Marine Atlas: Maximizing Benefits for Kiribati

OCEAN VALUES

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

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 man- grove ecosystems and the protection they provide against erosion, they are often the subject of conservation programmes and are commonly included in national biodiver- sity 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 sed- imentation. As such, seagrass beds effec- tively help protect against waves and limit coastal erosion. In addition to protecting the coast, Kiribati’s coastal habitats also act as nursery areas for fish and support food security, livelihoods, tourism and other human activities. Sea- grass meadows and mangroves are also recognized as important carbon stores, with the preservation of healthy mangrove sys- tems contributing to climate change action. There are around 258 hectares of man- groves in Kiribati (Ellison, 2009), with four types of mangroves, namely Te Nikabubuti (white mangrove), Te Aitoa (black mangrove), Te Tongo Buangi (oriental mangrove) and Te Tongo (red mangrove). Mangroves are found on many of Kiribati’s islands, however, there is limited detailed information on their dis- tribution. They are being planted as part of the Environment and Conservation Division and the Kiribati Adaptation Program – Phase III to enhance coastal protection. But while coastal habitats are some of the most pro-

ductive 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”). As described, three of the key coastal habitats in Kiribati are coral reefs (see also chapter “Shaping Pacific Islands”), sea- grasses 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, including fish, molluscs, worms, crustaceans, echinoderms, spong- es, tunicates and other cnidarians. Coral reefs provide many benefits to people living in coastal areas, including food provision, supporting artisanal and commercial fish- eries, tourism opportunities and coastal protection. And Kiribati is a nation of cor- als—the islands are either surrounded by fringing reefs or built as coral atolls, making reefs an important coastal habitat. Seagrass beds are highly diverse and productive ecosystems that can harbour hundreds of associated species from all phyla, for example, juvenile and adult fish, epiphytic and free-living macroalgae and microalgae, molluscs, bristle worms and nematodes. There is limited information on the distribution of seagrass beds in Kiribati, with one to two species present in the country (Brodies and N’Yeurt, 2018). Seagrass has been documented from Aba- iang, Abemama, Kuria and Kiritimati (Awira et al., 2004). Seagrass maps have not been presented in the map of coastal habitats as there are currently no publicly available data that adequately capture the distribution of seagrass in Kiribati.

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 bio- physical features of Kiribati’s waters. While they are fascinating in their own right, the combination of features such as bathym- etry, geomorphology, currents, nutrients and plankton are also important factors in the distribution and health of Kiribati’s coastal habitats. Marine and coastal ecosystems provide a number of valuable services to Kiribati, a key one of these being coastal protection, which has two components: the preven- tion of erosion and the mitigation of storm surges. Healthy coastal ecosystems prevent coastal erosion by reducing the effects of waves and currents and they also help regu- late the removal and deposition of sediment (erosion and accretion). They also provide increased short-term protection against ep- isodic 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 for- ests, seagrass beds and coral reefs play an important role in stabilizing shorelines. As human density increases however, so too does the impact on these important coastal habitats. The role of mangroves in coastal stabili- zation is well known. They protect coastal areas from erosion, storm surges (especially during cyclones) and tsunamis. Their mas- sive root systems are efficient at dissipating wave energy and slow down tidal water so that suspended sediment is deposited as

MAXIMIZING BENEFITS FOR KIRIBATI

OCEAN VALUES

23