Measurements of the distance into the forest over which edge effects occur are variable, and may range over 300 feet. Therefore, a block of forest 1,000 feet square or almost 23 acres in size can support little more than 3-112 acres of interior habitat. A minimum of ten acres of forest is required, roughly circular in shape, to reliably support any interior habitat at all. Clearly then, every effort should be made to minimize disturbance to any forested blocks over ten acres in size. This includes road building and facilities development as well as the clearance of vegetation. Where disturbance does occur, it should be confined to the edges, which are already subject to more disturbance and more accessible to management. Since most disturbance in a forest occurs on the edges, large unbroken forest tracks require the least management of all landscape types and permit management budgets to be spent primarily on serving visitor and interpretive needs. The long-term management of smaller and narrower forested areas, which might not necessarily support interior habitat, is also facilitated by limiting the amount of edge condition created and sustaining a less fragmented pattern. Long-term management costs will be reduced and long-term maintenance of native communities will be fostered.
Continuity Continuity is as important to natural systems as configuration. Islands of habitat isolated from surrounding natural areas experience a decline in native species diversity and are less adaptable to stress over time. Management and proposed alterations in current forest patterns should always encourage, rather than reduce, the continuity of natural habitats. Critical forest linkages should be protected and missing links should be reestablished through management. This is equally important at all scales of the landscape.
Natural Processes A major goal of management is to undertake the least intervention necessary to achieve the desired condition. In all cases, where natural processes regulate and sustain the habitat, the need for outside management diminishes while the health of the whole landscape system is improved. Environmental conditions have been substantially altered by man's activities over time and severely compromise the long-term prospects for the sustenance of complex natural systems. Some impacts are virtually global, such as the greenhouse effect, and can only be minimally offset by actions within the park. The maintenance of expansive forest cover is somewhat helpful, for example. Others, such as acid rain are expressed more regionally and can be substantially impacted by activities and regulations at the federal and state levels. Still others are operative almost entirely at the local level and
EARTHWORKS LANDSCAPE MANAGEMENT MANUAL
G-2