Clearly biodiversity is important in our world as it contributes to the maintenance of our health, economy and lifestyle.
Extinction is the loss of species.
Due to human influences, many new causes for a lack of biodiversity and extinction have arisen.
The main reasons for species becoming endangered or extinct are:
- Loss of habitats
- Introduction of exotic species and competition from domestic animals
- Over-harvesting by (illegal) hunting
- Pollution and global environmental change
- Natural selection
Loss of habitats
Massive destruction of natural habitats throughout the world has been brought about by agriculture, urban development, forestry, mining and environmental pollution. Marine life has also been affected. About one third of the planet’s marine fish species rely on coral reefs. At the current rate of destruction, about half of the reefs could easily be lost in the next 20 years. About half the world’s forests have been cut down by deforestation during the last 30 years for reasons such as: the world demand for timber; wood can be used as a fuel; land is needed for farming; new roads; demand for paper and packaging. As well as the reduction in biodiversity caused by the loss of habitats, forests help to maintain a balance of carbon dioxide and oxygen in the atmosphere.
Introduction of exotic species and competition from domestic animals
Many exotic species are accidentally introduced, such as certain weeds and insect pests. Others are deliberate. For example, foxes, rabbits and cats were taken to Australia aboard European ships and have since ruined Australia’s indigenous wildlife. The introduction of exotic species and development of domestic animals have caused many native species to become endangered or extinct as they cannot deal with the competition because for example, the foreign species may breed faster or have a biological advantage such as the ability to survive from a wider range of foods.
Over-harvesting by (illegal) hunting
This also includes deforestation once more, as wood is systematically cut for heating purposes or charcoal production. Many of the larger mammals such as leopards and polar bears are endangered because of man’s excessive hunting for their hide, tendons, meat, fat and flesh.
Pollution and global environmental change
The lack of care in disposal of rubbish has recently caused the death of many animals, for example, dolphins, turtle whales and penguins routinely swallow plastic bags mistaking them for food and therefore die.
PCBs are persistent organic pollutants and have been used as an insulating material in electric equipment, such as and , and also in and in . Their use has been banned or severely restricted in many countries since the 1970s and 80s because of the possible risks to human health and the environment.
An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. Oil spills affect marine life by physical contamination or by smothering or by the bioaccumulation of the toxic components of oil in animal and plant tissues.
Natural Selection
The organisms that are better adapted to their environment are more likely to survive and reproduce offspring that are successful. There is a struggle for survival (competition between animals of the same species), with only those with the best genetic advantages surviving. These individuals reproduce and pass on their successful characteristics to their offspring, giving the next generation a selective advantage. When the environment or conditions change, the features needed to survive in it changes, so natural selection is continuous process. Natural selection can also maintain variation if there is no need to change and therefore stabilises a population.
