Ag practices threaten climate goals: study

Research team presents an inventory of land-use contributions to carbon dioxide, methane and nitrous oxide emissions

A recently published paper in Nature says a new study at the University of California, Irvine, showed that rising emissions from agricultural land clearing and land-use practices will jeopardize climate change goals unless major changes are made.

The Paris Agreement climate change accord signed in 2015 aims to limit global warming to less than two degrees C, ideally 1.5 C, compared to pre-industrial levels.

The research team presented the most thorough inventory done to date of land-use contributions to carbon dioxide, methane, and nitrous oxide emissions from 1961 to 2017.

“Our team began working on this analysis way back in 2012 and made progress in fits and starts over the years as we tried and failed to get funding to support the work,” said senior author Steve Davis, associate professor of earth system science.

“It was a terrific postdoctoral researcher, Chaopeng Hong, who finally carried it over the finish line.”

Countries in Latin America, Southeast Asia and sub-Saharan African had the most pronounced surge in land-use emissions while East Asia, South Asia and the Middle East produced fewer greenhouse gases from land-use change. However, those regions’ agricultural emissions continued to grow as production tried to keep up with population expansion.

While more affluent countries in North America, Europe and Oceania showed negative land-use change emission, there was substantial farm-generated pollution.

“We estimated and attributed global land-use emissions among 229 countries and areas and 169 agricultural products,” said lead author Chaopeng Hong, postdoctoral scholar in Earth system science. “We looked into the processes responsible for higher or lower emissions and paid particularly close attention to trends in net CO2 emitted from changes in land use, such as converting forested land into farm acreage.”

The report stated that land-use area data of 150 food crops and 11 fibre crops harvested for each country between 1961 and 2017 were obtained from the United Nations Food and Agricultural Organization. The organization also provided details on the area of pasture in each country.

Livestock was defined by type and density. Food crops included cereals, fruits and vegetables, pulses, oil and sugar crops and spices, while seven meat and dairy products included pork, beef, buffalo, sheep and goat meat, poultry, eggs and milk.

Davis said many regions where land-use change is the major source of emissions have been working to reduce emissions and slow deforestation. Some of these efforts have had the co-operation of higher-income countries and environmental organizations.

“While the situation in low-income countries is critical, mitigation opportunities in these places are large and clear,” he said. “Improving yields on already cultivated land can avoid clearing more carbon-dense forests for cultivation of soybeans, rice, maize and palm oil, thereby drastically reducing land-use emissions.”

The authors of the report also suggest that emerging nations can lessen emission intensity of agriculture by adopting more efficient tilling and harvesting methods, better soil and livestock waste management, and by reducing food waste.

The paper highlights some promising technological solutions such as new ways of cultivating rice that create less methane and dietary supplements for cattle that reduce their harmful emissions.

They wrote that recent research has demonstrated some promising mitigation options in which rice cultivars and non-continuous rice-paddy flooding practices may achieve substantial reductions in methane while also increasing yields. In pilot studies, dietary supplements for cattle reduced methane emissions up to 95 percent.

“The report is aimed not just at individual farmers or landowners, but at decision makers in government or business who are in a position to impose new policies or better enforce those that already exist,” he said. “Our results show that emissions from clearing of new land is indeed continuing in some regions, and it is a clear priority to avoid this clearing but that isn’t to say it will be easy.”

They note that Europe has the lowest land-use emissions at 0.5 tons per person per year. The figure is substantially higher elsewhere.

“Feeding the planet may always generate substantial greenhouse gas emissions,” said Davis. “Even if we get emissions down to European levels worldwide, with expected population growth we could still be looking at more than five gigatons of land-use emissions per year in 2100, an amount at odds with ambitious international climate goals.”

While the research team has had little feedback to the report from farmers, they would welcome input.

“We need to put policies in place that support and reward farmers who are trying to reduce their emissions so that additional costs they take on do not disadvantage them in the marketplace.”

The project included researchers from the University of California, San Diego, Colorado State University, Stanford University and Germany’s Max Planck Institute for Meteorology.

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