(introduction...)

Building on the above concepts and principles, a conceptual framework of cumulative environmental change can be developed. The framework is based on an input-process-output model.

• Input is represented by sources of cumulative environmental change (i.e., human actions). Sources are characterized by time, space, and the nature of the perturbation.

• Process is manifested in pathways of cumulative environmental change which are distinguished as additive or interactive.

• Output is exemplified by the resulting cumulative effects, broadly differentiated as structural or functional.

There are three components of the conceptual framework, that is the source, pathways, and effects. They are interconnected in as much as there is a cause and effect relationship between components, together with feedback mechanisms. The various pathways may stimulate other sources of cumulative environmental change and an effect itself may become a source, or activate other pathways, of cumulative environmental change. The following discussion briefly elaborates on each of the three components of the conceptual framework.

Table 9.2 A typology describing the source of cumulative environmental changes applied to three examples of human-environment interactions