1. Effects of climate change on coastal habitats
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 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

3. Coastal habitats

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 tonnes of arc shells (Te Bun or Kaikoso) harvested per year from intertidal flats in Tarawa, Kiribati)

5. Coastal habitats: role
Mangroves
Seagrasses

6. 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

7. Existing threats
+SST

8. Projected climate change
1980–1999
average
2035
2050
2100
Air temperature (°C)
27.4
+0.5 to +1.0
+1.0 to +1.5
+2.5 to +3.0
Sea surface temperature (°C)
27.3
+0.7 to +0.8
+1.2 to +1.6
+2.2 to +2.7
Rainfall: equatorial (%)
Rainfall: subtropics (%)
n/a
+5 to +20
-5 to -20
+10 to +20
Sea level (cm)
+6a
+20 to +30
+70 to +110
+90 to +140
Ocean pH (units)
8.1
-0.1
-0.2
-0.3
Tropical cyclones 9
Number of tropical cyclones may decrease but likely to be more intense
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: mangroves

11. 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

12. 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

13. Overall vulnerability
Sea surface temperature
Solar radiation
Ocean chemistry
Cyclones & storms
Rainfall patterns
Sea level
Nutrients
Mangroves 2035
Very low
Low
Moderate
High
2050
Very high
2100
Sea grasses
2035

14. Projected habitat change
Loss of habitat area
Year
Mangrove area (%)
Seagrass area (%)
2035
-10 to -30
< -5 to -20
2050
-50 to -70
-5 to -35
2100
-60 to -80
-10 to -50

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

16. 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

17. Conclusions
Mangroves, sea grasses and intertidal flats (with coral reefs) support coastal fisheries
Coastal habitats 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 critical
Coastal fisheries will be impacted as habitats degrade