February 1, 2022

expert reaction to modelling study of animal agriculture and greenhouse gas emissions

A modelling study, published in PLOS Climate, has looked at animal agriculture and greenhouse gas emissions.

Dr Jem Woods, Reader in Sustainable Development at the Grantham Institute – Climate Change and the Environment, said:

“This is one of a number of high profile papers that have considered the GHG emissions from the global food system alongside the potential for changing diets to mitigate those emissions. These articles generally estimate that the global food system contributes between a quarter to a third of total greenhouse gas emissions and also highlight the high share of those emissions caused by meat and dairy consumption (Poore & Nemecek, 2018; IPCC Special Report on Land and Climate Change, 2019).  It is therefore a logical and legitimate question to ask how changing diets might impact on future emissions and highlight the potential co-benefits of changing diets at a global level to mitigate climate change and improve health by reducing non-communicable diseases.

“This seems like an extremely ambitious timeline and would need to be supported by substantive behavioural change analysis that is able to account for geographic and cultural differences in diets. I do not believe that yet sufficient scientific evidence that the rates and scales of behaviour change in dietary preference are feasible.”

Prof Dominic Moran, Professor of Agricultural and Resource Economics at the Global Academy of Agriculture and Food Security, said:

“The analysis is robust, but the scenario is extreme and implausible and not helpful in policy terms since parts of the world are unlikely to make the transition that is required.  There are good (livelihood) reasons for this in low-income countries with limited economic alternatives.  There are also likely to be significant ecosystem effects (positive and negative) from removing livestock in extensive grazing systems where they have a positive role in the ecosystem.

“The scenario is unfeasible – there is no plausible economic model that would do this in 15 years – unless by prohibition or a swingeing emissions tax or permit system.

“Some lands unsuitable for cropping can be used for extensive grazing with the possibility of these systems being net zero depending on use of grass types and possible animal genetic modification (plus in some cases waste management).  We need more exploration of these first.

“This sort of analysis always has some value in providing orders of magnitude within which the debate can take place.  We already know (e.g. from sixth carbon budget report by the Climate Change Committee) that the ag/livestock contribution to emissions mitigation needs to be ramped up.  The real question now is, how low can we get emissions and by what policy instruments – sermons, carrots or sticks?  My money is on introducing graduated carbon pricing into the sector.”

Prof Toby Mottram, Digital Agritechnology Ltd and formerly of Royal Agricultural College, said:

“The model does not consider the viability – in terms of geographic, cultural and nutritional constraints – of switching to plant-based agriculture worldwide, and some regions, such as the drylands of sub-Saharan Africa, may be unsuitable for culturing crops. Also, the analysis focuses on terrestrial agriculture, excluding aquaculture and fishing.

“Change the assumptions and the whole thing falls to pieces.  Meat consumption is rising globally as is healthy child growth and development, those two are linked.  Denying the reluctant vegetarians the opportunity to gain the benefits of eating meat products would be immoral just as their incomes are rising to enable them to afford it.  A reduction in meat consumption would certainly help some people’s health parameters but those who eat least benefit most from high quality animal proteins.  One could add a lot of other areas than sub-Saharan Africa that are not suitable for growing crops. 

“The big problem the promoters of alternative proteins face is that the production cost of cultured meat needs an animal plasma feed stock and pharmaceutical grade processing and no-one can has yet scaled up to bring the cost down to anything like the cost of poultry and other meat products.  Replacing rotational regenerative farming with monocultures of soya and palm oil grown to provide feedstock for the alt-protein market would lead to further nitrogen pollution and soil degradation/erosion.  The land needs animals as part of a balanced soil management strategy and we might as well eat the product.

“The real problems lie in aviation, concrete production, road transport, coal mining etc. which contribute 85% of the anthropogenic GHGs – not livestock, or sentient farmed creatures as we prefer to call them.”

Prof Heiko Balzter, leader of the UKRI Landscape Decisions Programme and University of Leicester, said:

“Eating less meat is good for the climate. Switching to an entirely plant-based diet is certain to have a huge beneficial effect on stabilising the global climate. However, it is an extreme scenario that raises many questions as well. For example, what would happen to biodiversity if grazing was stopped entirely? How would people’s diets change – would everyone have access to a balanced supply of foodstuffs? And how would organic agriculture work without manure as fertilizer?

“I see this study as an important contribution to the debate about how we can prevent catastrophic climate change, but it should be read as a scenario taken to the extreme. We need a holistic systems approach to decide how we can reduce our greenhouse gas footprint.”

Dr Mike Rivington, senior scientist at the James Hutton Institute, said:

“The research takes a simplified overview approach to the issue of greenhouse gas emissions from the livestock sector, but adequately demonstrates the large potential for reducing climate change risks by moving to a plant-based diet, by both reducing the levels of methane and nitrous oxide emissions from livestock systems, and in capturing carbon through the restoration of land cleared for animal production.

“This presents a ‘win-win’ overall opportunity to fight climate change, but will require substantial behavioural change by consumers. A rapid phase-out over 15 years is feasible but will need care in how transition to a plant-based diet is achieved to avoid excess negative consequences on rural communities based on livestock systems. There are also likely to be associated human health benefits from a reduction in highly processed meat consumption.”

Dr Jonathan Foot, Head of Environment at the Agriculture and Horticulture Development Board, said,

“Overlooking its distinct lack of independence, as a study conducted by the CEO of a leading plant-based company, the report is yet another flawed modelling study using scaled up global emissions. With oversimplified assumptions to draw unrealistic conclusions about the impact of removing livestock from food production.

“Failure to consider whether such a move would produce enough food for a growing global population, or the socioeconomic impact on developing countries is a grossly significant omission. Not to mention the impact on global soil health and nutrition, and our realistic ability to increase global crop lands, considering the effects of climate change such as increasing temperatures, floods, and drought.

“Livestock and crop production are intrinsically linked, removing one greatly impacts the productivity of the other. Regionality is key when assessing sustainability, as many areas of the globe are very well suited to livestock production, thanks to ideal temperatures, plentiful rain, and grass. The marriage between well managed grasslands and grazing livestock can and does provide highly sustainable food production, like we see here in the UK.”

‘Rapid global phaseout of animal agriculture has the potential to stabilize greenhouse gas levels for 30 years and offset 68 percent of CO2 emissions this century’ by Michael B. Eisen and Patrick O. Brown was published in PLOS Climate at 7pm UK TIME on Tuesday 1 February 2022.

DOI: https://doi.org/10.1371/journal.pclm.0000010

Declared interests

None received.