Joining the dots: hydrology, freshwater ecosystem values and adaptation options

Abstract The objective of this research was to investigate and test the necessary steps in developing an adaptation planning framework for freshwater biodiversity. We used Tasmania as a test case to demonstrate how downscaled climate model outputs could be integrated with spatially resolved hydrological models and freshwater biodiversity data. This enabled us to scope adaptation actions at local, regional and state scales for Tasmania, and to explore how priorities might be set. To achieve this integration we quantified how different climate change scenarios could affect the risks to biodiversity and ecosystem values (‘biodiversity assets’) in freshwaters, the scope and types of adaptation actions, and assessed the strengths and weaknesses of the policy and planning instruments in responding to climate change. We concluded that downscaled climate modelling, linked with modelling of catchment and hydrological processes, refines projections for climate-driven risks to aquatic environments. Spatial and temporal hazards and risks can now be compared at a variety of scales, as well as comparisons between biodiversity assets (e.g. relative risk to riparian vegetation v. in-stream biota). Uncertainties can be identified and built into adaptation processes. Notwithstanding this progress, we identified a number of issues that need to be addressed in order to increase confidence in this process. The main issues for improved and timely modelling are: frameworks for using and downscaling outputs from improved global climate models as they become available; better data on thermal tolerances of freshwater biota; and, improved methods for predicting key water temperature variables from air temperature and other biophysical predictors. Improvements are also needed in updating and maintaining high quality biodiversity data sets, and better spatially explicit information on the contributions of groundwater to surface waters and rates of recharge. The list of adaptation options available is extensive, but the key challenge is to organise these options so that stakeholders are not overwhelmed. Scenario modelling that incorporates explicit tools for comparing costs, benefits, feasibility and social acceptability should help with setting priorities but require further development. A review of current Australian policies revealed a variety of responses driven by both water reform and climate change agendas. Many agencies are actively revising their policies to accommodate adaptation. However, we note that much of the reform of the water sector in the last 10–15 years has aimed to improve certainty for non-environmental water uses. Under the National Water Initiative, governments have agreed that entitlement holders should bear the risks of reduced volumes or reliability of their water allocations as a result of changes in climate. The key opportunity for adaptive uptake of climate adaptations is by developing and periodically reviewing water management planning tools. Pathways need to be developed for integrating the traditional evolution of planning and policy with the needs for climate change adaptation for aquatic ecosystems. Formal mechanisms for the uptake of knowledge about identified risks into policy and legislative instruments remain under-developed. An even bigger challenge is to integrate multiple adaptation strategies (sometimes at different scales) to achieve specific adaptation objectives within regions or catchments—especially where a mix of water management and non-water management is required.