Determining the greenhouse gas reduction potential of regenerative agricultural practices

New Zealand’s greenhouse gas emissions are heavily influenced by agricultural activities, which account for 48% of total emissions. Most of these emissions come from methane from animals, followed by nitrous oxide emissions from soils (mostly associated with urine deposited by animals and fertilisers).

Soil and plants (particularly trees) also influence net greenhouse gas emissions through carbon capture and release. Increasing soil carbon stocks has been proposed as one way to reduce atmospheric carbon dioxide concentrations.

‚ÄúNew Zealand soils have high soil carbon compared to many other countries, but from a greenhouse gas perspective it is change in soil carbon stocks that is important,’ says Dr Paul Mudge, portfolio leader for climate change adaptation and mitigation at Manaaki Whenua – Landcare Research, and a key contributor to the report Determining the greenhouse gas reduction potential of regenerative agricultural practices.

‚ÄúThere is good evidence that changes in land use in New Zealand can increase or decrease soil carbon stocks, and research is now looking at whether specific management practices have a big impact on soil carbon stocks.’

The report examines the four main claims made about how regenerative agriculture could reduce net GHG emissions:

1. Regenerative agriculture soils are a greater sink for carbon than other agricultural soils
2. Increased plant diversity with better nutritional quality leads to a reduction of methane emissions from animals
3. Regen soils have high methanotrophic capability (methane-consuming microbes)
4. Regen soils produce less nitrous oxide

Regenerative Agriculture (RA) can potentially contribute to mitigating climate change via a reduction of greenhouse gas (GHG) emissions from agriculture and increases of soil carbon stocks. The global potential for such reductions is considerable, but the feasibility of such reductions is disputed among scientists. This report aims to give an overview of the processes known, or suspected, to achieve GHG reductions, and to describe how such contributions can be verified and quantified.

The report begins with an overview of the main facts about agricultural GHG emissions and soil carbon storage. This is followed by a section explaining the different claims for how RA can mitigate GHG emissions and the knowledge context on which each claim is based. Four main sections then discuss the practical challenges to investigating these claims and the available methods to overcome the challenges. The final section summarises the knowledge gaps and recommends priorities for future research.