Download Share Sources: Photo: Aidenvironment. In , forestry and other land use comprised about 10 percent of global emissions. Remaining land suitable for cropland or pasture lies mostly in tropical biomes—about three quarters of tropical forests, woodlands, and savannas are suitable. Forests are often cleared to meet local food needs for smallholder farmers, but demand for global commodities like oil palm and soybeans is becoming the dominant driver.
Today, emissions from raising livestock and growing crops are the dominant driver of agricultural emissions. Fossil fuel use, including transport, is responsible for only about 10 percent of total agricultural emissions. Since , emissions from farming practices have increased by about 1 percent each year, while emissions from deforestation and other land uses related to agriculture declined.
Agricultural emissions from deforestation, while still very large, have dipped slightly over the period, and comprise a smaller share of total emissions over time.
Download Share Source: 6. Dominant sources of agricultural greenhouse gases GHGs include carbon dioxide CO 2 from tropical deforestation, methane CH 4 from livestock and rice production, and nitrous oxide N 2 O from fertilizing or burning croplands. Agriculture is responsible for about half of global methane emissions. Ruminant livestock, including cows and sheep, digest their food through enteric fermentation, which produces methane.
Burning biomass to prepare fields is another methane-maker, as is applying manure to fields. Another major methane source? Rice grown in paddies, where bacteria break down biomass submerged in the fields. Methane emissions from irrigated rice fields account for about 11 percent of emissions from agricultural management.
Sixty percent of all anthropogenic N 2 O emissions are from agriculture. Nitrous oxide emitted into the atmosphere is a major GHG because it is times more effective at warming than CO 2.
Most N 2 O is produced after croplands are fertilized, when soil microbes convert some of the applied nitrogen from fertilizer and manure into N 2 O.
Due to a non-linear relationship between application and emissions, as more nitrogen fertilizer is applied, a greater fraction of the applied nitrogen is converted to N 2 O. Nitrous oxide is also produced when crop residues are burned.
Because tropical forests and grasslands are dense with trees and plants, clearing them releases much more carbon than in temperate areas. At the same time, tropical croplands tend to be less productive than their temperate counterparts. In fact, newly cleared tropical cropland releases about three times more carbon per ton of crops produced than similar cropland in temperate parts of the world.
While non-agricultural emissions of tropical countries account for just 14 percent of global GHGs, when emissions from deforestation are included, the emissions add up to a third 31 percent of the global total. Today, most countries in predominantly temperate areas, including the U. Native forests on suitable land for farming were cleared long ago.
However, wealthier countries contribute to land clearing indirectly, as their demand for crops or livestock often drive deforestation in poorer countries. Photo: John Haslam. Between and , about half of tropical deforestation occurred in just two countries. Brazil accounted for 34 percent of tropical deforestation, mainly due to producing timber, cattle, and soybeans. Indonesia accounted for 17 percent of tropical forest loss, mostly driven by the expansion of oil palm and wood plantations.
Emissions from agricultural management are similarly concentrated in just a few places. More than half the nitrous oxide from croplands comes from three countries: China 31 percent , India 11 percent , and the U. Similarly, producing just three crops—wheat, maize, and rice— accounts for roughly half of global N 2 O emissions from agriculture.
Finally, nearly two thirds of methane emissions from rice cultivation are from China 29 percent and India 24 percent. While different strategies are appropriate to particular world regions, some promise higher mitigation of agricultural GHGs. Practices that intensify production on existing pasture and croplands have the highest potential because they avoid deforestation.
Download Share Source: Not including fisheries, the global potential is estimated to be about 7. In general, mitigation means sustainable intensification, or producing more food on global croplands and pastures that have already been cleared, with less emissions.
Right now, the scope for intensifying production on existing croplands is promising. First, in both developing and developed countries, there are significant cropland areas where the current yield is well below the attainable crop yield for that climate zone.
The excess levels of nitrogen and phosphorus have caused the once-beneficial nutrients to become pollutants. Roughly half the nitrogen in synthetic fertilizers escapes from the fields where it is applied, finding its way into the soil, air, water, and rainfall. After soil bacteria convert fertilizer nitrogen into nitrates, rainstorms or irrigation systems carry these toxins into groundwater and river systems. Accumulated nitrogen and phosphorus harm terrestrial and aquatic ecosystems by loading them with too many nutrients, a process known as eutrophication.
Nutrient pollution is a causal factor in toxic algae blooms affecting lakes in China, the United States, and elsewhere. Parts of the Gulf of Mexico are regularly afflicted in this manner. Nitrogen accumulation in water and on land threatens biodiversity and the health of native plant species and natural habitats. In addition, fertilizer application in soil leads to the formation and release of nitrous oxide, one of the most harmful greenhouse gases.
With the global population continuing to skyrocket, the tension will continue to grow between continued agricultural growth and the ecological health of the land upon which humans depend. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. National Geographic Society.
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Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. For thousands of years, humans have modified the physical environment by clearing land for agriculture or damming streams to store and divert water. As we industrialized, we built factories and power plants.
For example, when a dam is built, less water flows downstream. This impacts the communities and wildlife located downstream who might depend on that water.
Use these resources to teach your students how humans modify the physical environment and the compounding impacts those changes have. To irrigate is to water crops by bringing in water from pipes, canals, sprinklers, or other man-made means, rather than relying on rainfall alone.
Agriculture is the art and science of cultivating the soil, growing crops and raising livestock. Encyclopedic entry. To address these long-standing issues, more effort and co-operation is needed between farmers, policymakers, and the agro-food value chain. In addition, the twin policy challenge of ensuring global food security for a growing population while improving environmental performance will require raising the environmental and resource productivity of agriculture, enhancing land management practices, minimising pollution discharges, curtailing damage to biodiversity, and strengthening policies that avoid the use of production and input subsidies which tend to damage the environment.
To help countries improve the sustainability of agriculture, the OECD has developed recommendations on how to develop cost-effective agri-environmental policies , how to manage water issues for agriculture , how to deal with climate change challenges , and how to preserve biodiversity and manage ecosystem services related to agriculture. We have also developed insights on the potential environmental impact of agriculture policies by identifying possible policy mis-alignments and how to jointly address sustainability and productivity growth goals.
To support this work and help governments assess whether the policies they have in place are most likely to boost productivity and minimise environmental damage, the OECD developed a set of agri-environmental indicators AEIs More specifically, the AEI database can be used to:. The AEIs are freely available to access and download — you can either query the complete database , or explore a specific theme or country below. New data spanning two decades shows that while most OECD countries increased their agricultural production, the environmental performance of the sector has seen mixed results.
Read more Access the complete database , or browse by theme:.
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