AUTHORS’ INTRODUCTION:
“Beaver (Castor canadensis) provide a striking example of how animals influence ecosystem structure and dynamics in a hierarchical fashion. Initially beaver modify stream morphology and hydrology by cutting wood and building dams. These activities retain sediment and organic matter in the channel, create and maintain wetlands, modify nutrient cycling and decomposition dynamics, modify the structure and dynamics of the riparian zone, influence the character of water and materials transported downstream, and ultimately influence plant and animal community composition and diversity (Naiman and Melillo 1984, Naiman et al. 1986). In addition to their importance at the ecosystem level, these effects have a significant impact on the landscape and must be interpreted over broad spatial and temporal scales as beaver population dynamics shift in response to disturbance, food supply, disease, and predation. Although once more prevalent than they are today, beaver-induced alterations to drainage networks are not Localized or unusual. Where beaver remain largely free of management or trapping, their activities may influence a large proportion of streams in a drainage network; and these alterations may remain as part of the landscape for centuries (Ives 1942, Johnston and Naiman 1987, Rudemann and Schoonmaker 1938).”
“Alteration of North American Streams by Beaver” Author(s): Robert J. Naiman, Carol A. Johnston, James C. Kelley
Source: BioScience, Vol. 38, No. 11, How Animals Shape Their Ecosystems, (Dec., 1988), pp. 753
762.