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Abstract:
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"Loss of biodiversity, reduction of forests, and declining fish stocks in the oceans are examples of major problems facing the emerging global society. The scale and diversity of human activites cause large scale alterations in the various ecosystems. Many of the changes are unwanted and some are clearly viewed as detrimental to the future utility of various resource systems. The many efforts around the world to change and improve the management of renewable resources attests to that.
"Yet, we do not have any theoretical foundation for conclusions about the size of the causal impact on ecosystem characteristics of proposed changes, only beliefs about the probable direction. The knowlegde we have about the behaviour of ecosystems in response to human activity is practical, gained through centuries of mutual adaptations between social system and ecosystem. Or it is presented in broad common sense terms such as the increased pressure on resources coused by an indreasing number of people. As a basis for recommendations of policy this is not sufficient.
"Among the forces affecting the development of an ecosystem, we need to distinguish causal factors which can be manipulated by political decisions from other human impacts and from the various natural forces affecting the ecosystem. We need to know why and under which conditions a certain politically chosen course of action will work to improve the desireable qualities of an ecosystem."
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