ASSESSING THE ECOLOGICAL EFFECTS OF HABITAT CHANGE - MOVING BEYOND PRODUCTIVE CAPACITY

Productive capacity can be defined as the ''ecological effect'' end of a habitat change --> ecological effect cause-effect pathway. Determin ing whether and how a habitat manipulation, either inadvertently or de liberately, will affect productive capacity is the key analytical step of habitat management. We describe a process to ensure that this step is conducted in a manner that is rigorous and relevant. The process h as four components: (1) determination of management objectives, (2) id entification of indicators, (3) analysis of cause-effect pathways Link ing habitat changes to ecological effects, and (4) determination of st rategies to effect desirable habitat change. The core of the process i s the third step, in which we propose the use of hypotheses-of-effect, a network of cause-effect linkages leading from habitat change to eco logical effects, to ensure rigorous assessment of possible effects. We illustrate the process using examples of timber management effects on migratory brook trout (Salvelinus fontinalis) and urbanization effect s on littoral warmwater communities. We argue that this process, in ad dition to providing a rigorous means of assessing the evidence relevan t to a particular issue, also provides an effective tool for examining uncertainty. We advocate the adoption of this process by management a gencies as a method for adaptive habitat management.