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Example of Cumulative Effects Analysis

Last Page Update: July 29, 2010 
Cumulative Effects Analysis
 
For each cumulative effect issue:
1.      Determine geographic and temporal scope. 
You need to set the boundaries for each resource, and the boundaries will often differ for different issues. The geographic and temporal scope should encompass the extent of the direct and indirect effects of the proposed action and alternatives.  
 
The geographic scope is generally based on the natural boundaries of the resource affected, rather than jurisdictional boundaries. For example analyzing water quality, the watershed is likely the appropriate geographic boundary. For analyzing air quality, the airshed is likely the appropriate geographic boundary. Be sure to provide a rationale for the boundary you select.
 

CEQ has recommended the following geographic areas to be considered in setting geographic boundaries for analysis:

Defining the temporal scope for analysis should generally be based upon the duration of the effects of the proposed action or alternatives. Note: it is the duration of the effects of the action that is relevant here, not the duration of the action itself. Timeframes, like geographic scope, can vary by resource.
 
Typically, setting these boundaries is something you first consider in scoping; initially set in the description of the Affected Environment; and then revisit after preliminary effects analysis. 
 
2.      Describe the effects of past actions within the geographic scope. You must consider past actions, regardless of who took the action, within the geographic scope to provide context for the cumulative effects analysis. Past actions can usually be described by their aggregate effect without listing or analyzing the effects of individual past actions. BLM NEPA Handbook 6.8.3.4. Typically, the affected environment section will provide a description of the aggregate effect of past actions.
{build graphic for Fig. 6.3 for steps 2, 3, 4, 5}
 
3.      Describe the effects of other present actions within the geographic scope. Collect information on ongoing actions, regardless of who will take the action, within the geographic and temporal scope. This should be addressed in scoping. Describe the direct and indirect effects of these actions. 
 
4.      Describe the effects of reasonably foreseeable actions within the geographic and temporal scope. Collect information on reasonably foreseeable actions, regardless of who will take the action, within the geographic and temporal scope. This should be addressed in scoping. The BLM NEPA Handbook explains that, for the BLM, reasonably foreseeable actions are those for which there are existing decisions, funding, formal proposals, or which are highly probable, based on known opportunities or trends. You cannot limit reasonably foreseeable future actions to those that are approved or funded. On the other hand, you are not required to speculate about future actions that are merely possible, but not highly probable based on information available to you (Handbook 6.8.3.4). Describe the direct and indirect effects of these actions.     
 
5.      Describe the direct and indirect effects of the proposed action and each action alternative. You need the analytical conclusions from your analysis of the direct and indirect effects of the proposed action and alternatives for the cumulative effects analysis. For more information on how to analyze direct and indirect effects, refer to Analyzing Impacts course (1620-10).
 
6.      Put together the effects of past, present, reasonably foreseeable actions with the effects of the proposed action and describe the interaction among the combined effects. Sometimes you combine them by adding the effects together, other times you combine the effects by subtracting them. In the earlier example, BLM is proposing to restore 4 acres of habitat for a listed species. Forest Service is proposing to restore 2 acres of habitat for the same species. The cumulative effect is the restoration of 4 acres plus 2 acres, for a total increase of 6 acres of habitat, increasing the current level of 1,000 acres to 1,006 acres. In a different example, BLM is proposing to restore 4 acres of habitat for a listed species, and the Forest Service is proposing to remove 2 acres of habitat for the same species. The cumulative effect is the restoration of 4 acres minus the removal of 2 acres, for a net increase of 2 acres of habitat, increasing the current level of 1,000 acres to 1,002 acres.
 
7.      Describe the relationship of the cumulative effects to any thresholds. Interpret what the cumulative effect would mean for the resource. Identified thresholds, such as regulatory or biological thresholds, can establish a useful point of comparison for interpreting the impact on the resource.
 
 
Tips about Cumulative Effects
  • You must name/describe the Cumulative Effects Study Area for each resource for which you are analyzing cumulative effects.
  • You must describe the applicable Past, Present, and Reasonably Foreseeable Future Actions to the degree appropriate for the level of cumulative impact. For some resources we simply describe the CESA and then state there are no issues of concern. The greater the degree of cumulative impacts, the greater the effort we have to make to describe the PPRFFAs and their contribution to the cumulative effects and the summation of those impacts.
  • Do not simply restate the direct and indirect impacts of the proposed action and alternatives.
  • You must address the cumulative impact of each alternative and, if feasible, compare them against each other to enable the decision maker to balance the impacts of the alternatives and make a reasoned decision. Although it is not required to analyze the cumulative impacts of a beneficial impact to a resource, it may be wise to do so if that analysis will enable the decision maker to make a better decision.
  • You must draw a conclusion about each alternative (e.g. the negligible cumulative impacts are not an issue of concern). You must not leave an open-ended statement that does not draw a conclusion or state a quantitative value. (e.g., the mines on the Carlin Trend will cumulatively emit arsenic, mercury, and cyanide compounds into the atmosphere) ( it is open-ended because it doesn't tell us how much and therefore doesn't tell us anything about the risk or the need for mitigation - that one was a big loser in court). 
 
Cumulative Effects Example--Timber Sale
 
How would commercial thinning of the stand affect northern spotted owl dispersal habitat?
 
Geographic scope –The RMP EIS described the effective scale for evaluating northern spotted owl habitat as approximated by the sixth-field watershed and that description is incorporated here by reference (RMP EIS, Chapter 4, p. 5). As such, the geographic scope for the analysis of this issue is the Warm Creek sixth-field watershed.
 
Temporal scope – Within 15 years of treatment, stand growth would re-establish dispersal habitat conditions in the stand. As such, the timeframe for analysis of this issue is 15 years after harvest.
Affected Environment - This analysis is tiered to the RMP EIS, which analyzed the current condition of northern spotted owl dispersal habitat within the sixth-field watershed. That analysis concluded that 60% of the watershed is currently dispersal habitat, which provides for adequate dispersal conditions to allow movement of owls among blocks of nesting habitat (RMP EIS, Chapter 3, pp. 15-18). That analysis is incorporated here by reference. Dispersal conditions for owls in the watershed have not changed since the RMP EIS in a way that would alter the analytical conclusions in the RMP EIS.
 
Past Actions - The effects of past actions on northern spotted owl dispersal habitat in the Warm Creek watershed were analyzed in the description of the affected environment in the RMP EIS (Chapter 3, pp. 15-18). The RMP EIS analysis described that forests across the region historically would have provided approximately 80% dispersal habitat. Past clearcut timber harvest removed dispersal habitat, resulting in the current condition of 60% dispersal habitat. The current dispersal habitat within the watershed provides for adequate dispersal conditions to allow movement of owls among blocks of nesting habitat. That analysis is incorporated here by reference.
 
Present Actions - There are no ongoing actions that are affecting northern spotted owl dispersal habitat in the Warm Creek watershed.
 
Reasonably Foreseeable Actions - The RMP EIS analyzed reasonably foreseeable actions that would affect northern spotted owl dispersal habitat within the Warm Creek watershed. That analysis described future timber harvest that is highly probable to occur on BLM-administered lands, Forest Service land, and private land that would result in loss of dispersal habitat and forest growth that would result in increase in dispersal habitat. That analysis concluded that forest growth within the watershed would result in a net increase in the amount of dispersal habitat of 5% of the watershed over the next 15 years. Therefore, the Warm Creek watershed, which already provides adequate dispersal habitat, would improve in dispersal conditions in the future (RMP EIS, Chapter 4, pp. 81-83). That analysis is incorporated here by reference.
 
Proposed Action - Alternative 1 would reduce the stand density below the 40% canopy closure threshold for dispersal habitat, resulting in the removal of 100 acres of dispersal habitat until stand growth reestablishes 40% canopy closure in 15 years. This 100-acre loss represents 1% of the current dispersal habitat within the watershed. Alternative 2 would maintain more than 40% canopy closure in the thinned stand, resulting in no removal of dispersal habitat.
 
Put together the effects –
No Action
80%=baseline
60%=past actions (timber harvest)
60%=present actions (none)
65%=future (BLM, FS, and private timber harvest)
 
Action Alt 1
80%=baseline
60%=past actions (timber harvest)
60%=present actions (none)
65%=future (BLM, FS, and private timber harvest)
64%=proposed action (heavier commercial thinning)
 
Action Alt 2
80%=baseline
60%=past actions (timber harvest)
60%=present actions (none)
65%=future (BLM, FS, and private timber harvest)
65%=proposed action (lighter commercial thinning)
 
Describe the relationship to any thresholds - As described in the RMP EIS, watersheds with more than 50% dispersal habitat are considered adequate to allow movement of owls among blocks of nesting habitat (RMP EIS, Chapter 3, p. 15). That analysis is incorporated here by reference. The watershed currently provides adequate dispersal conditions and dispersal conditions will improve in the future under both Alternative 1 and Alternative 2. The loss of dispersal habitat that would result from Alternative 1 would not lower the amount of dispersal habitat below the 50% threshold; in fact, forest growth would result in an overall net increase in dispersal habitat under Alternative 1. 
 
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How would commercial thinning of the stand affect water temperature in Warm Creek?
 
Geographic scope – at what point downstream is there no measurable temperature change resulting from the proposed action or alternatives? There would be no measurable temperature change from the commercial thinning where Warm Creek meets the Cold River. As such, the geographic scope for analysis of this issue is the watershed for Warm Creek. 
 
Temporal scope – how long would a temperature change resulting from the proposed action or alternatives be detected? Short-term effects of the proposed action on stream temperature would be greatest during the first year following harvest because the stand would provide the least stream shading. Therefore, the short-term timeframe for analysis is 1 year after harvest. Within 5 years of treatment, stream shading would return to pre-treatment levels. At that time, the proposed action or alternatives would no longer have any effect to temperatures in Warm Creek. As such, the long-term timeframe for analysis of this issue is 5 years after harvest.
 
Affected Environment - Current water temperature in Warm Creek is 58.0 degree Fahrenheit, based on water monitoring conducted by BLM. Past clearcut timber harvest and road construction removed stream shading, raising water temperature in Warm Creek. Prior to past timber harvest and road construction, water temperature in Warm Creek was approximately 56.0 degrees, based on comparison to reference streams of similar size in nearby watersheds that have experienced no timber harvest or road construction. Warm Creek is not listed under 303(d) of the Clean Water Act for water temperature (RMP EIS, Chapter 3, p. 42).
 
Past Actions - The effects of past actions on water temperature in Warm Creek were analyzed in aggregate in the Affected Environment. Past clearcut timber harvest and road construction removed stream shading, thereby resulting in the current water temperature of 58.0 degrees Fahrenheit. Prior to past clearcut timber harvest and road construction water temperature in Warm Creek was approximately 56.0 degrees, based on comparison to reference streams of similar size in nearby watersheds that have experienced no timber harvest or road construction.
 
Present Actions - Upstream of the proposed project area, private land is currently being cleared for pasture. After clearing, the riparian area along 500 feet of Warm Creek will be maintained in an open condition with no stream shading, resulting in an increase in stream temperature of Warm Creek 1.0 degree Fahrenheit.
 
Reasonably Foreseeable Actions - BLM has proposed a wildlife habitat restoration project that would create snags in a riparian stand along Warm Creek. Downstream from BLM land, a stand of industry-owned timber is approaching 60 years old. The company has recently begun road work in the area; based on this investment, the timber market, and industry practices in the region, BLM concludes that it is highly probable that the company will clearcut the stand in the next few years. The clearcut harvest would result in an increase in stream temperature of 0.5 degrees Fahrenheit. 
 
Proposed Action - Immediately after harvest under Alternative 1, reduction in stream shading would result in a 0.2 degree Fahrenheit temperature increase in Warm Creek. Immediately after harvest under Alternative 2, a lighter thinning prescription, reduction in stream shading would result in a 0.1 degree Fahrenheit temperature increase in Warm Creek. There would be no measurable temperature change where Warm Creek meets the Cold River. Within 5 years of treatment, stream shading would return to pre-treatment levels, resulting in no further effect on stream temperature.  
 
Put together the effects –
No Action
56.0=baseline
58.0=past actions (clearcut + roads)
59.0=present action (pasture conversion)
59.5=future (industry clearcut)
 
Action Alt 1
56.0=baseline
58.0=past actions (clearcut + roads)
59.0=present actions (pasture conversion)
59.5=future action (industry clearcut)
59.7=proposed action (heavier commercial thinning)
 
Action Alt 2
56.0=baseline
58.0=past actions (clearcut + roads)
59.0=present actions (pasture conversion)
59.5=future actions (industry clearcut)
59.6=proposed action (lighter commercial thinning)
 
Describe the relationship to any thresholds - In evaluating the significance of the proposed commercial thinning, only the effects of the BLM proposed action (i.e., a 0.2 or 0.5 degree increase in water temperature) count towards significance. If that 0.2 or 0.5 degree increase in water temperature would increase water temperature above some regulatory or biological threshold, there would be a potential for a significant impact. There are no connected or cumulative actions with effects that can be prevented or modified by BLM decision making.  The present action of land-clearing for pasture is not connected with the BLM action, and its effects cannot be prevented or modified by BLM decisionmaking. The reasonably foreseeable timber harvest on industry land is not currently proposed and, even if it were, its effects could not be prevented or modified by BLM decisionmaking. As such, the harvest is neither a connected nor a cumulative action. 
 
Warm Creek is not currently 303(d) listed for temperature. Warm Creek provides habitat for resident trout, which experience sub-lethal adverse effects in water temperatures above 60.0 degrees Fahrenheit. Because the cumulative effects of past, present, and reasonably foreseeable actions would not result in temperatures above 60.0 degrees Fahrenheit, there would be no adverse effects to trout in Warm Creek.