Adaptation tipping points of urban wetlands under a drying climate

Abstract. Urban wetlands experience considerable alteration to their hydrology, which typically contributes to a decline in their overall ecological integrity. Wetland management strategies aim to repair wetland hydrology and attenuate wetland loss associated with climate change. However, decision makers often lack the data needed to support complex social environmental systems models, making it difficult to assess the effectiveness of current or past practices. Adaptation Tipping Points (ATPs) is a method that can be useful in these situations. The method assesses thresholds exceedance of ecological objectives obtained from policy and informs about the effectiveness of the management strategy to the delivery of certain social or environmental goals. Here we trial the method on an urban wetland in a region experiencing a markedly drying climate. ATPs were defined by linking key ecological objectives identified by policy documents to threshold values for water depth. We then used long-term hydrologic data (1978–2012) to assess if and when thresholds were breached. We found that from the mid-1990s declining wetland water depth caused ATPs for the majority of the wetland objectives. We conclude that the wetland management strategy has been ineffective from the mid-1990s when the region's climate dried markedly. Empirical verification of the ATP assessment is required to validate the suitability of the method. However, in general we consider ATPs to be a useful desktop method to assess the suitability of management when rigorous ecological data are lacking.