Conservation state of the mangrove forests of Bonaire, Caribbean Netherlands

Summary

In the Caribbean Netherlands, mangrove forests are found exclusively on Bonaire. where they hold critical ecological value and are protected under several international and regional frameworks, including the Ramsar Convention and the SPAW Protocol. Bonaire hosts four mangrove species, with the red mangrove (Rhizophora mangle) being dominant. The largest mangrove system is located in Lac Bay (~222 ha), with smaller patches in Lagun, Pekelmeer and other areas amounting to a total of ~236 ha. These forests offer essential ecosystem services, including coastal protection, carbon storage, and support for biodiversity and ecotourism. Despite their importance, mangroves on Bonaire face several threats, including siltation from terrestrial runoff, climate change, and more recently, large-scale influxes of Sargassum spp. brown algae. While the mangrove cover in Lac Bay remained relatively stable at approximately 239 ha between 1961 and 1996, a 6.6% decline was recorded between 1996 and 2022. In Lagun, the situation is even more severe, with nearly 46.2% of the mangrove area lost between 2014 and 2020. These declines are mainly attributed to backwater siltation, but also to anoxic conditions caused by decaying Sargassum spp. at the seaward fringe of the mangrove forests. As a result, the conservation status of Bonaire’s mangroves is classified as ‘unfavourable-inadequate’, which signals a need for continued and expanded conservation actions. Effective conservation efforts should be aimed at restoring water depth and circulation in the backwaters of Lac Bay and Lagun. This can be achieved by mechanical removal of accumulated sediment from the backwaters, reopening existing and historical tidal creeks to enhance tidal flow, and strategic placement of oil booms to block Sargassum spp. influxes into the mangrove forests. Other priorities include reducing overgrazing by free-roaming livestock in the hinterlands, reforesting the overgrazed hinterlands with native tree species, and building and maintaining water retention structures in these areas. Furthermore, implementing legislation to prevent excessive urban development and industrial activity in the watersheds of Lac Bay and Lagun is crucial to reduce downstream inflow of toxins, sediments, nutrients, and pathogens through surface runoff and groundwater. In conclusion, the situation on Bonaire underscores the importance of addressing land-based pressures, monitoring mangrove ecosystem health, and scaling up restoration efforts to prevent further degradation.