The water we eat: Methods for estimating water use of diets in changing food systems

Research output: ThesisDoctoral ThesisCollection of Articles


Water scarcity already affects more than half of the human population. The largest water consuming human activity, food production, is at the centre of the quest for sustainable use of this natural capital. How much resources are required to satisfy the global food demand depends on more than just the number of us and how much we eat. It is largely determined by what the human diets consist of and where the food is produced, as well as how much of it is lost and wasted. This dissertation focuses on water consumption in agriculture as a key determining factor in achieving food security. It does so by studying three overarching themes: the resource-saving effect of changes in human diets, modelling the supply chains within the complex food systems, and methods used to evaluate agricultural water use and its impacts. A substantial body of existing research aims to find relationships between consumer choices and resource use in agricultural production, but many aspects in the methodologies and in their results remain controversial. This dissertation points out challenges in using current methods to define alternative diets in global studies and presents a novel, optimisation-based method that adjusts diets according to chosen dietary guidelines and level of diet change. It combines the diet change analysis with food system models in a way that can capture interactions between different resource-saving measures and presents estimates of their global, regional and country-level potential to improve food security. A novel food system model, Aalto OptoFood was developed to allow analysing resource efficiency of large changes in food demand and in system dynamics, such as synergies between crop and livestock-based food production.The dissertation found that replacing livestock-based foodstuffs in human diets with crop-based alternatives is an efficient way to reduce agricultural water consumption. Theoretically, the water thus saved could supply food for up to 1.8 billion people. Yet, the opportunity cost of livestock in terms of water may be lower in practice. Shifting water from the production of one foodstuff to another requires the availability of other resources, such as suitable cropland. Non-arable rangelands may support livestock production that positively contributes to food security. Nevertheless, many current production systems depend heavily on water and land resources that could be more efficiently used for crop production. Optimal spatial distribution of production changes would allow diet change to preferentially reduce livestock with highest opportunity cost in terms of water, and offer high initial returns with relatively small changes. Finally, this dissertation uses the framework of the Cultural Theory to discuss how modelling outcomes are affected by decisions stemming from different worldviews. It argues that modellers should be conscious of such decisions and communicate them clearly to avoid real or perceived biases.
Translated title of the contributionSyömämme vesi: ruokavalioiden vedenkulutuksen arvioiminen muuttuvissa ruokajärjestelmissä
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Varis, Olli, Supervising Professor
  • Guillaume, Joseph, Thesis Advisor
  • Kummu, Matti, Thesis Advisor
Print ISBNs978-952-60-8672-9
Electronic ISBNs978-952-60-8673-6
Publication statusPublished - 2019
MoE publication typeG5 Doctoral dissertation (article)


  • water scarcity
  • food system
  • diet change
  • food loss
  • cropland
  • livestock

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