The scientific challenges of NEPA: Future directions based on 20 years of experience

January 1, 1990, marked the 20th anniversary of the signing of the National Environmental Policy Act (NEPA). Since this law was enacted, numerous institutions have assisted federal agencies in the implementation of NEPA, including the preparation of environmental impact statements and environmental assessments. The Ninth Oak Ridge National Laboratory Life Sciences Symposium was dedicated to the celebration of this anniversary. The symposium was held October 24--27, 1989, in Knoxville, Tennessee. The intent of the symposium was (1) to review what has been learned while performing NEPA assessments, (2) to summarize the state-of-the-art in methods and approaches, and (3) to define future opportunities and new approaches required to link high quality science to the decision-making process.