(August 2002) In a speech delivered at the American Museum of Natural History this May, UN Secretary-General Kofi Annan held that “at its core, [the World Summit on Sustainable Development (WSSD)] is about the relationship between human society and the natural environment.” The Secretary-General highlighted water as one of the five key areas where concrete results are both necessary and attainable. Water exemplifies the linkages between population, health, and environment: It sustains human and ecosystem health, food production, and social and economic development.

Why Is Freshwater so Important?

Freshwater is crucial to all living things. It is a precious resource for which there is no substitute. Though most of our planet is water, only 3 percent of the world’s water is freshwater. Much of our freshwater is locked in glaciers and icebergs and unavailable for human use. One quarter of the global population, or an estimated 1.5 billion people, lacks access to drinkable water. Critical aspects of freshwater availability include:

  • Population growth and water dynamics. In the last 70 years, the global population has tripled and is now over 6.2 billion. The demand on water resources has grown at double that rate. Though our numbers continue to grow, renewable freshwater resources are finite. We consume 54 percent of Earth’s annual available freshwater. If current consumption rates remain the same, this number could rise to 70 percent by 2025 due to population growth alone. If consumption rates grow globally to the current level of developed countries, senior researcher Stan Bernstein of the United Nations Population Fund estimates that up to 90 percent of our available water may be used every year.
  • Human health and sanitation. Health and well-being are intrinsically linked with access to safe, uncontaminated freshwater. An estimated 5 million to 12 million deaths each year are due to illnesses caused by dirty water, according to the National Wildlife Federation. The number of people who lack access to potable water is projected to double in the next 25 years. Half of the world’s population, 3 billion people, lack access to sanitation.
  • International conflict and security. Water may become one of the major contributing causes of international conflict as world water supplies continue to shrink. The Worldwatch Institute reports that there have already been violent protests as a result of a threat to sufficient irrigation supplies for farmers in China and Pakistan. Problems may be more prevalent in areas where water resources are already particularly scarce. The Middle East and North Africa region, home to 6.3 percent of the world’s population but only 1.4 percent of the world’s renewable freshwater, faces many challenges as tensions continue to grow between neighbors over water rights.
  • Ecosystem health. The world has lost approximately half of its wetlands. This loss reaches far beyond its effect on humans. Freshwater resources are essential habitats for animals and plants. As human demands on freshwater increase, the amount of freshwater available to other species decreases. This demand also threatens the availability of freshwater ecosystem services such as water filtration, fishery maintenance, and the moderation of extremes (for example, floods and droughts). An alarming number of freshwater species — including fish, dolphins, otters, mussels, and amphibians — are already either threatened, endangered, or extinct.


Stan Bernstein, “Freshwater and Human Population: A Global Perspective,” Yale School of Forestry and Environmental Studies Bulletin Series 107: 149.

Don Hinrichsen, Karin Krchnak, and Katie Mogelgaard, Population Water & Wildlife: Finding a Balance (Washington, DC: National Wildlife Federation, 2002).

Sandra Postel, “From Rio to Johannesburg: Securing Water for People, Crops and Ecosystems,” Worldwatch Institute World Summit Policy Brief 8 (July 16, 2002). 

For More Information

Heinrich Böll Foundation: www.worldsummit2002.org/issues/freshwater.htm

Worldwatch Institute: www.worldwatch.org

Buffy Baumann is the population, health, and environment fellow at PRB.