3.1 INTRODUCTION

Climate change poses a significant threat to the capacity of the world's freshwater ecosystems to provide critical water ecosystem services upon which both human and non-human systems rely (Bates et al. 2008). High degrees of exposure and sensitivity to climate change effects, amplified by the position of freshwater ecosystems in the landscape and constraints on their adaptive capacity due to intensive human use and modification, imply a high level of vulnerability among freshwater ecosystems to climate change (Vörösmarty et al. 2010; Capon et al. 2013). Rising temperatures, sea-level rise, and changes to the hydrologic cycle are all expected to alter the distribution and extent of goods and services supplied by freshwater ecosystems (Palmer et al. 2009). At the same time, dramatic increases in human demands for water ecosystem services, particularly provisioning services (e.g. water supplies for irrigation), are widely anticipated (UNESCO 2012; Salman and Martinez, this book). The importance of many regulating and supporting ecosystem services (e.g. water purification) for both human and non-human needs are also likely to grow under a changing climate (Capon et al. 2013). Indeed, the role of some water ecosystems services can be anticipated to become increasingly critical in relation to climate change mitigation (e.g. climate regulation) and adaptation (e.g. flood control). Effective human responses to climate change must therefore be underpinned by an understanding of climate change risks to water ecosystem services and options for their protection, restoration, or enhancement.

In this chapter we propose an ecosystem services-based approach to climate change adaptation to enable an integrated assessment of climate change risks that accounts for both human and non-human systems, as well as their interactions. Adopting ecosystem services as targets for managed adaptation can guide the prioritisation of adaptation measures so that low-regret options with multiple benefits are highlighted and perverse outcomes avoided. An ecosystem services-based approach also offers a basis for communication and education to engender public and political engagement in climate change adaptation decision-making.