The Challenge of Feeding the World Sustainably Summary of the US-UK Scientific Forum on Sustainable Agriculture (2021) / Chapter Skim
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2 Agriculture's Impacts on Biodiversity, the Environment, and Climate
2 Agriculture's Impacts on Biodiversity, the Environment, and Climate
Pages 8-17
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From page 8... ...
2019. Climate Change and Land: An IPCC Special Report on Climate Change, Desertification, Land Degradation, Sustainable Land Management, Food Security, and Greenhouse Gas Fluxes in Terrestrial Ecosystems.
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From page 9... ...
Even if all non-agricultural fossil fuel use was to stop, future greenhouse gas emissions solely from agriculture because of land clearing, ruminants, manure, rice, burning, and nitrous oxide from fertilized soils would, in total, accumulate so as to exceed the emissions limit set by the Paris Agreement for staying below a 2o Celsius global temperature increase. 3 Challenges from climate change are often multiple and linked, like drought and saltwater intrusion for farmers, or losses due to insect pests in a warming climate.
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From page 10... ...
.4 This has resulted in large increases of nitrogen in the environment, including nitrates in groundwater, runoff into rivers and coastal areas, and increases in the level of nitrogen oxides and nitrous oxide in the atmosphere. Nitrogen oxides and ammonium contribute to air pollution, with an estimated 19,000 people dying prematurely every year in the United States because of particulate matter caused by these and other agricultural emissions.
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From page 11... ...
Longer growing seasons and warmer winters will lead to more mineralization of nitrogen by microorganisms from insoluble organic forms to soluble and biologically available forms. Where fertilization rates exceed what crops need, the emissions of nitrous oxide into the atmosphere from unused nitrogen increase.8 For example, when growing switchgrass for biofuels, the production of nitrous oxide from excess fertilizer application could halve the climate benefits.9 Tailoring fertilizer rate to crop type and productivity could help avoid such losses.10 For example, crop yield maps can reveal areas within fields that routinely have lower productivity than other areas.
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From page 12... ...
By averaging across crop yields, greater crop diversity increases the year-to-year stability of national yields and the reliability of food production. Box 2-1 looks at some of the issues involved in protecting biodiversity while maintaining agricultural yields.
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From page 13... ...
These numbers are typically difficult to measure, but work in southern Ghana and northern India has provided useful data.b In both areas, many species of birds and trees decline in numbers when the land is used for agriculture, but these losses were reduced, compared with land sharing, under high-yield production combined with land sparing. Similar work in other parts of the world has arrived at similar conclusions.c In many cases, an even better approach is to designate some land for lowyield farming that is tailored to meet the needs of particular species.d High-yield farming can have many negative consequences, such as an increased use of pesticides, greater fertilizer runoff, soil degradation, and so on.
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From page 14... ...
The Current Trajectory As global population and per capita incomes continue to grow, demand for food will increase.17 Growing more crops for consumption by both people and livestock will require increasing yields on existing land or converting more wildland to cropland. Increasing yields on existing land implies decreasing the gaps between how much a given area of land is capable of producing and how much it produces today, which in the past has usually entailed increasing the use of fertilizer, irrigations, new kinds of cultivars, and other inputs to agriculture.
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From page 15... ...
At the same time, prices for major commodities like corn, soybeans, and wheat in the United States have dropped to historical lows. While these low prices benefit consumers, the lack of revenue flowing to farmers is a major reason why farmers in these countries and elsewhere rely heavily on subsidies, while conservation receives substantially less governmental support.
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From page 16... ...
The 2009 Royal Society report Reaping the Benefits: Science and the Sustainable Intensification of Global Agriculture, adapting an earlier analysis,23 defined sustainability as having four attributes:24 1. ersistence: the capacity to continue to deliver desired outputs over long periods of time P (human generations)
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From page 17... ...
Given the already substantial effects of agriculture on biodiversity and the environment, such a future is not sustainable. FIGURE 2-3 Under a business-as-usual scenario, land devoted to crops is projected to expand in many parts of the world, causing increased land clearing, greenhouse gas emissions, and extinctions.
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