Testing and developing a wetland assessment index in southeast Australia using aquatic plants

Abstract

The vegetation-based Hawkesbury-Nepean Wetland Assessment (HNWA) Index developed by Sainty and Jacobs (1997), was evaluated using three years of field survey data. Twenty-one wetlands that varied in geomorphology, dominant vegetation, hydrology, substrate and degree of human impact were assessed. Data from these wetlands were used to investigate the influence that taxonomic resolution (plant identification to family, genus or to lower ranks), species inclusion (all species recorded or only aquatic species recorded), spatial and temporal variability, cover class and scaling had on overall performance of the index. A modified water plant index was developed that is simpler and has a wider geographic application than other options available in Australian for on-ground wetland condition assessment using aquatic plants. Application of real data to the index highlighted the cumulative effects of error on summarising data into a single index and compounding effects to multimetric situations. © 2011 Royal Botanic Gardens and Domain Trust.