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Conserving Freshwater Ecosystems

Source: Precious Heritage:
The Status of Biodiversity in the United States
© The Nature Conservancy and NatureServe
 

Freshwater ecosystems—including rivers, lakes, and wetlands—provide virtually all of the easily accessible drinking water on the planet, and support a wide variety of other species, including fish and other aquatic organisms, wildlife and plants. Today these ecosystems suffer from the twin assaults of water depletion and water pollution—a degradation whose consequences are vast and severe.

A Global Crisis of Quantity and Quality
Freshwater not only gives life, it abounds with life. Migratory birds, ducks, panthers, deer and moose rely on rivers, lakes and wetlands at some point in their lives as they breed, feed and migrate. In addition to providing drinking water for people, freshwater ecosystems irrigate crops, nurture fish and other foods, process wastes, provide transportation and let us swim, boat and enjoy other forms of recreation. But in the past century we have severely strained Earth's freshwater ecosystems.

Like oil in the 20th century, water is becoming a resource crisis of huge proportions. As the planet's population rapidly expands, too much water is being siphoned out of rivers like the Colorado, the Rio Grande and China's Yellow, increasingly causing them to dry up before they reach the sea. Lakes such as the Sea of Galilee and the Aral have shrunk to a shadow of their former size. Our use of freshwater, especially in industrialized countries, is often wasteful and profligate. In developing countries the problem of pollution is magnified, with fewer environmental controls of effluents and municipal wastes.

River Flows—A Source of Life
During the past decade, scientists have learned that the natural flow patterns in river systems are one of the main variables driving the health of freshwater systems. The timing, magnitude, frequency and duration of flood flows, high flow pulses and low flows, as well as rates of change between these flow stages, send cues that trigger fish to spawn or migrate, provide access to important habitats for spawning and juvenile fish, and influence plants and aquatic animals that need moving water to survive. In addition, flow patterns affect other aspects of ecosystem health, like water quality, temperature, and vulnerability to invasive species.

The Conservancy is working to ensure sufficient Freshwater resources for people, plants and animals in places like Colorado's San Luis Valley
© Ron Semrod
 

In Utah's Green River, for example, the Colorado pikeminnow, a fish whose spawning is timed to take advantage of annual floods, was pushed to the brink of extinction when dams cut the duration and magnitude of flood flows. As the roller-coaster-like pattern of river flows flattened out, the pikeminnow could not survive in the tamed river environment.

Today, the flows of most of the nation’s rivers and an increasing number of rivers throughout the world are affected by dams, water withdrawals, and channel modifications. As our human population grows, our needs for freshwater are also increasing. Yet the water available to meet these needs remains the same, creating more and more pressure on increasingly limited freshwater resources.

Water for People, Water for Nature
In response to increasing concerns about future water supplies, governments and water planners around the world are exploring ways to sustainably manage freshwater resources to ensure there will be water for future generations. There is growing recognition that healthy freshwater ecosystems provide valuable natural services—such as water purification, plant and animal foods, flood control, recreation, nutrient cycling, and biodiversity maintenance—that are being lost because of improper water management.

The Nature Conservancy believes there is a way to find a balance between the freshwater needs of people and ecosystems. The Conservancy’s response to this challenge is to advocate Ecologically Sustainable Water Management (ESWM)—the compatible integration of human and natural ecosystem needs.

We believe that ecologically sustainable water management is attainable in the vast majority of the world’s river basins. However, we must act now to achieve this sustainability before our water supplies are further endangered and water for nature ceases to exist.