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.

Does water status of Eucalyptus largiflorens (Myrtaceae) affect infection by the mistletoe Amyema miquelii (Loranthaceae)?

The impact of soil salinity and host water status on the host / parasite association between Eucalyptus largiflorens (F.Muell.) and Amyema miquelii (Lehm. ex Miq.) Tiegh. was investigated in a semi-arid floodplain environment in southern Australia. Water status of potential hosts (i.e. uninfected E. largiflorens) was assessed at a range of sites with different soil salinities and then compared with mistletoe infection at the same sites. Pre-dawn leaf water potentials (Ψ) of uninfected E. largiflorens declined with increasing salinity, while leaf δ13C values increased. The proportion of infected E. largiflorens at each site decreased significantly with increasing soil salinity. A significant relationship was found between the proportion of infected trees at each site and leaf δ13C values, but not pre-dawn Ψ, of potential hosts. The impact of mistletoes on water status of infected trees was also investigated. Among infected trees, we found no significant relationship between mistletoe volume and either pre-dawn Ψ or leaf δ13C values of hosts. However, there was a significant relationship between host midday leaf Ψ and mistletoe volume, with hosts exhibiting increased stress as mistletoe volume increased. The data suggest that increasing water and / or salinity stress make E. largiflorens a less suitable host for A. miquelii.