Projected changes to coral reefs and mangroves

1. Projected changes to coral reefs and mangroves

2. Based on......

3. What we will discuss Projected changes to atmospheric and oceanic conditions Ecosystems supporting fish Fish stocks/aquaculture species Implications for economic development, food security and livelihoods Adaptations and policies to reduce threats and capitalise on opportunities

4. Outline • Requirements for good coral growth • Recent stresses on coral reefs • Projected effects on coral reefs • Mangroves

5. Requirements for good coral growth • Warm water temperatures • Shallow well-lit waters • Low sediment and nutrients • Right ocean chemistry Ω >3.3 • Warmest parts of oceans • Narrow temperature range

6. Corals must build skeletons fast enough to withstand natural forces of erosion tropical cyclones waves sunshine predators coral eaters

7. A special relationship • Symbiosis at heart of tropical coral reefs • Photosynthetic algae live within coral animal • Corals get enough energy for rapid calcification • Form structurally complex reefs • Home to thousands of other plants and animals

8. Stresses – higher water temperatures • Stressed corals lose algae (and their pigments) • Coral bleaching • Corals living only ~1-2oC below upper thermal limit • Too much fresh water also causes bleaching Healthy - unbleached Recently dead Stressed - bleached

9. Stresses - ocean acidification • 30% extra CO2 entered ocean • Prevents greater warming! • BUT changes ocean chemistry • Harder to form skeletons • Greater coral erosion

10. Ocean acidification: natural laboratory Lower pH = 2100 • High CO2 volcanic seeps, PNG • “Winners” = massive corals • “Losers” = branching, tabulate corals • Reduced coral diversity • Much simpler reef with lower pH Mid pH = 2050 Normal pH = now Fabricius et al 2011

11. Local stressors: reef status: Samoa

12. Projected effects of climate change

13. Projected climate change a = since 1960

14. Warmer water temperatures • Very high vulnerability • Increased bleaching, ~1% loss per year by 2035

15. More acidic ocean • Reefs have high vulnerability • Weaker reef frameworks

16. Stronger storms and heavier rainfall • Moderate vulnerability • More disturbances = less time to recover

17. Higher sea level • Some corals may keep up • Loss of deeper corals

18. Opportunities for management interventions Anthony & Maynard 2011

19. What CC means for coral reefs • Bleaching and diseases • Weaker skeletons • Physical destruction • Less time to recover between disturbances • Healthy reefs better able to cope • Can adaptation occur? Coral reefs will not disappear entirely BUT likely to be MUCH SIMPLER ECOSYSTEMS

20. Mangroves: role

21. Vulnerability of 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

22. Overall vulnerability of mangroves

23. Projected loss of mangroves in Samoa From 7.5 km2 today

24. Key adaptations • Build resilience of coral reefs and mangroves 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 of mangroves: • Provide for landward migration

25. Conclusions • Coral reefs and mangroves in Samoa 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 • Coastal fisheries that depend on these habitats will be affected as these habitats degrade