Finding a level playing field for mangroves

A hidden gradient of salinity stretches beneath mangroves. To understand how climate change affects this, it must first be measured.
Mangrove plants are highly adapted to the salinity and frequency of inundation by sea water from tides.

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BOGOR, Indonesia – To prepare for a rise in sea level, you should surely first know where sea level is. The dense mangrove forests around many of Asia’s coasts appear flat, but there is an invisible gradient hidden in them.

As you move landward from the sea, the amount of salt dissolved in the water decreases. The waters become less saline and more brackish, as seawater increasingly mixes with fresh water from rivers and other inland sources.

Change the sea level by even centimeters, and that hidden gradient of salinity will be immensely altered.

Mangrove plants are rooted in this water. They are highly adapted to the salinity and frequency of inundation by sea water from tides. There are dozens of species with various coping mechanisms.

Many have something unique to help them. These are specialised aerial roots which extract oxygen from the air. These ‘pneumatophore pumps’ enable them to grow in ‘anoxic’ sediments, where oxygen is scarce or absent.

The plants position themselves on the fringes or in the interior, according to their adaptive capacity. Some cannot survive if the water is too salty, or not salty enough.

The forest plays a key ecological role. The root structure serves as a sediment trap and protects the interior from heavy waves, storm surges. It may also protect it from future sea level rises.

If sea levels rise, to do anything meaningful to tackle the results, we need to know in some detail where sea level actually is, or was. We also need to know how mangroves play their roles, and react to tides and moving sediments. It may not be at all obvious.

At the Center for International Forestry Research (CIFOR), we have initiated a project that could provide new data on this …

Editor’s note: This is an excerpt of an article that appears in its entirety on the website of the International Union of Forest Research Organizations (IUFRO). To read the rest of this article — and to cast your vote for this article in a blog competition ahead of the IUFRO World Congress in October 2014 — click here.


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