The precautionary concept has become intrinsic to international environmental policy, especially with the adoption, in 1992, of the Rio Declaration at UNCED. Principle 15 of that Declaration provides that: "In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation." The challenge facing the international community is how to attain truly precautionary environmental policies. This challenge is one of changing perceptions as much as of changing institutions or technical mechanisms. It is a challenge to our way of viewing the world as much as to our views of the role of science, or the burden of proof. It also raises a question as to the role of legal and other regulatory instruments in implementing the precautionary principle. This question, however, lends itself to a multifaceted and multidisciplinary approach. After an introduction to the origins and development of the precautionary principle, 12 chapters explore a selection of themes relevant to the implementation of the principle. Where the relationship between international, national and local policies is concerned, a new concept is introduced: glocalization. The book concludes with a synthesis of the opportunities for, and constraints on, the implementation of the precautionary principle, as identified by the various authors.