Nosy Be seascape is part of the northern Mozambique Channel home to the second most diverse coral populations on the planet, with the highest species richness yet reported for the Western Indian Ocean in Northwest Madagascar in the Mitsio island group. WCS research has highlighted that efforts aimed at maintaining Nosy Be seascape reefs high diversity and intact ecosystems are least likely to be undermined by climate disturbances in the near term. For this reason, these reefs are considered a high priority for increased management efforts that will reduce additional human disturbances, such as fishing and pollution, in order to improve the chances for their persistence. Also, as the upstream end of the core high bio- diversity region for the WIO, this seascape is critically important for larval supply to downstream reefs, and thus for recovery following disturbances. This seascape is a mosaic of rich ecosystems: coral reefs and coral banks, mangroves - the region contains some of the most important mangroves in Madagascar, seagrasses, volcanic, karst or coral islands and islets, and bays.
The seascape of Nosy Be is one of the few areas within Madagascar and the Western Indian Ocean to accommodate even small populations of critically endangered sawfish. Whale sharks are also present throughout the year, especially around Sahamalaza, Iranja, and Nosy Be, along with a high diversity of sharks with 23 species identified. Further, WCS’s research has showed the presence of healthy and abundant populations of small coastal cetaceans and documented the northwest as one of the last refuges for Madagascar dugongs and a critical migratory corridor for humpback whales. Nosy Be is also an important site for the feeding and breeding of marine turtles, especially green and hawksbill turtles. Hawksbill turtles, which rarely nest in this part of the Indian Ocean, do nest in some locations in Nosy Iranja, which is also the most important nesting site for green turtles in Madagascar.
Nosy Be seascape is also a major seabird area for the western Indian Ocean with important sites for several species of seagulls and priority importance of last habitat islands for Madagascar fish eagle, endemic to Madagascar and listed in critical condition...
Threats
The exceptional marine biodiversity of Nosy Be seascape is facing a number of imminent threats including: unsustainable fishing practices; incidental by-catch of coastal dolphins in artisanal fisheries; poaching of marine turtles; oil exploration and planned drilling; a growing tourism industry; mangrove destruction for charcoal-making; and climate change impacts. The degradation of marine and coastal environments, lack of sustainable livelihood alternatives, and limited ability of local people to cope with these changes are thus increasing their vulnerability.
Responses
In order to reverse these trends and secure healthy marine ecosystems that support the local communities who depend on them, WCS has been involved in the establishment of marine protected areas in Nosy Be seascape for over a decade and lead the process of the creation of the Sahamalaza-Radama islands National Park, and two large co-managed Marine Protected Areas protecting over 700 square kilometers of critical marine habitats around Nosy Iranja and Mitsio islands groups.
WCS is also assessing cetacean diversity, distribution, abundance and threats in the seascape since 2008. WCS coastal cetaceans work in Northwest Madagascar has focused on two dolphin species, the Indo-Pacific humpback dolphin and the Indo-Pacific bottlenose dolphin, that appear to have abundant populations relative to other studied regions, as well as on the assessment of cetacean species diversity and distribution.