The need to address all scales and their connectedness is illustrated to a certain degree by the nested dolls; the toy is incomplete without all its members.
Photo by Michael J. Grodowitz
As is discussed in Boundaries and Classifications, we need to organize and simplify complexities to be able to think about them. Our thinking about an ecosystem and its connected nature can be guided by hierarchical levels of organization. One option for such organization is introduced here.
A 10-page paper from The Nature Conservancy (Poiani and Richter 1999) proposes four geographic scales of organization: local, intermediate, coarse, and regional. The paper is titled "Functional landscapes and the conservation of biodiversity." The four scales are associated with ecological levels of organization from species to populations to communities to ecosystems. The utility of this organization to the Corps is assistance in selecting a study area or project area of sufficient size to accomplish ecosystem objectives. To access the paper, go to http://conserveonline.org and search the Library for "Functional landscapes."
Aldo Leopold was a forester by training who developed an expanded view of natural resources in the 1930s and 40s. In his writings, he made an eloquent request to consider interactions.
If you are interested in learning about Aldo Leopold, go to this page: http://gargravarr.cc.utexas.edu/chrisj/leopold-quotes.html for selected quotes and a biography with other links.