Global water availability and requirements for future food production

A vegetation and hydrology model (LPJmL) was used to calculate green and blue water availability per capita, water requirements to produce a balanced diet representing a benchmark for hunger alleviation (3,000 kcal cap−1 d−1, here assumed to consist of 80% vegetal food and 20% animal products), and a new water scarcity indicator that relates the two at country scale. A country was considered water-scarce if its water availability fell below the water requirement for the specified diet, which is presently the case especially in North and East Africa and in southwestern Asia.

Under climate (derived from 17 General Circulation Models) and population change (A2 and B1 emissions and population scenarios), water availability per person will most probably diminish in many regions. At the same time the calorie-specific water requirements tend to decrease, due mainly to the positive effect of rising atmospheric CO2 concentration on crop water productivity which, however, is very uncertain to be fully realized in most regions. As a net effect of climate, CO2 and population change, hence, water scarcity will aggravate in many countries, and a number of additional countries are at risk of losing their present capacity to produce a balanced diet for their inhabitants.

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