Environmental impact of agriculture
The environmental impact of agriculture varies based on the wide variety of agricultural practices employed around the world.
Climate change and agriculture are interrelated processes, both of which take place on a global scale. Global warming is projected to have significant impacts on conditions affecting agriculture, including temperature, precipitation and glacial run-off. These conditions determine the carrying capacity of the biosphere to produce enough food for the human population and domesticated animals. Rising carbon dioxide levels would also have effects, both detrimental and beneficial, on crop yields. The overall effect of climate change on agriculture will depend on the balance of these effects. Assessment of the effects of global climate changes on agriculture might help to properly anticipate and adapt farming to maximize agricultural production.
At the same time, agriculture has been shown to produce significant effects on climate change, primarily through the production and release of greenhouse gases such as carbon dioxide, methane, and nitrous oxide, but also by altering the Earth's land cover, which can change its ability to absorb or reflect heat and light, thus contributing to radiative forcing. Land use change such as deforestation and desertification, together with use of fossil fuels, are the major anthropogenic sources of carbon dioxide; agriculture itself is the major contributor to increasing methane and nitrous oxide concentrations in earth's atmosphere.
One of the causes of deforestation is to clear land for pasture or crops. According to British environmentalist Norman Myers, 5% of deforestation is due to cattle ranching, 19% due to over-heavy logging, 22% due to the growing sector of palm oil plantations, and 54% due to slash-and-burn farming.
In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."
Genetic engineering has caused controversies.
Seed contamination is problematic.
- Depletion of underground aquifers through overdrafting.
- Ground subsidence.
- Underirrigation gives poor soil salinity control which leads to increased soil salinity with consequent build up of toxic salts on soil surface in areas with high evaporation. This requires either leaching to remove these salts and a method of drainage to carry the salts away.
- Overirrigation because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution.
- Deep drainage (from over-irrigation) may result in rising water tables which in some instances will lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage.
- Irrigation with saline or high-sodium water may damage soil structure owing to the formation of alkaline soil.
- Runoff causing surface water and groundwater-aquifer hydrologic cycle water pollution.
- Pesticide drift
- Pesticides, especially those based on organochloride
- Pesticide residue in foods
- Pesticide toxicity to bees
Plasticulture, the use of plastic materials in agriculture, raises problems around how to carry out the recycling of agricultural plastics.
Issues by region
- Hedgerow removal in the United Kingdom.
- Soil salinisation, especially in Australia.
- Phosphate mining in Nauru
- Methane emissions from livestock in New Zealand. See Climate change in New Zealand.
- Some environmentalists attribute the hypoxic zone in the Gulf of Mexico as being encouraged by nitrogen fertilization of the algae bloom.
The exponential population increase in recent decades has increased the practice of agricultural land conversion to meet demand for food which in turn has increased the effects on the environment. The global population is still increasing and will eventually stabilise, as some critics doubt that food production, due to lower yields from global warming, can support the global population.
- Agricultural pollution
- Agro-hydro-salinity model (for environmental impacts of irrigated agriculture)
- List of environmental issues
- Holistic management
- Livestock's Long Shadow - Environmental Issues and Options
- Report by the Food and Agriculture Organization of the United Nations
- Principles of Organic Agriculture
- Research Institute for Organic Agriculture
- Spatial agro-hydro-salinity model 9=(for environmental impacts of irrigated agriculture)
- Stock-free agriculture
- UN Report on Climate Change. Retrieved 25 June 2007.
- Hance, Jeremy (May 15, 2008). "Tropical deforestation is 'one of the worst crises since we came out of our caves'". Mongabay.com / A Place Out of Time: Tropical Rainforests and the Perils They Face.
- Alain Marcoux (August 2000). "Population and deforestation". SD Dimensions. Sustainable Development Department, Food and Agriculture Organization of the United Nations (FAO).
- ILRI, 1989, Effectiveness and Social/Environmental Impacts of Irrigation Projects: a Review. In: Annual Report 1988, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 18 - 34 . On line: 
-  Holistic Management International
- Environmental Issues in Animal Agriculture - Choices magazine article
-  Website with free articles and software on environmental impacts of irrigated agriculture like waterlogging and salinization
- Environmental Planning on Livestock and Poultry Operations describes several different planning processes that can be used on farms. It also includes links to several webcasts. Part of the Livestock and Poultry Environmental Learning Center