Man’s impact on his environment

Human population growth

Until recently, human population has been increasing   very slowly because of a high death rate due to:

1) high infant mortality due to poor nutrition and        poor protection to diseases.

2) Large number of people dying from epidemics        such as influenza (100,000,000 people killed in        1918) and black death.

Causes for rapid exponential increase in population growth in last 200 years

1) improved nutrition

2) improved medical services and living standards        reducing the mortality rate significantly, esp.        infants

3) Increased life span, so that more people reach        the age of reproduction

The effect of the development of agriculture and the advance in technology on the growth

of the human population

1) Agricultural developments include the       introduction of pesticides, chemical fertilizers       and high-yield crops. These, together with       advances in food storage and transportation       technologies led to a marked increase in food       supplies so that more human population can be       supported.

2) With the improvement in medical and scientific        technology, potential disease epidemics can        be controlled by vaccines, antibiotics and        insecticides. Accordingly, death rate        decreases, while the number of survival of        the babies increases. Thus there is a net        increase in population size.

To satisfy the need for rapid human population growth and development, humans have been over-using natural resources and polluting the environment at an alarming rate. It also creates problem of food shortage and overcrowding.

To know more about the human impacts on the environment, visit:

• http://resources.ed.gov.hk/biology/english/index.html

Problem of food shortage

1) Starvation problem

         Even with a greatly increased food production due to      the application of science to agriculture and the use of      machinery in farming, many parts of the world, particularly      the developing countries, still face starvation.2) Malnutrition problem

    Even if a person receives enough energy from rice or wheat bread, he may still suffer from malnutrition. Growth of the human body requires a supply of amino acids which are rare in plant proteins. But animal proteins are expensive and many people of the world cannot get an adequate supply of these proteins.

Problem of energy shortage

    Energy for driving machines and doing other works is now obtained from coal, oil, gas and other fossil fuels.

    By the end of the 20th century, the supply of readily available oil and natural gas will be low and the cost to obtain new supplies will be so high that it will be necessary to use other sources of energy

    Nuclear energy and solar energy will become more important to man in the near future.

Problem of lack of space

    People living in overcrowded conditions may suffer more accidents, mental illnesses and other undesirable effects.

    The expanding world population increases the demand for land, and consequently the amount of land per person decreases.

    The problem can be partly overcome by careful land management, such as using a piece of land for different purposes, such as housing, recreation, water storage, and so on.

The present situation of food supply of the world1) About two thirds of the world's population are        existing on a diet of under 10,000 kilojoules per        day - the limit below which the diet is not enough        for normal living.

2) Many people are not getting a well balanced diet,        e.g. the supply of animal protein is extremely        short in many regions.

3) About one fifth of the world's population have         plenty of food, and some even suffer from         diseases caused by over-eating. In fact, the rich         nations make up only one third of the world's         population but eat over half of the world's food         supply.

Factors contributory to the world's food problem1) Poor people cannot afford to buy the food. It is also       expensive to transport food from say Europe to      Africa. Rich countries also will not produce more food      unless some profits are made.

2) Low food production in some areas is due to water       shortage, poor climate, poor soils, lack of farming       equipment, lack of fertilisers and a lack of skilled       farmers.

3) Changes in weather conditions (such as drought) can        also bring about famine

4) A larger population will use more space for housing and         so reduce the area of land available for agriculture.

5) Up to 50% of food is wasted between the field and        the consumer. Poor harvesting causes grain to be        spilled and broken open, and fruit to be bruised.        Damp food goes mouldy during storage, and badly        stored food can be ruined by insects and rats.

6) The demand for meat by rich nations causes waste, and        hunger. A third of the world's grain is fed to        livestock to produce meat for the rich. But it takes        16 Kg of grain to produce 1 Kg of beef. In addition, it        takes 30 times as much land to produce the same        amount of animal protein as plant protein.

If grain was fed to the local poor it would support ten   times more people than grain fed to livestock. Land   at present used to produce meat for America and   Europe could be used to grow millet, maize, sorghum,   cassava and other crops to feed the hungry.

7) Many developing nations use their best farm land to        grow tobacco, sugar, coffee, tea, cotton and other       'cash crops' to earn money in the export market        instead of reserving such land for growing the more       'essential' crops to feed the hungry.

8) Farmers in some countries do not have the benefit of        modern knowledge and machinery to use land most        effectively.

Means of increasing agricultural production and food supply

1) Cultivation of new land

    The draining of swamps, the irrigation of deserts and the reclamation of land lost by erosion can provide much valuable land which previously would have little value in farming. Irrigation often means the construction of dams and reservoirs to store water until it is needed. It also involves the making of channels to carry the water to the fields where crops are growing.

2) Exploiting the seaa) By more careful control to avoid overfishing, a

        continual supply of fish as a source of food can         be maintainedb) Exploiting producers in the sea which are previously         not eaten or not much eaten, e.g. seaweeds and         planktons

3) Fish farming - ponds are stocked with young fish and        fertiliser is added to get maximum growth

4) The use of machinery

   This allows the land to be prepared and the crops harvested quickly, so that the farmer may be able to grow more crops on the same land. He is also less dependent on the weather.

5) Changes in pattern of farming

a) Growing of two crops at the same time so that bare        patches between plants are reduced.b) The making use of natural vegetation as a food        source

6) Intensive animal rearing

a) Chickens are reared in cages to reduce their         movement and so loss of energy. They are kept at         an optimum temperature and given just the right         minimal balance of food for maximum growth.         They are killed after three months, which is the         time they will have grown the most.

b) Breeding of new varieties of plants and animals by        selective crosses. These may produce a greater        yield of food, or varieties which are more        resistant to pest and disease. Other cattles have        been bred to produce more milk, or to fatten        more quickly. Cereal crops have likewise been        bred to give a bigger yield or improved nutritional        value.

Ecological characteristics of cultivated fields compared with those of natural ecosystems

The effects of intensive agriculture

1) Uncultivated soil is a complex living ecosystem. As fast       as minerals are extracted from it by plants they are       replaced by other minerals from the nitrogen cycle,       animal droppings and the decay of dead organisms.       This balance between the plants, the animals and the       environment gives the community stability.     Uncultivated soils are protected from hot sun and        driving rain by a cover of vegetation and are bound        together by plant roots.

2) The natural ecosystem is damaged by modern          agricultural methods.

a) The natural sequence of life, death, and decay is        replaced by intensive cultivation in which plants are        removed before they can rot away and replenish the        minerals they have extracted. b) Soil structure is continually disrupted by ploughing         and added chemicals.c) Modern methods destroy many of the living things         which maintain soil fertilityd) The natural community of many species is replaced by        fields containing largely one species (a monoculture).        This encourages certain pests, because they have         plenty of food. The use of pesticides to kill them also         kills many natural animals.

e) A lack of plants on freshly ploughed soil may         increase soil erosion due to action of wind or water.f) The continuous harvesting of crops from time to         time mean that some minerals (esp. nitrates)          㢀 removed from the soil have no chance of being          recycled.g) Extensive use of fertiliser may destroy natural         species in the soil. Surplus fertiliser runs off        into streams, where it causes massive plant         growth.This chokes up waterways, even killing fish.h) Heavy machinery used on farms compresses the soil         making it to have poor drainage and difficult for         plants to grow. Again many natural species are          destroyed by moving heavy machinery.

Extensive use of inorganic fertilizers

Prolonged, or excessive use of inorganic fertilizer    damages soil. It can lead to

  the breakdown of soil crumbs,

  a slow reduction in soil humus, and

   an accumulation of organic acid.

Effects on soil structure

Why needed?

    To maintain adequate supply of minerals to plants as continuous harvesting of crops remove minerals from the soil and stop their recycling

Other effects

1) Too much of any mineral ions may be harmful to       the plants.     A high concentration of salts in the soil may       prevent the roots to absorb enough soil water.     Many micro-elements are toxic at only slightly       higher levels.

2) Mineral salts leached from the soil into rivers or        streams may stimulate a rapid growth of algae.        Finally the dead bodies of the algae provide        food for the rapid growth of bacteria, leading       to a drop in oxygen level so that many active       aquatic animals, such as fish and shrimps, may die.

Use of pesticides

Why needed

Many organisms compete with man for food and they    may destroy large amounts of crop plants or other    food products and pesticides are poisonous chemicals    used to kill them and include:

Insecticides - to kill insects

Fungicides - to kill fungi

Herbicides - to kill weeds

Effects of pesticides

1) Beneficial as well as harmful organisms may be killed.       For example, insecticides may kill beneficial insects       such as honeybees which help the pollination of       flowering plants.

2) The natural predator of pests are also killed at the       time pests are killed. Pest population, in the absence       of their predators, may then recover rapidly from       small numbers and exceed their original size.

3) Frequent use of a particular pesticide may favour the       development of resistant strains of pests.

4) Some pesticides, such as DDT, are very stable        compounds and they may stay inside the bodies of        organisms without being broken down or excreted.        They may accumulate at successive steps in a food        chain. Since the biomass is greatest at the level of        the producers and it decreases rapidly along the food        chain, the concentration of the pesticide increases up        the food chain and may reach toxic level at the        highest trophic level.

For instance, DDT sprayed into the field may be washed   or leached into the surrounding water and is originally at   a very low level.

By active absorption, DDT is concentrated in the cells of   the water plants.

Since a small fish feeds on a large amount of water plants   and a large fish feeds on a lot of small fish and a bird on   a large number of large fish, DDT may reach such a high   concentration that the birds are killed.

0.04

10

50

75 birds (tertiary consumers)

large fish (secondary consumers)

small fish (primary consumers)

water plants (producers)

• Pollution:

– The addition of any substances to the environment that can cause harmful effects to the ecosystem as a result of human activities

– May arise from substances present in various wastes (industrial, domestic or agricultural), or from some forms of energy such as heat and sound

• Pollutant:

– Any substance that causes pollution

What are the effects of air pollutants on the environment and human health?

• Major causes of air pollution:– Combustion of fossil fuels in motor vehicles (which

emit exhaust fumes) and power stations– Production of industrial waste gases in factories and

industrial plants, which emit smoke– Combustion of refuse in incinerators

• Major pollutants:• Carbon monoxide and carbon dioxide• Oxides of sulphur and nitrogen• Lead compounds• Carbon particles

General ecological effects of smokeSmoke from factories and domestic fires contains soot,   ash and grit.

If they are breathed in, these particles accumulate in   the lungs. The alveoli walls become coated with   particles. This causes disease in which the sufferer   has shortness of breath and breathing is difficult   after exercise.

Infection may lead to bronchitis, shown by a continual   cough.

Smoke and grit block the stomata (breathing pores) in   plants reducing their growth.

• Produced when fossil fuels are incompletely burnt• As it combines with haemoglobin, it reduces the oxygen-

carrying capacity of the blood. • This may cause dizziness, headache, fainting and even

death

Carbon monoxideCarbon monoxide

• The extensive burning of fossil fuels and deforestation lead to an increase in the level of atmospheric carbon dioxide

• This give rise to the greenhouse effect

Carbon dioxideCarbon dioxide

Why does deforestation lead to a rise in the level of atmospheric carbon dioxide?

Problems related to increasing atmospheric temperature:

May lead to gradual melting of polar ice caps, leading to the rise of sea level. Eventually, many coastal and low lying regions in the world will be submerged under water, and habitats will be destroyed

To know more about the greenhouse effect, visit:

• http://www.smy.fi/koulut/carbon/

• Produced mainly through the burning of fossil fuels

• Present in the smoke released by power stations and factories, and also in exhaust fumes from motor vehicles

• They are acidic gases and dissolve in rain water to form acid rain

Sulphur dioxide and oxides of nitrogenSulphur dioxide and oxides of nitrogen

These acidic gases may be carried in the air for long distances before falling as acid rain. Hence, it may affect a large area

To know more about acid rain, visit:

• http://artsci.shu.edu/biol3341aa/EnvToxWeb/acid%20rain%20home.htm

Ecological effects of acid rain1) Damage to plants

     Acid rain, combined with sulphur dioxide gas and ozone, are blamed for the death of large areas of forests in Europe, Scandinavia, Britain and the U.S.A., together with crop damage valued at millions of pounds a year.      Leaves turn yellow and fall off and roots are damaged so they can no longer absorb minerals. This makes a plant more likely to be killed by drought and severe winters, and more susceptible to attack from pests which would have little effect on healthy plants.

2) Damage to soils

     Acids changes soil pH and make them less fertile. They cause essential minerals to be washed away by rain and release poisonous chemicals, like aluminium and mercury, which are normally insoluble, and so harmless.

3) Damage to buildings    Acid rain are corrosive and can seriously damage buildings and seriously destroy works of art made from limestone and marble.

They also cause irritation to the eyes and the lining of the breathing system.

4) Other effects

Various forms of wastes

  detergent, garbage, plastics and metal can

A) Domestic wastes, e.g.

B) Agricultural wastes, e.g.  inorganic fertilizers and manure

C) Industrial wastes, e.g.

  crude oil, hot water, soluble heavy metal compound

usually include:1) wastes from our body (urine and faeces) and2) detergent from washing

Domestic sewageDomestic sewage

Human wastes Human wastes are rich in bacteria which act

as pathogens. Typhoid ( 腸熱 ), dysentery (痢疾 ) and diarrhoea ( 腹瀉 ) are the most common diseases spread by water contaminated with sewage. Proper disposal of faeces and public sewage works prevent this form of pollution.

They are also rich in organic nutrients. When they are released into water bodies (rivers or    seas), they

  reduce the amount of sunlight entering the water  promote the growth of putrefying bacteria and     fungi which multiply rapidly  The decomposers also deplete dissolved oxygen in     the water & produce toxic wastes into the water.  Such conditions cause the death of active aquatic     animals such as fish, which require clean, well     oxygenated water

point at which sewage is discharged into the river

distance down river

dissolved oxygen

clean water organisms

ammoniabacterial population

Effect of sewage on a river

Putrefaction also releases ammonia, which is    changed into nitrate by nitrifying bacteria.The increase in nitrate content in water promotes    a rapid growth of algae, resulting in an algal    bloom, of which red tide is one example. Dissolved oxygen is used when the algae respire,   especially at night or when they are decomposed   after death.This caused the death of fish.

Detergents

They may also produce a layer of foam to develop on   water surface, which may:

Even at 0.1 ppm, detergents themselves can reduce the rate    at which water can absorb oxygen from the air by 50%.

1) reduce the amount of sunlight available        to organisms 2) reduce the diffusion of oxygen into       the water, leading to suffocation       and death of aquatic organisms.

Garbage1) Biodegradable, e.g. food

residue,    fruit peelings, paper, etc.

   If these wastes are not disposed   properly diseases may spread (i.e. by

pests such as rats) bad smells will be given off from the decomposing materials

2) Non-biodegradable, e.g. plastic and metal can

Harmful gases generated into atmosphere when incineratedIf disposed at landfill sites, they would accumulate & cause    land pollution

Agricultural wasteAgricultural waste

include fertilizers, pesticides and animal wastes (e.g. faeces)

Fertilizers • Provide minerals for plant growth• But when excessive nutrients are washed into

water bodies by the action of rain, they may induce algal bloom that leads to death of fish as oxygen is depleted and toxic wastes accumulated.

Pesticides • Used to control pests, e.g. DDT

Animal wastes, e.g. those from pig and poultry • If they are discarded into water bodies, they will produce similar

effects as domestic sewage• The organic substances will stimulate the growth of

microorganisms and algae, resulting in the production of toxic substances and depletion of oxygen and hence death of aquatic organisms

When these chemicals are washed into water bodies by    rain water, they may contaminate aquatic organisms and    become concentrated in organisms along the food chain,    reaching toxic levels in the top consumers

Industrial wasteIndustrial waste

include chemicals, leaked oil and hot water

• Industrial wastes are released into the waters from tanneries, dyeing and bleaching factories, electroplating factories, chemical factories, etc.

ChemicalsChemicals

• If these chemicals are taken up by aquatic organisms, they will be transferred and accumulate in the body of organisms along the food chains. Though present at very low level initially, they can reach toxic level in the top consumers.

• They contain a wide variety of chemicals such as dyes, detergents, cyanides and heavy metal compounds such as those of lead and mercury

• When people eat contaminated seafood, heavy metal ions will     accumulate in our internal organs and cause heavy metal poisoning.

• Crude oil may leak from oil tankers during transport, or arise as industrial oil waste, causing serious impacts on marine life

Leaked oilLeaked oil

To know more about oil spill, visit:

• http://artsci.shu.edu/biol3341aa/EnvToxWeb/oil%20spill%20home.htm

•  It spreads as thin layer over large area of      water surface and reduces the penetration      of light and dissolving of oxygen into water.

• Further, oil can coat the feathers of seabirds, making them       unable to keep warm or fly. They are also poisoned when      they attempt to clean themselves

They even block gills and other  respiratory organs of animals, stopping  respiration and causing death.

•  They also get washed up onto beaches and foul shores, driving      away bathers & also destroys a wide variety of life when it      reaches the shores

• Water is often used for cooling in power stations, industrial plants and factories. Hot water is usually discharged directly into water bodies

Hot waterHot water

• Hot water is a water pollutant because:– Less oxygen dissolves in water at a

high temperature– Metabolic activities of organisms

increase with temperature, which further reduces the amount of dissolved oxygen in water

• Thus organisms may die from suffocation

• Offensive noises may lead to noise pollution

• These are mainly produced by road traffic, pile drivers, pneumatic drills, machines in building sites and factories, air-conditioners, etc.

• Noises from domestic areas such as mah-jong, radios and television can also cause noise pollution

Noise pollutionNoise pollution

• The level of noise is measured in decibels

• Constant exposure to noises above 50 decibels could cause irritation, stress and nervous fatigue.

• Exposure to very loud noises may damage the ear and cause temporary or permanent hearing loss, depending upon the intensity and duration of the sound level, and may eventually lead to partial or complete deafness

20A quiet home

60A ringing telephone

75-85Road traffic

100A noisy factory

115Pile driving

120A jet aeroplane

Approximate level (decibels)Sources of noise

To test your knowledge about this chapter, visit:

• http://web.ukonline.co.uk/webwise/spinneret/eco/maneco.htm

Constant subjection to high noise levels in factory   workers may result in progressive hearing deterioration

Excessive noise may also cause psychological stress:

physical and mental fatigue and lack of concentration

In industrial situations, it results in lowered efficiency, a   reduced work rate, increased absenteeism, and a higher   potential for accidents and injuries.

In non-work environment, psychological noise effects   have an effect on sleep and thus may affect the   maintenance of a healthy body and mind.

Harmful effects of common pollutants on human healthHarmful effects of common pollutants on human healthPollutant Effect on human health

Dust or particulate matter deposited along the respiratory tract

irritation, mucous secretion & phlegm   formation, resulting in excessive   coughing

Carbon, dust & cigarette smoke

emphysema - distension of alveoli and   substantial decrease in overall   surface area of lungs, tuberculosis,   bronchitis, lung cancer, pneumonia,   etc.

Sulphur dioxide lung damage, bronchitis

Carbon monoxide forms carboxyhaemoglobin,   preventing oxygen uptake by blood,   even causing loss of consciousness   and death

Harmful effects of common pollutants on human healthHarmful effects of common pollutants on human healthPollutant Effect on human health

Organic sewage & other   toxic chemicals in   effluents from domestic   or industrial sources

Health affected when human directly   consume such kinds of polluted water or   when they consume marine life living in   these waters

Pathogen in sewage in   water

diseases such as typhoid, cholera or   hepatitis A

Heavy metals, e.g. lead   and cadmium

displace calcium from bones and cause   them to become brittle. They concentrate   in the liver and kidneys and cause damage   and malfunctioning of these organs

mercury, lead and copper

the nervous system is susceptible and may   result in brain damage or damage to   peripheral nerves causing uncoordinated   muscular control and poor eyesight

Natural resources:Anything humans obtain from the natural environment for use Examples: Timber, fish, fresh water and fossil fuels

ConservationConservation

        The wise use of natural resources so as to The wise use of natural resources so as to give man the give man the greatest sustainable benefit to present generation while maintaining its potential to meet the needs and aspiration of future generation..It is not just preservationIt is not just preservation - the maintenance of - the maintenance of all things in their natural conditions without all things in their natural conditions without any changes.any changes.

Over-exploitation:The over-use of natural resources, which

may eventually lead to their exhaustionimproper use of natural resources may lead

to destruction of habitats, impact on wildlife, pollution etc.

Renewable resources

• Resources that can be regenerated fairly rapidly through natural processes

• Examples: Timber, fish and fresh water

• If the resources are used faster than they are regenerated, they may become depleted.

Proper use and management of renewable resources become increasingly important to      ensure that rate of harvest      does not exceed rate of regeneration

What are renewable and non-renewable resources?

Non-renewable resources

• Resources that cannot be regenerated through natural processes in short time scales. They take over millions of years to form

• Examples: - Fossil fuels (petroleum, coal and natural gas)- Minerals (e.g. iron and aluminum)

• If these resources continue to be extracted rapidlyThey will be exhausted eventuallyWe should use non-renewable

resources wisely

aluminium

What are the undesirable effects of deforestation?

• Deforestation:The clearance of forests by humans for various purposes, including agricultural development, industrialization, urbanization and timbering

• Forests may also be destroyed by natural means such as forest fires

The use of timber to make furniture and paper A forest fire

• Trees can recover gradually after forest fires or controlled timbering.

• However, excessive deforestation will cause resource depletion and other environmental problems

• Environmental problems arise from deforestation:

– Destruction of habitats

– Loss of nutrients

– Soil erosion

– Increase in atmospheric carbon dioxideTo know more about deforestation, visit:

• http://www.geocities.com/lucilite/index.html

Destruction of habitats• Forests provide shelters and

food for wildlife. • The clearance of forests results

in destruction or modification of habitats for these organisms

Loss of nutrientsLoss of nutrients• Trees lock up nutrients that

are available for other organisms.

• The removal of trees results in a loss of these valuable nutrients in the ecosystem

Soil erosion• Deforestation means that trees,

which previously acted as umbrella, is removed and rain can hit the soil directly. The surface soil is washed away, esp. since there are no tree roots to hold the soil together

• Nutrients brought down to water bodies could generate pollution problems

Increase in atmospheric carbon dioxideIncrease in atmospheric carbon dioxide

• Trees absorb carbon dioxide and release oxygen during photosynthesis. This is an important step in the carbon cycle.

• Extensive deforestation will increase the level of atmospheric carbon dioxide, as less carbon dioxide is used in photosynthesis, causing global warming.

• In the past 50 yrs., atmospheric carbon dioxide has risen from 300 ppm to 340 ppm adn may reach 375 pm by 2000.

Afforestation as a means of soil conservation

• Deforestation should be followed by      afforestation to achieve a balance between      harvest and renewal so that a continuous yield      of timber is maintained.

• It also protects the soil against the danger of       erosion.

Protecting endangered species     Due to human activities, large numbers of wild plants and animals are severely reduced in number. They could soon become extinct if conservation is not carried out. These organisms are known as endangered species

Giant panda Pleione formosana (orchid)

Rhinoceros

To view some pictures of endangered/ extinct animals, visit:

• http://www.nature.ca/notebooks/english/enexpg.htm

Can you give two examples of endangered species in Hong Kong?

Barking deer wild boar pangolin

South China red fox Otter

Other examples of endangered species protected by HK law

They are delicious food favoured by Chinese and are now protected from hunting

Why is the survival of some organisms endangered?• Natural causes: competition and natural disasters

• Human activities (major):– Uncontrolled destruction of natural habitats, e.g. clearing

of vegetation during city development, housing, factories, agriculture, deforestation and reservoir construction

– Over-harvesting and over-hunting of organisms (e.g. tiger skin, whale meat, turtle shells and meat)

3. Picking wild plants or hunting wild animals for fun4. Serious pollution problems

Can you name some organisms that are threatened by each of the above factors?

Name one country park and one marine reserve in Hong Kong.

What can we do to protect endangered species?1. Establishment of nature reserves to protect ecosystems (i.e. country parks, wetland parks, marine reserves, etc.) (e.g. shooting of birds & mammals are prohibited in Mai Po marshes in Deep Bay in NW of New Territories)

An abandoned farmland

2. Conversion of disturbed lands into habitats for organisms

3. Using biological techniques (such as artificial breeding) to breed endangered species and re-establish them in the wild.

5. Legislation to protect wildlife by controlling hunting of animals and collection of wild plants

Pitcher plant

4. Wild populations falling below a        certain critical level may face        extinction as different members        of it hardly ever meet. Hence,        they may be transferred to a zoo        where they are protected and        encouraged to breed, e.g. Panda

Panda

6. Educating people to protect endangered species, through education centres, campaigns, exhibitions, printed materials, etc.

5. Legislation to control import, export and possession       of endangered species, including specimens and       body parts

• Uncontrolled exploitation of natural resources will cause most of these resources to become exhausted. Further, the exploitation of some natural resources (e.g. fossil fuels) also causes pollution

• Thus preservation and wise uses of natural resources form an important area in environmental protection

Preserving Natural Resources

Why can exploitation of natural resources lead to pollution problems?

What are the undesirable effects of over-consumption of fossil fuels?

• Fossil fuels are the major source of energy used by humans.

• Rapid population growth leads to an increasing consumption rate of fossil fuels

• Results:

– Generation of air pollutants

– Resource depletion

– Accidental contamination of the environment

Generation of various air pollutants• Pollutants released into the

atmosphere when burning fossil fuels: Carbon monoxide, carbon dioxide, nitrogen oxides, sulphur oxides, hydrocarbons, particulates, etc.

• Results:

– Contamination of water bodies

– Reducing crop yields

– Global warming

– Health impacts

Accidental contamination of the environmentAccidental contamination of the environment

• Crude oil is usually transported by oil tankers or through pipelines

• Accidents may occur during delivery, and leakage of oil will contaminate the environment and affect the marine life

How to preserve renewable natural resources?

Harvest and regeneration must be kept in balance, so that a continuous yield is ensured

• When trees are harvested, young trees should be planted in the same site to ensure a future supply and to prevent soil erosion

TimberTimber

• Over-fishing should be prevented, especially during the breeding season to ensure a source of fish stocks. And the restriction of fishing activities helps the fish population to recover

FishFish

• Two farming practices to maintain soil fertility and prevent soil erosion:

1. Crop rotation- Growing different crops on a farmland in a

definite sequence

Minerals in soilMinerals in soil

potatoes (or another root crop)

barley or oats

broad beans (or peas)

wheat

It lowers the chance of mineral depletion, as different crops   extract minerals from the soil in different proportions/levelsIt prevents the establishment of weeds and pests, which are   usually species-specificThe nitrate content of the soil can be restored by including   leguminous plant (e.g. pea, which harbour nitrogen fixing   bacteria) in the rotation

2. Organic fertilizers or manure- These are mainly animal wastes and dead

organic matter- This maintains soil fertility without causing

undesirable changes to the soil

The need to preserve non-renewable fossil fuel

      Some experts predict that the earth's supplies of oil (which is a non-renewable resource) will only last another 60 years at the present rate of use. Hence we must conserve fuel by minimising wastage and using other energy sources.

How to preserve non-renewable natural resources?

• Use electrical appliances and machines which consume less energy, e.g.,- replacing light bulbs with fluorescent lights,- use public transport rather than private cars...

Better buildings insulation would mean less energy used for either heating or air conditioning.

Produce more efficient machinery

Wise use of fossil fuelsWise use of fossil fuels

• Try to avoid wastage of energy, e.g.,- switch off electrical appliances that are not in use (e.g. lighting or air conditioners),- do not use a boiler that keeps water hot all the time, etc.

Give two more examples of the wise use of fossil fuels in daily life.

• These alternatives can be used to generate electricity:1. Solar energy

– use solar panels to trap light energy from the Sun2. Hydroelectric power

– use the down flow of water from a reservoir to drive turbines

Uses of alternative energy sourcesUses of alternative energy sources

3. Wind power – construct large turbines to be driven by wind

4. Nuclear energy – build nuclear power stations to make use of nuclear reactions

The use of nuclear energy is regarded as a potential hazard to the environment. Do you know anything about this?

How to make full use of natural resources by recycling?

Another way to preserve natural resources is to make full use of them. This can be done by recycling

Recycling is the conversion of used materials into new and useful materials or products. Examples are,

1. Manufacturing new (recycled) paper from waste paper

2. Recycling of metallic materials (e.g. aluminum cans and disused vehicles)

• Cotton wool wastes from the textile industry can be used for growing mushroom

• Pig and chicken wastes can be used as fertilizers after treatment

• Apart from preserving natural resources, recycling also helps to reduce the pressure of waste disposal and treatment

• Certain types of plastics and tyres can be recycled for manufacturing purposes

To play an interesting game about recycling, visit:

• http://www.epa.gov/recyclecity/

How to control air pollution?The following are some common measures to reduce

air pollution. In some countries, the government may have established laws to enforce these measures1. Catalytic converters- installed in the exhaust system of vehicles to convert pollutants into harmless gases

2. Petrol with lower sulphur content     This means that the waste gases generated will

contain less sulphur oxides so that the chance of producing acid rain is reduced.

3. Unleaded petrol     Lead is added to engines to keep them from “knocking” due to uneven burning of fuels and hence improve engine performance. However, lead added can escape in the exhaust fumes. Falling in rain, lead can eventually build up in the soil, be absorbed by vegetation, and enter the food supply. Lead is toxic to humans, affecting people's nervous system, and small children are at particular risk. For children under age 7, even a mild case of lead poisoning may cause mental retardation or behavioural disorders. A heavier dose may cause serious, permanent brain damage and death. The solution to this problem is to use unleaded or lead-free petrol though such petrol may cost more.

4. Motor vehicles are checked regularly for monitoring the quantity of dust particles released in exhaust gases. They are also required to be fitted with exhaust filters.

5. Height of chimneys     Legislation may require chimneys to be of

certain height to allow dispersal of smoke

6. Electrostatic precipitators- installed in power stations,

factories, restaurants, etc. to trap dust particles in the waste gases

7. Alternative energy sources - Energy sources that generate less pollution- Ethanol, natural gas and electric energy can be used to power vehicles- Solar energy can be used for domestic purposes- Hydroelectric power and wind energy can be used to replace fossil fuels for generating electricity

To know more about local efforts in controlling air pollution, visit:

• http://www.epd.gov.hk/epd/english/environmentinhk/air/air_maincontent.html

How to control water pollution?

• To avoid the accumulation of toxic chemicals in the environment, industrial wastes containing toxic chemicals such as lead and mercury compounds must be treated before they are discharged into water bodies

• Legislation is helpful in setting the limits of harmful chemicals that can be released into the environment

• DDT has been banned in many countries and is replaced by biodegradable insecticides

Treatment of industrial wastesTreatment of industrial wastes

• Domestic sewage are treated in sewage treatment plants, in which sewage is converted into less harmful form before being discharged into water bodies

Treatment of domestic wastesTreatment of domestic wastes

A simplified diagram of the sewage treatment processes

To test your knowledge about the principles of sewage treatment,

visit:

• http://web.ukonline.co.uk/webwise/spinneret/microbes/sewag.htm

• Sedimentation – large solid substances settle down at the bottom of settling tanks to form sludge

• Decomposition – the fluid in oxidation pond is bubbled with air to stimulate the breakdown of organic substances into inorganic substances by putrefying bacteria and fungi. Then the fluid is filtered for removing microorganisms and any remaining organic particles

• Fermentation – fermentation by anaerobic bacteria in digester produces methane gas (which can be used as a fuel to drive sewage treatment plant) and dried solid serves as fertilizer

Besides controlling water pollution, state two other benefits of sewage treatment.

Water pollution problem in New Territories

   Serious due to large amounts of pig and poultry manures poured into rivers

   Reduced by legislation to stop uncontrolled discharge of animal wastes

The following treatment can also be applied:1. Ground flushed with water to keep farm clean and make      it easier to collect the manure

2. Manure pumped into tank in which the solid waste is      separated from the liquid portion by filtration or      sedimentation.3. Liquid waste is passed into an aeration tank where      suspended particles are decomposed by micro-      organisms before it is released.

A) Separation of solid waste from the    liquid portion by filtration or sedimentation

solid waste

solid waste

B) Solid waste collected, dried and        used as fertiliser

liquid waste

C) Aeration of liquid waste

D) Effluent to river for        irrigation