WRI Content Archive

Please visit www.wri.org for the latest WRI resources & materials.
In This Publication

Watersheds of the world: Ecological value and vulnerability

Purchase print version
($30.00)

Current Page For This Publication

Carmen Revenga, Siobhan Murray, Janet Abramovitz, and Allen Hammond

Synopsis

Analyzes global data at the watershed level, assessing 145 watersheds worldwide. Focuses on watershed as ecological units, and the risks human degradation may have on their ability to provide ecological services and maintain the biodiversity within them.


Often extending across one or more international boundaries, watersheds play a critical role in the natural functioning of the Earth.

  • Hydrologically, watersheds integrate the surface water run-off of an entire drainage basin.
  • Economically, they play a critical role as sources of water, food, hydropower, recreational amenities, and transportation routes.
  • Ecologically, watersheds constitute a critical link between land and sea; they provide habitat -- within wetlands, rivers, and lakes -- for 40 percent of the world's fish species, some of which migrate between marine and freshwater systems.
  • Watersheds also provide habitat -- within the terrestrial ecosystems such as forests and grasslands -- for most terrestrial plant and animal species; and they provide a host of other ecosystem services -- from water purification and retention to flood control to nutrient recycling and restoration of soil fertility -- vital to human civilizations.

Watersheds have often been managed hydrologically -- although frequently in piecemeal fashion rather than as an integrated unit -- to provide flood control and sources of water for irrigation or to improve navigation. Most major rivers of the world have been altered through channelization, dams, or drainage of wetlands, often with great benefit to human societies.

However, watersheds have generally not been viewed, or managed, as units. Integrated management of both economic and ecological attributes of a watershed is admittedly difficult, because watersheds often span sectors of economic activity as well as international borders.

Such cross-sectoral and regional approaches to management are likely to be essential, if the ability of watersheds to continue to provide ecological, hydrological, and economic services is to be sustained.

To provide a quantitative basis for integrated management approaches, what is needed is to be able to characterize watersheds and gauge the nature and pattern of threats to them in quantitative terms.

Data on the distribution of human populations, plant and animal species, the pattern of economic activities, and other relevant variables have only rarely been collected and analyzed by watershed units, making a global perspective on watersheds impossible to attain.

ISBN: 1-56973-254-X

200 pages

1998

PDF Downloads

Images & Multimedia