Monitoring biodiversity is not as simple as monitoring other environmental characteristics,
such as air or water quality for which there are well established standards or benchmarks. The
biodiversity values of an area undergo considerable fluctuations as a result of natural processes.
These natural variations need to be identified and monitored so that they can be taken into account in evaluating the results of project interventions. Moreover it is often difficult to assess the impact of project activities on biodiversity in the short term. Therefore monitoring must rely on indicators of likely success rather than absolute measurements of biodiversity.