Research findings from two new studies show that dramatic efforts are needed to reduce the impact of greenhouse gas emissions from agriculture.

Scientists from the US have warned that the targets set under the Paris climate agreement cannot be met without an emissions reduction target for agriculture. The scientists calculated, for the first time, the extent to which agricultural emissions must be reduced to meet the new climate agreement's plan to limit warming to 2°C in 2100. They said curbing emissions from transport and energy will not deliver sufficient reductions, and that agriculture must play its part.

Scientists from the the University of Vermont and the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) have estimated that worldwide agriculture must reduce non-CO2 emissions by 1 gigaton per year by 2030. However, the research suggests the sector is currently way off the mark as far as reductions go; current interventions to reduce agriculture’s emissions are set to deliver less than half the reductions needed to meet modest emissions targets (21-40% of the mitigation required, according to the scientists).

Although 119 countries included mitigation of agricultural emissions in pledges submitted to the UN’s Framework Convention on Climate Change (UNFCCC) last year, no-one yet knows how these promises will be delivered. Lini Wollenberg, leader of the CCAFS Low Emissions Development research program, based at the University of Vermont, described the findings as “A reality check.” Wallenberg said, "Countries want to take action on agriculture, but the options currently on offer won't make the dent in emissions needed to meet the global targets agreed to in Paris. We need a much bigger menu of technical and policy solutions, with major investment to bring them to scale."

Agriculture (not including land use change) contributes an average of 35% of emissions in developing countries and 12% in developed countries today. However, scientists who worked on the paper said countries’ food needs must also be considered in work to slash farming’s emissions footprint. Professor Pete Smith from the University of Aberdeen, who also worked on the paper, said, "We need to help farmers play their part in reaching global climate goals while still feeding the world. Reducing emissions in agriculture without compromising food security is something we know how to do. A lot can already be done with existing best management practices in agriculture. The tough part is how to reduce emissions by a further two to five times and support large numbers of farmers to change their practices in the next 10 to 20 years.”

Though they said existing recommendations could shave a significant chunk off agricultural air pollution, the researchers said new technologies, extra funding and significant political will will need to be brought to bear in order to meet the targets agreed in Paris last year.

Their recommendations include.
 
For government:
more rigorous carbon pricing, taxes and subsidies that would support efforts to reduce emissions;
governments and the private sector adopting sustainability standards that include reduced emissions in agriculture;
improving the reach of technical assistance for farmers to provide locally sensitive ways of reducing emissions (which could be made easier using phones or over the internet);
Encouraging shifts towards more sustainable diets

For farmers:
Focusing more attention to sequestering soil carbon;
Increasing agroforestry,
Decreasing food loss and waste

Agriculture - biggest contributor to fine particulate pollution across much of the world

In a second study, researchers from Columbia University’s Earth Institute warned that emissions from farms outweigh all other human sources of fine-particulate air pollution in much of the United States, Europe, Russia and China. These emissions primarily come in the form of ammonia from nitrogen fertilisers and animal waste. The particulate pollution not only contributes to climate change, but also causes disease and death in humans.

Diseases related to fine particulate air pollution have been estimated to cause around 3.3 million deaths each year globally. Although their findings are alarming, the Columbia researchers said they are not new; many regional studies, especially in the United States, have shown it as a prime source of fine-particulate precursors (ammonia from farms mixes with other emissions from industrial sources to create the fine particulate matter).

According to the researchers, more than half the aerosol ingredients in much of the eastern and central United States come from farming. In Europe and China, the effect is even stronger. The aerosols form mainly downwind of farming areas, in densely populated places where farm emissions combine through a series of chemical reactions with those of cars, trucks and other sources.

The study’s lead author Susanne Bauer, ”We expect population to go up, and to produce more food, we will need more fertiliser. This is not against fertiliser. Many places [around the world] need more of it.”

Bauer added that forecast reductions in emissions from industrial sources could mean a reduction in fine particulate pollution that agriculture is driving. A study this January showed that global industrial nitrogen oxide emissions declined from 2005 to 2014, even as farm emissions boomed (though not in the fast-growing economies of China and India). This could reduce some of the deleterious health effects, but not necessarily the global warming impacts. Massive leaps in production of artificial nitrogen fertilisers are set to lead to more emissions from these sources, which have a high global warming potential (The Columbia researchers suggested Africa will see large increases in emissions, whereas Europe’s emissions will remain stagnant).

Johannes Lelieveld, lead author of a study on the health effects of particulate pollution which appeared in Nature last year disagreed with the more optimistic findings of the Columbia-NASA research. Lelieveld said, "The article underscores that all source categories should be controlled. One should be cautious about suggesting that food production could be increased [without increasing pollution].”

He said any reduction in particulate matter pollution "critically depends" on the assumption that societies will successfully curb industrial emissions. Lelieveld cited the recent scandal over Volkswagen's fraudulent auto-emissions controls, and pointed out that even with the recent reductions in industrial pollution, most nations including the United States still have large areas that exceed the World Meteorological Organization's recommended maximum of 10 micrograms of fine particulates per cubic meter.

Though they maintain that immediate human health impacts might be reduced, if industrial emissions fall as forecast, the Columbia scientists agreed that agricultural pollution raises other concerns. In addition to the atmospheric pollution the CCAFS researchers warn against in their study, the Columbia researchers said more targeted fertiliser use is a necessity as “Vast quantities” of excess fertilisers are washing off fields each year, polluting huge watersheds, contributing to huge "dead zones" like those which appear in the mouth of the Mississippi River each year.