The precautionary principle, or precautionary approach, has emerged over recent decades as a widely and increasingly accepted general principle of environmental policy, law, and management. It is an approach to uncertainty, and provides for action to avoid serious or irreversible environmental harm in advance of scientific certainty of such harm. While an important and intuitively sensible principle, the acceptance of the precautionary principle into law and policy and its implementation in practice have been marked by controversy and confusion.