NPS Director's Order 12: Conservation Planning, Environmental Impact Analysis and Decision Making Back to EQD
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White Sands National Monument, NM2.9 Overview of the NEPA Process — Impacts

Grand Canyon National Park, AZAn impact differs from an issue. An issue describes an environmental problem or relationship between a resource and an action(s). Impact analysis predicts the degree to which the resource will be affected (see 4.5(g) for more information). Impact topics are derived from issue statements, and should be quite specific. For example, if the impact of building a lodge on the north rim of the Grand Canyon to visitor views is confined to the view of the Colorado River from a 200-meter section of one trail, the impact topic should be “views of the river from a 200-meter section of the trail” rather than “views of the canyon from the north rim.” This helps keep the analysis (and documents) focused and analytical.

To help decision-makers completely understand how a resource will be affected, you must include considerations of context, intensity, duration, and timing (1508.27). The following categories of impacts must be considered and analyzed for any park proposal and its alternatives, regardless of how the analysis is documented (CE, EA, or EIS). Impacts, effects, and environmental consequences are synonymous throughout this handbook and the CEQ regulations.

Further Links:

NPS NEPA Analysis Process

Implementation Methodology Example (Get the Adobe Acrobat PDF Reader 5.0 to read the document.)

A. Direct effects (1508.8)

These are impacts that are caused by the alternatives at the same time and in the same place as the action. For example, grading a building site removes soil and vegetation at the site and, if an archeological resource is present, destroys surface and subsurface deposits.

B. Indirect effects (1508.8)

Indirect effects are impacts caused by the alternatives, that occur later in time or farther in distance than the action. For instance, if allowing a utility to string a transmission line through your park to serve a nearby town is something you reasonably expect will ultimately result in increased growth and encroachment of development on park boundaries, these indirect impacts need to be included in the NEPA document analyzing the transmission line. Implementing a day-use reservation system may have indirect socioeconomic impacts on neighboring businesses or concessions inside the park. These are examples of impacts occurring later in time.

The alternatives may also have indirect effects that occur farther in distance from the action. For instance, discharging effluent into a river would affect the water quality far from the actual site of the release. You do not need to call out direct or indirect effects specifically in a NEPA document, although cumulative impacts do need to be identified separately.

C. Cumulative effects (1508.7)

Cumulative effects are “additive” impacts to a particular resource. An EIS or an EA analyzes them without regard to land ownership (i.e., cumulative effects may occur from actions on private or other agency land), and it includes impacts of actions in the past, the present, and the reasonable foreseeable future (see section 2.4, cumulative actions).

Although it is clear that CEQ does not want agencies to segment their proposals into pieces that have less potential for significant impact alone than when viewed together (see 1.4 (F)), the requirement to analyze cumulative impacts goes much farther than this. A complete picture of forces already acting upon a particular environmental resource is essential in making reasonable decisions about the management of that resource. If sources of impact exist, whether they are on private or public land, or whether they were taken in the past, are ongoing now, or have a reasonable chance of occurring in a future when the impacts of the proposal are also ongoing, their combined impacts give decision-makers and the public a clear idea of the “absolute” impact the resource is experiencing. For instance, if your park is proposing clearing vegetation to build a campground in the middle of important elk winter range, last year’s timber cut on the adjacent federal forest in elk winter range has an additive impact on the elk population and must be part of the cumulative impact. A large housing development proposed for next year on private land in elk habitat is also going to have an adverse effect, and this should be included if you believe it is reasonable to assume the homes will be built.

For the example above, cumulative impacts can extend over entire watersheds, or thousands of square miles of elk range. Yet, because the action causing an impact is farther away from the park’s proposal, in time or geographically, it often has a diminishing additive impact. The IDT is critical in deciding which actions, activities, or sources of impact to include in a cumulative impact analysis, and the team should use common sense in deciding the extent of the cumulative impacts “boundary” (see section 2.8 (A)). Although a multitude of actions may contribute impact infinitesimally to the same resource that the NPS proposal is expected to affect, only those that resource specialists feel are clear contributors or that can feasibly be analyzed need to be included. As a general rule, the farther removed an action is from the project area or the project start date, the less need there is for detailed and exact analysis of the action’s cumulative impacts.

The analysis of cumulative impacts may be particularly important for larger-scale park planning or resource management efforts. To return to the elk example, if elk winter range is a resource that you believe is important to maintain in pristine condition within the park, but a migration corridor between it and elk summer range is proposed for development, knowing how the developed corridor will affect the elk population may be important in deciding how to manage the park’s winter range.

Further Links:

Guidance and Cumulative Effects

Yosemite Lessons Learned

Considering Cumulative Effects Under the National Environmental Policy Act

D. Impairment

The impact analysis must also include a finding on whether or not the actions contained in the alternatives would “impair” park resources. (See Section 1.4, NPS Management Policies 2001 — formerly DO-55 — and this section 1.2E of this handbook.)

Further Links:

See also DO-12 section 4.7

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