Human impact on the environmentHuman impact on the environment (or anthropogenic environmental impact) refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society (as in the built environment) is causing severe effects including global warming, environmental degradation (such as ocean acidification), mass extinction and biodiversity loss, ecological crisis, and ecological collapse.
DeforestationDeforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests at present. This is one-third less than the forest cover before the expansion of agriculture, with half of that loss occurring in the last century.
2007–2008 world food price crisisThe world food price crisis refers to a period of time when the cost of food increased significantly and had a profound impact on the availability and affordability of food for people around the world. This crisis is often characterized by sharp spikes in the prices of key staple foods such as wheat, rice, and corn, as well as other agricultural commodities such as sugar and oil. The causes of the world food price crisis are complex and multifaceted, but they generally involve a combination of factors including droughts and other weather-related events, increased demand for biofuels, trade policies, and financial speculation.
Mechanised agricultureMechanised agriculture or agricultural mechanization is the use of machinery and equipment, ranging from simple and basic hand tools to more sophisticated, motorized equipment and machinery, to perform agricultural operations. In modern times, powered machinery has replaced many farm task formerly carried out by manual labour or by working animals such as oxen, horses and mules. The entire history of agriculture contains many examples of the use of tools, such as the hoe and the plough.
Population declinePopulation decline, also known as depopulation, is a reduction in a human population size. Over the long term, stretching from prehistory to the present, Earth's total human population has continued to grow; however, current projections suggest that this long-term trend of steady population growth may be coming to an end. Until the beginning of the Industrial Revolution, the global population grew very slowly, at about 0.04% per year. After about 1800, the growth rate accelerated to a peak of 2.
