Resilient Reefs and Mangroves: Ecosystem-Based Adaptation to Climate Change

Both coral reefs and mangroves have suffered serious losses over the last several decades due to local human impacts.  They now face even greater challenges associated with adapting to the various effects of higher concentrations of carbon dioxide in the atmosphere - expecially temperature increases, acidificaiton, and sea level rise.  Adaptation can involve both resistance (withstanding stress) and resilience (recovering from damage caused by stress).    For coral  reefs, high temperature events are already causing serious mortality, and 2010 is expected to be an especially damaging year in many locations around the world. Evidence for increasing tolerance to high temperatures (due to physiological adaptation or selection for resistant genotypes) is limited at the scale of communities, despite several decades of episodically extreme temperatures and the documentation of small scale adaptive potential.  The responses of corals to acidification are only now being explored in depth, and although species appear to vary in their sensitivity, information on adaptation is largely lacking.  Sea level rise would normally not be a threat to corals, but could be if growth rates are reduced for other reasons, since corals depend on light for photosynthesis.  In general, reef resilience has been the focus of conservation biologists, leading to an emphasis on improving local conditions, but there is growing concern that resilience alone will not be adequate given the increasing frequency of damaging events.  For mangroves, the effect of sea level rise has been the primary concern.  Here, the main obstacle to adaptation is availability of landward space into which to expand.  The role of mangroves as potential carbon sinks should help create financial incentives for providing space for landward migration.