The evolution of fire management has paralleled to some extent the evolution of ecological thought. The Park Service Organic Act (1916) spoke to "conserving the natural and historic objects ..." as if resources within parks were but a collection of objects. As the concept of ecosystems developed, so did the idea that the magnificent objects in our national parks were closely tied to other parts of the ecosystem. Conserving natural objects or natural ecosystem states, then, depended on conserving the natural processes associated with them. By the mid-1960s, we had altered some of these natural processes for 50 to 100 years. How could we restore these systems to where they should have evolved had we not interfered with certain natural processes at an earlier time? Guidance was provided by policy (the Leopold Report of 1963 was adopted as official policy) and by legislation, particularly the Wilderness Act.