How much meat should we eat? Improved estimates accounting for food
system dynamics influencing water use
Abstract
Eating less livestock products can reduce agricultural resource use, but
it has also been argued that a portion of livestock products does
sustainably contribute to food security. Given that diet change impacts
arise through modification of food production systems, evaluating such
changes requires explicit modelling of system dynamics. This paper uses
a novel global integrated optimisation model, “Aalto OptoFood”, to
investigate changes in water use when replacing livestock protein with
plant-based protein sources in human diets and reallocating associated
cropland and pasture. Our findings reveal that the first cuts are the
deepest – moderate reductions in livestock protein decrease water
consumption more than suggested by comparing global average crop and
livestock water productivities. Further reductions show diminishing
returns, with no clear optimum. In terms of water use, it is beneficial
to eat less livestock products, even if there is no clear case for or
against universal adoption of a vegan diet.