Causes & Effects of Pollution

· Human activities have led to the pollution of land, water and air
· Pollution comes from a variety of sources, including industry and manufacturing processes, waste and
discarded rubbish, chemicals from farming practices, nuclear fall-out, and untreated sewage.

Pollutant Source Effect

Untreated or raw Inhabited areas with sewage Eutrophication of rivers and lakes
sewage released into rivers, lakes
Chemical waste Heavy metals like mercury are Many chemicals persist in the environment.
released from industries, i.e. they do not break down but keep on acting
pesticides may come from farms on organisms. Some accumulate at the top of
the food chain as they pass from one trophic
level to the next ultimately killing organisms
at the top of the chain. Bioaccumulation.

Discarded rubbish Plastics and other synthetic Many are non-biodegradable, i.e. they are not
materials from homes, industries broken down by decomposers such as bacteria.
They are an eyesore and may remain for a
very long time in the environment. They take
up valuable space in landfills.

Fertilisers May be washed of farms by rain Eutrophication of rivers and lakes like raw
water sewage
Pesticides, insecticides Sprayed onto crops in farms May accumulate within food chains, may kill
and herbicides useful organisms, may result in loss of
biodiversity.
Nuclear fallout Accidental leakage from nuclear Radioactive particles may increase risk of
plants, explosion of nuclear bomb cancer,
May cause mutations that are passed down
generations

Plastic Pollution
· Plastics are non-biodegradable. They are not broken down by bacteria and fungi.
o They may choke animals and small animals may become trapped in them
o If they break down or are burnt, they may release toxic substances
· Disposal:
o Plastic is generally disposed of by burying in landfills and may eventually release toxins over years
o If not discarded will become an eyesore

Female Hormones
· Female contraceptive hormones are excreted in urine and water supplies
o Sewage treatment will not remove them
o They may cause feminisation of male aquatic organisms, such as fish and frogs (development of
female characteristics and loss of urge to reproduce). Sperm count may be lowered
o These hormones can reduce the sperm count in human males, lowering fertility

Eutrophication
· This is the excessive growth of plants and algae in rivers and lakes. It is caused by sewage or fertiliser
because they contain nitrates and phosphates which promote their growth.
o Increased plant and algal growth blocks sunlight so water plants and algae at the bottom start to
die
o aerobic bacteria multiply as they feed on the remains of the plants and algae
o the bacteria finish the dissolved oxygen in the water
o as a result aquatic organisms such as fish which need the oxygen migrate or die off

1 of 4
Acid Rain
· Combustion of fossil fuels that contain sulfur impurities e.g. coal creates sulfur dioxide
o This is released into the atmosphere where it dissolves in droplets of water forming a weak acid.
o The weak acid falls to the ground as acid rain.
o Acid rain corrodes leaves and reduces the rate of photosynthesis. Plants grow slowly and are stunted
because of the low rate of photosynthesis
o Soil also becomes acidic. The low pH may kill useful bacteria in the soil such as nitrogen-fixing
bacteria

Climate Change
· A greenhouse gas is a gas that absorbs infrared radiation from the Sun so it remains trapped in the Earth’s
atmosphere. This causes the Earth’s average temperature to rise.
· There are many greenhouse gases, the most important are:
o Carbon dioxide
o Methane

· The greenhouse effect works in the following way:

o The Sun emits rays that enter the Earth’s atmosphere
o The heat bounces back from the Earth’s surface
o Some heat is reflected back out into space
o Some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere – this is
normal
o However, as the levels of greenhouse gases in the atmosphere rise due to human activities the
Earth’s average temperature rises beyond normal (an enhanced greenhouse effect), causing global
warming or climate change.

How the greenhouse effect works

Consequences of increased global warming:

· Ocean temperatures increase which causes:
o polar ice caps to melt
o sea levels to rise resulting in flooding
· Increasing atmospheric temperatures can cause extremes of weather like storms, flooding, drought. These
extreme weather events can lead to:
2 of 4
 o changes in/ loss of habitats
o disruption of food chains and a decrease in biodiversity
o increase in migration of species to new places
o increased spread of pests and disease

Conservation
Sustainable Resources
· We use many resources from the Earth; some, such as food, water and wood, are sustainable resources:
those which are produced as rapidly as they are removed from the environment so that they does not run
out.

· Some resources, such as fossil fuels (coal, oil and natural gas), are non-renewable because what is used
cannot be replaced. Fossil fuels are used mainly as:
o an energy source
o as raw materials for many other products – e.g. almost all plastics start with petroleum as a raw
material
Therefore they must be conserved by reducing the amount we use and finding other, sustainable
resources to replace them.

· Some products, especially those made from paper, plastic, glass or metal, can be reused and recycled – this
reduces damage to the environment and reduces the amounts of raw materials and energy needed to make
new products

· Other resources, such as forests and fish stocks, can be maintained – enabling us to harvest them
sustainably so that they do not run out in the future.

Sustainable Development
· Sustainable development is defined as development providing for the needs of an increasing human
population without harming the environment
· This means that conflicting demands must be balanced, e.g.:
o local people must be able to utilise the resources in their immediate environment but large
companies need to make money from resources such as forests and fish also
o the needs of humans for land with the needs of the animals and plants to be in a particular habitat
o the need to balance what people need now with what future populations might need
· For development to occur sustainably, people need to cooperate at local, national and international
levels in the planning and management of resources

Sustaining Forests
· Forests are needed to produce paper products and provide wood for timber
· Much of the world’s paper is now produced from forests in which similar trees are replanted when mature
trees are cut to ensure that there will be supply in the future
· Tropical hardwoods such as teak and mahogany take many years to regrow but are highly desirable for
furniture. The use of these types of wood is now more sustainable due to the introduction of several
schemes designed to monitor logging companies and track the wood produced
· Education helps to ensure that loggers and consumers are aware of sustainable practices

Sustaining Fish Stocks

· Managing fish stocks sustainably includes:
o Controlling the number of fish caught each year (quotas)
o Controlling the size of fish caught (to ensure there are enough fish of a suitable age for breeding
remaining)
o Controlling the time of year that certain fish can be caught (to prevent large scale depletion of
stocks when fish come together in large numbers in certain areas to breed)

3 of 4
 o Restocking (breeding and keeping offspring until they are large enough to survive in their natural
habitat before releasing them)
o Educating fishermen and consumers as to local and international laws so they are aware of types of
fish not to trade in

Sewage Treatment

Endangered Species
· An endangered species is at risk of becoming extinct
· There are several reasons why a species can become endangered – the population of the species may fall
below a critical level due to
o hunting
o climate change
o pollution
o loss of habitat
o introduction of non-native species that outcompete native species
· Endangered species can be helped by conservation measures such as:
o education programmes
o captive breeding programmes
o monitoring and legal protection of the species and of their habitats
o seed banks as a conservation measure for plants – seeds of endangered plant species are carefully
stored so that new plants may be grown in the future

Endangered Species
· A species may be at risk of becoming extinct if there is not enough genetic variation in the population as
random changes in the environment may quickly cause extinction. This is because the remaining organisms
are all very similar and may not have the adaptations to survive such changes
· There are moral, cultural and scientific reasons for conservation programmes, including:
o reducing extinction rates of both plant and animal species
o keeping damage to food chains and food webs to a minimum and protecting vulnerable
ecosystems (eg the rainforests)
o protecting our future food supply and
o maintaining nutrient cycles and possible sources of future medical drugs and fuels

4 of 4