How Greenways Work: A Handbook on Ecology
Originally published as a handbook by the National Park Service Rivers and Trails Conservation Assistance Program and QLF/Atlantic Center for the Environment.
By Jonathan M. Labaree, October 1997
This is a handbook for those private citizens and public officials all over America who are working to create outdoor recreation opportunities and protect wildlife and our environment by establishing corridors of open space called greenways.
Greenways connect. They tie together people, parks, historic sites, and natural areas. They follow streams and rivers, ridgelines, abandoned rail lines, hedgerows, canals, and other transportation corridors. All are unique, created through local initiative and reflecting a consensus of community needs and concerns.
Preserving and restoring the natural world, especially near where we live and work, is one of the nation's most important conservation goals-- and providing greenways may be one of the most beneficial and effective conservation strategies to accomplish it. To do this job effectively, we need to know about specific functions and values, and the respective planning and management strategies to implement them.
Through the emerging science of landscape ecology, we are learning more and more about the importance of the "linkage" that greenways provide in maintaining and restoring ecological processes and in maintaining the health of a landscape. Unfortunately much more research needs to be done before we can develop explicit criteria and strategies to protect the ecological functioning of each kind of corridor and environment for the nation's tremendously varied landscape and ecosystems.
The purpose of this handbook is to serve as an introduction into ways in which we can design and manage greenways to fulfill their ecological potential. Greenways offer a whole range of benefits beyond traditional ones - open space and recreation - that are making greenways a popular conservation strategy. They can also meet very important ecological needs. Ensuring that a greenway fulfills its ecological potential rests upon understanding how a landscape functions and the role greenways can play in that functioning.
When we look out over what appears to us as a distinct piece of nature, such as an alpine meadow, we must realize that our view is but one of many. We cannot see groundwater flowing out of the surrounding wooded slopes bringing nutrients, minerals, and microorganisms into the meadow's soil. We do not notice the mice and ants constantly moving seeds within and beyond the meadow's edge. The hawk soaring overhead does not confine itself to the field, but hunts and nests elsewhere. The glacier that formed the valley, depositing sediment and creating ancient lakes, has long since retreated.
So much movement and activity should convince us to consider the meadow as an intricate series of connections with its surroundings rather than an isolated patch of grass and flowers. A change in perspective that will help us to grasp ecological functioning is to see nature as a system of interconnected, interdependent, and ever-changing parts.
"Part" can refer to any number of elements within a landscape: a river, mountain, field, glacier, lake, barrier island, forest. Basing land conservation on ecological criteria means protecting not just these physical elements, but their interactions, or functions, as well. Greenways, being linear, are best suited to protect parts of the natural landscape which are also linear. These linear landscape elements are called environmental corridors. The challenge for conservationists is to design greenways so they protect corridors and their functions.
Of the many functions of corridors, this handbook focuses primarily on those functions related to wildlife and to water resources (elaborated in chapters III and IV). Before diving into specifics, however, it is important to understand the way in which our modifications to the environment influences natural balances (covered in Chapter I) and the ecological functions of corridors that we hope to maintain when creating greenways (Chapter II).
There is much more to establishing a greenway than locating it properly in the landscape; managers will be continually challenged in their effort to maintain their greenway's ecological functioning (such issues are the subject of Chapter V). While this handbook emphasizes ecology, other issues are important to people involved in greenway projects: designing the greenway so it is a pleasant place to be; avoiding conflicts between different uses; or capitalizing on economic benefits that a greenway can bring to a community. There are references throughout the text to other publications which deal with these topics in greater depth.
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Updated March 16, 2007