BIOLOGICAL OXYGEN DEMAND
If untreated sewage is discharged into fresh water, it will be decomposed by bacteria in the water. These will multiply rapidly and use up all the oxygen present, so that fish and other animals will die. Biological oxygen demand (BOD) means the demand for oxygen created by the presence of organic material in water. Untreated sewage has a high BOD because it is rich in organic material. The organic waste from intensive farming, e.g. high density pig units, can be so concentrated that it overwhelms the capacity of sewage works, leading to effluent with high BOD.
EUTROPHICATION
This is the appearance of rich growths of algae, called algal blooms, which form on the surface of water. It can be caused by the presence of excess nitrates from neighboring over-fertilized fields, and phosphates from detergents. When these masses of algae die, they also create a high BOD and may cause the death of fish. [Read more...]
What are the effects of Water Pollution?
What are the Effects of Air and Land Pollution?
Pollution is the harm caused to the biosphere, i.e. life on earth, by waste substances or other side-effects of human activity. This includes noise as well as carbon dioxide and radioactive discharges. [Read more...]
Consequences of uncontrolled Population Growth
FOOD SHORTAGES
Food shortages lead to malnutrition and starvation. Malnutrition means under-feeding, i.e. receiving a diet lacking sufficient energy or other essentials such as vitamins or protein. Starvation means death from lack of food.
OVERCROWDING
Overcrowding leads to an increase in disease, crime, vandalism, drug-taking, etc.
COMPETITION FOR LAND
Competition for land causes increased possibilities of wars and disturbances.
DEFORESTATION
Deforestation as trees are cut down for fuel and to provide more space for agriculture leads to: [Read more...]
Population and the Development of Agriculture
The number of people in the world grew steadily from about 6000 BC until about 1800 AD, chiefly due to slow improvements in agriculture. In earliest times, human beings lived by hunting and gathering the available food over a large area, as the Bushmen and Inuit (Eskimos) still do in a few cases. The development of settled agriculture made larger populations possible. [Read more...]
