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Mangroves Could Protect Coastlines from Storms, Sea Level Rise

LONDON, Jul 31 2015 (IPS) - The importance of mangroves in protecting coastal areas under threat due to sea level rise caused by climate change may have been underestimated, according to new research.

A joint study between researchers at the University of Southampton in the United Kingdom and the Universities of Auckland and Waikato in New Zealand looked at how mangrove forests respond to elevated sea levels.

 

Dr. Barend van Maanen of the University of Southampton said in a statement: “As a mangrove forest begins to develop, the creation of a network of channels is relatively fast. Tidal currents, sediment transport and mangroves significantly modify the estuarine environment, creating a dense channel network.

“Within 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 millimetres per year until the area is no longer inundated by the tide.”

The team predicted what happens to different types of estuaries and river deltas when sea levels rise.

Taking New Zealand mangrove data as the basis of a new modelling system and using cutting-edge mathematical simulations, they found areas without mangroves are likely to widen from erosion and more water will encroach inwards, whereas mangrove regions prevent this effect. This is likely due to soil building up around their mesh-like roots and acting to reduce energy from waves and tidal currents.

In modelling sea level rise in the study, the ability of mangrove forests to gradually create a buffer between sea and land occurs even when the area is subjected to potential sea level rise of up to 0.5 mm per year. Even after sea level rise, the mangroves showed an enhanced ability to maintain an elevation in the upper intertidal zone.

Associate Professor Karin Bryan of the University of Waikato said, “In New Zealand, mangroves have been traditionally viewed as undesirable as they take over areas where there were once sandy beaches. In other countries, this is not the case as they are seen as a buffer for climate change in low level areas.”

Other studies have shown mangroves have the ability to remove carbon from the atmosphere and protect people from hazards such as tsunamis.

Associate Professor Giovanni Coco of the University of Auckland said, “As we anticipate changes caused by climate change, it’s important to know the effect sea level rise might have, particularly around our coasts.

“Mangroves appear to be resilient to sea level rise and are likely to be able to sustain such climatic change. The implications for the New Zealand coastline are considerable and will require new thinking in terms of sediment budgets and response to climatic changes.”

 
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