On Friday (2nd February 2012), mangrove enthusiasts in Singapore gathered in Earth Lab, Department of Geography, National University of Singapore to attend Benjamin “Ben” Brown’s talk titled “Ecological mangrove rehabilitation – principles and case studies from Florida and Indonesia”. The talk was hosted by Prof. Dan Friess a.k.a. Mangrove Man himself.
Who is Ben Brown? Here is a brief introduction of Ben- he is the Director of Mangrove Action Project (MAP) Indonesia. Hailing from Ann Arbor,Michigan, Brown has been involved in coastal environmental education and community awareness for almost 20 years. Read more about Ben here.
What is Mangrove Action Project (MAP)? It is a non-governmental organization which focuses on conservation and restoration of mangrove forest (and other coastal ecoystems) worldwide while promoting community-based sustainable management of mangroves. MAP has several regional offices in the U.S. and in some Asian countries, of which Ben is heading its regional office in Indonesia.
The overall message of Ben’s seminar was to highlight the importance of understanding the ecology of mangrove establishment and mangrove geomorphology prior to mangrove restoration for successful and cost-effective restoration of mangroves.
Here below are some highlights of the seminar:
Mangroves are losing out to human kind
They are being destroyed for multiple purposes mainly unsustainable developments including shrimp aquaculture (shrimp ponds), charcoal production and logging, oil exploration and extraction, tourism and urbanization and urban expansion. Shrimp aquaculture is the biggest threat to mangroves of Indonesia.
Blocking water bodies = mangrove death!
Mangrove death may occur when nearby mangrove areas are altered without the knowledge of hydrology, especially modification of tidal creeks or water bodies that support the vegetation area. From various case studies pointed out in the talk, the blockage or damming of creek (e.g. dykes to prevent influx of saltwater into coconut plantations or isolation of shrimp ponds) have resulted in mangrove death by exposure of hypersaline water (no input of freshwater) or erosion (loss of sedimentation input). MAP reinstates the flow of water i.e. the connectivity of freshwater and saltwater inputs in mangroves by drilling holes through the man-made dykes. Hydrology reinstalled!
Mangroves can be uplifted by the tsunami, if not destroyed!
Even mangroves may not survive from after-effects of a tsunami. Indian Ocean Tsunami in Year 2004 raised up elevation of coral reefs and mangrove areas in Acheh. This has lead to massive coral death (and bleaching) due to prolonged emersion/exposure to air and drying out of mangroves. Mangroves at higher elevations are now competing with terrestrial forests for space and survival. Even if the mangroves survive, their propagules will not be dispersed (due to little the no-longer existence of sea flooding for dispersal) nor established (due to the change in soil properties for e.g. soil type, temperature and soil moisture).
Mangrove survival depends on its flooding properties
-Mangroves establishment is highly dependent on frequency of its inundation/flooding and inundation range, which in turn dependent on surface elevation (high, medium and low elevations).
-The knowledge of the surface elevation allow distinction of inundation zones within a mangrove, of which, mangrove species are selective towards specific inundation zones which they thrive in. For e.g., Avicennia spp. are pioneer species in Southeast Asian mangroves and would normally be found on low surface elevation/more frequently inundated zones.
Hmmh, where I shall plant mangroves?
Ben also highlighted another mistake of other mangrove restoration projects. Most mangroves do not grow at low elevation i.e. below mean sea level. Although mangroves have the ability to tolerate lack of oxygen, prolonged lengths of water immersion (which may lead to accumulation of hydrogen sulfide toxicity) does not bode well for them, particular that of seedlings (young plants). Hence mangrove replanting by other parties are often not successful as seedlings are planted at low elevation mangrove sites.
Planting Grass for Mangrove Restoration?
-Mangrove restoration at certain areas can be carried out with grass on bare grounds to assist natural mangrove recruitment when mangrove propagules are trapped by the grass. The grass will be removed eventually after the seedlings have grown.
Mangrove Restoration without replanting them. How?
-MAP approaches mangrove restoration through basic natural processes i.e. termed ecological mangrove restoration (EMR). Therefore, contrary to other mangrove restoration organizations, MAP does not implement nor advocate mangrove planting; the organization believes in natural establishment of mangroves from existing mangrove plants in a degraded site.
Therefore, it focuses to revert the modified topography and hydrology of a site to its natural conditions (prior to the modification) which in turn allows natural regrowth or succession of mangrove plants. This approach is more cost-saving (because mangrove propagules do not come cheap!) and growth rate of planted mangroves is slower than natural growth itself.
-A more detailed step-wise approach on EMR are simplified as below :-
Understand the biology i.e. characteristics of individual mangrove (tree or shrub) species and their communities, especially that of reproduction patterns, distribution ranges and seedling establishment;
Understand the normal hydrology that controls the distribution and successful establishment and growth of targeted mangrove species;
Assess the severity of the modified of the mangrove and the causes that currently prevent natural regrowth of mangrove species i.e. natural secondary succession;
Select appropriate restoration areas through application of Steps 1-3, that are both likely to succeed in rehabilitating a forest ecosystem and are cost effective. This includes recruitment of labor to carry out the projects, including adequate monitoring of their progress and resolving land ownership/use issues necessary for ensuring long-term access to and conservation of the site;
Design the restoration program and utilize natural volunteer mangrove recruitment for natural plant establishment and long-term assessment for the mangrove site.
Read in more detail about EMR here.
Communities awareness and involvement in mangrove restoration and conservation
Ben ended his talk with by mentioning several approaches that have been conducted by MAP to raise awareness within the local community and get them involved in mangrove restoration, monitoring and conservation projects . In Indonesia, there is a need to convince locals to stop conversion of mangroves into shrimp ponds since they are regarded as short-term cash cows. Therefore, incentives are given to locals to convince them on keeping mangroves for the more valuable profits gained from its ecosystem services. Mangrove-based products and recipes are being introduced to locals.
Woman groups are also involved in monitoring mangrove restoration sites.
After the talk, there were multiple discussions/chatter on-going among the mangrove enthusiasts from different walks of life-all hyped for future mangrove plans in Singapore!
In summary, the seminar was very informative and the multiple case studies in the seminar highlighted the efforts made by Ben, Iona and his MAP team. Kudos to MAP Indonesia! Terima Kasih (Thank you in Indonesian and Malay) Ben for the your inspiring talk and best wishes for MAP Indonesia from Mangrove Action Squad!