The Mangrove is a unique habitat. Neither fully marine, nor terrestrial, they bridge the border between land and sea. Existing in tropical and sub-tropical regions, the mangrove tree has a very unique trait which enables them to colonise this zone.
For most plants, salt is toxic, damaging metabolic processes, resulting in mortality of the plant. But the mangrove tree suffers a daily intrusion of sea-water with the tide, and to survive, has therefore been forced to adapt to withstand salt.
There are three main mechanisms that the mangrove uses to withstand salt:
- Exclusion: Simply by being selective about which ions enter inside the plant, the roots can prevent up to 90% of salt entering inside
- Extrusion: White mangroves have special salt glands, whereby salt is excreted at the base of the leaf
- Accumulation: Other mangroves will accumulate the salt in their leaves, eventually shedding these when saturated with salt
The next problem that mangrove trees face, is becoming submerged in seawater – How do they breathe?
This comes in the form of many weird and wonderful roots. From stilt roots, common in the red mangrove, which literally raises the tree above the incoming tide of water, to pneumatophores which act like a snorkel, sticking up into the air from the soil below (black mangroves), and finally the knee root (white mangrove), the mangrove has successfully adapted to the incoming tide. In these roots, there are special pores called lenticels, which allow the exchange of gases between the root and the surrounding air.
FUN FACT: Some mangrove propagules, or ‘live-young’ can survive up to a year floating in the water before it is stranded in a suitable location to grow.
So what makes the mangroves important?
- The complex tangle of mangrove roots is the perfect hiding spot for young fishes and other marine animals wishing to evade predation. Many parent animals take advantage of this, laying their eggs and/or giving birth in these protected locations. Studies have shown that 25 times more fish exist on reefs in close proximity to mangroves, in comparison to areas where mangroves have been removed!
- The fish, crustaceans, and other marine creatures living in the mangroves contribute millions of dollars every year to the economies of 118 countries which have mangroves bordering their coastlines, and are a rich source of protein for the local communities
- Mangroves and their associated fauna and flora, are a source of natural medicines and timber
- The roots and vegetation of the mangrove work to slow down wave energy. This means that we are protected from damage during tropical storms and tsunamis.
- Mangroves are one of the largest carbon sinks existing today – mangroves sequester carbon 100 times faster than terrestrial habitats!
- Mangroves have a cultural importance for many communities around the world – for example indigenous Australians use the mangroves as a place to teach children about fishing and gathering.
Sadly, there has been a dramatic decline in mangrove forests around the world. Mangroves are cut down to make way for industry, housing, over-exploitation of timber, and to make shrimp farms – which are promptly abandoned after a few years of use.
Here at Soneva Jani, we are lucky to live alongside this incredible ecosystem!
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