A species becomes extinct or endangered because of any one or a combination of five human activities:
- Over-harvesting
- Introduction of Invasive species
- Loss of habitat
- Islandisation
- Pollution
Over harvesting:
Over harvesting refers to the hunting of a species in a sustained manner beyond the natural regenerative capacity of the species. A recent case in point is the hunting of the Houbara bustard, a desert bird by the Arab royalty and sheiks. They believe that the bird is a aphrodisiac. The bird population has really declined alarmingly. A team of researchers found that, from 1998 to 2001, Houbara numbers dropped 63% in China, 60% in Kazakhstan, and 50% in Oman.
Introduction of Invasive species:
Some species of birds and animals become endangered and eventually become extinct when humans unintentionally introduce invasive species in their habitats. Island birds are particularly prone to this problem. After living and thriving on Islands without any natural enemies, some species of birds loose their capacity of flight. Over thousands of years, they also loose their fear of predators. Most of them nest in conspicuous locations. When humans arrive on the island, they unintentionally introduces mammals like mice, cats, monkeys and dogs. These animals hunt these defenceless birds and consume their eggs in such great numbers that after a point, it becomes difficult to save a species from brink of extinction. The dodos of Mauritius, the Moas & Kheas of Newzealand are all cases in point.
Loss of Habitat:
Most birds are dependant on the environment for their sustenance either for their food, finding mates, building of their nests and raising of their young. When the environment is disturbed in some manner, birds become threated as a consequence. In the recent years, many of the wetlands have been destroyed to make way for construction projects. Many forests have been felled to make way for agricultural lands. The great Indian bustard is endangered because of the decline in the extent of grasslands. It is also the case with Indian courser.
Islandisation:
This refers to the creation of islands or pockets of forests, wetlands in previously continuous stretches of habitats. Creating Islands is a big threat to birds because the populations become increasingly isolated from one another and in a drought year, one population can get completely destroyed in one area without being replenished from another. A simple act of laying a road across a forest can serve to create islands. Ant-eaters in Brazil used to flying in the dark canopy do not cross over to the other side of the road and become increasingly isolated.
Pollution:
Many water bodies become the dumping ground for construction debris. The water bodies are also places where sewage water is let into. Many industries use rivers and lakes to dump their waste chemicals. These chemicals are extremely toxic to all forms of life and kills the fish, amphibians and other aquatic species. They also poison the birds which depend on the aquatic life for food. On a much larger scale, human activity causes global warming which increases the global temperatures that change some environments to such an extant that many species including plants shift their locations to a temperature zone that they are accustomed to and with it the birds. Sometimes it becomes difficult or impossible for forests to advance because of the cities, villages and towns which infringe upon them.
