Definition

CIA is the analysis of all effects on an area from one or more activities as they accumulate over time and space.

Elements

1. Cumulative effects can result from an accumulation of effects from numerous activities.
2. Cumulative effects can result from a combination of effects from one activity.
3. In either case, cumulative effects can be different in nature (e.g. synergistic), larger in magnitude, greater in significance, more long-lasting, and/or greater in spatial extent than is the case with individual effects.

Issues

1. Data Management. The amount of data required to identify and predict cumulative effects is likely to be much greater than for individual effects, as is the extent and complexity of data manipulation. Increased data requirements mean increased costs (and time). The expected results must be weighed carefully against the resources required.
2. Uncertainty. Much uncertainty already exists with the identification and prediction of environmental effects. This is only increased with cumulative effects, particularly as manipulative and synergistic effects are considered.
3. Operational Problems. Methods available for environmental impact analysis are not directly applicable to cumulative impact analysis because they usually address only first-order, cause-effect relationships. Thus, methods have to be developed or adapted for use in CIA.
4. Scale. Cumulative effects may not be restricted to the area in which the activity is taking place, and indeed may cross political (i.e. district and regional) boundaries. This poses a potential problem in that inter-district co-operation and co-ordination may be required for addressing cumulative effects, but the institutional framework for accomplishing this may not be in place.

Questions to Address

1. Given the issues just presented, how can consideration of cumulative effects be incorporated into day-to-day planning activities and decisions?
2. Do we need to predict cumulative effects within some specified level of certainty, or is it sufficient to identify the probable existence and relative magnitude of these effects?
3. Can we impose constraints on future development because of effects that have accumulated over time from pre-existing activities?
4. If we do not impose constraints at some point, how do we achieve sustainable management?
5. Can a consent be denied or an activity not permitted because of the precedent that might be set for future development, based on cumulative effects that may result?

A SUGGESTED METHOD FOR IDENTIFYING CUMULATIVE EFFECTS

The diagrams presented here provide a means of identifying, or "flagging", cumulative effects. This method does not lend itself to measurement or prediction, but it does allow for identification of potential cumulative effects. This technique is derived from both the matrix and overlay methods and requires a series of matrices for either different levels of effects (as in Diagram A) or for the cumulative effects of several activities (Diagram B). Once individual matrices are completed, the composite that results from overlaying them will highlight areas for particular attention.

Figure 6.4 Diagrams A and B