CIE Categories Archives: 21. Human Influences on Ecosystems

21.4) Conservation

21.4) Conservation


Sustainable resource: is one that is produced as rapidly as it is removed from the environment so that it does not run out.

Sustainable development: is development providing for the needs of an increasing human population without harming the environment.


Non-renewable resources such as fossil fuels need to be conserved because the stocks of them on the planet are finite.

It can be conserved in the following ways:

  • By increasing the use of renewable energy (wind energy, solar energy, hydroelectric power).
  • By improving the efficiency of energy use (better insulation, smaller car engines, more public transport).


Sustaining forest and fish stocks:

  • Some resources, such as forests and fish stocks can be maintained with careful management.
  • This may involve replant land with new seedlings as mature trees are felled and controlling the activities of fishermen operating where fish stocks are being depleted.
  • There are three main ways of sustaining the numbers of key species. These are:

1) Education

  • Local communities need to be educated about the need for conservation. One they understand its importance, the environment they live in is more likely to be cared for and the species in it protected.

2) Legal quotas

  • In Europe the Common Fisheries Policy is used to set quotas for fishing, to manage fish stocks and help protect species that were becoming endangered through overfishing.
  • Quotas were set for each species of fish taken commercially and also for the size f fish. This was to allow fish to reach breeding age and maintain or increase their populations.

3) Restocking

  • Where populations of a fish species are in decline, their numbers may be conserved by a restocking programme.
  • This involves breeding fish in captivity, then releasing them into the wild.
  • However, the reasons for the decline in numbers need to be identified first.
  • if pollution was the cause of the decline, the restocked fish will die as well, issue of pollution needs to be addressed first.



  • Products such as paper, glass, plastic and metal can be reused or recycled.


Sewage treatment:

  • Microorganisms, mainly bacteria and protoctista, play an essential part in the treatment of sewage to make it harmless.
  • Sewage contains bacteria from the human intestine that can be harmful.
  • These bacteria must be destroyed in order to prevent the spread of intestinal diseases.
  • Sewage also contain substances such as soap and detergent from household wastes and chemicals from factories. These too must be removed before the sewage effluent is released into the rivers.
  • Inland towns have to make their sewage harmless in a sewage treatment plant before discharging the effluent into rivers.
  • A sewage works removes solid and liquid waste from the sewage, so that the water leaving the works is safe to drink.
  • In a large town, the main method of sewage treatment is by the activated sludge process.


Sustainable development:

  • This is a complex process, requiring the management of conflicting demands. As the world’s population grows, so does the demand for the extraction of resources from the environment.
  • However, this needs to be carried out in a controlled way to prevent environmental damage and strategies need to be put in place to ensure habitats and species diversity are not threatened.
  • Planning the removal of resources need to be done at local, national and international levels.
  • This is to make sure that everyone involved with the process is aware of the potential consequences of the process on the environment, and that appropriate strategies are put in place, and adhered to, to minimise any risk.


Endangering species and causing their extinction:

  • Anything that reduces the population of a species endangers it (puts it at risk of extinction).


Climate change:

  • This is a natural, uncontrollable process, but processes like global warming are made worse by human activity.


Habitat destruction:

  • Can be caused by a number of things – pollution biggest factor, fishing activity and dredging ships.
  • Lead to destruction of habitats leaving species homeless.



  • Global warming caused by pollution leading to rapid changes in climate in certain.
  • As a result the conditions will change, causing the environment to change and the species being no longer suited to it and struggle to survive.
  • Eg polar bear – arctic ice melting – cannot swim very well.


Introduced species:

  • Some species of animal are not introduced deliberately into different ecosystem, but find they way in due to man’s activities and then upset food chains.



  • Extreme hunting species of animals can cause extinction.


Conservation programmes:

  • If the population of a species drop, the range of variation within the species drops, making it less able to adapt to environmental change.
  • The species could, therefore, be threatened with extinction.
  • When animal populations fall, there is less chance of individuals finding each other to mate.


Habitats can be conserved in a number of ways:

  • Using laws to protect the habitat.
  • Using wardens to protect the habitat.
  • Reducing or controlling public access to the habitat.
  • Controlling factors, such as water drainage and grazing, that may otherwise contribute to destruction of the habitat.
  • Monitoring and protecting species and habitats.
  • Captive breeding and reintroductions – possible to boost a species numbers by breeding in captivity and releasing the animals back into the environment.
  • Seed banks – way of protecting plant species from extinction. They include seed from food crops and rare species. They act as gene banks.


Reasons for conservation programmes (CP – not pokemongo related, word just too long cbf writing it):

Reducing extinction:

  • CP strive to prevent extinction. Once a species become extinct its genes are lost forever.
  • So we are also likely to deprive the world of genetic resources.
  • The chances are that we will deprive ourselves not only of the beauty and diversity of species but also of potential sources of valuable products such as drugs.


Protecting vulnerable environments:

  • CP are often set up to protect threatened habitats so that rare species living there are not endangered.

Maintaining ecosystem functions:

  • There is a danger of destabilising food chains of a single species in that food chain is removed.
  • Crops are grown for food, extraction of drugs and the manufacture of fuel.
  • Crop growth has major impacts in ecosystems, causing the extinction of many species and reducing the gene pool.
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21.3) Pollution

21.3) Pollution


Sources and effect of pollution of land and water.


  • eg DDT controls spread of malaria by killing mosquitos which carry the protoctist parasites that cause the disease.
  • Remains in the environment after it has been sprayed and can be absorbed in sub-lethal doses by microscopic organisms – can enter food chains and accumulate as it moves up them.
  • Persist for a long time in the soil, rivers, lakes and bodies of animals, including animals.



  • If herbicides do not break down straight away, they can leach from farmland into water systems. such as rivers and lakes, where they kill aquatic plants, removing the producers from food chains.
  • Herbivores lose their food source and die or migrate. Carnivorous animals are then affected as well.
  • May blow onto surrounding land and kill plants other than weeds putting rare species of wild flowers at risk.


Nuclear fall-out:

  • Leak from a nuclear power station or nuclear explosion
  • Radioactive particles carried by the wind or water and gradually settle in the environment.
  • If radiation has long half-life, it remains in the environment and is absorbed by living organisms. The radioactive material bioaccumulates in food chains and can cause cancer in top carnivores.


Sources and effects of pollution of water.

Chemical waste:

  • Many industrial processes produce poisonous waste products.
  • Electroplating produces waste containing copper and cyanide. If these chemicals are released into rivers they poison the animals and plants and could poison humans who drink the water.
  • Any factory getting rid of its effluent into water systems risks damaging the environment.
  • Some detergents contain a lot of phosphate. This is not removed by sewage treatment and is discharged into rivers.
  • The large amount of phosphate encourages growth of microscopic plants (algae).


Discarded rubbish:

  • The domestic waste from a town of several thousand people can cause disease and pollution in the absence of effective means of disposal.
  • Much ends up in landfill sites, taking up valuable space, polluting the ground and attracting vermin and insects, which can spread disease.
  • Air pollution can be caused by burning waste.



  • Diseases like typhoid and cholera are caused by certain bacteria when they get into the human intestine.
  • The faeces passed by people suffering from these diseases will contain the harmful bacteria.
  • If this bacteria get into drinking water they may spread the disease to hundreds of other people.
  • For this reason, among others, untreated sewage must not be emptied into rivers.



  • When nitrates and phosphates from farmland and sewage escape into water they cause excessive growth of microscopic green plants.
  • This may result in a serious oxygen shortage in the water, resulting in the death of aquatic animals – a process called eutrophication.


  • A major problem with the use of fertilisers occurs when they are washed off the land by rainwater into rivers and lakes.
  • This leaching causes an increase in the levels of minerals such as nitrate and phosphate in the water, a process called eutrophication.
  • Eutrophication encourages the growth of algae. These form a green bloom over the water surface, preventing sunlight reaching other water plants.
  • These plants die because they are unable to carry out photosynthesis.
  • Bacteria decompose the dead plants, respiring and using up the oxygen in the water as they do this.
  • The low oxygen levels make it difficult for aquatic insects and fish to live, and eventually the lake may be left completely lifeless.


The degree of pollution of river water is often measured by its biochemical oxygen demand (BOD).

This is the amount of oxygen used up by a sample of water in a fixed period of time.

The higher the BOD, the more polluted the water is likely to be.

It is possible to reduce eutrophication by using:

  • Detergents with less phosphates.
  • Agricultural fertilisers that do not dissolve so easily.
  • Animal wastes on the land instead of letting them reach rivers.


Plastics and the environment:

  • Plastics that are non-biodegradable are not broken down by decomposers when dumped in landfill sites or left as litter.
  • This means that they remain in the environment, taking up valuable space or causing visual pollution.
  • Discarded plastic bottles can trap small animals; nylon fishing lines and nets can trap birds and mammals such as seals and dolphins.
  • As the plastic in water gradually deteriorate, they fragment into tiny pieces, which are eaten by fish and birds, making them ill.
  • When plastic is burned, it can release toxic gases.


The greenhouse effect and global warming:

  • Carbon dioxide is produced by burning of fossil fuels.
  • Methane is produced from the decay of organic matter and as a waste gas from digestive processes in cattle.
  • Carbon dioxide and methane are greenhouse gases.
  • They are called greenhouse gases as they trap heat in the earth’s atmosphere in the same way a greenhouse traps heat.
  • As the concentration of these gases increase in the atmosphere more heat is trapped, making the atmosphere warmer. This is called enhanced greenhouse effect.
  • It is causing global warming –Earth’s average temperature is rising.


Global warming is causing the following problems:

  • Melt polar ice caps, causing flooding of low-lying land;
  • Change weather conditions in some countries by increasing flooding or reducing rainfall;
  • Cause the extinction of some species that cannot survive at higher temperatures.


Causes and effects on the environment of acid rain

The ‘greenhouse effect’ and global warming:

  • Increase in carbon dioxide and methane concentrations in the atmosphere have caused an enhanced greenhouse effect.
  • With emissions being produced daily, a large imbalance is being created which is enhancing the greenhouse effect and making it stronger.
  • As there are naturally occurring greenhouse gases in the atmosphere that help keep the Earth warm, additional amounts of these gases leads to more heat being trapped on the planet.
  • This extra heat is causing global warming as well as affecting the Earth’s weather patterns.


Pollution by contraceptive hormones:

  • When women use the contraceptive pill, the hormones in it (oestrogen or progesterone) are excreted in urine and become present in sewage.
  • The process of sewage treatment does not extract the hormones, so they end up in water systems such as rivers, lakes and the sea.
  • Their presence in this water affects aquatic organisms as they enter food chain.
  • male frogs and fish can become ‘feminised’ (they can start producing eggs in their testes instead of sperm).
  • This causes an imbalance between numbers of male and female animals.
  • Drinking water, extracted from rivers where water from treated sewage has been recycled, can also contain the hormones.
  • This has been shown to reduce the sperm count in men, causing a reduction in fertility.
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21.2) Habitat destruction

21.2) Habitat destruction


Removal of habitats:

  • Farmland is not natural habitat but, at one times, hedgerow, hay meadows and stubble fields were important habitats for plants and animals.
  • Intensive agriculture has destroyed many of these habitats; hedges have been grubbed out to make fields larger, a monoculture of solage grasses has replaced the mixed population of a hay meadow and planting of winter wheat has denied animals access to stubble fields in autumn.
  • As a result, populations of butterflies, flowers and birds have cashed.
  • The development of towns and cities (urbanisation) makes a great demand on land, destroying natural habitats.
  • The crowding of growing populations into town leads to problems of waste disposal.
  • The sewage and domestic waste from a town of several thousand people can cause disease and pollution in the absence of effective means of disposal, damaging surrounding habitats.


Extraction of natural resources:

  • An increasing population and greater demands on modern technology means we need more raw materials for the manufacturing industry and greater energy supplies.
  • Fossil fuels such as coal can be mined, but this can permanently damage habitats, partly due to the process of extraction, but also due to dumping of the rock extracted in spoil heaps.
  • Oil spillages around oil wells are extremely toxic.
  • Once the oil seeps into the soil and water systems, habitats are destroyed.
  • Mining for raw materials such as gold, iron, aluminium and silicon leaves huge scars in the landscape and destroys large areas of natural habitat.


Marine pollution:

  • Marine habitats around the world are becoming contaminated with human debris.
  • This includes untreated sewage, agricultural fertilisers and pesticides.
  • Oil spills still cause problems but is gradually reducing.
  • Plastics are a huge problem: many are non-biodegradable so they persist in the environment.
  • Others form micro-particles as they break down and these are mistaken by marine organisms for food and are indigestible. They stay in the stomach, causing sickness, or prevent the gills from working efficiently.
  • Where fertilisers and sewage enter the marine environment, ‘dead zones’ develop where there is insufficient oxygen to sustain life.
  • Any form of habitat destruction by humans, even where a single species is wiped out, can have an impact on food chains and food webs because other organisms will use that species as a food source, or their numbers will be controlled through its predation.



The removal of large numbers of trees results in habitat destruction on a massive scale.

  • Reasons why: for timber, to make way for agriculture, roads and settlements and for firewood.
  • Animals living in the forest lose their homes and sources of food; species of plant become extinct as the land is used for other purposes such as agriculture, mining, housing and roads.
  • Soil erosion is more likely to happen as there are no roots to hold the soil in place. The soil can end up in rivers and lakes, destroying habitats there.
  • Flooding becomes more frequent as there is no soil to absorb and hold rainwater. Plant roots rot and animals drown, destroying food chains and webs.
  • Carbon dioxide builds up in the atmosphere as there are fewer trees to photosynthesis, increasing global warming. Climate change affects habitats.
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21.1) Food supply

21.1) Food supply


Modern technology has resulted in increased food production:

  • Agricultural machinery is used to clear the land, prepare the soil and plant, maintain and harvest crops to improve efficiency.
  • Chemical fertilisers are used to provide minerals to increase the yield of crops.
  • Pesticide is a chemical that destroys agricultural pests or competitors:
  • Herbicides are chemicals that kills plants that compete with the crop plant for root space, soil minerals and sunlight.
  • Insecticides are chemicals that destroy the insects that eat the damage the plants.
  • Selective breeding to improve production by crop plants and livestock, eg. cattle, fish and poultry.


The negative impact of monocultures:

  • The whole point of crop farming is to remove a mixed population of trees, shrubs, wildflowers and grasses and replace it with a dense population of only one species such as wheat or beans.
  • Monoculture: when a crop of a single species is grown on the same land, year after year.
  • In a monoculture, every attempt is made to destroy organisms that feed on, compete with or infect the crop plant.
  • So, the balanced life of a natural plant and animal community is displaced from farmland and left to survive only in small areas of woodland, health or hedgerow.


The negative impact of livestock production:

  • Intensive livestock production is also known as ‘factory farming’.
  • Chickens and calves are often reared in large sheds instead of in open fields.
  • Their urine and faeces are washed out of the sheds with water forming ‘slurry’.
  • If this slurry gets into streams and rivers it supplies an excess of nitrates and phosphates for the microscopic algae.
  • This starts a chain of events, which can lead to eutrophication of the water system.
  • Overgrazing can result if too many animals are kept in a pasture.
  • They eat the grass down almost to the roots, and their hooves trample the surface soil into a hard layer.
  • As a result, the rainwater will not penetrate the soil so it runs off the surface, carrying the soil with it.
  • The soil becomes eroded.


The problems of world food supplies:

  • There is not always enough food available in a country to feed the people living there.
  • A severe food shortage can lead to famine.
  • Food may have to be brought in (imported).
  • The redistribution of food from first world countries to a poorer one can have a detrimental effect on that country’s local economy by reducing the value of food grown by local farmers.
  • Some food grown by countries with large debts may be exported as cash crops, even though the local people desperately need the food.


Problems which contribute to famine:

  • Climate change and natural disasters such as flooding or drought; waterlogged soil can become infertile due to the activities of denitrifying bacteria, which break down nitrates.
  • Shortage of water through its use for other purposes, the diversion of rivers, building dams to provide hydroelectricity.
  • Eating next year’s seeds through desperation for food.
  • Poor soil, lack or inorganic ions of fertiliser.
  • Desertification due to soil erosion as a result of deforestation.
  • Lack of money to buy seeds, fertilizers, pesticides or machinery.
  • War, which can make it too dangerous to farm, or which removes labour.
  • Urbanisation (building on farmland); the development of towns and cities makes less and less land available for farmland.
  • An increasing population.
  • Pest damage or disease.
  • Poor education of farmers and outmoded farming practices.
  • The destruction of forests, so there is nothing to hunt and no food to collect.
  • Use of farmland to grow cash crops, or plants for biofuel.
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