Studying the external threats problem

The emergence of external threats as a policy and management issue

The creation of Glen Canyon National Recreation Area

The Tar Sands leasing controversy

Protecting national parks from existing visibility impairment

Conclusion : Resolving external threats to national parks

Appendix 1. Key legislation from the Organic Act and its amendments

Appendix 2. Units in the U.S. National Park System

Appendix 3. Questionnaire that formed the basis of the State of the parks report.