This piece discusses the findings of a recent paper by de Ruiter and colleagues, Global cropland and greenhouse gas impacts of UK food supply are increasingly located overseas. The full abstract and citation are provided below.
This post is written by FCRN member Henri de Ruiter. Henri is a PhD Student at the University of Aberdeen and the James Hutton Institute. Henri graduated with a Master’s degree in Environmental Sciences from the University of Groningen, The Netherlands. He also holds a Bachelor’s degree in Behavioural and Neurosciences from the University of Groningen. His current PhD project considers the implications of meeting a healthy and environmentally sustainable diet for future land use.
Henri would welcome your thoughts on the paper. Add a comment in the field below this blog-post, but note that you need to be signed in as a member to write a comment.
The United Kingdom (UK) is increasingly dependent on external resources to meet its demand for food, and is outsourcing its environmental impact to other countries by importing more food. That is the main conclusion of our recently published paper in the Journal of the Royal Society Interface.
The aim of our study was to better understand the environmental consequences of a globalised food system. The magnitude of agricultural trade is very significant and growing: about a quarter of all food is traded internationally [1] and more than 20% of all global cropland area is used to produce exports [2]. While global studies give a good indication of the extent of agricultural trade and its environmental consequences, analysing a single country and a specific activity, i.e. food consumption, highlights the global effects arising from a nation’s consumption, and could inform policy-making. Therefore, we analysed the food supply of the UK and its consequences for two environmental indicators: the global cropland footprint and associated greenhouse gas emissions, for the period 1986 – 2009.
UK increasingly dependent on croplands overseas
Our analysis shows three major trends. Firstly, the UK is increasingly dependent on food imports and is currently importing almost half of its crops for feed and food, compared with 36% in 1987. It is important to note that we have only considered crops for food and feed in our analysis. We have not directly analysed the imports and exports of livestock products, such as meat and milk. Our estimate of self-sufficiency might therefore be lower than other self-sufficiency figures for the UK because the UK is generally more self-sufficient for animal products than it is for crops.
Secondly, the associated cropland footprint of the UK crop supply grew by 23% from 8,900 kha in 1987 to 10,922 in 2008 (both are 3-year means). The domestic cropland footprint decreased by 6%, while the cropland footprint abroad increased by 44%. Over two thirds of the UK cropland footprint is now located overseas (Figure 1). The EU is the major supplier of crops to the UK and has the largest share in the UK’s cropland footprint, while the importance of North America has decreased (from 14% to 5%), and that of South America increased (10% to 21%). The decline of
North America’s importance might be linked to its domestic corn ethanol program, although this remains contested [2]. Crops responsible for the largest cropland footprint are cereals and oil crops, with soya beans responsible for the largest footprint abroad (1,502 kha or 20% of the cropland footprint abroad), with significant shares for cocoa beans (12%) and wheat (10%) as well.
Figure 1. Share of domestic cropland and cropland abroad in the total cropland footprint of the UK food supply.
Thirdly, the associated greenhouse gas emissions, excluding land use change emissions, remained relatively constant. Emissions associated with fertilizer application have decreased slightly because UK and European fertilizer application rates have declined over the studied period, while imports of rice have increased, causing rice emissions (high due to methane generated in rice paddies) to increase. Including land use change emissions leads to a rise in the total emissions from 19.1 Mt CO2e in 1987 to 21.9 Mt CO2e in 2008. Land use change is responsible for the largest share in the emissions (64%), highlighting the importance of land use change emissions.
Complexities of global food supplies
To arrive at these results, we needed to address several issues. Firstly, we needed to deal with the fact that bilateral trade data only report the final country of import, and not the place of production. For instance, a significant share of tropical fruits in the UK is imported from Europe, a non-producing region for tropical fruits, making the calculation of the associated cropland footprint difficult. Therefore, we used a dataset based on FAOSTAT, recently developed by researchers at the Institute of Social Ecology in Vienna [2]. It allows flows of crops and livestock products to be traced and consistently allocated to cropland areas in over 200 countries.
We then used the calculated cropland footprint to estimate emissions for these areas, quantifying those arising from synthetic fertilizer and manure application, rice cultivation and land use change. National synthetic fertilizer application and manure application figures were converted to crop-specific values, using data from FAOSTAT, the International Fertilizer Association and Fertilizers Europe. For land use change emissions, we followed Audsley et al. (2009) in the assumption that all land use change emissions are ultimately caused by total human demand, and hence all agricultural area should carry the same burden per hectare [3]. At the same time, it can be argued that some crops should carry a heavier burden, because they grow on newly established croplands rather than on long-established croplands. Therefore, we used normalisation factors based on crops’ relative expansion rates over the last decades [4]. For instance, soya beans, a crop for which cropland areas are rapidly expanding, receive a higher normalisation factor, than barley, for which cropland areas are declining. Our estimate for land use change emissions is considerably lower than the estimate by Audsley et al. (2009) (14 Mt CO2e vs. 101 Mt CO22) because we not consider land use change emissions attributable to grazing areas (50% of land use change emissions in [3]), and use a different land use change emission factor, based on a more recent estimate of global land use change emissions [5].
Combining these methods allowed us to calculate the total cropland footprint of the United Kingdom and its associated greenhouse gas emissions.
Implications of our research
Our study shows that the UK imports, on average, commodities with a lower yield than it exports; hereby displacing environmental impact to other countries. This is different from the overall global trend where, on average, trade flows from high-yielding regions to lower yield regions [2], but consistent with the picture of the EU as a net displacer of environmental impact [6]. Intra-European trade between the UK and EU shows a trend consistent with the global picture: the UK imports high-yield commodities from the EU, particularly vegetables, and as such European trade contributes to a more efficient food system for the UK (defined in terms of greenhouse gas emissions and land use). See for instance [6], for a more extensive discussion on the role of the EU as a displacer of environmental impact.
Secondly, cereals, oilseeds and stimulant crops (e.g. cocoa beans and coffee), are responsible for the largest share in the total environmental impact. Crops for which it could be argued that they are not a necessary part of a balanced diet, such as sugar and stimulant crops, are responsible for about 15% of the total cropland footprint. A lower consumption of these crops, in combination with a lower consumption of animal products and thus of feed crops, could lead to a lower cropland footprint and associated greenhouse gas emissions. However, an important consideration is what would be grown on freed up cropland. Ideally, the available cropland would be used to grow crops that would benefit human health, while some of the land could be left for habitat restoration or carbon storage. For this, people would need to shift towards food items with lower environmental impacts that are also healthy, something that may prove very difficult in practice.
Lastly, our analysis shows the large share of land use change emissions in the total greenhouse gas emissions. Currently, there is no established method for dealing with land use change emissions, and our approach has several limitations. It assigns a relatively heavy burden to established croplands, whereas land use change emissions from recently cleared croplands are underestimated. There might be a trade-off between commodities grown on recently cleared croplands, such as soya beans, which have higher associated land use change emissions but a lower fertilizer use, and crops with high levels of intensification but lower emissions arising from land use change emissions [3-5, 7].
Steps ahead
Our study has some limitations which we hope to address in the near future. Firstly, we only looked at croplands. Including grazing areas would give us a fuller estimation of the land appropriation associated with the UK food supply. We consider emissions arising from fertilizer and manure application, rice cultivation, and land use change but no other sources, such as emissions arising from enteric fermentation. Dealing with animal products in a more direct way by including grazing areas and enteric fermentation would improve the current assessment.
Data on crop-specific fertilizer and manure application is sparse on a global level, while large variations exists on a sub-national scale. In theory, a more spatially aggregated dataset of crop-specific nitrogen application would improve our analysis, and the same is true for a more spatially aggregated method of dealing with land use change emissions. Our current approach to land use change emissions has some limitations, including the lack of obvious mitigation strategies other than improving yields or decreasing cropland areas.
Conclusion
Our study shows that the UK is increasingly outsourcing its environmental impact to other countries. If we want to reduce the environmental impact of the UK food supply it is not enough to only look at domestic production - we must address the total consumption of the UK.
Citation
de Ruiter H, Macdiarmid JI, Matthews RB, Kastner T, Smith P. 2016 Global cropland and greenhouse gas impacts of UK food supply are increasingly located overseas. J. R. Soc. Interface 13: 20151001. DOI: 10.1098/rsif.2015.1001
Abstract
Producing sufficient, healthy food for a growing world population amid a changing climate is a major challenge for the twenty-first century. Agricultural trade could help alleviate this challenge by using comparative productivity advantages between countries. However, agricultural trade has implications for national food security and could displace environmental impacts from developed to developing countries. This study illustrates the global effects resulting from the agricultural trade of a single country, by analysing the global cropland and greenhouse gas impacts of the UK's food and feed supply. The global cropland footprint associated with the UK food and feed supply increased by 2022 kha (+23%) from 1986 to 2009. Greenhouse gas emissions (GHGE) associated with fertilizer and manure application, and rice cultivation remained relatively constant at 7.9 Mt CO2e between 1987 and 2008. Including GHGE from land-use change, however, leads to an increase from 19.1 in 1987 to 21.9 Mt CO2e in 2008. The UK is currently importing over 50% of its food and feed, whereas 70% and 64% of the associated cropland and GHGE impacts, respectively, are located abroad. These results imply that the UK is increasingly reliant on external resources and that the environmental impact of its food supply is increasingly displaced overseas.
References
[1] D'Odorico, P., Carr, J. A., Laio, F., Ridolfi, L. & Vandoni, S. 2014 Feeding humanity through global food trade. Earth's Future. 2, 458-469. (doi:10.1002/2014EF000250).
[2] Kastner, T., Erb, K. H. & Haberl, H. 2014 Rapid growth in agricultural trade: effects on global area efficiency and the role of management. Environ. Res. Lett. 9, 034015. (doi:10.1088/1748-9326/9/3/034015).
[3] Audsley, E., Brander, M., Chatterton, J., Murphy-Bokern, D., Webster, C. & Williams, A. 2009 How low can we go? An assessment of greenhouse gas emissions from the UK food system and the scope to reduce them by 2050. Food Climate Research Network and WWF UK.
[4] Williams, A. G., Dominguez, H. & Leinonen, I. 2014 A simple approach to land use change emissions for global crop commodities reflecting demand. Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector, 8-10.
[5] Vellinga T.V., Blonk, H., Marinussen, M., Van Zeist, W., Starmans, D. 2013. Methodology used in feedprint: a tool quantifying greenhouse gas emissions of feed production and utilization. Wageningen, the Netherlands.
[6] Steen-Olsen, K., Weinzettel, J., Cranston, G., Ercin, A. E. & Hertwich, E. G. 2012 Carbon, Land, and Water Footprint Accounts for the European Union: Consumption, Production, and Displacements through International Trade. Environ. Sci. Technol. 46, 10883-10891. (doi:10.1021/es301949t).
[7] Van Middelaar, C.E., Cederberg, C., Vellinga, T.V., van der Werf, H.M.G., de Boer, I.J., 2013. Exploring variability in the methods and data sensitivity in carbon footprints of feed ingredients.
Int. J. Life Cycle Assess. 18, 768-782. (doi:10.1007/s11367-012-0521-9)
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