Journey to Planet Earth . Ecosystems: Freshwater

All organisms on the planet need water to survive.

Freshwater systems are created by water that enters the terrestrial environment as precipitation and flows both above and below ground toward the sea. These systems encompass a wide range of habitats, including rivers, lakes, and wetlands, and the riparian zones associated with them.

This analysis concentrates on the terrestrial water that is most accessible to humans: the water in rivers, lakes, and wetlands. Humans also rely heavily on groundwater, which is the only source of freshwater in some parts of the world.

The world's freshwater systems are so degraded that its ability to support human, plant and animal life is greatly in peril. As a result, many freshwater species are facing rapid population decline or extinction, and an increasing number of people will face serious water shortages.

Although water in rivers, lakes, and wetlands contains only 0.01 percent of the world's freshwater and occupies only one percent of the earth's surface, the global value of freshwater services is estimated in the trillions of U.S. dollars.

In 1997, 7.7 million metric tons of fish were caught from lakes, rivers, and wetlands, a production level estimated to be at or above maximum sustainable yield for these systems. Since 1990, freshwater aquaculture has more than doubled its yield and now accounts for 60 percent of global aquaculture production.

While many regions of the world have ample freshwater supplies, four out of every 10 people currently live in river basins which are experiencing water scarcity. By 2025, at least 3.5 billion people or nearly 50 percent of the world's population will face water scarcity.

Water-borne diseases from fecal pollution of surface waters continue to be a major cause of mortality and morbidity in the developing world.

In the United States, which has the most comprehensive data on freshwater species, 37 percent of freshwater fish species, 67 percent of mussels, 51 percent of crayfish and 40 percent of amphibians are threatened or have become extinct.

Source: World Resources 2000-2001

In Rivers Of Destiny, journey to four major river systems of the world to investigate environmental problems facing those whose lives depend upon the health of their river. Read the full description of this program or watch a video clip.

In On the Brink, examine how severe environmental problems can lead to political crises and increased hostilities around the world. Read the full description of this program or watch a video clip.

In Hot Zones, see how the increased spread of infectious diseases has altered global and local ecosystems. Read the full description of this program or watch a video clip.

In Future Conditional, investigate the link between environmental change and the future health of our planet, a future conditional on how we cope with the spread of toxic pollution. Read the full description of this program or watch the video clip.

Read Stories of Hope from the Journey to Planet Earth series focusing on freshwater ecosystems: