Projected changes to mangroves, seagrass and tidal flats

1. Projected changes to mangroves, seagrass and tidal flats Presented by Johanna Johnson

2. Authors This presentation is based on Chapter 6 ‘Vulnerability of mangroves, seagrasses and intertidal flats in the tropical Pacific to climate change’ in the book Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change, edited by JD Bell, JE Johnson and AJ Hobday and published by SPC in 2011. The authors of Chapter 6 are: Michelle Waycott, Len J McKenzie, Jane E Mellors, Joanna C Ellison, Marcus T Sheaves, Catherine Collier, Anne-Maree Schwarz, Arthur Webb, Johanna E Johnson and Claude E Payri

4. Coastal habitats: role • Mangroves, seagrasses and intertidal flats provide nursery and feeding areas for coastal fish and shellfish • Targeted invertebrates reside permanently in seagrasses (e.g. sea cucumbers and molluscs) • Maintaining these habitats is critical for coastal fisheries (e.g. 3,550 tonnes of inter/subtidal invertebrates are harvested per year in Fiji)

5. Coastal habitats: role mangroves seagrasses

6. Coastal habitats: Fiji • Large areas of mangroves (425 km2 ) and seagrass (16.5 km2 ) • Documented relationship between rainfall patterns and mangrove reproductive success • One of few places deep sea seagrasses have been reported, at Great Sea Reef • Provide over 17,000 tonnes of fish each year

7. Existing threats • Poor catchment management – transport of terrestrial sediments, nutrients and pesticides • Direct removal and/or damage of mangroves and seagrass • Sand mining impacts on intertidal flats • Natural disturbances +SST

8. Projected climate change a = since 1960

9. Vulnerability: mangroves • Most vulnerable to: • sea-level rise • decreasing rainfall • increasing cyclone intensity • Ability to adapt by migrating landward as sea-level rises but human barriers may constrain movement • Overall moderate vulnerability to climate change

10. Vulnerability: seagrasses • Most vulnerable to: • increasing air and sea temperatures • changed rainfall patterns (increasing terrestrial sediment and nutrient inputs) • more intense cyclones and storms • Seagrasses in estuaries, fringing reefs and lagoon habitats will be most impacted • Limited ability to adapt • Overall moderate vulnerability to climate change

11. Vulnerability: intertidal flats • Most vulnerable to sea-level rise • Ability to adapt by migrating landward as sea-level rises but human barriers and narrow atolls may constrain this • Overall low–moderate vulnerability to climate change

12. Overall vulnerability

13. Projected habitat change in Fiji Loss of habitat area: from 425 km2 (m) & 16.5 km2 (s)

14. Vulnerable PICTs • CNMI, FSM, Fiji, French Polynesia, Guam, Kiribati, New Caledonia, Palau, PNG, Samoa, Solomon Islands, Tonga, Vanuatu

15. Key adaptations • Build resilience of coastal habitats by addressing existing threats: • Integrated catchment management • Foster the care of coastal fish habitats • Manage and restore coastal vegetation • New measures to allow future adaptation: • Provide for landward migration of coastal fish habitats

16. Conclusions • Mangroves, seagrasses and intertidal flats (with coral reefs) support important coastal fisheries in Fiji • Coastal habitats in Fiji are expected to decline in area due to climate change • Acting now to manage existing threats and allow for future adaptation is vital for these habitats • Information on the distribution, diversity and area of these habitats, and future changes is a critical gap • Coastal fisheries that depend on these habitats will be impacted as these habitats degrade

17. Thank you j.johnson@c2o.net.au