Sustaining Healthy Freshwater Ecosystems
by Jill S. Baron, N. LeRoy Poff, Paul L. Angermeier, Clifford N. Dahm, Peter H. Gleick, Nelson G. Hairston, Jr., Robert B. Jackson, Carol A. Johnston, Brian D. Richter, and Alan D. Steinman
Summary
Fresh water is vital to human life and economic well-being, and societies extract vast quantities of water from rivers, lakes, wetlands, and underground aquifers to supply the requirements of cities, farms, and industries. Our need for fresh water has long caused us to overlook equally vital benefits of water that remains in stream to sustain healthy aquatic ecosystems. There is growing recognition, however, that functionally intact and biologically complex freshwater ecosystems provide many economically valuable commodities and services to society. These services include flood control, transportation, recreation, purification of human and industrial wastes, habitat for plants and animals, and production of fish and other foods and marketable goods. Over the long term, intact ecosystems are more likely to retain the adaptive capacity to sustain production of these goods and services in the face of future environmental disruptions such as climate change. These ecosystem benefits are costly and often impossible to replace when aquatic systems are degraded. For this reason, deliberations about water allocation should always include provisions for maintaining
the integrity of freshwater ecosystems.
Scientific evidence indicates that aquatic ecosystems can be protected or restored by recognizing the following:
• Rivers, lakes, wetlands, and their connecting ground waters are literally the “sinks” into which landscapes drain. Far from being isolated bodies or conduits, freshwater ecosystems are tightly linked to the watersheds or catchments of which each is a part, and they are greatly influenced by human uses or modifications of land as well as water. The stream network itself is important to the continuum of river processes.
• Dynamic patterns of flow that are maintained within the natural range of variation will promote the integrity and sustainability of freshwater aquatic systems.
• Aquatic ecosystems additionally require that sediments and shorelines, heat and light properties, chemical and nutrient inputs, and plant and animal populations fluctuate within natural ranges, neither experiencing excessive swings beyond their natural ranges nor being held at constant levels.
Failure to provide for these natural requirements results in loss of species and ecosystem services in wetlands, rivers, and lakes. Scientifically defining requirements for protecting or restoring aquatic ecosystems, however, is only a first step. New policy and management approaches will also be required. Current piecemeal and consumption-oriented approaches to water policy cannot solve the problems confronting our increasingly degraded freshwater ecosystems. To begin to redress how water is viewed and managed in the United States, we recommend:
1) Framing national, regional, and local water management policies to explicitly incorporate freshwater ecosystem needs.
2) Defining water resources to include watersheds, so that fresh waters are viewed within a landscape or ecosystem context instead of by political jurisdiction or in geographic isolation.
3) Increasing communication and education across disciplines, especially among engineers, hydrologists, economists, and ecologists, to facilitate an integrated view of freshwater resources.
4) Increasing restoration efforts using well-grounded ecological principles as guidelines.
5) Maintaining and protecting remaining freshwater ecosystems that have high integrity.
6) And recognizing human society’s dependence on naturally functioning ecosystems.
