The project has been initiated to demonstrate an alternative technique called Ecological Mangrove Rehabilitation (EMR). The objective of this technique is ecosystem restoration, rather than production forestry or erosion control etc. EMR is a six step process developed by MAP and Roy ‘Robin’ Lewis which involves consultation with local people to facilitate natural regeneration of mangroves by repairing and amending previously altered hydrology and topography. Further details can be found at MAP’s website.
Surprisingly, there is considerable potential for improving the implementation of mangrove rehabilitation as many projects fail, or fail to achieve their objectives, despite the huge amount of relevant published material. Failures are either ‘social’ – not taking into account the desires of the local people or involving them in a genuinely participative manner – or technical, often due to a failure to correct what has been altered previously. Most importantly the hydrology needs to be restored to facilitate the ecosystem to re-establish itself, whether EMR techniques are being used or not. A further area where mangrove projects can be improved is in the biodiversity. Traditional projects tend to include planting only a very few species, producing something akin to a monoculture plantation.
In the case of our site, the initial degradation was due to conversion from mangrove to aquaculture pond. The pond is located in the village of Bang Lang Da, which is within the Krabi Ramsar Site. Despite Ramsar status, aquaculture has proliferated in the Krabi estuary, resulting in a significant loss of mangroves.
Talking Mangroves
The process of consultation starts with identifying a suitable site and negotiating with the owner of the land to ensure that new mangrove would be preserved, not lost at the end of the project. Land tenure is a tricky business in Thailand, with conflicting laws and ill-documented ownership. At Bang Lang Da, discussions with local people explored the site’s history and what they wanted to see happen to it. The pond in question used to be mangrove – the site having been cleared of vegetation more than a decade ago, and the mangrove soil bulldozed laterally to form pond walls. The resulting 0.7ha pond was then used for aquaculture for about five years before being abandoned. This chain of events is common in coastal areas of the tropics and sub-tropics around the world.
In the last three years the mud wall adjoining the concrete sluice gate eroded sufficiently to re-establish tidal flushing inside the pond. However, the substrate is now too low relative to sea level to naturally regenerate due to the top soil removal during pond wall formation, soil compaction from machinery, and soil pore moisture loss when abandoned. In effect, the pond floor had been lowered from mangrove height to mudflat.
Consultation with the local community indicated that they would like to see mangroves back in that area, but with a good representation of Nypa palm (Nypa fruticans). The leaves of the palm are used by coastal folk to make roof sections and cigarette papers, and the insides of the fruit are edible and can be turned into snacks. They also catch and rear crabs, as well as fish in the mangrove area. Thus our objectives for mangrove ecosystem rehabilitation coincided suitably with their livelihood needs, as mangroves provide a habitat for those creatures.
Normally in such a project, WI-TO and MAP would train local people to develop a plan and to implement it themselves. However, this was the first time EMR had been put into operation in Thailand, and the budget was minimal. So with the agreement of the villagers, it was decided that WI-TO would execute this first rehabilitation as a more research-based project, while keeping in close contact with the village. Discussions were helped by the fact that WI-TO had worked with the village a few years previously during the DANIDA ‘Managing Protected Wetlands’ project and so knew the leader of the village crab-rearing group, Bang (i.e. Mr) Don. He has been very supportive of this EMR project and has taken a great interest in the work, even helping with the land preparation.
Getting Down to Business
The first task was to survey the pond to measure the height of the soil relative to sea level and the surrounding mangrove vegetation. This illustrated clearly that the substrate was 50cm-1m too low for Nypa and 30-80cm too low for other species. However, despite being saturated most of the time, the soil condition and biodiversity were excellent, as the tidal flushing had brought in a wealth of creatures. Salinity, measured at 28ppt, was higher than had been hoped but still within tolerance, and the pH was neutral. A minor channel ran diagonally across the pond and the soil was inundated almost every tide.
Work began in March 2009 to improve the drainage of the soil and amend the topography. In Florida, Robin Lewis has used heavy machinery to re-grade sites, as would be done on a building site. In Thai mangroves, it is illegal to use machinery without permission, and the budget meant we had to be disciplined. So the work to mimic the substrate undulation of natural mangrove is being done by hand; deepening and widening the existing channels and digging new channels. The spoil has been carefully piled into hills approximately 1m high. This has allowed the soil forming the banks of the channels and the hills to drain themselves more effectively, and produce substrate at the appropriate height for mangrove growth. These channels and hills mimic natural mangrove and mud lobster (Thalassina anomala) activity.
The creation of the hills and the restoration in general has provided an opportunity to test very practical ideas and solutions, including ‘dibbling’ of various seeds and propagules into the mud. Control plots and test dibbling plots on unaltered areas of pond floor have also been established. On selected hills, where mangroves are now growing, these plants are being monitored for height and leaf count. Hills left blank are monitored for natural regeneration, though it is too early to expect much. However initial results have been very encouraging, with six species already growing on the site.
Staff have also been able to experiment with all aspects of the project; the effectiveness of different tools, appropriate channel sizes and shapes, hill longevity, cost-effective ways of marking features, time taken to excavate unit areas and so on.
Money’s Too Tight to Mention
Bang Lang Da shows that a lack of money need not inhibit repairing or enhancing mangrove. Rather, the project emphasizes what is possible with training and determination. It is hoped that this demonstration site will inspire other communities and NGOs to rehabilitate their own degraded lands and abandoned aquaculture ponds. The traditional livelihood aspect of mangrove rehabilitation is not lost with EMR. It is just transferred from building and tending a nursery to the land preparation work mentioned above – work that should be carried out in conventional mangrove projects anyway.
Much of this learning has already been implemented in MAP’s concurrent project at Ban Talae Nok, Phang Nga province, further up the Thai coast from Krabi. There the community itself re-graded the inside of an abandoned pond and opened it up to tidal flushing, under MAP’s guidance, after a long period of consultation.
To disseminate the learning from Bang Lang Da, a blog has been established, the project has been showcased on APFED’s website and Wetlands International has channelled several study tours and groups to the site. If you would like to visit the site for yourself please get in contact with either K’ Asae Sayaka, Director of Wetlands International – Thailand Office or Jim Enright of Mangrove Action Project. And further help and support is available from a mangrove e-group.