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One of the most difficult aspects of environmental management is that we are dealing with a living system that reacts and adapts to management actions. Grazing just a few more cattle may allow thorny shrubs to invade and make a pasture useless. Catching just a few more fish may cause the entire fish population to collapse.
There is no precise way to determine the point at which such changes will occur. However, the probability of such change increases as the ecological system is moved further and further away from its natural state. Systems in their natural state are well adapted to natural disturbances, such as fire or storms. As human activities add stressors (e.g., chemical pollutants), extract resources (e.g., lumber), and change landcover (e.g., fragmentation of forests) the system becomes more vulnerable to radical change. Therefore, ReVA focuses on estimating how far the ecological systems have already been moved from their
natural state.
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