Marine Atlas: Maximizing Benefits for Fiji

HABITAT VALUES

HOME, SWEET HOME: COASTAL HABITATS Fiji’s famous hospitality extends to the thousands of species that call its coral reefs, mangroves and seagrasses home. These habitats house countless plants and animals that store carbon and help protect Fiji’s coastal inhabitants.

Protecting coasts

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 Fiji’s waters. While they are fascinating in their own right, the combination of features such as ba- thymetry, geomorphology, currents, nutrients and plankton are also important factors in the distribu- tion and health of Fiji’s coastal habitats. Marine and coastal ecosystems provide a num- ber of valuable services to Fiji, a key one being coastal protection. This has two components: the prevention of erosion and the mitigation of storm surges. Coastal ecosystems prevent coastal erosion by reducing the effects of waves and currents and also helping regulate the removal and deposition of sediment (erosion and accre- tion). 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. 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 erosion, storm surges (especially during cyclones) and tsunamis. Their massive root systems are ef- ficient at dissipating wave energy and slow down tidal water so that suspended sediment is depos- ited as the tide comes in, with only the fine parti- cles resuspended as the tide recedes. In this way, mangroves 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 pro- Coastal habitats can be highly valuable, as residents of the island of Ovalau experienced when they awoke to a 70-metre long ferry in their backyard. It had been pushed onto a shallow reef by Cyclone Winston (see also chapter “Stormy times”), which generated waves of up to 10 metres. Luckily, like most other Fijian islands, Ovalau is protected by reefs and mangroves that shelter the coast and its inhabitants. The effects of the cyclone would have been much worse without this coastal protection, and much costlier. Every year, reefs and mangroves mitigate damage to houses and hotels on the north and south sides of Fiji’s two main islands (Viti Levu and Vanua Levu), with an estimated worth of this mitigated damage of FJ$12.7–21.2 million (US$6.4–10.6 million) (Gonzalez, 2015).

A ferry beached by Cyclone Winston close to Levuka on the island of Ovalau.

grammes and are commonly included in national biodiversity action plans.

As described, three of the key coastal habitats in Fiji are coral reefs (see also chapter “Shaping Pacific Islands”), seagrasses and mangroves. The map of coastal habitats presents the distribution 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, in- cluding fish, molluscs, worms, crustaceans, echi- noderms, sponges, tunicates and other cnidari- ans. Coral reefs provide many benefits to people living in coastal areas, including food provision, supporting artisanal and commercial fisheries, tourism opportunities and coastal protection. Fiji is surrounded by a combination of fringing and barrier reefs. The Great Sea Reef, locally known as Cakaulevu, occurs along the north coast of Fiji and is the world’s third longest continuous barrier reef system. Seagrass beds are highly diverse and productive ecosystems that can harbour hundreds of associ- ated species from all phyla, for example, juvenile and adult fish, epiphytic and free-living macroal- gae and microalgae, molluscs, bristle worms, and nematodes. These beds occur in the sheltered waters of many of Fiji’s islands. However, seagrass maps have not been presented in the map of coastal habitats as there are currently no publicly available data that adequately capture the distribu- tion of seagrass in Fiji.

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, Fiji’s coastal hab- itats 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 contrib- uting to climate change action. Mangroves are found on many of Fiji’s islands, with extensive areas of mangroves on both Viti Levu and Vanua Levu. The social value of carbon sequestration by mangroves in Fiji’s EEZ is estimated to be worth about FJ$147.67 million (US$73.93 million) (Gonzalez, 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”, “From reef to ridge” and “Turning sour”).

MAXIMIZING BENEFITS FOR FIJI

HABITAT VALUES

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