Humans have had a profoundly adverse impact on the environment. Generally, people have not conducted activities such as manufacturing, transport, large-scale fishing, agriculture and waste disposal in moderation. This has led to degradation of land, air and water. While the full range of long-term consequences of human intervention on the environment has yet to be seen, some consequences are already taking effect, such as climate change.
Humans' failure to use land sustainably has led to its degradation. People clear forests to use the land either for agriculture or to settle on. Consequently, forest cover dwindles significantly, leading to soil erosion and extinction of plant species. Land animals have also declined in numbers, and some have even gone extinct due to human expansion that encroaches on their natural habitat and limits their ability to spread geographically.
The air has been the hardest hit element of the environment due to a variety of human activities. The transport sector contributes heavily to air pollution because most forms of transport -- including cars, planes and ocean vessels -- use one form of fossil fuel or the other, which when burned releases carbon dioxide and other gases into the environment. The manufacturing industry that grows exponentially with the expansion of the population is another source of air pollution. Manufacturing plants emit carbons and sulfurs that do not occur naturally in the environment, causing an imbalance in the quality and composition of air. Some air pollutants deplete the ozone layer and expose the Earth to dangerous radiation from the sun.
Human intervention in the environment causes water contamination and jeopardizes the supply and flow of clean, natural drinking water. Human activities such as waste disposal from residential, commercial and industrial places, oil spills and agricultural use of artificial fertilizers that contain hazardous chemical substances all contaminate water bodies. Pollutants are either directly deposited into lakes, rivers, seas and streams or hazardous substances are washed into them during the rainy seasons. The water element of the environment has also suffered from exploitation such as when humans overfish or aggressively hunt species such as sharks for their own purposes. The net effect of the contamination has been the death and reduction in diversity of marine life and scarcity of clean water.
Human activities in the environment can interfere with the planet's natural balance, making the Earth’s climate less stable and predictable. Occurrences such as unprecedented flooding; increased numbers of storms, hurricanes and typhoons; fiercer brush fires; and most notably tsunamis, which are uncommon in the Earth’s recent history, are being witnessed all across the world. Phenomena such as rising sea levels, unseasonably high temperatures and drought hint toward an environment that cannot take much more negative human intervention.