Managing Mangroves

If you’re thinking of planting mangroves as part of a coastal restoration project, pay close attention to the species you pick and where you plant them.

This common-sense counsel comes via a study of mangrove-restoration efforts in the Philippines. Mangrove forests covered more than 1.1 million acres throughout the archipelago in 1920. By the mid 1990s, that area had shrunk to just under 300,000 acres, according to Filipino scientists at the Southeast Asian Fisheries Development Center in Tigbauan and De La Salle University in Manila. The researchers attribute more than half the loss to the spread of "aquaculture ponds," where locals farm fish and shrimp.

Despite significant local and international investments in the country’s mangrove restoration efforts during the past 20 years, on average only about 10 to 20 percent of the newly planted mangroves survive long-term, the team reports. Among the reasons: New mangrove stands do not replace the aquaculture ponds that elbowed out the mangroves in the first place. Instead, the mangroves were planted in places where they never grew to begin with. And the species typically being planted is better suited to more-protected areas farther inland; it was picked largely because it’s easier to gather and replant, compared with species that are natural colonizers and would stand a better chance of survival.

The results, plus recommendations for improving the success of replanting efforts, appear in the current edition of Wetlands Ecology and Management.