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close this bookConducting Environmental Impact Assessment in Developing Countries (United Nations University, 1999, 375 p.)
close this folder9. Emerging developments in EIA
close this folder9.2 Cumulative effects assessment
close this folder9.2.1 Concepts and principles relevant to CEA
View the document(introduction...)
View the document9.2.1.1 Model of causality
View the document9.2.1.2 Input-process-output model
View the document9.2.1.3 Temporal and spatial accumulation
View the document9.2.1.4 Control factors Temporal and spatial accumulation

Time and space are generic to each of the components of the input-process-output model of cumulative environmental change. A temporal perspective recognizes that in an environmental system exposed to continuous or repeated inputs, the interval between each input may be insufficient for system recovery before the next input occurs, resulting in temporal accumulation. Processes with lengthy feedback loops may contribute to time delays. The output or system response may differ over the short and long term, as the response frequently requires critical thresholds to be reached before cumulative effects are apparent.

A spatial dimension is also evident. In environmental systems subjected to multiple inputs, such as those from non-point sources, the spatial proximity between inputs may be too small to disperse each input, resulting in spatial accumulation. The additive and interactive mechanisms of environmental processes at local scales may increase and contribute to regional environmental change. System responses may also involve cross-boundary movement or alter the spatial pattern of a landscape.