Importance of food-demand management for climate mitigation

This new paper published in Nature Climate Change, focuses on food demand-side climate change mitigation options. It suggests that if current trends continue, food production alone will reach (if not exceed) the global targets for total greenhouse gas emissions in 2050. Diet preferences are shifting globally toward meat-heavy western foods with a high GHG-impact and this, combined with a growing global population, imply that even if we manage to increase agricultural yields (through for example sustainable intensification), this will not be enough to meet projected food demands.

Shifting to healthier diets across the world and reducing food waste are therefore important parts of a combination of solutions needed to ensure food security and avoid dangerous climate the researchers argue.  

The researchers estimate that greenhouse gases from food production increase by 80% if meat and dairy consumption continues to rise at its current rate. To mitigate this, the authors urge people to limit their meat consumption to two 85g portions of red meat and five eggs per week, as well as a portion of poultry a day. [nb – it does not quantify milk and dairy]. Lead researcher Bojana Bajželj from University of Cambridge state in a BBC interview that:

“The average efficiency of livestock converting plant feed to meat is less than 3%, and as we eat more meat, more arable cultivation is turned over to producing feedstock for animals that provide meat for humans. /…/ The losses at each stage are large, and as humans globally eat more and more meat, conversion from plants to food becomes less and less efficient, driving agricultural expansion and releasing more greenhouse gases. Agricultural practices are not necessarily at fault here - but our choice of food is”.

The paper in more detail:

The paper models six core scenarios (see Table 1) which explore different combinations of yield increases and demand side measures (shifting diets and reducing waste).  Current Trends (CT) scenarios assume yields in each region will continue to increase at current rates. The Yield Gap (YG) scenarios assume that sustainable intensification will achieve yield gap closures in all regions. Both yield scenarios are set against three different options on the demand-side: (1) no changes to the system, (2) a 50% reduction in food and agricultural waste and (3) waste reduction as above plus a move towards healthy diets, meaning the average consumption of sugar, oil, meat and dairy is limited according to expert health recommendations.

Seven indicators are used to measure environmental impact: cropland area, pasture area, net forest area, tropical pristine forests, irrigation use, GHG emissions, fertiliser use.  As can be seen from Table 2 scenario YG3 0 – with a combination of sustainable intensification, food waste reductions and a shift towards healthier diets, overall emissions can be reduced by around 48%, and the use of land and impacts on forest/pristine forest cover are less than for any of the other scenarios.

Under  a sustainable intensification scenario (without any demand side measures), cropland would still need to expand by ~5%, pasture by 15%, and GHG emissions would increase by ~42% compared with current levels, even with currently-attainable yields being achieved world-wide.

 

This figure below shows the impact on GHG emissions under each of the 6 scenarios: under the CT1 (business as usual) agriculture accounts for almost all the ‘allowable’ emissions if we are to stick to a target of increasing global temperatures by no more than 2˚C.

Abstract

Recent studies show that current trends in yield improvement will not be sufficient to meet projected global food demand in 2050, and suggest that a further expansion of agricultural area will be required. However, agriculture is the main driver of losses of biodiversity and a major contributor to climate change and pollution, and so further expansion is undesirable. The usual proposed alternative—intensification with increased resource use—also has negative effects. It is therefore imperative to find ways to achieve global food security without expanding crop or pastureland and without increasing greenhouse gas emissions. Some authors have emphasized a role for sustainable intensification in closing global ‘yield gaps’ between the currently realized and potentially achievable yields. However, in this paper we use a transparent, data-driven model, to show that even if yield gaps are closed, the projected demand will drive further agricultural expansion. There are, however, options for reduction on the demand side that are rarely considered. In the second part of this paper we quantify the potential for demand-side mitigation options, and show that improved diets and decreases in food waste are essential to deliver emissions reductions, and to provide global food security in 2050.

Citation

Bajželj, B., Richards, K. S., Allwood, J. M., Smith, P., Dennis, J. S., Curmi, E., Gilligan, C. A., 2014, Importance of food-demand management for climate mitigation, Nature Climate Change doi:10.1038/nclimate2353

You can read the full paper here. You can find further coverage of the story from BBC here, from Cambridge University here and finally University of Aberdeen here.

There are a huge number of studies on dietary shift and GHGs on the FCRN website – some are top down global assessments and adopt a bottom up LCA approach.  See for example:

Exploring dietary guidelines based on ecological and nutritional values: A comparison of six dietary patterns

How Low Can We Go - GHG emissions from UK food system reduction by 2050

Climate benefits of changing diet

Study: health and GHG implications of reduced red and processed meat consumption in the UK

Environmental Impacts of Dietary Recommendations and Dietary Styles: Germany as an example   

Paper argues optimized livestock diets could reduce emissions 23 percent by 2030 – FCRN summarizes and comments on their approach and findings

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