Diet on trial: how we measure land footprints changes everything

Diet on trial: How accounting for land-use shapes the environmental verdict on our food

Optimising diets for environmental sustainability has become an important area of research. Life cycle assessment (LCA) is a key tool for quantifying the environmental impact of food systems, but a persistent challenge is how to account for land-use change — particularly deforestation embodied in feed and food supply chains. This study, published in the International Journal of Life Cycle Assessment, investigates how different methodological choices for assessing land-use change influence the calculated global warming potential (GWP) and cost-efficiency of optimised diets, using Danish pig production as a case study.

The analysis reveals that methodological choices — whether to use marginal or average land-use attribution, how to spatially allocate deforestation across feed crops, and which temporal boundaries to apply — produce substantially different GWP estimates for the same dietary scenario. In some cases, the choice of method shifts the ranking of dietary alternatives, meaning that a diet appearing optimal under one accounting framework may look considerably worse under another. This methodological sensitivity has major implications for dietary guidelines and food sustainability labelling.

For Danish pork specifically, the inclusion of soy-driven deforestation in feed — attributing land-use change from Brazilian or Argentine soy cultivation — can more than double the estimated GWP of pork production compared to models that omit or underweight this factor. The results argue for greater transparency and standardisation in how LCA practitioners handle land-use change, particularly in supply chains with significant tropical deforestation exposure.

The environmental verdict on our food depends critically on the assumptions hidden inside our accounting frameworks. As dietary guidance becomes ever more central to climate policy, ensuring that LCA methods are robust, transparent, and consistent is not a technical nicety — it is a matter of public importance.