The role of food in climate change has emerged as one of the defining challenges of our age. The journey of a steak, fruit or salad from the vast agricultural lands to the plates on our table leaves a significant footprint on the environment.
At the heart of this challenge is the extraordinary use of fertilizers and the increasing demand for meat from a growing global population.
As earth, climate and atmospheric scientists, we track global greenhouse gas emissions and have published the most comprehensive assessment to date of nitrous oxide, or N₂O, a potent greenhouse gas from food production.
After carbon dioxide and methane, N₂O is the most important greenhouse gas that humans release into the atmosphere. Although there is less N₂O in the atmosphere than carbon dioxide, it is 300 times more potent at warming the planet and remains in the atmosphere, trapping heat, for more than a century. Today, atmospheric N₂O levels are approximately 25% higher than before the Industrial Revolution and are still increasing at an increasing rate.
We found that globally the management of fertilizers and animal manure is driving the increase in N₂O emissions and its rapid accumulation in the atmosphere. This is more than a climate issue. N₂O also depletes the ozone layer, which protects people from harmful sun rays. Nitrogen runoff from fields also pollutes waterways, increases harmful algal blooms and creates oxygen-depleted dead zones.
The increase in N₂O emissions is alarming, but today people have the knowledge and many technologies to reverse this trend.
Where do N₂O emissions come from?
Before the Industrial Revolution, natural sources of N₂O from microbes living in forest soils and oceans were roughly equal to natural N₂O-consuming sinks in the air, so atmospheric concentrations of N₂O were relatively constant.
However, human population and food demand increased rapidly and this natural balance was disrupted.
We found that human activities alone have increased N₂O emissions by 40% over the past four decades, while agriculture contributes approximately 74% to total anthropogenic N₂O emissions.
The largest human sources of N₂O are agriculture, industry, and the burning of forests or agricultural waste.
Nitrogenous fertilizers, which are widely used in agriculture, are one of the biggest contributors. Fertilizers are responsible for 70% of total agricultural N₂O emissions worldwide. Animal manure from intensive animal husbandry contributes approximately 30%. A smaller but rapidly growing source is aquaculture, such as fish farming; especially in China, where it has increased twenty-fivefold in the last 40 years.
Besides farming, industrial processes such as the production of nylon, explosives and fertilizers, and the burning of fossil fuels also contribute to N₂O emissions, but to a lesser extent than agriculture.
N₂O emissions by country
Emissions vary widely from country to country for a range of social, economic, agricultural and political reasons.
Developing economies such as China and India have had a strong N₂O trend over the last four decades as they increased agricultural productivity to meet the food demand of their growing populations.
China is the largest producer and user of chemical fertilizers. The Zero Increase in Fertilizer Use Action Plan by 2020, published in 2015, helped reduce these N₂O emissions. But industrial N₂O emissions continued to increase.
In Brazil and Indonesia, clear-cutting of forests to make room for crops and livestock, combined with increasingly intensive agricultural practices, has increased nitrogen losses from natural sources and increased greenhouse gas emissions.
Africa has opportunities to increase food production without increasing nitrogen fertilization. But North African countries have more than tripled their emissions over the past two decades, mainly due to the significant increase in animal populations in Africa.
However, a few regions have managed to reduce some of their N₂O emissions through more sustainable practices.
Although the European Union, Japan and South Korea have successfully reduced anthropogenic N₂O emissions over the past 40 years, they remain major emitters globally; The declines in the 1990s were largely due to the chemical industry. Nitrogen uses in agriculture have also become more efficient; but he still has work to do. Its emissions from direct application of manure and manure have decreased slightly and have recently stabilized.
While agricultural emissions continue to rise in the U.S., industrial emissions have declined slightly, leaving overall emissions fairly steady.
How to reduce N₂O emissions?
Tackling the challenge of reducing N₂O emissions requires a combination of policy interventions, technological innovation and individual actions. For example:
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Similarly, innovations in livestock management, such as nutritional supplements and improved waste management practices, can reduce the amount of N₂O from cattle.
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Industries, particularly nylon and fertilizer production, can deploy existing, affordable technologies to reduce nearly all of their N₂O emissions. This is an easy win in terms of application and climate. Most of the world has already done this, leaving China and the US responsible for most of the remaining industrial N₂O emissions.
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Consumers can also make plant-based foods a larger portion of their diet. You don’t have to go vegan unless you want to, but reducing the frequency and portion sizes of meat and dairy consumption can be healthy for both you and the environment. Environmentally friendly practices like composting food waste and reducing fertilizer use on lawns also help.
Overall, a holistic approach combining policy, technology and individual actions is needed to address N₂O emissions and combat climate change. These strategies, where governments, industries and citizens work towards a sustainable future, can help ensure food security and environmental sustainability for future generations.
This article is republished from The Conversation, an independent, nonprofit news organization providing facts and authoritative analysis to help you understand our complex world. Written by: Hanqin Tian, Boston College; Eric Davidson, University of Maryland, Baltimore; Pep Canadall, CSIROand Rona Louise Thompson, Norwegian Air Research Institute
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Hanqin Tian receives funding from the National Science Foundation and the U.S. Department of Agriculture.
Eric Davidson has received funding from NSF, USDA, DOE, and NASA. It is affiliated with the University of Maryland Environmental Science Center and Spark Climate Solutions.
Pep Canadall receives funding from the Australian National Environmental Science Program – Climate Systems Centre.
Rona Louise Thompson receives funding from the European Commission through the Horizon Europe Programme.