Biology Chapter 9 Form 4
HUMAN ACTIVITIES THAT ENDANGER THE ECOSYSTEM Human activities, such as development, transportation and industrialisation, are essential to fulfil human needs and to maintain human life. At the same time, however, these activities can upset the balance of the natural environment and damage the ecosystem. Examples of human activities that can endanger the ecosystem are:
Deforestation
Logging Deforestation is the permanent removal of trees from the forests. Deforestation is needed for logging, agriculture, road developments, mining, the building of dams, etc. These have nevertheless resulted in a rapid clearing of forests which has detrimental effects.
The effects of uncontrolled deforestation are:
E r o s i o n a n d l a n d s l i d es es
Forests act as a giant sponge which releases water slowly into rivers. Deforestation causes the top soil to be exposed to rain and wind. This will lead in soil erosion and landslides at hill slopes when there is heavy rain. The rivers can become silted with soil and this can cause flash floods. Climatic ch anges As trees undertake the process of photosynthesis which causes carbon dioxide to be absorbed and oxygen to be released, deforestation leads to a decreased amount of carbon dioxide being absorbed from the atmosphere. The increase of the carbon dioxide can produce the green house effect and lead to global warming. Damaging n atural habitats Deforestation destroys the natural habitats of numerous plants and animals. This leads to a decrease in biodiversity and the loss of potential uses of plants for medicine. Extinction When the natural habitats of plants and animals are destroyed, the animals and plants can become extinct and be lost forever.
Intensive Agricultural Practices
Intensive agricultural practices Intensive agricultural practices often involve the massive clearing of trees from the forests. Such clearing is needed for commercialisation such as farming and the rearing of livestock. In addition, pesticides, herbicides and fertilisers which are being used in the farming and rearing of livestock can lead to soil and river pollution.
Industrialisation
Industry
Industrialisation is important to sustain human life. However, at the same time, industrialisation requires the usage of a large amount of energy and other natural resources which are derived from fossil fuel and metal ores. The demand for energy and natural resources requires mining of the fossil fuel and metal ores which will lead to the destruction of the environment. The demand of energy also leads to the building of new dams resulting in the deforestation of large areas of forests and flooding of large areas of land. The burning of fossil fuel for energy generation also leads to the emissions of carbon dioxide, sulphur dioxide and nitrogen dioxide which are harmful to the environment.
A Growing Human Population
A lot of people walking on the street The growing human population has a detrimental effect on the ecosystem. This growth increases the demand for food, homes and transportation. These demands in turn result in more land being cleared for farming and livestock to cater for the increased demand on food. More buildings are being built to cater for the increased need for accommodation.
The increase of the human population also increases the amount of domestic and industrial wastes. These wastes, if not managed properly, would cause pollution. In addition, an increased human population also increases the demand for transportation. This leads to more vehicles on the road and increased air pollution from the release of gases from the vehicles.
EFFECTS OF UNPLANNED DEVELOPMENT AND MISMANAGEMENT OF THE ECOSYSTEM Unplanned development and mismanagement of the ecosystem will result in many undesirable effects. Examples are:
Soil Erosion
Soil erosion Soil erosion occurs when the vegetation on the top soil is removed. When this happens, the top soil is exposed to rain and wind. The thin layer of the top soil is removed by rain as well as by wind. This results in the erosion and thinning of the top soil.
Flash Floods
Flash flood Flash floods are caused by the rapid rising of water in low-lying areas when there are continuous heavy downpours. They occur when:
Landslides
Landslides Landslides result when the earth along the hill slopes collapses. They take place because of the following:
Heavy landslides cause misery to human life. They result in a loss of lives and property and disruptions to the road transport system.
Pollution Pollution can be defined as any undesirable change in the environment due to the release of harmful substances following undesirable human activities. There are four types of pollution, namely:
Air Pollution
Air pollution from open burning Air pollution is the change in the composition of air due to the presence of pollutants (gases or particles) in high concentrations that can be harmful to life as well as to the environment
Sources of Air Pollution There are various sources of air pollution. These include:
Motor vehicles use fossil fuel which emits carbon dioxide, carbon monoxide, sulphur dioxide, dust, etc. Industries also use fossil fuel as their source of energy. Open burning produces a great amount of smoke, dust and carbon dioxide. This in turn can cause hazes and affect visibility and human health.
Effects of Air Pollution on Human Health
People wearing mask Air pollution is detrimental to human health. The continuous inhaling of polluted air can cause various ailments such as bronchitis, emphysema and cancer of the lungs and silicosis. It also affects the eyes, causing them to become irritated and leading to conjunctivitis and other problems.
Effects of Air Pollution on Buildings
Corrode building Air pollution also reacts with the structural components of buildings such as the brick works, paint and the metal components.
Effects of Air Pollution on Plants
Dying tree Air pollution also damages plants by oxidising the cellular components and enzymes of the plants. The air pollution causes the leaves to turn yellow. This process is known as chlorosis (a reduction in the amount of chlorophyll). Prolonged exposure to air pollution causes the plants to weaken, be infected by diseases and eventually, the plants die.
Effects of Air Pollution on the Climate There are various effects of air pollution on the climate such as
T h e Fo r m a t i o n o f A c i d R a i n
The formation of acid rain involves various stages. In the first stage, the large amounts of sulphur dioxide and nitrogen dioxide released from factories and vehicles combine with atmospheric water vapour/droplets. This combination produces sulphuric acid and nitric acid in the water droplets. The presence of acid in the water droplets causes the pH to drop below 5.0. The next stage is that rain is formed by these water droplets. This rain is acidic due to the presence of the sulphuric and nitric acid. Acid rain produces an adverse effect on plants and animals. It causes the destruction of the chlorophyll in the leaves. The leaves turn yellow and the plants become devoid of sufficient nutrients and eventually die. The acidic rain leads to the accumulation of minerals in rivers, lakes and ponds. This contamination causes the aquatic plants and fish to be killed. The following summarises the effects of acid rain:
Water Pollution
Water pollution Water is important to support life on earth. Without it, there will be no life on earth. Water pollution can be harmful to living organisms. The growing human population has increased the level of water pollution. The main source of water pollution is from domestic products such as sewage and detergents. Agricultural activities, such as the excessive use of fertilisers and pesticides, also contribute to water pollution. Industrial activities lead to the discharge of industrial wastes which are also causes of water pollution.
Eutrophication
Algal bloom One of the main effects of water pollution is eutrophication. Eutrophication is a process where the water in ponds or lakes becomes rich in dissolved nutrients (nitrates and phosphates) produced from fertilisers or sewage. The high concentration of dissolved nutrients promotes the growth of algae and blue green bacteria which cover up the surface of the ponds or rivers.
As a result, sunlight is prevented from reaching the algae and aquatic plants at the bottom of the water. Photosynthesis cannot take place and they die. The decomposition of dead plants by the aerobic bacteria uses more oxygen in the water and reduces its concentration. This in turn increases the biochemical oxygen demand (BOD). The BOD is an indication of the amount of dissolved oxygen in water. A lower BOD indicates that a high amount of oxygen has dissolved in the water while a higher BOD indicates that a low amount of oxygen has dissolved in the water.
The BOD for clean water is less than 1 part per million (ppm; in highly polluted water with human wastes, the BOD is between 200-400 ppm. Oil Pollution
Oil spill Oil spills also contribute to the pollution of water and can cause a major environmental disaster to aquatic life. The layer of oil on the surface of water prevents sunlight from penetrating into the water and also reduces the exchanges of oxygen from dissolving into the water. These occurrences prevent the aquatic plants from undergoing the process of photosynthesis and they will eventually die.
Oil spills also cause animal furs and feathers to be covered with the oil. As a result, the movement of the animals will be restricted and the animals will finally die. Thermal Pollution
Thermal pollution is the release of an excessive amount of heat into the environment. The pollution occurs when the used air or water in a cooling system is returned to the environment. The high temperature upsets the environment and endangers living organisms. The sources of thermal pollution are the factories, nuclear reactors, electric power stations and tall glass buildings. When factories, nuclear reactors, and electric power stations are built near rivers and lakes, the water from these rivers and lakes are used in the cooling system. The hot used water from the cooling system is returned to the rivers and lakes, causing their
water temperature to rise above the normal level. The high water temperature negatively affects the aquatic plants and animals in the rivers and lakes. Noise Pollution
drilling work Noise pollution is man-made noise that disrupts the environment. Excessive noise pollution is harmful to living organisms. The sources of noise pollution are vehicles, aeroplanes and trains, music, entertainment and drilling machines as well as noise caused by piling at construction sites.
Excessive and very loud noise can damage the ear drums as well as the cells in the inner part of the ear leading to hearing loss and deafness. The threshold of the normal sound suitable for the ear is in the range of 40-60 decibels. Sounds of higher decibels, such as the sound of a jet engine (> 125 decibels) and piling at construction sites (>100 decibels) are not suitable for the ears and should be avoided.
