Questioning the feasibility of the “4 per 1000” goal to sequester carbon in soil and slow climate change

International group of leading scientists suggest goal is unattainable in many situations, but still good for improving soil quality.

UN plans to mitigate global warming by burying atmospheric carbon in the ground to enrich soil are laudable but currently flawed, conclude a group of scientists from five international research institutes across Europe and the United States.

The experts address a goal to offset rises in atmospheric greenhouse gas concentrations by increasing the storage of carbon in soil by four parts per thousand (4P1000) per year. The goal was launched at COP21, the 21st annual Conference of Parties to review the United Nations Framework Convention on Climate Change (UNFCCC), in Paris in 2015.

“The point we are making is that the rate of carbon accumulation in soil that is suggested, 0.4% per year every year for 20 years, is almost certainly unattainable in many situations,” says David Powlson, Lawes Trust Senior Fellow at Rothamsted Research in the UK. Using data from Rothamsted's Long-term Experiments Powlson and his colleagues at the institute are already studying the feasibility of changes in land use and farming practices that achievement of the UN goal would require.

“It would therefore be unwise for policy makers to rely on this rate of carbon sequestration across the globe,” Powlson adds. “It would be best to focus on regions and situations where it can more easily be achieved. However, no-one wishes to criticise the positive and laudable aims of the initiative.”

Powlson, a leading expert in soil carbon, is co-author of the opinion paper published in Environment Science & Technology. The paper, which focuses on the role of nitrogen in trapping carbon in soil, echoes reservations among many soil scientists about the goal’s misunderstanding of basic chemistry.

“In principle, the 4P1000 goal is great,” says Jan Willem van Groenigen, professor of soil quality at Wageningen University in the Netherlands and the paper’s lead author. “Generally speaking, more carbon is good for almost any soil. If we could combine that with slowing down climate change, that would be a double win. The problem is that the numbers don’t add up.”

The soils of the world contain around three times the amount of carbon in organic matter as currently held in carbon dioxide in the atmosphere. Increasing this stock by 4 parts per thousand per year could, in theory, fully compensate the rise in atmospheric carbon dioxide. But to store more carbon in the soil, other nutrients are needed, such as nitrogen.

“You cannot build a house with a pile of bricks and no mortar,” says Kees Jan van Groenigen, senior lecturer in climate and environmental science at the University of Exeter in the UK and co-author of the paper. “Similarly, you cannot produce soil organic matter with only carbon. You need enormous amounts of nitrogen.”

Where the nitrogen would come from is unclear, he says. “For example, to store the quantity of carbon to achieve the 4P1000 goal, you would need extra nitrogen equivalent to 75% of current nitrogen fertilizer production every year, and for it to be in the right places. Practically speaking, that is just impossible.”.

Does this mean that we should abandon the 4p1000 goals? Absolutely not, says Jan Willem van Groenigen: “Let’s not throw away the baby with the bathwater. The 4P1000 goals are a great inspiration to do everything that farmers, soil scientists, agronomists and policy makers can to help fight global warming and, at the same time, improve our soils.”

In an appeal to the scientific community, he calls for more study of the role of nutrients in reaching the 4P1000 goal. “For instance, this could mean that additional soil carbon should be stored in areas where nutrients are also available. In other soils, the best approach might be to focus on minimizing emissions of other greenhouse gases, such as nitrous oxide and methane.”

The opinion paper was written by colleagues from the University of California at Davis, Northern Arizona University (USA), Wageningen University and Research Centre (Germany), University of Exeter (UK) and Rothamsted Research (UK) 

Publication

Contacts

Parasitic wasps avoid the smelly feet of ladybirds

Scientists at Rothamsted Research have identified chemicals in ladybird foot odour that are actively avoided by tiny parasitic wasps, which attack aphid pests.

Rothamsted rescues what may be Britain's rarest plant

Record numbers of a critically endangered plant have been found on the Rothamsted farm this summer.

Intelligent soil sampling saves time and money

A new computer program could revolutionise land management by making the sampling process more cost effective and ensuring more sustainable use of our soils.

How parachute spiders invade new territory

Researchers have developed a new model that explains how spiders are able to 'fly' or 'parachute' into new territory on single strands of silk.

Pages

Rothamsted Press Office

For further information, please contact:
Professor Angela Karp (comms@rothamsted.ac.uk), Tel: +44 (0) 1582 938 855

About Rothamsted Research

We are the longest running agricultural research station in the world, providing cutting-edge science and innovation for over 170 years. Our mission is to deliver the knowledge and new practices to increase crop productivity and quality and to develop environmentally sustainable solutions for food and energy production.

Our strength lies in the integrated, multidisciplinary approach to research in plant, insect and soil science.
Rothamsted Research is strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC)

About BBSRC

BBSRC invests in world-class bioscience research and training on behalf of the UK public. Our aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.

Funded by Government, BBSRC invested £473M in world-class bioscience, people and research infrastructure in 2015-16. We support research and training in universities and strategically funded institutes. BBSRC research and the people we fund are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Our investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.

More information about BBSRC, our science and our impact.
More information about BBSRC strategically funded institutes.