Endangered EcosystemChapter 9

Human activities that endanger an ecosystem

1. The increase in world’s population as well as increasing usage of the natural resources have effects on the ecosystem.

2. Human activities have threatened the ecosystem. These activities are

i. Deforestation (uncontrolled logging and mining activities)

ii. Burning of fossil fuels due to increase in the number of motor vehicles

iii. Increasing usage of fertilisers and pesticides in agriculture

iv. Increase in domestic and industrial waste

Deforestation

Deforestation causes soil erosion, landslides, flash floods and climatic changes.

Deforestation causes destruction of millions of hectares of forests.

This means loss of habitats for many species of flora and fauna.

This causes the extinction of plants, animals and microorganisms.

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Deforestation

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Pollution

Changes in physical, chemical and biological characteristics of the natural environment that are cause by human activities.

The various types of pollution are:i. Air pollutionii. Water pollutioniii. Thermal pollutioniv. Noise pollution

Air Pollution

Air pollution occurs when there is an increase in pollutants such as gas, smoke, dust and soot in the atmosphere which are harmful to human, animal and plant lives.

Air pollutionSource Pollutant

sEffects

Factories and industries (Burning of fossil fuels such as petroleum, diesel and gas)

Sulphur dioxide

•Irritates the eyes, respiratory tracts and lungs.•Dissolves in rain to form acid rain. Acid rain lowers pH of the soil making the soil infertile for plants as well as damaging trees and crops. Acid rain lowers the pH of lakes causing death of aquatic organisms. It corrodes metal structures in bridges and buildings

Oxides of nitrogen

•Causes bronchitis and cancer of respiratory organs•Damages lung tissues•Eye, lung, nose and throat irritation•Dissolves in rain to form acid rain.

Dust •Dirty buildings•Worsen the symptoms of asthma and can cause lung disease•Blocks stoma pore and is deposited on leaves. This prevents gaseous exchange and lowers the rate of photosynthesis

Air pollution

Source Pollutants Effects

Motor vehicles

Carbon monoxide

•Combines with haemoglobin to for carboxyhaemoglobin causing less oxygen to be transported by haemoglobin causing death•In small amounts, it can impair alertness, causes headaches.

Lead •causes retardation in children•Causes coma or death

Soot, smoke •Causes haze•Interferes the respiratory process because it irritates the nose and lungs as well as damages the cells lining in the alveoli•Reduces visibility•Blocks the stoma pore thereby reducing rate of photosynthesis

Air pollutionSource Pollutants Effects

Burning of rubbish, solid waste, forest and fossil fuels

Carbon dioxide

•Causes the green house effect and global warming•Increase the atmosphere temperature•Changes in climate•Polar ice caps melt, causing floods

Smoke, soot

•Haze causes conjunctivitis, sore throat and flu•Causes inflammation of the respiratory tract which can lead to bronchitis•Prevents light from reaching earth’s surface•Blocks stoma pore thereby reducing photosynthesis

Agriculture activities that use agrochemicals such as pesticides. Insecticides and herbicides

•Can be passed on in food chain and causes harm to organisms when accumulated in the body

Water pollution

Source Pollutants Effects

Discharge of domestic wastes into rivers

•Untreated sewage (human and animal faeces)•Detergents•Rubbish

•Causes the growth of bacteria that causes diseases such as cholera, typhoid•The increased concentration of nitrates and phosphates in the untreated sewage increases the number of microorganisms and leads to eutrophication.•The organic substances are decomposed by the bacteria using the oxygen in the water. This reduces oxygen content of the water and causes the death of aquatic organisms.•Detergents reduces the concentration of oxygen in the water and this can cause death of aquatic organisms.•Non-biodegradable rubbish reduces the sunlight from reaching the plants in the river.

Water pollutionSource Pollutants Effects

Discharge of industrial wastes

•Organic wastes form agriculture-based factories that process agriculture products such as palm oil, rubber, cocoa and others•Heavy metals from electronic factories such as mercury, arsenic, lead, zinc and copper•Oil, grease, suspensions and liquid wastes from factories producing chemicals, paints, metals, textiles and ink•Toxic wastes from factories producing agrioultural products such as insecticides, fertilisers, pesticides and herbicides

•Toxic chemicals accumulate in the organisms via the food chain. This results in poisoning of aquatic organisms and human.•The toxic substances can damage organs and can cause cancer and nervous disorders in man•Organic substances are decomposed by the bacteria. This reduces the concentration of oxygen in the water.

Water pollution

Source Pollutants Effects

Discharge of agriculture wastes

•Nitrates and phosphates from fertilisers and faeces.•Agrochemicals such as insecticides, pesticides, herbicides and fertilisers.

•This results in eutrophication.•These chemicals are toxic and harmful as they pass through food chains and accumulate in the tissues of animals and man. It can damage the organs in the body and can cause cancer.

Oil spills from oil tankers

Oil •Pollute the beaches•Causes death of sea birds and aquatic organisms in the sea

Acid Rain Burning of fossil fuels such as coal and

gas in industries, power stations and domestic boilers release the gases: sulphur dioxide (SO2) nitrogen oxides (NO and NO2)

These gases dissolve in the water vapour in the atmosphere to form sulphuric acid and nitric acid.

These acids fall as acid rain. The pH acid rain is less than 5.0 th

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Acid Rain

Eutrophication

Eutrophication occurs as a result of leaching of fertilisers and sewage into the river, lakes or ponds.

The fertilisers and sewage ahve a high concentration of nitrate and phosphates that encourage rapid growth of algae. The resulting population explosion is called algal bloom.

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Eutrophication

The excessive growth of algae covers the surface of the lakes, ponds or rivers. This prevents sunlight from reaching the bottom of the water bodies. Hence the aquatic plants cannot photosynthesise and eventually die.

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Eutrophication

As dead organic matter accumulates at the bottom of the lakes, rivers or ponds, aerobic bacteria decomposes it using the oxygen in the water.

The concentration of oxygen in the water decreases and this results in the death of aquatic organisms such as fish.

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Biological Oxygen Demand (BOD)

Biological oxygen demand is the amount of oxygen used by the microorganisms such as bacteria and algae that decompose organic matter in a sample of water.

The BOD measurement provides an indication of the level of water pollution.

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Biological Oxygen Demand (BOD)

When the BOD is high, the dissolved oxygen level is low, there is a high level of pollution in the sample of water with organic matter.

When there is a large amount of organic waste in the water, there is a large number of aerobic bacteria to decompose the waste.

The process of decomposition requires oxygen.

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Biological Oxygen Demand (BOD)

Hence, the dissolved oxygen levels in the water decreases. The BOD value is high.

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Thermal pollution

Thermal pollution is due to the release of excess heat into the environment.

It causes the temperature of the water to rise above the normal value.

Sources and effects of thermal pollution: Discharge of hot water from factories,

nuclear reactors, electric power stations

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Thermal pollution

Water is used as a cooling agent. The hot water is channelled to the rivers and lakes causing the temperature of the water to increase.

The level of dissolved oxygen decreases as oxygen becomes less soluble in the water.

Some aquatic organisms die because they can only survive in a certain range of temperature.

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Thermal pollution

This causes a change in the species composition of the aquatic ecosystem.

The increase in temperature increases the rate of decomposition of organic matter and thus increase the BOD value. The concentration of oxygen in the water decreases, causing the death of aquatic organisms.

Increase in temperature encourages rapid growth of algae. This increases the BOD value.

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Noise pollution

This pollution occurs where there is excessive noise in the environment and disturbs the tranquility of life.

Sources: aircrafts trains construction areas factory machines and equipment traffic

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Noise pollution

Effects: can lead to deafness can develop and aggravate stress related

problems such as high blood pressure, ulcers, headaches and depression.

will stimulate and increase the production of adrenalin. This increases heartbeat rate, blood pressure and respiration rate. The blood vessels constrict and the muscles become tense.

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