Philippine mangrove planting strategy needs urgent rethink
The Philippines is rehabilitating its mangrove forests, but local researchers say the government is planting the trees in the wrong areas and pumping large amounts of money into big but less successful projects.
Mangrove forests have been shown to protect shorelines during storms and typhoons, and preventing coastal erosion.
But in a study published in the latest issue of Ambio, Maricar Samson and Rene Rollon from the University of the Philippines, write that there is a widespread tendency to plant mangroves in areas that are not their natural habitat.
Mudflats, sandflats, and seagrass meadows have been converted into Rhizophora mangrove forests. But in these areas, many of the seedlings die because some of these places have a nutrition deficit and the species is not suited to withstand the strong wave currents or winds.
"All stakeholders should revisit our 'strategies' in our mangrove forest management programs," Samson told SciDev.Net.
He says a more rational focus for mangrove restoration would involve the replanting of mangroves in brackish water ponds, especially those that are abandoned or under-utilised.
These environments are the original habitat of mangroves and the best locations are on areas above the mean sea level and flooded by tides less than one-third of the time.
"The reversion of ponds to mangrove areas will not be straightforward as the government should provide a scheme and a mechanism on how the pond-to-mangrove conversion will be done," Samson says.
Ma. Junemie Hazel Lebata-Ramos, from the Aquaculture Department of the Southeast Asian Fisheries Development Centre (SEAFDEC), says pond aquaculture is currently one of the largest threats to mangrove forests worldwide. "To prevent cutting of mangroves and still provide fisheries/aquaculture products to the growing population, mangrove-friendly aquaculture should be promoted," Ramos told SciDev.Net.
Another study, published in Wetlands Ecology and Management last month (June) also found that inadequate ecological knowledge is leading to planting of the wrong mangrove species at inappropriate sites. Hardier mangrove species, such as S. alba and A. marina should be planted in more exposed areas to ensure higher survival rates, say the researchers.
The researchers from SEAFDEC and De La Salle University in the Philippines, found that planting costs for high-cost government-led mangrove projects had increased from US$100 per hectare to over US$500 per hectare — primarily due to the cost of overheads associated with such large-scale projects. Despite the investment, only 10–20 per cent of trees planted survived.
Conversely, a small local project achieved a 97 per cent survival rate for its mangroves. The researchers point to the 'shared interest' of the community involved, who lived next to the site and were able to contribute to its maintenance.
The authors say that a higher rate of survival is gained from smaller projects implemented by local governments in cooperation with local communities.
Wetlands Ecology and Management (DOI 10.1007/s11273-008-9101-y)