A rapid assessment method for coupling anthropogenic stressors and wetland ecological condition

摘要

South Africa faces growing impacts on wetlands and limited resources for conducting assessments. In response, a method for the rapid assessment of ecological condition based on the impacts of human stressors on hydrogeomorphic processes and vegetation responses was developed. The rapid assessment method, referred to as WET-Health, divides wetlands into hydrogeomorphic (HGM) units that are assessed individually. Results are then combined into a composite health score for the wetland system being evaluated. Deviation from the natural reference condition is examined for three separate but interlinked components of ecosystem health: hydrology, geomorphology and vegetation. The spatial extent of the HGM unit affected by a human impact is estimated and the intensity of the impact in the affected area is scored on a scale of 0 (no impact) to 10 (complete transformation) based on pre-determined indicators that are rated using clear scoring guidelines. Extent and intensity are combined to give an index of the level of departure from the natural reference condition. An assessment is also made in each module of the likely trajectory of change of the wetland. This paper describes the method in order to reflect on the central approach and highlight its heuristic and hypothesis generating value.