The combined power of different ecosystems for the protection and resilience of coastal regions.

A group of scientists discovered recently that the combination of coral reefs, seagrasses and mangrove, provides greater protection to coastal regions than any individual habitat or combination of two habitats.

This study, held in Belize (Caribbean sea), and published in July of 2016 (Guannel et al., 2016), aimed to quantify the coastal protection services provided by marine habitats in different geomorphologic settings, climate conditions and sea-level rise.

It was investigated and quantified the individual and combined services provided by three different habitats (coral reefs, seagrasses and mangrove) and its relative importance in hurricane and normal conditions (non-storm), through 9 years (2005-2013), using current and future projections of sea-level rise.

Several scenarios of presence or absence of habitats were studied, considering the current framework of sea-level rise, a future framework with predicted sea-level rise of 1 m, and several reversible factors in simulated conditions (e.g. wave heights, flooding levels, volume of mud bed scoured, etc.).

It was found that the complementarity of these three habitats makes them more capable to protect coastal communities against wave and storm impacts, than one habitat individually or than the combination of two. However, this effectiveness depends on the habitat conservation status, local geomorphology, habitat location and stress conditions.

The simulation of future conditions of sea-level rise showed that reefs with living corals maintain their protection effectiveness and increase their vertically aggregation with increasing depth, while the dead coral reefs, with sea-level rising, become shallower and weaker, due to the waves’ action and erosion, losing its protection capacity.

Coral outcrop on Flynn Reef

In storm conditions, it was found that the coral reefs and seagrasses contribute positively to the reduction of erosion potential, through dissipation of wave energy. On the other hand, the mangrove forests reduce the flooding level and drag of mud and are the unique habitat, considered in this study, with potential to moderate the storms effects. The combination of these three habitats provides therefore greater benefits of coastal protection and increased resilience of coastal regions.

seagrass

This study reinforces the importance of using integrated approaches to assess the coastal protection services provided by marine habitats in elaboration of conservation or restoration plans.

Source

Guannel, G.; Arkema, K.; Ruggiero, P.; Verutes, G. (2016). The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience, PLoS ONE 11(7): e0158094, doi:10.1371/journal.pone.0158094

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