Development of a wetland plant indicator list to inform the delineation of wetlands in New South Wales

Abstract

Wetlands experience fluctuating water levels, so their extent varies spatially and temporally. This characteristic is widespread and likely to increase as global temperatures and evaporation rates increase. The temporary nature of wetlands can confound where a wetland begins and ends, resulting in unreliable mapping and determination of wetland areas for inventory, planning or monitoring purposes. The occurrence of plants that rely on the presence of water for part or all of their life history can be a reliable way to determine the extent of water-affected ecosystems. A wetland plant indicator list (WPIL) could enable more accurate mapping and provide a tool for on-ground validation of wetland boundaries. However, this introduces the problem of the definition of ‘wetland plant’, especially with species that can tolerate, or require, water level fluctuation, and that respond to flooding or drought by adjusting their morphology or phenology (i.e. ‘amphibious’ plants and those that grow only during drawdown). In this study we developed a WPIL through a process of expert elicitation. The expert decisions were compared and standardised for each species. It is envisaged that this work will lead to a comprehensive listing of wetland plants for Australia for the purposes of planning, mapping and management.