Archive for the ‘Environmental Systems’ Category

  • Distinguish between biotic and abiotic (physical) components of an ecosystem.

*Biotic: refers to the living components of an ecosystem. (the community)

*Abiotic: refers to the non-living factors of an ecosystem. (the environment)

Ecosystems are made up of living and non-living components. The living part of the environment consists of the organic part of the ecosystem; animals, plants, algae, fungi and bacteria. These are called biotic components. The non-living part of the environment is made up of physical components such as; air, light, water, temperature, soil, minerals and climatic atmosphere. These are called abiotic components. These two components work together to sustain the environment.

  • Define the term trophic level.

Trophic level refers to the feeding level within a food chain. It is the position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains.

  • Trophic level 1 – producer
  • Trophic level 2 – herbivore (primary consumers)
  • Trophic level 3 – carnivore (secondary consumers)
  • Trophic level 4 – carnivore (tertiary consumer)
    • Identify and explain trophic levels in food chains and food webs selected from the local environment.

    *Producer: The organism in the ecosystem that converts abiotic components into living matter, they help the ecosystem by producing new biological matter.

    *Consumer: These organisms cannot produce their own food, so they eat other organisms to get the energy and matter they need.

    * Decomposer: Feed on dead biomass which is created by the ecosystem.

    *Herbivore: Only feed on producers.

    *Carnivore: Feed on all organisms including producers and consumers.

    *Top carnivore: This organism can not be eaten by any other organism.

    Sun: Provides the abiotic matter to the grass

    Grass: Producer and autotroph, provide food for the deer.

    Deer: The primary consumer and herbivore of the grass.

    Wolf: The secondary consumer/Top consumer and carnivore, feeds on the deer and cannot be eaten by any other organism.

    Ecosystems contain many interconnected food chains that form food webs. Food chains always begin with the producers (usually photosynthetic organisms), followed by primary consumers (herbivores), secondary consumers (omnivores or carnivores) and then higher consumers (tertiary, top). Decomposers feed at every level of the food chain.

    Diagrams of food webs can be used to estimate the knock-on effects of changes to the ecosystem.

    Biomass and energy decrease at each trophic level so there is a limit in how much trophic levels can be supported in a ecosystem. Energy is lost as heat at each stage of the food chain, on only energy stored in biomass is passed on to the next trophic level. After 4 or 5 trophic levels there is not enough energy to support another stage.

    Local example: (Lake in Sweden)

    Producer: Freshwater shrimp

    Primary consumer: Bleak

    Secondary consumer: Perch

    Secondary consumer: Northen Pike

    Top consumer: Osprey

    • Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.

    Pyramids are graphical models showing the quantitative differences between the trophic levels of an ecosystem. There are three types:

    • Pyramids of numbers: This records the number of individuals in each trophic level.

    • Pyramid of biomass: This represents the biological mass of the standing stock at each trophic level at a particular point in time. Biomass should also be measured in units of energy, such as J m-2. They can show greater quantities at higher trophic levels because they represent the biomass present at a given time. Both pyramids of numbers and biomass represent storages.

    • Pyramid of productivity: This shows the flow of energy through each trophic level. Measured in units of flow gm-2 yr-1 or Jm-2 yr.

    In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore pyramids become narrower as one ascends.

    • Discuss how the pyramid structure affects the functioning of an ecosystem.

    This Youtube clip explains the interactions in food chains and the vulnerability of the top carnivores.

    • Define the term species, population, habitat, niche, community and ecosystem with reference to local examples.

    *Species: A group of of organisms that interbreed and produce fertile offspring. If two species breed together they create a hybrid, this cannot produce viable gametes and is sterile.

    *Population: A group of the same species living in the same area at the same time, and can interbreed.

    *Habitat: The environment in which a species normally lives.

    *Niche: Where and how a species lives. A species share of a habitat and the resources in it.

    *Community: A group of populations living and interacting with each other in a common habitat.

    *Ecosystem: A community of inter-independent organisms and the physical environment they inhabit.

    • Describe and explain population interactions using examples of named species.

    Ecosystems contain many interactions between the populations, the interactions are varied and can be divided into; competition, predation, mutualism and parasitism.

    *Competition: A common demand by two or more organisms upon a limited supply of a resource; for example, food, water, light, space, mates, nesting sites. It may be intraspecific or interspecific.

    *Parasitism: A relationship between two species in which one species (the parasite) lives in or on another (the host), gaining all or much (in the case of the partial parasite) of its food from it.

    *Mutualism: A relationship between individuals of two or more species in which all benefit and non suffer.

    *Predation: This is when on animal or plant hunts and eats another animal.


    Here are 3 Youtube links about Interspecific interactions.

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    • Explain the concept of an ecological footprint as a model for assessing the demands that human populations make on their environments.

    The ecological footprint of a population is the area of land, in the same vicinity as the population, that would be required to provide all the population’s resources and assimilate all its wastes. As a model, it is able to provide a quantitative estimate of human carrying capacity. It is, in fact, the inverse of carrying capacity. It refers to the area required to sustainability support given population rather than the population that a given area can sustainably support.

    Ecological footprints can be increased by:

    • greater reliance on fossil fuels
    • increased use of technology and energy (but technology can also reduce the footprint)
    • high levels of imported resources (which have high transport costs)
    • large per capita production of carbon waste (high energy use, fossil fuel use)
    • large per capita consumption of food
    • a meat-rich diet

    Ecological footprints can be reduced by:

    • reducing use of resources
    • recycling resources
    • reusing resources
    • improving efficiency of resource use
    • reducing amount of pollution produced
    • transporting waste to other countries to deal with
    • improving country to increase carrying capacity
    • importing resources from other countries
    • reducing population to reduce resource use
    • using technology to increase carrying capacity
    • using technology to intensify land

    There are many plans and innovations being set to reduce the ecological footprint in the future, this is funded by the MEDCs who have the biggest problems with their ecological footprints.

    • Calculate from appropriate data the ecological footprint of a given population, stating the approximations and assumptions involved.

    The ecological footprint calculation is very complex, however approximations can be obtained through the steps outlined in this figure:

    The total land requirement (ecological footprint) can then be calculated as the sum of these two per capita requirements, multiplied by the total population.

    This calculation clearly ignores the land or water required to provide any aquatic and atmospheric resources, assimilate wastes other than CO2, produce the energy and material subsidies imported to the arable land for increasing yields, replace loss of productive land through urbanzation, and so on.

    Factors used in a full ecological footprint calculation would include those in the following list:

    • bioproductive (currently used) land: land used for food and materials such as farmland, gardens, pasture and managed forest
    • bioproductive sea: sea area used for human consumption
    • energy land: an amount of land that is required to support renewable energy instead of non-renewable energy. The amount of energy land depends on the methods of energy generation ad is difficult to estimate for the planet
    • built land: land that is used for development such as roads and buildings
    • biodiversity land: land required to support all of the non-human species
    • non-productive land: land such as deserts is subtracted from the total land available

    There are factors ignored when calculating the ecological footprint which influence the amount of land a population needs to support itself:

    • the land or water required to provide and aquatic and atmospheric resources
    • land or water needed to assimilate wastes other than carbon dioxide
    • land used to produce materials imported into the country to subsidize arable land and increase yields
    • replacement of productive land lost through urbanization

    If everyone on Earth had the same lifestyle as the ones in the MEDCs, many Earths would be needed to support the global population.

    • Describe and explain the differences between the ecological footprints of two human populations, one from an LEDC and one from a MEDC.

    Data for food consumption are often given in grain equivalents, so that a population with a meat-rich diet would tend to consume a higher grain equivalent than a population that feeds directly on grain.

    The standards of living between MEDCs and LEDCs  change according to the resource consumption, energy usage and waste production, disparities should be expected between the ecological footprints of LEDCs and MEDCs. LEDCs have small ecological footprints as MEDCs have much greater rates of resource consumption. This is partly because MEDCs have higher incomes and the demands for energy resources is high. MEDCs consume a lot of resources as they are wasteful, they also have more waste and pollution. LEDCs are the opposite with lower consumption as people do not have too much to spend. The economy of the country forces them to recycle many resources, however they are developing and they’re ecological footprint is increasing. MEDCs use twice as much energy in their diet provided by animal products than LEDCs.

    • Discuss how national and international development policies and cultural influences can affect human population dynamics and growth.

    Many policy factors influence human population growth. Domestic and international development policies (which target the death rate through agricultural development, improved public health and sanitation, and better service growth by lowering mortality without significantly affecting fertility.

    Some analysts believe that birth rates will come down by themselves as economic welfare improves and that the population problem is therefore better solved through policies to stimulate economic growth.

    Education and birth control encourages family planning. Parents may be dependent on their children for support when they get older and this may create an incentive for more children.

    Urbanization  may also be a factor in reducing crude birth rates.

    Policies directed towards the education of women, enabling women to have greater personal and economic independence, may be the most effective method for reducing population pressure.

    • Describe and explain the relationship between population, resource consumption and technological development, and their influence on carrying capacity and material economic growth.

    Because technology plays such a large role in human life, many economists argue that human carrying capacity can be expanded continuously through technological innovation. For example, if we learn to use energy and material twice as efficiently, we can double the population or the use of energy without necessarily increasing the impact imposed on the environment. However, to compensate for foreseeable population growth and the economic growth that is deemed necessary, especially in developing countries, it is suggested that efficiency would have to be raised by a factor of 4 to 10 to remain within global carrying capacity.

     

    • Explain difficulties in applying the concept of carrying capacity to local human populations.

    If one were to examine the needs of a given species and the resources available, it could be possible to estimate the carrying capacity of that environment for the species. This is problematic when it comes to the human population for many reasons like:

    • Resources used by humans are much more than any other species and when this source becomes limited humans begin to substitute one resource for another. The use of resources change from person to person, lifestyle to lifestyle, time to time and population to population.
    • Developments in technology increase the changes of the resource consumption.
    • The human population also import resources very often which come from outside their environment, which makes the grow beyond the boundaries set by their local resources and lets their carrying capacity increase. This however does not affect the global carrying capacity.

    These variables make it almost impossible to make reliable estimates of carrying capacities for the human populations.

    *Carrying capacity: The maximum number of a species or ”load” that can be sustainably supported by a given environment.

    Here we can see 3 models of a population growing and approaching carrying capacity.

    *Optimum population: the number of people which when working with all the available resources, will make the highest per capita economic return. it shows the point at which the population has the highest standard of living and quality of life.

    Standard of living is the result of the interaction between physical and human resources and can be expressed as:

    Standard of living: (natural resources X technology) / population

    *Over-population: this happens when there are too many people compared to the resources and technology available for the standard of living. They suffer from natural disasters such as droughts and famine, low incomes, poverty, poor living conditions and a lot of emigration.

    *Under-population: this happens when there are too many resources in one area that is too much for the people living there. Countries like this could export their surplus food, energy and mineral resources.

    • Explain how absolute reductions in energy and material use, reuse and recycling can affect human carrying capacity.

    Human carrying capacity is determined by the rate of energy and material consumption, the level of pollution and the extent of human interference in global life-support systems. While reuse and recycling reduce these impacts, they can also increase the human carrying capacity.

    *Recycle: when a household or industrial waste is reused and made into another product, like plastic, metals and paper.

    *Re-use: when a product is used more than once by returning it to the manufacturer or processor each time. This is very energy efficient and more efficient than recycling.

    *Reduce: this is when energy use is decrease for example turning off the lights when not needed or using the amount of water needed in a kettle.

    *Substitution: when using one resource over the other, the use of renewable source over a non-renewable source is a major benefit to the environment.

     


    • Describe the Earth’s water budget.

    There is only a small part of the Earth’s water that is fresh water, and of this over 80% is in the form of ice caps and glaciers, 0.6% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage. This means that most of the Earth’s water budget is not directly accessible by human populations. Fresh water is therefore an extremely limited resource. (precise numbers are not needed on exam)

    *Turnover time: The time it takes for water to completely replace itself in part of the system it is in, this charges from different parts of the systems.

    The degree to which water can be looked at as renewable or non-renewable depends on where it is found in the hydrological cycle. Renewable water resources are renewed yearly or even more frequently, however groundwater is non-renewable resource.

    • Describe and evaluate the sustainability of freshwater resource usage with reference to a case study.

    Irrigation, industrialization, and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle gives humans fresh water but we are taking up so much water from the underground aquifers that there is no time for it to replenish.

    The demand of water has increased in both MEDCs and LEDCs, as populations are increasing as well as agriculture changing and expanding industry. MEDCs need more water as they wash more often, water their gardens, and wash their cars. This means that the increasing use of water is making the demands higher. Water is not an infinite resource and has to be controlled more carefully, and new water resources need to be found.

    Water can be managed if individuals and communities make changes and this should be supported by the government. Water should not be over used or wasted so that it is insured it can be enough for everyone.

    This can be reached by:

    • making new buildings water efficient (rainwater for sanitation and showers)
    • fitting new homes with more water-efficient appliances (dishwashers and toilets)
    • expand metering to encourage households to use water more efficiently
    • in some rural areas drought resistant crops should be planted to reduce the need for irrigation
    • organic fertilizers cause less pollution and bio-control measures can be used to reduce crop pests

    Environmental philosophies:

    Environmental philisophies: plan to manage resources sustainability without diminishing them to a degree where they become non-replenishable. Techno-centrists would argue that solutions can be found to sustain both human population and overcome unsustainable use of water resources.

    As populations grow, greater demands are made on water resources. Water resources are now becoming a limiting factor in many societies, and the availability of water for drinking, industry and agriculture need to be considered. Many societies now are dependent on groundwater which is non-renewable. As societies develop, water needs to be increased. The increased demand for water can lead to inequity of use and political consequences. When water supplies fail, populations will be forced to take dramatic steps, such as mass migration. Water shortages may also lead to civil unrest and wars.

    CASE STUDY

    Water shortages in the Middle East:

    Water shortages in the Middle Eastern countries are very common and as time passes their water supply is decreasing. Even though the region only inhabits 5% of the world’s population, it only has 0.5% of the worlds fresh water. It is predicted that the water supply will decrease from 3430 cubic meters per year to a 667 cubic meters by 2025. This is causing countries such as Israel who is suffering from a major drought to stop pumping from their major pumps of fresh water. Many factors have lead to the demand of more water and the droughts have made this worse. Despite the shortages Israel is still sharing their supply with neighbouring country Jordan. Israel is building at the moment plants that supply a third of the countries water supply and a few more plants are also going to be completed in 2013 which could double this amount. Future water shortages could lead to conflicts between the neighbouring countries.


    • Outline the issues involved in the imbalance in global food supply.

    There is enough food on the world to feed us all, however there is an imbalance in the food supply globally. Many people from the LEDCs are suffering from not getting enough energy, proteins and minerals. Around 3/4 of the world’s population is not eating enough and an average of 1 million are going hungry, the majority of these people lives in the LEDCs. It is estimated that every 6 seconds a child dies of hunger.

    The price of food plays a major role here, if prices were to just increase by 10% it could lead to an increase of 40 million people in food poverty. However even though there is such a huge group of people in need of food there is a surplus of food in the MEDCs with markets producing to much food for the population.

    This has lead to people in the MEDCs to consumer more food then they need as the MEDCs increased wealth has allowed them to buy more. There are import tariffs imposed by the MEDCs to make the import of food more expensive, which can ruin the exporting countries.

    In the LEDCs they make money for the country through food production, from crops such as sugar cane and tobacco. So they need this production for making money but when the MEDCs increase import tariffs the LEDCs are in trouble.

    MEDCs want to make money from products in the country and not let the imported goods become the cheaper choice. Despite all this prices of food in the MEDCs is fairly expensive as seasonal foods have disappeared as imports fill gaps. The struggle in the LEDCs to make money has caused prices to rise, this makes it difficult for the population to afford local productions.

    Climate changes have also affected the LEDCs as droughts for example reduce the amount of growing land. Global warming could lead to countries suffering from high temperatures which could destroy crops.

    As more land is used for settlement and industry, there is an increase in intensifying production on existing farm land. MEDCs food production is complex as it involves high levels of technology, low labour and high fuel costs. MEDCs have become more technocentric.

    Agriculture in the LEDCs are in contrast and have low levels of technology, lack of capital and high levels of labour.

    • Compare and contrast the efficiency of terrestrial and aquatic food production systems.

    *Second law of thermodynamics: states that energy goes from a concentrated form (like the sun) to a dispersed form (like heat), the  availability of energy to do work therefore diminishes on the system becomes increasingly disorder. It explains how energy transformations in living systems can lead to loss of energy from the system. The order in living systems is only maintained by constant input of new energy from the sun.

    We get to see from the second law of thermodynamics that energy conversion through food chains is inefficient and that energy is lost by respiration and waste production at each level within the food web.

    Energy in sunlight -> producer (90% energy lost) -> primary consumer (9% energy lost) -> secondary consumer (0.9% energy lost)

    100% -> 10% -> 1% -> 0.1%

    Terrestrial systems:

    Most food is harvested from low trophic levels (producers and herbivores). Systems that produce crops are more energy efficient then those which produce livestock. This is because energy is greater in proportion in the low trophic levels. Even though it is efficient to use arable systems, many cultures still use livestock as part of their farming system. Taste and cultural demand play a major role in this and the animals also provide a source protein which is essential for the human diet. Animals are also used as working animals in some cultures.

    Terrestrial farming systems are divided into several types:

    • Commercial farming: is farming for profit, often of a single crop
    • Subsistence farmer: produces only enough yo geed their family with non to sell for profit

    Both commercial and subsistence can be intensive or extensive farms.

    • Intensive farms: take a small area of land but aim for a high input
    • Extensive farms: are large in comparison to the money and labour put into it

    The efficiency of the system can be calculated by comparing outputs to inputs per unit area of land.

    Aquatic systems:

    Due to human taste, most food harvested is from the higher trophic levels where the total storage is much smaller. There is less energy then crop production, although energy conversion is aquatic systems are more efficient then terrestrial chains, the system receives less sunlight then terrestrial chains.

    • Compare and contrast the inputs and outputs of materials and energy (energy efficient), the system characteristics, and evaluate the relative environmental impacts for two named food production systems.

    Terrestrial Systems:

    Intensive Charolais beef production in France:

    In Western Europe the Charolais beef is one of the beef brands chosen. Through selective breeding and genetic engineering bloodlines that puts weight on exist but has a low fat cover. Charolais lives under controlled conditions, they are fed with high proteins and treated with antibiotics to make sure they are healthy. Lots of energy is used in transporting and processing the finished meat.

    Cattle raised outdoors however grown on single monoculture ( cultivation of a single crop on a farm or in a region or country) grass land in large fields with a high stock rate. To keep the productivity of these fields going, large amounts of fertilizer are used.

    This intensified farming e the 1940’s with the aim of producing cheaper meat has led to habitat loss as they have been removed to make bigger fields and cases of Eutrophication have increased as excess use of fertilizers and large amounts of slurry produced in the system enter water courses. Fear of causing antibiotic resistance in human bacteria through bioaccumulation.

    Inputs:

    • energy for food distribution
    • food supplements
    • selective breeding and genetic engineering (system characteristics)
    • indoor rearing
    • fertilizers to maximize grass production
    • antibiotics and hormones

    Outputs:

    • cheap meat (socio-cultural)
    • habitat destruction to make bigger fields (environmental impact)
    • antibiotic resistance
    • Eutrophication

    Nomadic cattle grazing of the Himba:

    The Charolais beef production can be contrasted with the Nomadic cattle grazing of the Himba. The Himba people are from North West Namibia, they survive by being Nomadic hunters/grazers. They also have a tight bond with the cattle they graze. During the dry seasons the Himba move their cattle from area to area until the grass is used up until the raining season, they go to better pastures. Cattle to the Himba are very important as they provide; meat, milk, skins and even dung for fires. Prestige between the Himba is seen by how many cattle they have, not the size of the cattle. The cattle during the dry season may start competing with herbivores. This has increased especially with global warming drought periods. This can lead to soil erosion as extra grazing pressure removes the grasses that hold the top soil together.

    Input:

    • nomadic grazing moving from place to place so land has a chance to recover
    • cattle survive on low grade natural forage with no supplements
    • during drought cattle die as grass disappears adding patches of nutrients to the soil (environmental impact)

    Outputs:

    • Himba cattle provide meat, milk and fuel (dung)
    • owning cattle gives status in community (socio-cultural)
    • during drought times Himba cattle compete with wild grazers for food this can lead to soil erosion as well as food shortage (environmental impact)
    • Discuss the links that exist between social systems and food production systems.

    There are many links between social systems and food production system. Examples given are shifting cultivation, wet rice agriculture (South-East Asia) and agrilbusiness

    Shifting cultivation

    Shifting cultivation supports small communities and sometimes individual families. It is also known as ”slash and burn” agriculture, as new land is cleared by cutting down small areas of forest and setting fire to them. Ash fertilizers the soil for a while and the clearing produced enables crops to grow. When the land can’t be used any more, the farmer goes to a new land area. Once the land has recovered, farmers go back to the land.

    This is performed in many tropical forest areas, such as the Amazon regions. This is possible as there is low population density. If population densities increase too much, old land is returned too before fertility has been restored, this encourages shifting cultivation. There are people who have close connection with nature, like shifting cultivators in the Brazilian Amazon. They show a closer connection between social systems and ecological systems than the societies living away from natural systems, such as city dwellers. Urban capitalists in Brazil are more likely to view the interior of a country as a new frontier, and the rainforest as a resource for development and cash (technocentric approach). The lack of understanding of the nature makes them underestimate the true value of natural resources. They may also make decisions which produce wasteful and damaging actions.


    Wet rice ecosystem of South-East Asia

    Padi field agriculture has become the dominant form of growing rice in South- East Asia. It is intensive subsistence farming, using high labour but low technology. As there is a high population, a lot of food is needed. Especially rice as it is part of the Asian diet as well as their culture. Padi fields are placed by rivers and areas that flood naturally, so that the fields get new deposits of silt and increased fertility. They should be placed in heavy clay soils, as sand and light textured soils are not suitable as water drains away. Warm weather and high rainfall help productivity all year round.

    Agribusiness

    Supply most of the products found in supermarkets. Many have travelled long distances from around the world. Its a non-seasonal climate food supply throughout the year, so once-seasonal crops are available year-round in MEDCs.

    The aim of agribusiness is to maximize productivity and profit to compete with the global market. This is large scale monoculture, intensive use of fertilizers and pesticides, mechanized ploughing and harvesting, and food production geared to mass markets including export.

    This type of agriculture has a huge impact on the environment, with loss of biodiversity, and increased run-off pollution. National political economies encourage agribusiness as it supports the national income, this had lead to many people living off farming to move into the towns and cities to get new work.

    • Outline how soil systems integrate aspects of living systems.

    Soil forms the Earth’s atmosphere, lithosphere (rocks), biosphere (living matter) and hydrosphere (water). Soil is what forms the outermost layer of the Earth’s surface.

    Soils are important to humans in many ways:

    • soil is the medium for plant growth, which most of foods for humans are grown in
    • soil stores freshwater, 0.005% of world’s freshwater
    • soil filters materials added to the soil, keeping quality water
    • recycling of nutrients takes place in the soil when dead organic matter is broken down
    • soil is the habitat for billions of micro-organisms, as well as other larger animals
    • soil provides raw material in the forms of peat, clay, sands, gravel and minerals

    Soil has matter in all three states:

    • organic and inorganic matter form the solid state
    • soil water form the liquid state
    • soil atmosphere forms the gaseous state

    * Soils are an important source for humans and take time to develop and therefore be counted as a non-renewable resource.

    The Soil System

    O – Organic Horizon:

    • l – undecomposed litter
    • f – party decomposed litter
    • h – well decomposed humus

    A – Mixed mineral-organic Horizon:

    • h – humus
    • p – ploughed in field or garden
    • g – gleyed or waterlogged

    E – Eluvial or leached Horizon:

    • a – strongly leached, and ash coloured
    • b – weakly bleached, light brown

    B – Illuvial or deposited

    • Fe – iron deposited
    • t – clay deposited
    • h – humus deposited

    C – Bedrock or parent material

    • r – rock
    • u – unconsolidated loose deposits

    Transfers of materials (including deposition) results in reorganization of the soil. There are inputs of organic and parent material precipitation, infiltration and energy-outputs include leaching, uptake by plants and mass movement. Transformations include decomposition, weathering and nutrient cycling.

    • Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity.

    Soil structure depends on:

    • Soil texture ( the amount of sand and clay )
    • dead organic matter
    • earthworm activity

    For optimum struction, variety of pure sizes are required to allow root prevention, free drainage and water storage. Pore spaces over 0.1 mm allow roots growth, oxygen diffusion and water movement where as pore spaces below 0.5 mm help store water.

    Clay:

    • fertile in temperate locations
    • in tropical areas clay is permeable and easily penetrated by roots
    • nutrient deficient / easily  leached in tropics

    The more clay present in soil the higher the force needed to pull a plough.

    Different soil types have different levels of primary productivity:

    • sandy soil – low
    • clay soil – quite low
    • loam soil – high

    Primary productivity of soil depends on:

    • mineral content
    • drainage
    • water-holding capacity
    • airspaces
    • biota
    • potential to hold organic materials

    *Shrinking limit: state which the soil passes from having a moist to a dry appearance.

    *Plastic limit: occurs when each ped is surrounded by a film of water sufficient to act as a lunricant.

    *Liquid limit: occurs when there is sufficient water to reduce cohesion between the peds.

    *Field capacity: maximum amount of water  that a particular soil can hold.

    • Outline the processes and consequences of soil degradation.

    *Soil degradation: the decline in quantity and quality of soil. It is also erosion by wind and water, biological degradation (loss of humus and plant or animal life), physical degradation (loss of structure, changes in permeability), chemical degradation (acidification, declining fertility, changes in pH, salinity).

    Causes of degradation:

    • Overgrazing: reduces the vegetation cover and allows the surface to be vulnerable to erosion. Dry regions are vulnerable to wind erosion.
    • Deforestation: removed of woodland cause roots in the soil to die and exposure to erosion if on slopes.
    • Cultivation: exposure of the bare soil before/after planting can cause large amounts of run-offs and create rills and gullies. Irrigation in hot areas can cause salinization.
    • Climate change: the higher the  temperature and changing precipitation patterns can lead to direct impacts on soil. Higher temperatures cause higher decomposition of organic matter. More precipitation and flooding cause more water erosion and droughts cause more wind erosion.

    Many forms and causes of degradations:

    • Water erosion ( 60% of soil degradation)
    • Wind erosion
    • Acidification (toxification), when the chemical composition of the soil is changed.
    • Eutrophication (nutrient enrichment).
    • Desertification can be caused in extreme cases.
    • Climate can intensify the problem and effect of hydrology.

    This shows that the soil degradation’s damage is world spread and has occurred on 15% of the world’s total area.

    • Outline soil conservation measures.

    Strategies for combating soil degradation is not so common or widespread and to reduce this risk farmers are encouraged and informed about the processes and conservation methods. Farmers are in the need of beginning with extensive management practices like organic farming, afforestation, pasture extension, and benign (gracious) crop production. However to make this work there is a need of policies.

    There are a few methods to reduce or prevent erosion, which can be mechanical or vegetation cover and soil husbandry.

    Mechanical methods: are used to reduce water flow including bunding, terracing, and contour ploughing. The goal is to prevent and slow down the movement of rain water down the slopes.

    Cropping and husbandry methods:

    This method is used against water and wind damage.

    It focuses on:

    • keeping the crops safe as long as possible
    • keeping the ground and place of the crop stable after harvesting
    • planting a grass crop

    Grass crop keeps the action of the roots in binding the soil and also it decreases the action of wind and rain on the soil surface. with increased organic content it allows the soil to hold more water and reduce the mass, movement and erosion and stabilizing the soil structure.

    To prevent damage to the soil structure, care should be taken to reduce the use of heavy machinery is necessary especially on wet soils and ploughing on soils that are sensitive to erosion.

    Management of salt-affected soils:

    The three main ways of managing salt-affected soils is by:

    • flushing the soil with water and leaching the salt away
    • putting chemicals to replace sodium ions on the clay and colloids with calcium ions for example by using gypsum a calcium sulphate
    • reduction in evaporation losses to reduce the upward movement of water in the soil

    Summary of the conservations methods:

    Both socio-economic and ecological factors have been ignored and integrated approach to soil conservation is needed, non-technological factors like population pressure, social structures, economy and ecological factors can determine the appropriate technical solutions. There are a variety of methods to use like  strip and ally cropping, rotation farming, contour planing, agroforestry, adjusted stocking levels mulching, use of cover crops, construction of mechanical barriers such as terraces, banks and ditches.

    • Outline the range of energy resources available to society.

    Energy can be generate by both non-renewable and renewable resources:

    • Renewable resources like solar, hydroelectric, geothermal, biomass, and tidal schemes are all sustainable as there is no depletion of natural capital. These energy resources can be large-scale for a whole country or small-scale for houses or communities for example.
    • Non-renewable resources however cannot be replenished at the same rate it is used which leads to depletion of the stock, examples of these are fossil fuels like coal, gas and oil. Nuclear power can be considered as a non-renewable source as the source of fission is uranium, which is non-renewable.

    Energy consumption is much greater in the MEDCs as the LEDCs do not have the technology to have such energy resources used. MEDCs use a lot of energy from fossil fuels as it was not that it caused pollution and global warming when first adapted as a primary source of energy generation. The main reason for non-renewable energy consumption being used is that it is the cheaper and easier choice. Renewable sources of energy are a bit slow when being adopted globally, compared to non-renewable sources it is expensive and still be newly used which makes them vulnerable to failures. Non-renewable resources are generally cheaper and can be burned directly. The technology at the moment is ready for this type of energy and no set-up costs are required. The cost of the non-renewable energy is likely to increase as the stocks will be depleted, especially the resources that are easily to mine, leaving the resources harder to mine. Which will cost a lot to reach. This will make fossil fuels more expensive and then renewable energy sources will be more popular and used more.

    • Evaluate the advantages and disadvantages of two contrasting energy sources.

    NON-RENEWABLE ENERGY:

    Fossil fuels:

    Pros:

    • cheap
    • plentiful
    • technology exists
    • oil can be transported over long distances by pipeline

    Cons:

    • contributes to climate change (builds up carbon dioxide in atmosphere)
    • unsustainable (liquidation of stock over time)
    • will become difficult to extract ( becomes dangerous as they go further into the sea or deeper into the ground)
    • oil spillages and pipelines burst damage ecosystems ( expensive to clear up)
    • mines clear up habitat from surface
    • coal not easily transported over long distance

    Nuclear Energy:

    Pros:

    • does not emit carbon dioxide
    • technology is available
    • vast amounts of electrical energy produced by a single power plant
    • very efficient ( 1kg uranium contains 20000 times more energy than 1kg of coal

    Cons:

    • nuclear waste is VERY dangerous, remains for thousands of years with no solution found yet
    • the more power plants, the higher risks of having a disastrous failure somewhere in the world
    • uranium is the energy source which is scarce and a non-renewable source with a estimated time of 30-60years left before depletion (depending on demand)
    • time to plan/build a nuclear plant is 20-30 years

    RENEWABLE ENERGY:

    Pros:

    • no pollutants released
    • will not  run out (renewable hello)
    • small ecological footprint

    Cons:

    • expensive to set-up
    • need to set them up
    • might spoil environment for people living nearby

    Hydroelectric power:

    Pros:

    • blocked lake can be used for leisure, irrigation and electricity generation
    • once built they are cheap to run

    Cons:

    • vast areas may be flooded, which causes loss of homes, farmlands and displacement of people
    • expensive
    • erosion rates increase
    • might silt up area and become unusable

    Tidal Power:

    Cons:

    • expensive
    • might be harmful to wildlife
    • needs good tidal range

    Solar energy:

    Pros:

    • solar energy with insulation is cheaper than fossil fuel energy when heating homes

    Cons:

    • expensive
    • useless in winter in northern countries

    Wind Power:

    Cons:

    • no wind = no energy
    • placement is critical, needs constant wind

    Biofuel:

    Cons:

    • produces emissions
    • requires large areas of land to plant biofuel crop
    • pushes up food prices
    • locals do not get enough food
    • may destroy surrounding ecosystems to grow on

    Wastes:

    Pros:

    • available
    • does not deplete natural gas
    • useful way of getting rid of waste

    Cons:

    • global warming gases released into atmosphere

    Geothermal energy:

    Pros:

    • no pollution

    Cons:

    • needs to be buried deep into the ground for greater heat capture
    • Discuss the factors that affect the choice of energy sources  adopted by different societies.

    MEDCs have higher energy demands than LEDCs, as they depend on energy for many things such as transport, heating, air-conditioning, cooking and all other aspects of their lives.

    The choice of what energy source should be used is different to countries. Some have large oil, coal and gas reserves and that makes fossil fuels an obvious choice for an energy source. However generation of energy also depends on its availability, economy, cultural, environmental and technological factors. When an energy resource is available and close, it is more easier and efficient to use.

    Culture fears based on the fear of nuclear accidents and waste, have made it quite unpopular to choose. Cultural and tradition means that non-renewable resources are favoured, and the places with renewable energy resources are limited. Renewable energy sources are not being used so much globally which means that it is still not ready to meet current demands. Renewable sources can be used more if the production prices of the non-renewable sources are increased. This may better the environment as higher costs of the fossil furls means that peoples view will change. Peoples interest in renewable resources has led to an increased demand for renewable and non-pollution sources. This leads to a greater investment and research into more alternatives or improvements.