United Nations Environment Programme (UNEP)
Global  Environment Outlook-1 - The Web version

Chapter 4: Looking to the Future

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Human Health

Projected Trends

It is projected that the demographic and health transitions already observed for industrial countries can also occur elsewhere if conditions are favourable.

As noted in the section on use of land and food production, it is projected that food supply is likely to be adequate at a global level. An adequate food supply will have a positive effect on the health of the global population. Local famines and malnutrition caused by climate disturbances, poor socio-economic conditions, and inequity within and among nations remain a threat, however.

Despite the projected global availability of adequate water, water scarcity is projected to occur in several regions (Gleick, 1996; Hoekstra and Vis, forthcoming; UN/SEI, forthcoming). Even without considering the problems associated with obtaining adequate water of suitable quality, such local water scarcity problems constitute an even more serious risk for health than food shortages do, partly because it is more difficult and expensive to trade water among regions than it is to trade agricultural products.

Given the crucial importance of water for health and the projected increase in domestic water demand, a special study addressed the "water satisfaction rate." This is the ratio of the per catchment water supply (the result of calculating the monthly surface runoff and ground-water recharge from monthly precipitation and potential evaporation data) to the total demand in the catchment area (domestic, industrial, and agricultural demand).

The rate was calculated for all major (1,165) river basins except those with very low population densities (Klepper et al.,1995; Klepper, forthcoming). Thus, the analysis applies to 53 per cent of the global land area, where 95 per cent of the total population lives. Flows of upstream subbasins to downstream basins and the distribution of supply and demand within a subbasin were taken into consideration. Calculations for each drainage basin were based on monthly averages for the years reported, with the calculations for 2015 and 2050 assuming years with average climate characteristics.

The study results for 1990 show that about 27 per cent of the world population, living in about 12 per cent of the total land area, had (directly or indirectly) severe to moderately severe problems with getting sufficient fresh water; 44 per cent of the world population, living in about 18 per cent of the total land area, had moderate to little water quantity problems. Twenty-four per cent of the world population, living in 22 per cent of the total area, had no water quantity problems. The remaining 5 per cent of the world population, living in the 47 per cent land area with very low population density, has not been included in the study. (See Figure 4.22.) The areas most affected were West Asia and parts of India, Africa, and the United States.

The projected changes in global water demand assuming conventional development (Table 4.1) are as follows: water withdrawal in 2050 compared with 1990 is 2.12 times greater for domestic use; for industrial use, it is 2.37 times greater; and for agricultural use, it is 1.06 times greater. For 2015, preliminary results show that the areas with severe to moderately severe water quantity problems increase slightly (14 per cent). However, areas without water quantity problems decrease significantly (from 22 per cent to 18 per cent), and areas classified as having moderate to few water quantity problems increase (from 18 per cent to 21 per cent). (See Figure 4.22.)

For the period 2015 to 2050, this trend continues. Areas with severe to moderate water quantity problems show a slight increase (from 14 per cent to 16 per cent), areas without water quantity problems continue to decrease (from 18 per cent to 15 per cent), and areas classified as having moderate water quantity problems more or less stabilize (from 21 per cent to 22 per cent). (See Figure 4.22.) Translating these percentages into absolute numbers of people produces the following: the number of people who will face severe water quantity problems by 2050 will almost double from 1.5 billion in 1990 to 2.1 billion in 2015 to 2.8 billion in 2050; the number of people who will face moderate to almost no water quantity problems will also double (an increase from 2.4 billion in 1990 to 3.4 billion people in 2015 to 4.7 billion in 2050); and the number of people with no water quantity problems will increase less (from 1.3 billion in 1990 to 1.7 billion in 2015 to 2.2 billion in 2050). (See Figure 4.23.)

Under the assumptions analysed here, the availability of sufficient fresh water will have to be a continuous topic of concern and will affect a growing number of people. The improvements in efficiency that are assumed in the projections do not diminish the overall pressures on fresh-water resources.

For additional studies on the current fresh-water resources situation and the concerns for the future, the reader is referred to the draft Global Freshwater Assessment prepared by United Nations agencies and the Stockholm Environment Institute for the fifth session of the Commission on Sustainable Development.

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