a-level environmental studies teacher guide teacher guide: unit

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Teacher Resource Bank

GCE Environmental Studies

Unit 4 ENVS4 Biological Resources and

Sustainability

• Teachers notes

Teacher Resource Bank / GCE Environmental Studies / Teachers’ Notes Unit 4 / Version 1.0

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Unit 4 ENVS4 Biological Resources and Sustainability

Introduction

The factors controlling human population growth are considered in relation to the demands placed upon the planet’s resources and life-support systems, particularly the biotic resources of food and forest products. Food production and forestry systems are analysed, with particular emphasis on the limiting factors affecting productivity, the environmental problems caused by these systems and the ways in which problems can be addressed. The study of the sustainability of human lifestyles allows synoptic consideration of the other modules of the Specification. The general approach should address the issue of developing more sustainable lifestyles.


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UNIT 4 – Biological Resources and Sustainability

3.4.1 Human Populations

The impact of individuals on the environment

A comparison of population numbers and per capita consumption on overall resource use. Candidates should consider the per capita consumption rates for different resources in a range of different countries and compare these with their population growth rates. eg energy, water, food, metals The population / resource balance – the concept of sustainability Candidates should be aware that the environmental impact of individual lifestyles varies greatly and is influenced by many factors:

• Affluence eg the ability to buy more goods and the energy needed to manufacture and operate them.

• Personal choices eg whether to buy recycled goods, low-energy appliances, organic foods, how to travel.

• Products and services available eg the availability of products and services that have a lower environmental impact: public transport, recycling facilities, energy supplies

Education for responsible global citizenship – Agenda 21 This is the UN initiative to encourage the inclusion of sustainable objectives in the plans and actions of governments, governmental organizations, NGOs and other groups.

3.4.2 Food Production Systems

Nutrition

Autotrophic nutrition This is the basis of all agriculture as all food production relies directly or indirectly on photosynthesis eg crops, livestock, dairy products, farmed fish Heterotrophic nutrition Candidates should have a basic understanding of animal nutrition in terms of:

• The efficiency of food utilization - much of the food that is eaten is not digested and therefore is not assimilated.

• An animal's digestive system may be adapted to enable it to live in a habitat that cannot be exploited by other species.

• Food chain efficiencies are always well below 100%, so the amount of energy available drops rapidly as it passes along successive trophic levels.

• (No biochemical details of nutrition are required).



Herbivores eat plant foods, eg cattle, sheep, poultry, some farmed fish such as carp. They are near the start of food chain and make more efficient use of the energy that entered the food chain; Those that can digest cellulose with symbiotic gut bacteria can eat foods unavailable to other livestock. Ruminants such as cattle and sheep can graze poor pasture land which may have no other agricultural uses. Omnivores eat both plant and animal foods, eg pigs; They can be fed on wastes:

• food processing waste eg dairy waste, sugar refinery waste; • waste food eg from schools, hotels.

Carnivores eat animal foods, eg many farmed fish such as salmon and trout are fed on fish waste and low value fish.

Agroecosystems

An agroecosystems is a modified natural ecosystems to optimize the production of human food, including consideration of wider issues such as resource usage and environmental impacts. Principles of agroecosystems Factors which affect the selection of food species:

• environmental factors eg climate, soil fertility, topography, pests • social factors eg horse meat is unpopular in the UK • religious factors eg hindus do not eat beef, jews do not eat pork • ethical choices eg environmental concerns have increased the popularity of low air-mile and

organic foods • technological factors eg the availability of irrigation, pesticides, fertilizers, mechanisation

Manipulation of the food species

• This is done to increase its saleability, yield and suitability for cultivation. eg by selective breeding, GM, use of hormones

Control of the environment This is done to maximise yield and marketability. eg control of water and nutrient supplies, temperature, light levels, pest populations

Manipulation of the food species

Population control • Increasing the population density of the food species can increase productivity but can increase

competition and make the spread of disease easier. • The optimum livestock stocking densities depends upon the agroecosystem involved.

eg different stocking densities for lowland and upland sheep. Monocultures

• A monoculture involves the growth of a single crop over a large area



Advantages:

• ease of management eg pesticides and fertilizers can be easily applied

• low labour inputs eg the use of larger tractors and harvesters

• economies of scale eg the use of large machines and low labour requirements make cultivating monocultures cost effective

Disadvantages:

• The ease of colonisation by pests and the rapid spread of pests and disease increases the reliance on pesticides.

• The reliance on mechanization requires large fossil fuel inputs. Genetic manipulation An outline of the principles is required, with advantages, disadvantages and limitations. Selective breeding, outbreeding and crossbreeding

• Outbreeding involves breeding between individuals that are not closely related. • To delete undesirable characteristics.

eg to prevent recessive inherited diseases, such as deformed spines and poor lung development in cattle.

• To enhance desirable characteristics eg yield, growth rate, nutritional value.

• To combine different desirable characteristics eg Zebu cattle (heat tolerance) × Ayrshire cattle (high milk yield).

Artificial insemination This allows sperm from males to make large numbers of females without having to move the adults. Semen can be frozen so it can be transported all over the world and stored for many years for future breeding. Embryo transfer Hormone treatment of pedigree females can be used to produce large numbers of eggs. After in vitro fertilization these can be implanted into other females so many more offspring can be produced. Selective breeding has produced varieties that have: Improved food conversion ratios eg faster crop growth rates, increased Gross Growth Efficiency of livestock eg short stemmed cereals convert more energy into harvestable crop

Desirable qualities eg better taste, improved nutritional content

Pest and disease resistance eg potatoes that are resistant to fungal disease

Uniformity of appearance eg fruit of the same size and shape to suit retail needs

Timing of growth stages eg cereal crops that are all ready for harvest at the same time



Dependence on husbandry by humans eg highly productive crops that rely on high fertilizer and water inputs genetic crop uniformity may require the purchase of F1 hybrid seeds every year Vegetative propagation

• To enable the production of large numbers of genetically identical individuals. • Some crop plants reproduce vegetatively eg strawberries • Plant cloning is widely used

eg Cuttings - cut stems are planted in a growth medium, often after hormone treatment to encourage growth Micropropagation - small tissue samples are grown on a sterile growth medium

• Animal cloning is still being developed. Genetic engineering – GM crops and livestock

• Genetic engineering/transgenics/Genetic Modification (GM) involves the artificial transfer of genes between different species.

• The use of GM crops is widespread in the USA and is expanding in the EU, Brazil, India and other countries.

• The advantages and disadvantages of GM crops are not fully proven Stated advantages of GM crops Increased growth rates eg high crop yields have been reported for cotton and soya, but may not have been sustained

Improved nutritional value eg high vitamin A content in Golden Rice

Increased pest resistance eg Bt-corn

Ease of management eg use of weedkillers on resistant crops

Tolerance of unfavourable conditions eg drought-resistant cotton and corn are being developed

Stated disadvantages of GM crops Genetic contamination eg pollen from GM crops being transferred to other crops

Misuse of pesticides eg overuse of the weedkiller roundup on roundup-ready soya

Control of agriculture by corporations eg the control of seed supplies by agricultural corporations

Development of superweeds eg Glufosinate-resistant oilseed rape crossbred with the weed charlock to produce a herbicide-resistant weed

Threats to biodiversity. The transfer of GM pollen to wild plants changes natural gene pools. GM livestock Techniques are still being developed. Possible advantages include: disease resistance, high Omega-3 content in beef



Agrochemicals used to manipulate the food species Plant growth hormones Plant hormones are used to control various aspects of plant growth. eg delay fruit tree blossom until after the last frosts

increase sap flow in rubber trees seedless fruit

Animal hormones Steroid hormones These increase the Gross Growth Efficiency of livestock and produce more lean, less fatty meat. Risks Meat which still contains the hormones may affect those that eat it eg An artificial female hormone caused the development of female secondary sex

characteristics in men and premature puberty in girls. BST This is not a steroid hormone. It increases milk production in dairy cattle. It is not active in humans. Artificial control of the environment

• A limiting factor is any factor that can reduce the rate of a process if it is short supply. • An understanding of limiting factors can help to increase food production

Temperature

• Glasshouses: use of heaters to maintain or increase the rate of photosynthesis. • Heating in intensive livestock rearing units is used to reduce the food energy needed to keep

warm. Light

• Artificial lights can be used to increase the rate of photosynthesis. eg winter lighting in greenhouses

• Control of lighting can influence the timing of livestock breeding. eg hens lay eggs when the day length is long.

Carbon dioxide

• Fossil-fuel based heaters can be used in glasshouses to increase the rate of photosynthesis. Water

• Drainage, irrigation and humidity control can be used to maintain turgidity, allow nutrient uptake and reduce waterlogging.

Wind velocity

• Shelterbelts can be used to reduce frost damage, transpiration and physical damage and maintain soil temperature by reducing cooling. They also reduce soil erosion.

Nutrient availability

• Macronutrients are needed in large quantities - eg nitrogen as nitrate ions, phosphorus as phosphate ions, potassium as ions.

• Micronutrients are needed by plants in smaller quantities. eg zinc, copper, iron



Nutrient application methods: • Natural fertilisers – manure, compost, bonemeal, dried blood. • Artificial fertilisers – ammonium nitrate, calcium phosphate. • Cultural methods - growth of leguminous crops and green manures

Natural fertilisers such as manure are often cheap waste products that help maintain soil structure, reduce soil erosion and provide food for soil biota. But they are often bulky, difficult to apply and may not contain all the required nutrients.

Artificial fertilisers have controlled composition and are convenient to apply. But they do not add organic matter or maintain soil biota. They are also energy-expensive to manufacture and are more likely to cause water pollution.

Green manures are fast growing plants that are grown between other crops. They are ploughed in to add to soil fertility.

Legumes such as beans, peas and clover have root nodules with symbiotic nitrogen-fixing bacteria.

Crop rotation helps to spread the demand for nutrients by growing different crops each year, often in a four year cycle.

Adding lime to very acidic soils increases nutrient availability. pH control

• Nutrient uptake by roots involves ion exchange, including the loss of hydrogen ions from the roots.This is more difficult in acidic soils where there is a high H+ concentration. The addition of lime helps to neutralise acids and to raise the pH.

Manipulation of energy flow

• Short, simple food chains convert a greater proportion of the original photosynthetic energy into food than longer food chains. Eating plant foods is therefore more energy-efficient than eating meat.

• Energy use by livestock can be reduced by restricting movement and keeping them warm to reduce heat loss. This increases the amount of food energy incorporated into new growth.

Control of competition Other species can reduce the productivity of crops or livestock in several ways:

• They may eat the food or make it inedible • They may compete for water, light or nutrients • They may cause or spread disease

Pest control methods Weeding Weeding can be done by hand or mechanically. Removing weeds reduces competition for water, light and nutrients between the crop and weeds. Mulching Mulching involves adding a layer of material on the soil surface. eg shredded crop waste or bark

It prevents the seeds of competitors from germinating or young plants from growing. Crop rotation Crop rotation involves growing a different crop each year on a cycle of 3, 4 or 5 years. This prevents pest the build-up of pest populations (and the exhaustion of nutrients).



Barrier crops Barrier crops reduce chance of pest finding the crop. eg onions protect carrots from root fly attack due to their strong smell. Culling The selective killing of competitors can keep their population to a level where damage is acceptable. eg killing of rabbits or deer Biological control Biological control involves the introduction of predators, pathogens or parasites of the pest. eg Whitefly control by chalcid wasp; Cactoblastis moth introduced to Australia to control the prickly pear cactus. Predator habitats Habitats can be provided for the natural predators of pests. eg hedgerows, beetle banks. Polyculture/companion crops This involves growing combinations of crops to maximize production.

One crop may benefit another by creating a microclimate, providing nutrients, distracting pests, deterring pests or supporting pollinators. eg banana trees protect coffee bushes from extremes of tropical climates. In the Phillipines, banana, maize, peppers and sweet potatoes are grown together. Pesticides Chemical pesticides kill by disrupting physiological functions, usually by enzyme inhibition.

Contact herbicides kill by damaging leaf surface tissue. Contact insecticides kill insect pests by being absorbed into the insect directly without being absorbed by the crop.

Contact pesticides can be washed off, only protect sprayed surfaces and do not protect new growth.

Systemic

Systemic pesticides protect the entire plant, cannot be washed off, will protect new growth, but can remain in the crop that is eaten. Integrated control This involves the use of a combination of techniques, chosen according to cost, convenience, effectiveness and environmental impact eg a range of cultural and biological techniques which reduces the need for the use of chemical pesticides. Antibiotics These are used in several ways:

• to treat bacterial infections – used when needed; • to prevent bacterial infections – continual use; • to reduce gut bacteria populations and so increase the Gross Growth Efficiency of the livestock.

Risks of excessive or unnecessary use of antibiotics:

• strains of antibiotic-resistant bacteria may develop, thus making disease-control more difficult, including human diseases.

• pesticides are absorbed via leaves or roots and are transported in the sap.



Environmental and social impacts of agriculture

Habitat impacts Forest clearance Much of the farmland in NW Europe, NE N America, SE Asia and S America used to be forests. Drainage of wetlands Wetlands are often on low lying, flat land that provides fertile, easy to farm land if it is drained. eg The fens, river flood plains, US prairie wetlands, Everglades of Florida, the Carmargue in France Ploughing of grasslands Natural grasslands with seasonal rainfall are often ideal for cereal cultivation eg prairies of N America, savannah grasslands of Africa, Russian steppes Reduction of biodiversity The conversion of natural ecosystems to simplified agricultural systems causes a reduction of biodiversity, often of rare indigenous and endemic species. Traditional farming methods often provided new habitats that could be colonized by wildlife species, but these may be lost with the introduction of modern intensive techniques. eg chalk grasslands, wet meadows, hay meadows GM contamination Pollen from GM crops may alter the gene pools of wild plants and non-GM crop varieties. Pollution pesticides: caused by toxicity, non-selectivity, bioaccumulation and biomagnification

nutrients: fertilisers on fields, leached nutrients after ploughing, farmyard drainage and slurry, silage fluids causing eutrophication and aquifer contamination

methane from livestock and padi fields contributing to global climate change. Changes to the hydrological cycle Irrigation can cause reduced river flow downstream of the water abstraction point or aquifer depletion causing drying of surface water features and reduced spring flow

Evapotranspiration may change on irrigated farmland compared with previous vegetation. eg reduced transpiration compared with previous forest or increased transpiration compared with grassland

Increased surface runoff may occur after rain due to soil compaction caused by use of machinery and loss of soil organic matter and biota. Accelerated soil erosion Soil erosion is a natural process with the soil present being the result of the balance between the processes of formation and loss.

Soil is produced slowly by processes involving weathering, organic sorting and decomposition. Erosion can be very fast if the natural features that reduce erosion are removed. The mechanisms of soil erosion wind blow erosion - dry soil particles are carried by the wind rain splash - soil particles are dislodged by raindrops, most being carried downhill

surface run-off - soil particles are carried by water flowing over the ground surface



Natural features of soil that reduce erosion Vegetation Vegetation cover reduces wind velocity and can reduce the impact of raindrops. Roots help to hold soil particles together. Organic matter Soil organic matter, including humus produced by decomposition, help to hold soil particles together. Dead organic matter on the soil surface reduces raindrop impact and protects the soil from winds. High infiltration rate A high infiltration rate reduces runoff. Soil biota and organic matter increase the infiltration rate. The Universal Soil Loss Equation (USLE) This can be used to estimate the rate of soil erosion based on the effect of a range of climatic, edaphic and land use factors. A = R x K x L x S x C x P Where: A = the rate of erosion R = rainfall erosivity factor K = soil erodibility factor L = slope length factor S = slope gradient factor C = cropping management factor P = erosion prevention factor Human activities that increase the risk of soil erosion Deforestation

• less vegetation to intercept rainfall • fewer roots to hold soil together • less leaf litter to protect soil from wind, increase infiltration and reduce runoff • soil organic matter content may decline • increased wind speed at ground level

Overgrazing Reduced vegetation cover has the same effects as deforestation. Livestock hoofs damage roots, loosen soil and make it more likely to be washed or blown away. Reducing soil organic matter content This is caused by not adding organic matter as a soil conditioner. Reduces humus levels and produces looser soils which are more likely to be washed or blown away. Reduced soil biota Soil organisms are important in breaking down dead organic matter, producing humus, organic sorting, preventing compaction and increasing soil aeration and infiltration rates. eg worms, detritivores, decomposers Ploughing vulnerable soils Produces looser soils which are more likely to be washed or blown away. Cultivating steep slopes Increases the risk of rainsplash and runoff erosion by removing protective vegetation and loosening soil.



Soil compaction Use of machinery and the loss of soil biota increases compaction which can increase runoff erosion. The effects of soil erosion Reduced productivity as the most fertile topsoil is lost Sedimentation in rivers and reservoirs which makes rivers shallower, and reduces the storage capacity of reservoirs Flooding downstream caused by more rapid runoff and reduced river channel capacity Coastal sedimentation when turbid flowing river water slows down Increased atmospheric particulate levels due to wind erosion Desertification as lower productivity and vegetation cover reduces transpiration and subsequent rainfall Landslides when erosion on hillsides is sudden, following vegetation loss, reduced root binding and heavy rain that causes waterlogging Soil conservation techniques Cultivation of long-term crops to reduce the length of time when the land would have no crop and be exposed to a higher erosion risk. Contour ploughing and tied ridges to produce horizontal furrows across sloping landscape which increase the rate of water infiltration and reduce the velocity and amount of surface runoff.

Terracing to produce fields across sloping landscape which increase the rate of water infiltration and reduce the velocity and amount of surface runoff. Windbreaks to reduce the wind velocity at ground level and therefore its ability to blow away the soil. Multicropping Growing two or more crops on a field at the same time, but with different planting and harvesting times, means the field is never completely exposed to wind and rain. Strip cropping Planting different crops in neighbouring long narrow fields with different planting and harvesting times, means the field is never completely exposed to wind and rain. Mulching A surface layer of dead plant material increases infiltration, reduces runoff, helps to incorporate more organic matter into the soil and protects from wind Soil conditioning and increasing organic matter Materials such as manure and compost increase the organic matter and humus content of the soil. The improved crumb structure reduces erosion. Social impacts of agriculture Any change in land use will affect the lifestyles, employment and the quality of the people that live in the area. The misuse of the land and pollution can result in the loss of natural productivity leading to famine in extreme cases. eg rural depopulation in the UK famine refugee movements in N Africa



Pollution, soil erosion and sedimentation can affect people in other areas. eg eutrophication and pesticide pollution damaging fisheries in Lake Naivasha, Kenya sedimentation deposited on coral reefs in SE Asia, E Africa Increased rural food production has also changed population distribution by producing the surpluses that enable people to live in areas where food cannot be grown, such as cities. The production of cash crops can replace subsistence farming causing subsistence farmers to become landless and a reduction in food supplies for the local population. eg expansion of biofuel production: sugar cane in Brazil, oil palms in SE Asia flowers and luxury salad vegetables in E Africa

Agricultural energetics

Agroecosystems require energy subsidies in the form of fossil fuels, human labour, machinery and locomotive energy, mechanical power for the application of fertilisers, energy to manufacture agrochemicals. The relationship between energy inputs and harvestable product Productivity = yield/unit area Efficiency = yield/unit input The most productive farms are often the least efficient as the high productivity is achieved by proportionally greater inputs.

Intensive / extensive systems Intensive systems achieve a high yield with high inputs on a limited area of land eg energy as labour or machinery

materials as fertilisers, pesticides capital to pay for machinery, chemicals

Intensive agriculture is often very productive but inefficient. eg arable farming in SE England, battery livestock production, market gardens Extensive systems spread the inputs over a larger area. Yield per unit area is lower, but the yield per unit input is higher. eg cattle ranching in Australia, upland sheep farming in the UK, cereal growing in Australia Candidates should be able to compare the energy ratios of different agricultural production systems and different crop plants and animals. Energy Ratio is calculated as the energy output (harvested yield) per unit of energy input (from all sources)



Social/economic/political factors which influence agricultural production

The role of trade organisations, subsidies, pricing and infrastructure eg the Common Agricultural Policy (CAP) which controls agricultural activities through grants and subsidies and manages agri-environmental incentives.

In the USA production of wheat, cotton, soya, rice and other products is subsidized by giving farmers payments in addition to the market price they receive.

Farmers in India and Zambia receive subsidized fertiliser supplies In some countries irrigation water is subsidised

Financial support can help maintain national food security and support the rural economy but it can distort free trade and make imports from other countries artificially uneconomic. Consumer purchasing choice has increased the demand for Fairtrade, organic and locally produced foods. Trade barriers Restricting imports can protect national production but can inhibit the development of agricultural activities in other countries, such as LEDCs that could have benefited economically from increased exports. Responses to over-production and resource exhaustion The set-aside scheme allowed farmers to receive an income for farmers that took land used to grow unwanted products out of production, but was kept it in a condition that could be brought back into production if needed.

Milk quotas restrict the amount of milk farmers can produce, to prevent over production.

Diversification involves farmers producing new products or providing services that reduce reliance on products that are being over-produced: non-food crops, conservation cropping, organic farming, recreation, small-scale industry.

Farmers may be paid to reduce productivity to protect important habitats eg Environmentally Sensitive Areas, Countryside Stewardship Scheme (both phased out) and aspects of the Environmental Stewardship Scheme.

The effect of world trade Candidates should be able to discuss the effect of world trade on income and food production in Less Economically Developed Countries. Increased land sustainability Schemes intended to increase sustainability include management agreements such as ESA, Countryside Stewardship Scheme, subsidies for conversion to organic production and planning and development controls.



3.4.3 Aquatic Food Production Systems

Fishing

Factors controlling marine productivity The difference in the productivity of continental shelves and open oceans Productivity is controlled by limiting factors, especially phosphate nutrient supplies.

Phosphates are most available for biological productivity where upwellings, ocean currents and coastal inputs increase supplies near the sea surface. Fish populations The maximum biomass that can be supported depends on food supplies.

Young fish are recruited to the adult population to replace losses.

Young fish that are not recruited will not survive.

Growth of adult fish increases biomass but reduces the maximum number of fish that can be sustained.

Natural mortality and losses due to fishing create vacancies that can be filled by juvenile fish. Maximum Sustainable Yield Breeding normally produces more young than can survive as there are insufficient spaces in the adult population.

Mortality caused by fishing may be replaced by juveniles that would not otherwise been recruited to the adult population.

If too many adults are caught there will not be enough young to replace them.

The greatest harvest that can be removed without reducing the future population is the Maximum Suatainable Yield (MSY). Estimating the MSY requires accurate information on: current adult biomass reproduction: egg production, juvenile survival recruitment to the adult population Fishing above the MSY is overfishing and will cause a decline in adult biomass. Overfishing can often be detected by reduced catches, a reduction in average age of adult fish and more rapid growth of the fish that do survive. Fishing techniques Candidates should consider a range of techniques in terms of the selectivity of the catch, environmental impacts and energy inputs. Trawling: pulling a bag-shaped net through the sea is an unselective method and can catch a wide variety of species, including non-target species (by-catch).

Trawling on the seabed can also cause great physical damage eg to coral, seaweed beds

Midwater trawls have lower by-catch but can kill some non-target organisms eg porpoises caught in bass trawls



Long-lining: Long fishing lines reduce the by catch of using nets but can catch other species on the hooks eg albatrosses, turtles and sharks

Purse seining: a net is cast around a shoal of fish, drawn tight then pulled in. It is possible to selectively catch particular species. eg tuna, mackerel, sardines,

Drift netting: nets supported by floats catch species such as tuna and herring but also catch by-catch species eg dolphins, whales, turtles and sharks

Factory ships: these allow the processing and preservation of large quantities of fish which allows fishing fleets to operate far from their home ports. Long-distance fleets use a lot of fuel Environmental impact of fishing By-catch Dolphins caught by pair trawling. Whales, dolphins, turtles, sharks caught in drift nets Ghost fishing Fish, lobsters etc caught by discarded or lost fishing gear Seabed damage Coral reefs damaged by nets. Foodchain effects Some species become more common if their predators are over-exploited Reduced food supply for predators, increased food supply for competitors. Effects of fishing on fish stocks overfishing caused by exceeding the Maximum Sustainable Yield changes the biomass and age structure of the population eg cod, herring, tuna. Management of marine production systems Catch quotas setting a limit on the numbers or biomass that can be caught Net design increased mesh size so smaller fish can escape mesh is not diagonal to the direction of pull so small fish escape more easily escape hatches that larger organisms can push open eg turtles limit on total net size Fishing effort limits a limit may be set on the number of fishing days, boat size or engine size Exclusion zones: leaving unfished areas where breeding may continue unhindered may increase the catchable population in surrounding areas. eg Lundy Island, Lamlash Bay Arran Closed-seasons fishing may be banned for part of the year eg during the breeding season



Minimum catchable size to allow fish a chance of surviving longer to breed and to increase the juvenile biomass Captive breeding to boost the wild population eg the release of captive bred lobsters

Aquaculture – fish farming

The principles of aquaculture Stock selection for desirable characteristics eg colour, growth rate, tolerance of high population density Breeding collection of eggs and milt (sperms), fertilization, raising of young fish Control of disease immunisation use of antibiotics reduced stocking density Control of competition exclusion/killing of predators/competitors Nutrition for herbivores - provision/growth of plant foods for carnivores - provision of food from waste/low value fish catch Manipulation of the environment (temperature , O2, light levels) temperature control - growth rate, dissolved oxygen levels

dissolved oxygen - survival of sensitive species eg trout, salmon

light levels - control of breeding Case studies: candidates should be able to explain the management techniques used and environmental impacts of an aquaculture activity eg salmon farming in Scottish sea lochs shrimp farming in mangrove swamps Environmental problems caused by aquaculture Organic wastes – deoxygenation, nutrient enrichment, increased turbidity Escapes effect on wild gene pool - farmed gene pool may include undesirable characteristics eg bright colour causing vulnerability to predation

non-native species may compete with native species eg signal crayfish in the UK Lice may spread disease from farmed fish to wild fish



Use of pesticides may cause local pollution Loss of habitat/biodiversity where fish farms are constructed

pollution

killing of predators eg seals, herons, cormorants, otters Impact on tourism where large-scale operations affect the scenery Coastal erosion caused by mangrove loss where mangrove forests are destroyed to build farms eg tropical shrimp farms Effect of harvesting wild fish populations to provide food eg overfishing of sandeels has reduced seabird survival The energetics of aquatic food production The energy efficiency ratios of fishing and fish farming Both fishing and aquaculture have a range of levels of intensities

Both usually require large energy subsidies

Both involve higher trophic levels than in agriculture

Aquaculture usually requires food energy inputs from fishing



3.4.4 Forestry

Forest resources

The forest crop is a source of renewable resources Timber eg for building construction, furniture, path boards, railway sleepers

Tropical hardwoods eg mahogany, teak Temperate hardwoods eg oak, beech, ash Boreal softwoods eg pine, spruce

Fuel especially in LEDCs, increasingly in MEDCs (coppiced biofuel) Food fruit and seed crops - food harvest or genetic resource for breeding programmes eg cacao, coffee, papaya, mango, citrus, Brazil nuts, pine nuts Fibres cellulose for paper Medicines eg quinine from the cinchona tree for malaria treatment aspirin from willow bark taxol from the yew tree to treat cancer Life-support services provided by forests Atmospheric regulation by absorbing carbon dioxide and releasing oxygen in photosynthesis A habitat and wildlife refuge especially in a diverse forest of indigenous tree species with a varied age structure Regulation of the water cycle by increasing evapotranspiration and reducing the rate and volume of surface runoff. Climate regulation by controlling the water cycle and controlling heat balance of the area due to a low albedo and high heat capacity of the water in the trees Soil conservation reducing soil erosion caused by wind and water and increasing the amount of organic matter incorporated into the soil. Shelter and a microclimate by reducing insolation and wind speed at ground level while increasing humidity by transpiration Recreation and amenity uses eg for walking, cycling, camping, nature study, orienteering, motor sports



Forest production The products to be harvested are taken from a wild community or grown in a plantation. Harvests from wild communities produce lower yields than from plantations

• fewer productive plants • more competitors • no genetic selection

Plantations have a simpler ecological structure than natural forests

• species diversity - small range of species selected for economic productivity • simple age structure - large areas often planted at the same time • stratification - fewer vegetation layers due to low species diversity and simple age structure • smaller number of other species due to fewer interspecies relationships. Tree species are often

exotic and don't support indigenous wildlife Candidates should compare the consumption of forest products in different societies MEDCs - mainly for building construction, furniture, paper LEDCs - mainly for fuel, building construction, furniture The sources of UK timber and timber products Imported wood and wood products (85% of total consumption)

• 45% pulp and paper • 40% sawn wood • 15% wood panels

UK production (15% of total consumption) 95% softwood

• 40% for paper • 30% wood panels • 25% sawn wood

5% hardwood • 3% fuel • 2% sawn wood

Deforestation

Causes of deforestation Harvesting above the Maximum Sustainable Yield for fuel and timber Insufficient replanting to replace removed trees Clearance for other land uses, including agriculture, mineral extraction, road construction, reservoirs. Maximum Sustainable Yield and sustainable management To keep exploitation below the MSY the rate of growth must be the same or greater than the rate of harvesting. A true consideration of sustainability includes an assessment of issues such as biodiversity, impact on the hydrological cycle and soil erosion, pollution from fertilizers and pesticides and energy inputs The Forest Stewardship Council (FSC) The FSC was set up following the Rio Summit (1992). It accredits the sustainability of individual forestry operations.



The environmental, social and economic consequences of deforestation Loss of species diversity – natural forests usually have a greater biodiversity than the ecosystems which replace them. Loss of the resources and place to live for indigenous people eg Yanomami of the Amazon rainforest Loss of tradeable resources and materials Loss of a carbon reservoir that would help combat Global Climate Change Reduced evapotranspiration which may cause reduced rainfall downwind Increased ground albedo which may alter the local heat-balance and climate Loss of visual amenity Loss of recreational/ecotourism opportunity Selective logging has lower impacts than clear felling The contradiction of deforested MEDCs criticising LEDCs for wanting to exploit their forests. Many MEDCs (including the UK) were mainly covered by forest before they were cleared to produce farmland and support the growing population and industrial development.

Similar changes are taking place in LEDCs now. Financial difficulties caused by debt and the world trade system can trap LEDCs into making decisions, such as forest clearance, that produce short-term economic benefits but cause longer-term environmental problems.



3.4.5 Sustainability

Candidates should consider the fact that modern lifestyles often change to provide a higher level of material benefit and comfort at the expense of the environment, less affluent communities, future resources supplies and the ability of Earth to support life. This section should focus on using the knowledge gained in studying other topics to develop an awareness of the underlying principles of sustainability and the reasons for studying this subject.With an increasing global population, the development of technologies that exploit or damage the environment and evidence of environmental damage, the need to address this problem is increasingly urgent. Conversely, our increasing understanding of how the planet functions and how we cause problems empowers us to solve these problems and plan for a better future. Candidates should be able to use their knowledge of all modules to identify human activities that are unsustainable and suggest strategies that would create more sustainable lifestyles. Attempts to achieve sustainable development Global objectives of sustainable development (Brundtland definition), with particular reference to:

• air, water and land quality • transport systems • waste management / minimisation • awareness raising in the community • Agenda 21 (Rio de Janeiro1992). • Candidates should be able to discuss the above issues as a consequence of considering the

issues they study in the following sections. Unsustainable Lifestyles Candidates should address the question: Is our use of resources sustainable and, if not, how can we make it so? Candidates will be expected to comment critically on the reliability of different forms of data to analyse a range of issues related to sustainability. What can individuals, groups and the authorities do at the local, national and international level? Biotic resources: plant and animal species and their habitats. How does changed land use affect biodiversity?

• deforestation/wetland drainage/grassland ploughing • urbanisation • reafforestation

The change in the rate and pattern of extinctions.

• a comparison of background extinction rates and rates caused by human actions • locations where extinctions are most rapid

Maintaining biodiversity Local, national and international initiatives to protect biodiversity



Water resources Freshwater supplies Are exploitable resources diminishing?

• aquifers eg Australia, USA • lakes eg Aral Sea, Sea of Gallilee • rivers eg Colorado, rivers flowing into the Aral Sea

Reducing wastage Local, national and international initiatives to develop more sustainable exploitation Physical resources: minerals, rocks, aggregates, metals Are we running out of exploitable metals and minerals?

• resource wastage and unnecessary use • availability of high-grade ore deposits • development of new technologies

Energy resources The increasing reliance on energy Are we running out of fossil fuels? Changes in estimates of reserves

New recovery techniques

Restrictions on use • pollution concerns • habitat damage

Consequences of current global patterns of consumption, including inequality of use and expected increases in use

• pollution • impact on LEDCs

Global climate change – fact or fiction?

• evaluation of conflicting evidence How can energy use be made sustainable? Use restrictions/controls

Use of low carbon energy resources

Carbon sequestration Food production The changes in the relative and absolute numbers of people suffering starvation and hunger Distortion of local food production, long distance transport (eg airfreight) of foods to satisfy demand in more affluent countries.

The consequences of global consumption patterns on producing areas. Is GM the answer to food supply problems? Local/ organic production – can it provide enough?

Is organic agriculture more sustainable?

How can food production be made sustainable?



Human populations The effects of affluence on resource exploitation and environmental degradation

• energy use and pollution • water exploitation • mineral exploitation

The positive feedback of poor living conditions and uncertainty of the future on population growth. The environmental implications of a growing human population eg increased demand for food, water, consumer goods; increased waste and pollution generation; increased demand for land for housing and food production. The political, social, cultural and economic factors which regulate human population size and density. the economic impact of children on the family;

the social status of children;

the role of surviving children in supporting the elderly;

the effect of social stability and the infant mortality rate on the confidence of parents in their children’s survival;

the availability of health care and family planning resources;

the different rates and timing of changes in death and birth rates, resulting in population growth. Candidates should be able to use the Demographic Transition Model (as a graph) to show how the relationship between birth and death rates controls population growth and size. The effect of the uneven distribution of resources on this positive feedback mechanism. Artificial control of the environment has allowed increased supplies of food and other resources to be provided. This has allowed human populations to rise above the natural carrying capacity. This may reduce the ability of the planet to support human society sustainably.

a-level environmental studies teacher guide teacher guide: unit

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