NEPA, enacted in 1970, is a procedural law that directs federal agencies to consider the environmental consequences of their actions. To do so, agencies must prepare either an environmental assessment or the more rigorous environmental impact statement if environmental consequences are likely. Both include public participation and anticipated consequences for several alternative actions.

“It’s a look at the effects in context and intensity,” said Kim Smolt, NEPA and litigation specialist for the Forest Service. “Opinion doesn’t enter into it. We look at things that are site-specific.”

The Forest Service must show that it has met every law in their environmental documents, she said.

Analysis is based on recent science, such as what an animal might need for habitat and what effects a particular project would have on that habitat, she said. Much of their analysis is based on models, and professional judgment is based on scientific training and experience, she added.

The one thing that NEPA does not force an agency to do is choose the most environmentally friendly alternative. It also allows an agency to categorically exclude an action if it has been shown consistently to have no significant environmental impacts.