Habitat loss  Agriculture  Pollution  Development  Transportation  War

Agriculture has wiped out entire ecosystems at one time. There are many types of agriculture e.g. slash-and-burn agriculture and grazing of domestic animals.

Slash-and-burn agriculture has caused many man-made disasters in the past and Indonesia is no exception. In 1998, a man-made disaster occurred over vast areas of the Indonesian islands of Sumatra and Kalimantan(Borneo), when fire spread a haze of death and destruction over Indonesia. Malayasia, Singapore, Thailand and the Phillipines were also affected. The fires and the smoke caused hundreds of human deaths and untold destruction to the natural flora and fauna in the region.

The distribution of wildlife has also been affected by agriculture. Once California(U.S.A) had many animals living in the Central Valley, but it has now been converted into the most pesticide-soaked agricultural region in the United States.

Areas where populations are exploding rapidly such as Kenya, have increasing problems. It's population level is increasing by 4% per year. This is putting increasing pressure on marginal and submarginal land for use as grazing and cultivation areas. The sad part is that this land is currently occupied by game parks which is now severely threatened.

Desertification

Overgrazing caused by agricultural expansion has caused desertification. This process is occuring at an alarming rate, as 6% of Earth's ice-free surface is currently desert and another 28% is currently undergoing the process of desertification. An area twice the size of Belguim, is converted. The problems caused by desertification include declining of rainfall, dominance of undesirable plant species and erosion. In addition, agricultural activities require water to be piped from other areas, effectively causing the drying up of streams and rivers by damming and rechanelling. This also affects the terrestrial and aquatic systems.

Pesticides

The use of insecticides and herbicides has had an enormous effect on wildlife. The two main problems are that wildlife leaves the areas that are sprayed and the poison threatens countless numbers of species.

The danger with pesticides is that very few decomposers produce enzymes that can breakdown the synthetic molecules of the pesticides. Most noted of these materials are the chlorinated (or halogenated) hydrocarbons, such as dichloro-diphenyl-trichloro-ethane (DDT) and its products (DDD and DDE) of slow, spontaneous, partial decomposition. Since World War II (1939 - 1945), vast quantities of these materials have been applied to forests and farmlands, either a dust or in sprays with an oil base. Something that is almost as bad is the polychlorinated biphenyls (PCB's) that have been discharged into streams. Laws were passed in many states and nations forbidding the use of chlorinated hydrocarbons except in emergencies. But the manufacture continued for sale to undeveloped countries - as it was not realised that it did not matter where the poison was injected into the atmosphere.

DDT and its related compounds penetrate the integument(outer layer) of any insect that it comes into contact with. It destroys natural predators and parasites, which would otherwise help control the pest and this upsets many food chains which are unrelated to the original pest.