Marine Atlas: Maximizing Benefits for Vanuatu
HOME, SWEET HOME: COASTAL HABITATS Vanuatu’s famous hospitality extends to the thousands of species that call its coral reefs, mangroves and sea- grasses home. These habitats house countless plants and animals that store carbon and help protect Vanuatu’s coastal inhabitants.
tsunamis. Their massive root systems are efficient at dissipating wave energy and slow down tidal water so that suspended sediment is deposited as the tide comes in, with only the fine particles resuspended as the tide recedes. In this way, man- groves help build their own environment. Given the uniqueness of mangrove ecosystems and the protection they provide against erosion, they are often the subject of conservation programmes and are commonly included in national biodiversity action plans. Seagrasses are another important coastal habitat that form extensive meadows in the coastal areas they colonize. Their leaves can also slow currents, and their roots and rhizomes trap the sediments in which they grow, thereby enhancing the stability of the substrate. Seagrasses can also dissipate the energy of waves by up to 40 per cent, which can in turn increase the rate of sedimentation. As such, seagrass beds effectively help protect against waves and limit coastal erosion. In addition to protecting the coast, Vanuatu’s coastal habitats also act as nursery areas for fish and support food security, livelihoods, tourism and other human activities. Seagrass meadows and mangroves are also recognized as important carbon stores, with the preservation of healthy mangrove systems contributing to climate change action. The social benefit of carbon sequestration by mangroves in Vanuatu’s EEZ is estimated to be worth up to US$4 million (Pascal et al., 2015). But while coastal habitats are some of the most productive and valuable marine habitats, they are
by the same token some of the most vulnerable to human activities (see also chapters “Reefs at risk” and “Turning sour”). The map of coastal habitats presents the distribu- tion of coral reefs and mangroves. Shallow coral reefs form some of the most diverse ecosystems on Earth. Despite occupying less than 0.1 per cent of the world’s ocean surface, they provide a home for at least 25 per cent of all marine species, including fish, molluscs, worms, crustaceans, echi- noderms, sponges, tunicates and other cnidarians. Coral reefs provide many benefits to people living in coastal areas, including food provision, support- ing artisanal and commercial fisheries, tourism op- portunities and coastal protection. The islands of Vanuatu are surrounded by fringing reefs, making this an important coastal habitat. Mangroves are Vanuatu’s most extensive wetland vegetation type (Bani & Esrom, 1993). They occur on nine different islands, but the most extensive stands are found off eastern Malekula and the Maskelyne Islands (Laffoley, 2013). Seagrass beds are highly diverse and productive ecosystems that can harbour hundreds of associated species from all phyla, for example, juvenile and adult fish, epi- phytic and free-living macroalgae and microalgae, molluscs, bristle worms, and nematodes. These beds occur in the sheltered waters of many of Vanuatu’s islands, with nine different species iden- tified. However, seagrass maps have not been pre- sented in the map of coastal habitats as there are currently no publicly available data that adequately capture the distribution of seagrass in Vanuatu.
The previous set of maps in the “Supporting values” section of the report took us on a journey from the ocean floor all the way to the surface, demonstrating the colourful biophysical features of Vanuatu’s waters. While they are fascinating in their own right, the combination of features such as bathymetry, geomorphology, currents, nutrients and plankton are also important factors in the dis- tribution and health of Vanuatu’s coastal habitats. Coastal protection is a key ecosystem service with two components: the prevention of erosion and the mitigation of storm surges. Coastal ecosys- tems prevent coastal erosion by reducing the effects of waves and currents and also helping regulate the removal and deposition of sediment (erosion and accretion). Furthermore, they provide increased short-term protection against episodic events, including coastal floods and storm surges. The benefits of this protection against extreme weather events include minimizing damage to homes, buildings and other coastal infrastructure and on important resources such as crops. Residents of many of Vanuatu’s islands came to realize these benefits in March 2015, when Cy- clone Pam was the second most intense cyclone to ever affect the South Pacific and the most intense and devastating in Vanuatu’s history. How- ever, without the protection that coral reefs and mangroves provide to most of Vanuatu’s islands, the damage could have been a lot worse. Every year, reefs and mangroves mitigate damage to houses and hotels across Efaté, Malekula and Es- píritu Santo by up to US$23 million, demonstrating just how valuable marine and coastal ecosystem services are to Vanuatu. Coastal habitats such as mangrove forests, sea- grass beds and coral reefs play an important role in stabilizing shorelines. As human density in- creases however, so too does the impact on these important coastal habitats. The role of mangroves in coastal stabilization is well known. They protect coastal areas from ero- sion, storm surges (especially during cyclones) and
MAXIMIZING BENEFITS FOR VANUATU
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