The role of demographic change—that is, change in population size, composition, and distribution—in environmental change is widely acknowledged to be an important one, but the specific relationship between population and the environment is still incompletely understood. Demographic factors as a whole are commonly recognized as one of the primary global drivers of human-induced environmental change, along with biophysical, economic, sociopolitical, technological, and cultural factors (Orians and Skumanich, 1995; WWC, 2000; Hunter, 2000). But these factors do not exist in isolation—the influence of each of these factors on the environment is interrelated with the others. For example, an...

Earth is called the water planet, and 71 percent of its surface is covered with water. In addition to the water on the surface, there is water in underground aquifers, glaciers, icecaps, and the atmosphere. But very little of this water is available for human use, even including that amount needed for ecosystems to function properly. This chapter describes the earth’s water cycle, freshwater ecosystems, and the processes that naturally recycle freshwater on the earth. It also discusses water availability and the natural and human causes for changes in the water supply.

Although the total amount of water on earth...

Water use is commonly analyzed according to three categories or sectors: agricultural, industrial, and domestic or municipal.¹ Water utilization in each sector is influenced by many factors, including population variables such as growth, distribution, and composition. This chapter explains how changes in each sector affect the demand for freshwater by a given population.

Demand varies geographically. There are many regional differences in the demand for water. Agricultural demand ranges from zero percent of total freshwater withdrawals in the Maldives to 99 percent in Afghanistan, Nepal, Guyana, and Madagascar. Industrial use ranges from a low of zero percent in several countries...

Demographic factors affect consumption of water and the quality and health of natural ecosystems both directly and indirectly. As discussed earlier, population growth is usually hypothesized as one of the most important factors threatening the sustainability of water systems. Urbanization, migration, and number of households are demographic factors that are less commonly associated with demographic effects on water resources, although they are also important. Other factors that affect water use tend to be indirectly linked to population—income levels, a rise in living standards, modifications to landscapes and land use, contamination of water supplies, and inefficiency of water use caused...

While demographic variables and their influence on water resources are a popular topic in papers discussing world water resources, especially by advocacy groups, the reciprocal influence of water resources on demographic variables is far less discussed in the context of water resource issues. However, the results of such influences are equally important, and are directly or indirectly responsible for millions of cases of illness and death worldwide every year.

Urban areas often create waste in quantities greater than the amount that can be absorbed by the surrounding environment. Growing cities often devalue and reduce their own water sources via pollution,...

As the previous chapters have made clear, various demographic factors are working together to place stress on water resources by increasing demand for water, while decreasing supplies through pollution and destruction of freshwater ecosystems. At the same time, polluted waters are adversely impacting human populations through disease and mortality. Whether or not a water crisis is imminent, measures need to be taken to reduce the pressures on water resources well in advance of their collapse. Measures aimed at ameliorating this seemingly intractable situation can approach the challenge in different ways. One is to attack the problem by influencing the demographic...

The introductory chapter of this study considered the idea of a worldwide water crisis brought on by increasing global population, and concluded that studies arguing that such a crisis is imminent are probably alarmist and overreaching the predictive ability of the available data. Instead, it was argued that a different model of interaction between demographic variables and water resources must be used to examine the future of water worldwide.

The preferred model includes demographic factors and water resource variables, with myriad factors dampening or heightening the relationship between these variables (see Figure 7.1). An examination of these factors together, rather...