Death of mangroves spell doom for Sabah's mud crabs

The Daily Express 20 Jul 08;

Tawau: As food prices soar and people scream for greater food security, Sabah's much sought-after wild mud crabs are dying in their mangrove habitats, at the hands of planters.

This large-size mud crab was found dead inside what looks like an intact pocket of sub-tidal mangrove forest in Bombalai that had been cleared and is now under investigation.

Mud crabs dead in their habitat - how is that possible one might ask. Because its connection with the ebb and flow of tides has been cut off while the last poodle of seawater has been bled dry into a deep drain dug around it by a planter who had also cleared a 20-acre provisional lease mangrove forest (6994) for oil palm, possibly involving tracts of State mangrove forest reserves as well.

Habitat fidelity is characteristic of mud crabs and this fixed trait is probably the downside of their survival where there is a penchant for mangrove clearance.

Tidal and sub-tidal mangrove forests are their fixed homes. They can't migrate to the oil palm estates or the rainforests and survive. So Sabah be warned.

Little by little, a bit of clearing here, a bit of wetland draining there, the bitter truth is that the State's boast of being a seafood paradise may suddenly become history.

When the still affordable seafood runs out, a lot of people will suffer - from the seafood gatherers to restaurants to transporters of the seafood and tourists.

One kilo of mud crab costs RM60 at hawker stalls in Bukit Bintang but it's just RM24 in popular seafood restaurants around KK.

However, abundant seafood can remain only if this generation actively protects wild crabs, etc, in their natural habitat, i.e. Sabah's mangrove forests.

The action of mud crabs on the mangrove forest floors also contribute to abundant fish stocks. The mangrove crabs improve the nutritional quality of the mangal mud for other bottom feeders by mulching the mangrove leaves.

Marine biologists always say where mangrove forests are abundant, fish populations are also abundant in the adjacent coastal waters. Mangrove forests generate high nutrient density and diversity for its nearby waters which makes it extremely productive.

Metaphorically, mangrove forests work like a "bridge" between terrestrial and marine environments. A "bridge" that transfers matter and energy from the land to the sea forming the base of many marine food webs.

This key nutrient transporting dynamic is the reason why a wide diversity of animals is found in estuary mangrove swamps. Because they are constantly replenished with nutrients transported by fresh water runoffs.

Fushed by the ebb and flow of the tides, they support a bursting population of bacteria and other decomposers and filter feeders.

It is an ecosystem that supports billions of worms, protozoas, barnacles, oysters sponges and other invertebrates which are the food of fish and shrimps.

Many fish species that live as adults on the coral reefs live in the mangrove as juveniles.Which is why mangroves are the 'Nursery Habitats' for these species and whose presence increases the population of these fish in the nearby reefs!

However, mangrove forests can perform this crucial seafood enriching role only if the tidal links are maintained.

In the Bombalai saga that was highlighted by Daily Express on Saturday, the planter had on the one hand dug drains to dry off any remnant seawater from a handsome pocket of beautiful mangrove trees where the dead crab was found and built bunds to keep the tides out.

Daily Express received many calls from concerned nature lovers stressing that the Tawau Forestry Department insist on the developer reopening the blocked tidal link to enable the ebb and flow of sea tides to once again flush nutrients in and out.

This means making him fill the drain back, restore the original land profile so that sea tides can move freely in and out again. It is left to the Forestry Director to ensure this since he has already detained the planter's excavator.