Coastal adaptation with ecological engineering, Cheong et al. 2013

Because of the multiple threats and uncertainties of a changing climate, protecting coastal areas simply by building new seawalls (or some other such inflexible, single-tactic approach) is unlikely to be the most effective option. Instead, combined coastal adaptation strategies to allow for a dynamic response to multiple stressors are increasingly preferred. Climate scientists and coastal managers are mainstreaming inclusion of climate change into an Integrated Coastal Zone Management framework, aimed at promoting the activities of the different coastal sectors by coordinating government agencies and private participation.

Contrary to a “regret-risking option,” a no- or low-regret option is adopted to generate a net social benefit irrespective of the future outcome of climate change. Revamping early warning systems, preventing land reclamation, improving housing and transportation, capacity development in education, poverty reduction, and efforts to build resilient ecosystems are examples of a low- or no-regret options.

Traditional engineering, while sometimes protective of coastal communities, has undesired effects, such as eroding non-target, neighboring coastline and destroying adjacent ecosystems. By contrast, eco-engineering tools emphasize positive interactions among species that boost ecosystem productivity and stability, and therefore the strength of the ecosystem to withstand and buffer heavy storms, thus protecting coastal communities.

For example, sea-grasses planted with clams at their roots grow faster and in turn increase total fixed carbon. Oyster reefs attenuate up to 95% of wave height, control turbidity by removing algae, bacteria, and suspended organic matter, improve water quality through their filtration capacity, and enable seafood supply and thus job creation and recreation. Oyster reefs also support breeding ground for economically valued species, such as blue crab, red drums, flounder and spotted sea trout.

In mangroves, transplants planted in close proximity rather than the traditional spread pattern allows for a shared benefit of positive interaction that enhances plant growth and biodiversity. Restored mangrove ecosystems alleviate the impact of moderate tsunami waves, while the roots trap sediment and elevate the land surface, allowing for adaptation to sea-level rise. Intact mangrove also provides local employment as well as breeding grounds for fish.

Marshes dampen wave actions and reduce shoreline erosion, increase fish production, and are compatible with levee designs on the marshes’ landward edges that are nature-friendly. In the Netherlands, for instance, levees built to prevent flooding during storms were covered with thick grass to maintain their integrity, while the seaward marshes reduce the levees’ exposure to wave action; grasses were then grazed by sheep to provide milk and meat for consumption.

The synergy of ecology and engineering is key to addressing uncertainties related to climate-induced stressors. The combination of traditional and eco-engineering approaches coupled with the evaluation to measure the effectiveness of eco-engineered structures facilitate better decision making and prioritization of options.