Mangrove Forests May Save Coasts from Sea Level Rise

First Posted: Jul 23, 2015 12:01 PM EDT

There may be an environmentally friendly way to protect coastal areas from sea-level rise: save the mangroves. Scientists have found that mangrove forests actually help protect coastlines from rising seas.

Coastal estuaries and recesses in coastlines that form bays receive the run-off from erosion on steep catchments, which give them the tendency to fill in over time. As they infill, the movement of the tidal currents over the shallow areas create networks of sandbanks and channels. The sand banks grow upward to keep pace with water-level changes, while the channels get deeper to efficiently drain the excess water out to see.

In this latest study, the researchers took New Zealand mangrove data as the basis of a new modeling system to see what would happen to different types of estuaries and river deltas during sea level rise. They found that areas without mangroves are more likely to widen from erosion, which causes more water to encroach inwards. However, areas with mangroves actually prevent this effect, and soil is more likely to build up among their roots and act to reduce energy from waves and tidal currents.

"As a mangrove forest begins to develop, the creation of a network of channels is relatively fast," said Barend van Maanen, one of the researchers, in a news release. "Tidal currents, sediment transport and mangroves significantly modify the estuarine environment, creating a dense channel network. With the mangrove forest, these channels become shallower through organic matter from the trees, reduced sediment resuspensions (caused by the mangroves) and sediment trapping (also caused by the mangroves) and the sea bed begins to rise, with bed elevation increasing a few millimeters per year until the area is no longer inundated by the tide."

The findings reveal that mangroves could play a crucial role in buffering areas from sea level rise as climate change continues. In fact, the study suggests that areas should consider implementing mangrove forests where sea level rise might be a major concern.

The findings are published in the journal Proceedings of the Royal Society A.