The Scientific Imperative for Defending Small Streams and Wetlands

Expertise: Organic matter biogeochemistry and microbial ecology of stream ecosystems Expertise: Distributions and roles of freshwater invertebrates including exotic and endangered species Expertise: Hydrology, fluvial geomorphology, stream and wetland restoration, and water quality Expertise: Plant population and community ecology American Rivers and Sierra Club, sponsors of this publication, are extremely grateful for the contributions the authors have made in describing the ecological importance of headwater streams and wetlands and the benefits they provide to humans. We extend special thanks to Judy Meyer for coordinating the project. We also thank editors Mari N. Jensen and David Sutton. O ur nation's network of rivers, lakes and streams originates from a myriad of small streams and wetlands, many so small they do not appear on any map. Yet these headwater streams and wetlands exert critical influences on the character and quality of downstream waters. The natural processes that occur in such headwater systems benefit humans by mitigating flooding, maintaining water quality and quantity, recycling nutrients, and providing habitat for plants and animals. This paper summarizes the scientific basis for understanding that the health and productivity of rivers and lakes depends upon intact small streams and wetlands. Historically, federal agencies have interpreted the protections of the Clean Water Act to cover all the waters of the United States, including small streams and wetlands. Despite this, many of these ecosystems have been destroyed by agriculture , mining, development and other human activities. The extent to which small streams and wetlands should remain under the protection of the Clean Water Act is currently (2003) under consideration in federal agencies and Congress. Extensive scientific studies document the significance of these small systems and form the basis for this paper. Further references are provided at the end of the document. We know from local/regional studies that small, or headwater, streams make up at least 80 percent of the nation's stream network. However, scientists' abilities to extend these local and regional studies to provide a national perspective is hindered by the absence of a comprehensive database that catalogs the full extent of streams in the United States. The topographic maps most commonly used to trace stream networks do not show most of the nation's headwater streams and wetlands. Thus, such maps do not provide detailed enough information to serve as a basis for stream protection and management. Scientists often refer to the benefits humans receive from the natural functioning …