitudes. Found in Chile’s Atacama Desert because little evaporation in western Europe, where rain-bearing storms arrive takes place over the cold water. In contrast, the warm regularly thanks to the jet stream, and the east coasts of Gulf Stream ocean current affects the climate of Asia, North America and New Zealand. The Sun’s rays are western Europe. weaker at this latitude. 64  Section B: 5 Ecosystems °C Fairbanks mm 20 100 0 80 –20 60 40 °C Oxford mm –40 20 30 120 0 20 100 J F MAM J J A S OND 80 °C Kazachye mm 10 20 120 Tropic 0 60 10 100 40 0 80 of Cancer –10 20 –10 60 –20 0 J F MAM J J A S OND –20 40 –30 20 –40 0 J F MAM J J A S OND Equator Tropic °C mm Bilma 40 40 of Capricorn °C Bulawayo mm 300 30 30 40 °C Manaus mm 200 20 20 30 40 500 10 10 20 100 30 400 10 0 0 300 J F MAM J J A S OND 20 0 0 200 J F MAM J J A S OND 10 100 0 0 Key Deciduous forest Temperate grassland J F MAM J J A S OND Tropical rainforest Coniferous forest Desert and semi-desert Tropical monsoon forest Savanna grassland Tundra Mediterranean Temperate evergreen forest Alpine and ice desert Figure 5.13 World distribution of global ecosystems Geographical skills Each global-scale ecosystem in Figure 5.13 has several 3 Are there any unusual features or anomalies? distributional features. Choose one ecosystem and take Perhaps the ecosystem is found at an unusually the following steps: high or low latitude in some places. 1 What is the overall pattern? Does the ecosystem 4 Can you support your answer with data? Is it circle the Earth at a particular latitude? Or is it possible to estimate the width of the band of found only in particular regions? vegetation in thousands of kilometres, or the 2 Can you name the continents or any particular distance it lies from the Equator? places where it is found? Activities 1 Look at Figure 5.13. From the climate graphs: 3 Kilimanjaro is a six kilometre high mountain located a) Identify the annual rainfall that deciduous forest close to the Equator in Africa. At its base it is needs. surrounded by tropical rainforest. Describe how you b) State the minimum and maximum annual think the vegetation on Kilimanjaro changes with temperatures for the tundra ecosystem. increasing altitude. 2 Draw a table showing the three types of forest. In 4 Look at Figure 5.13. Is temperature or rainfall the one column, describe the associated climate. In most important influence on whether a place is a another column, briefly describe the characteristics desert? Explain your answer. of the trees. Type of forest Climate Characteristics 65 6.1 6 Tropical rainforests ✪ KEY LEARNING Tropical rainforest The tropical rainforest occupies only seven per cent of the world’s land ³ The physical surface, but it contains many useful resources. It is also valuable in the fight characteristics of the against global warming (page 74). The main areas of tropical rainforest are tropical rainforest in the Amazon basin (Brazil), Central Africa and South East Asia (Figure 6.1), ³ Interdependence within with the largest area of tropical rainforest in the Amazon. the ecosystem ³ Biodiversity and its issues Arctic Arctic Ocean Ocean GREENLAND What are the physical characteristics of the ASIA tropical rainforest? NORTH AMERICA EUROPE North Atlantic There are two main characteristics North Pacific Ocean North Pacific AFRICA Ocean that distinguish the tropical Ocean rainforest from other biomes: Douala Equator climate Indian Ocean vegetation. AUSTRALIA SOUTH South Pacific AMERICA South Atlantic Climate Ocean Ocean Because tropical rainforests occur on Key or close to the Equator, the climate Distribution of tropical rainforests is typically warm and wet. Annual temperatures average around 26°C Figure 6.1 The global distribution of tropical rainforests and show little variation from day to 30°C day or month to month (Figure 6.2). Annual rainfall usually exceeds 2,500 millimetres. This 750 mm abundant supply of water feeds the huge rivers, such 25°C Total annual as the Amazon in Brazil and the Congo in Central rainfall = 4,000 mm Africa, which are an impressive physical feature of Annual average 20°C Temperature 500 mm temp. 27°C tropical rainforests. Precipitation Vegetation 10°C Tropical rainforests are renowned for their rich 250 mm vegetation cover. Particularly spectacular are their very tall trees, typically 30 to 45 metres in height. (For more about the vegetation, see Section 6.2.) 0 mm 0°C J F M A M J J A S O N D Soils Precipitation Temperature The soils of the tropical rainforest are mainly thin and Figure 6.2 The climate at Douala (Cameroon) poor. So, how is there so much luxuriant vegetation? The answer lies in the rapid recycling of nutrients known as Most of the forests’ vital nutrients are locked up in: the nutrient cycling (Figure 6.3). the biomass – living vegetation and animals the litter – dead wood and leaves, and animal remains on the ground. 66  Section B: 6 Tropical rainforests The warm, humid conditions cause the litter to decompose very quickly. The little rain that reaches the forest floor often washes away Biomass litter nutrients before they become part of the All living things in the ecosystem, soil. It is not surprising that rainforest soils are both plants and rather infertile. Nonetheless, plants can pick up animals enough nutrients from the soil to survive. Many nutrients are stored in large, thick trees. Nutrients fall to the Plants take up ground when plants nutrients which are How is the tropical rainforest and animals die dissolved in soil interdependent? Litter Soil Figure 6.4 shows the main components of the Dead organic Developed by Nutrients become tropical rainforest ecosystem: climate (rain and material such as the mixing of dead part of the soil fallen leaves or tree organic material sunlight), soil, vegetation (trees and plants) and when dead matter trunks and dead with decomposes animals. The arrows show how they interact to animals weathered bedrock create an interdependence (Section 6.2). The diagram also shows people. It is possible for native people (indigenous tribes) to live as part Figure 6.3 The nutrient cycle of, and in harmony with, the ecosystem. Equally, we will see in Section 6.3, and elsewhere in this book, that people ht Evapotranspiration (p re Ra n lig y) can badly upset the ecosystem’s balance. c in Su nerg ip ita (e tio Animals n) Why is there so much biodiversity People Harvesting Animals in tropical rainforests? fruits eating plants Animals Understory excreting Trees and dying Tropical rainforests are renowned for their high level of plants Roots taking biodiversity. It is higher than in any other biome. More than Leaves up nutrients Leaves falling and falling plants dying two-thirds of the world’s plant species are found in these