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3.3.    Environmental pressures and environmental change

3.3.1.      Natural variability, pressures and perturbations

The natural environment is highly variable in time and space, and can change slowly over time as a result of a continuously increasing pressure (stressor) or during major events (perturbation) outside the normal range in which the system exists (Turner et al. 2003). While perturbations such as major floods and droughts clearly exist outside of the local social-economic-ecological system, these events could be considered internal phenomena for the global level (Gallopín 2006). These perturbations represent direct hazards to human settlements and typically require engineering solutions to reduce the sensitivity and exposure of population and infrastructure; such is their potential for human and economic loss. More gradual changes, such as decreased groundwater availability, are typically a function of how the social-economic-ecological system operates and represent over-exploitation and mismanagement of natural resources.