Scientists Say Focus on Farming Emissions Required to Reach Climate Goals

The colored arrows represent nitrous oxide fluxes. Yellow arrows indicate anthropogenic, or human-caused, emissions. Green arrows show natural sources’ nitrogen contributions. Blue arrows indicate how much nitrogen is naturally removed from the atmosphere by sinks. (Photo credit: Modified from Tian et al. 2020, Nature; Global Carbon Project and International Nitrogen Initiative)

(CN) — The world may not meet widely agreed upon goals for fighting climate change because of the use of nitrogen fertilizer in the food production industry, according to a study released Wednesday.

Nitrous oxide, like other greenhouse gases, traps heat in the atmosphere by absorbing the sun’s radiation. It typically persists for about 114 years in the atmosphere, and is much more potent than carbon dioxide. Over 100 years, one pound of nitrous oxide can warm the atmosphere about 300 times more than an equivalent amount of carbon dioxide will.

Research conducted by an international team of 57 scientists, whose findings were published Wednesday in Nature, indicates that atmospheric nitrous oxide has climbed 20% from pre-industrial levels, and that its growth is accelerating.

In 1750, according to the researchers, nitrous oxide accounted for 270 parts per billion, an atmospheric concentration that grew to 331 ppb by 2018.

This is a swifter growth than any other greenhouse gas’ emissions and may mean that even the highest projected warming scenarios are underestimating the impact that rising N2O emissions will have on global average temperatures.

“The dominant driver of the increase in atmospheric nitrous oxide comes from agriculture, and the growing demand for food and feed for animals will further increase global nitrous oxide emissions,” Hanqin Tian, lead author of the study and a climate scientist at Auburn University, said in a statement. “There is a conflict between the way we are feeding people and stabilizing the climate.”

A farmer harvests soybeans in a field near Concordia, Mo. (AP Photo/Charlie Riedel, File)

Nearly three-quarters of the United States’ N2O emissions originate from agricultural soil management, including the use of fertilizer, whose introduction in the 1960s alongside pesticides sparked a “Green Revolution” that brought with it rising crop and livestock yields as well as expanding emissions.

The lion’s share of these emissions originate from East Asia, South Asia, Africa and South America. The dozens of scientists — representing 14 nations and 48 research institutions — say that China, India and the U.S. primarily pollute via synthetic fertilizers, while the use of livestock manure accounts for most of the emissions from Africa and South America.

“Current emissions are tracking global temperature increases above 3°C [37.4°F], twice the temperature target of the Paris Agreement,” Stanford University climate scientist and study co-author Robert Jackson said in a statement.

The Paris Agreement, an international agreement signed by nearly every member of the United Nations in 2016, set ambitious goals for world governments that sought to pull humanity from the brink of runaway climate change. The agreement asks world governments to coordinate to keep the Earth from reaching global mean temperatures at 2°C above pre-industrial levels, or 35.6°F.

Former President Barack Obama signed the climate accord in April 2016, but President Trump withdrew the United States from the agreement last November, claiming it was “draconian” and “unfair” to the U.S., the nation responsible for more carbon dioxide emissions than any other country between 1850 and 2014.

Though carbon emissions from manufacturing, energy production, logistics and transportation dominate the climate change discourse in the U.S., the scientists warn that a myopic focus on CO2 will make reversing global warming more difficult.

Carbon dioxide, the globe’s most concentrated greenhouse gas, is produced when hydrocarbon fuels such as coal, natural gas, oil and wood are burned. The second-most prevalent greenhouse pollutant is methane, mostly emitted by cattle livestock and rice paddies’ natural fermentation.

“Failure to include N2O within climate mitigation strategies will necessitate even greater abatement of CO2 and methane,” the authors write in the report. “Although N2O mitigation is difficult because nitrogen is the key limiting nutrient in agricultural production, this study demonstrates that effective mitigation actions have reduced emissions in some regions — such as Europe — through technological improvements in industry and improved efficiency of nitrogen use in agriculture.”

The scientists said that Europe’s nylon manufacturers voluntarily removed nitrous oxide from their production processes and added that the European Union’s emissions trading scheme successfully mitigated the continent’s emissions.

Study co-author Wilfried Winiwarter, a senior researcher at the International Institute for Applied Systems Analysis’ Air Quality and Greenhouse Gases Program, said that not all hope is lost.

“Europe is the only region in the world that has successfully reduced nitrous oxide emissions over the past two decades,” Winiwarter said in a statement. “Industrial and agricultural policies to reduce greenhouse gases and air pollution and to optimize fertilizer use efficiencies have proven to be effective. Still, further efforts will be required, in Europe as well as globally.”

The study recommends farmers reduce excess use of nitrogen in their crops and use more precise and efficient methods of applying fertilizer.

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