Adaptation services of floodplains and wetlands under transformational climate change.

Adaptation services are the ecosystem processes and services that benefit people by increasing their ability to adapt to change. Benefits may accrue from existing but newly used services where ecosystems persist or from novel services supplied following ecosystem transformation. Ecosystem properties that enable persistence or transformation are important adaptation services because they support future options. The adaptation services approach can be applied to decisions on trade-offs between currently valued services and benefits from maintaining future options. For example, ecosystem functions and services of floodplains depend on river flows. In those regions of the world where climate change projections are for hotter, drier conditions, floods will be less frequent and floodplains will either persist, though with modified structure and function, or transform to terrestrial (flood-independent) ecosystems. Many currently valued ecosystem services will reduce in supply or become unavailable, but new options are provided by adaptation services. We present a case study from the Murray-Darling Basin, Australia, for operationalizing the adaptation services concept for floodplains and wetlands. We found large changes in flow and flood regimes are likely under a scenario of +1.6°C by 2030, even with additional water restored to rivers under the proposed Murray-Darling Basin Plan. We predict major changes to floodplain ecosystems, including contraction of riparian forests and woodlands and expansion of terrestrial, drought-tolerant vegetation communities. Examples of adaptation services under this scenario include substitution of irrigated agriculture with dryland cropping and floodplain grazing; mitigation of damage from rarer, extreme floods; and increased tourism, recreational, and cultural values derived from fewer, smaller wetlands that can be maintained with environmental flows. Management for adaptation services will require decisions on where intervention can enable ecosystem persistence and where transformation is inevitable. New ways of managing water that include consideration of the increasing importance of adaptation services requires major changes to decision-making that better account for landscape heterogeneity and large-scale change rather than attempting to maintain ecosystems in fixed states.