In addition to the physical influences on habitat patterns discussed in Chapter 5, there is a historical context associated with human activities that must be understood to explain changes in the vertebrate communities that we have observed over the past several hundred years and the patterns that we see today. Native Americans likely maintained more open landscape conditions through use of agriculture and fire than what may have been first described by European settlers (Boag 1992). Humans are a part of ecosystems and they have been on some continents for millennia. The influx of European humans into the North American environment led to changes in forest cover and distribution that were quite different from the historic conditions that occurred up to that point. There are several factors that have occurred since the arrival of European humans onto the North American continent that set the context for management of habitat in North American forests.
The distribution of vegetation is faced with three dominant current pressures that might change habitat quality for many species at a much more rapid rate than has occurred historically: (1) land use, (2) global climate change, and (3) invasive species. These forces represent a significant common ground between foresters and wildlife biologists. Discussions about how to manage forests for products and habitat for species fall silent when forests are replaced by other systems.