In 2050, however, the total Asian population will be 5.54 billion, exceeding its allowable maximum (5.40 billion), and that in Africa will be 2.05 billion, approaching its allowable maximum (2.101 billion). As for the world's two most populous nations, the population of India in 1995 is already equivalent to the maximum allowable (0.93 billion) and is expected to exceed the maximum allowable level by 600 million, and that of China will also exceed the maximum allowable level (1.40 billion) even before 2025, and will be in excess of it by 120 million in 2050.
In Cohen's equation, both U and L represent utilization-efficiency rates of water resources. Column (3) of Table 3 (Condition 2) and Column (2) of Table 4 show the maximum allowable populations obtained by the same calculation but with the assumption that the combined efficiency, U(1-L) has been improved by 75% (Condition with 75% improved efficiency). By this assumption, the maximum allowable populations of the world and of the major regions are 72% greater than those in the "standard condition", and both of the populations of Asia (including China and India) and Africa will be below the maximum allowable level throughout the 21st century.
(3) Assumption： 20% of energy intake is from meat.
Intake of lkcal of energy from meat requires ten times the amount of plants (i.e., land and water as well) needed to take in lkcal from grains. If the proportion of meat increases, therefore, the "water stress" becomes greater. Assuming that 20% of 2,350kcal is obtained from meat, the constant of the Cohen equation, 10, is reduced to 8.2 (= 10 x 0.8 + 1 x 0.2). The maximum allowable populations in the "standard condition" and "75% improved condition" corrected by this new coefficient are shown in Columns (4) and (5) of Table 3, and Columns (3) and (4) of Table 4.
In the corrected "standard condition" (20% taken from meat), the maximum allowable world population is 16.9 billion, and estimated future populations are below this level in 2050, and even 2150 (10.8 billion).
