Effects of climate change on coastal habitats

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 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

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. 1800 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
  19801999 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 -5 to -20 10 to 20 -5 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 Number of tropical cyclones may decrease but likely to be more intense 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 lowmoderate vulnerability

13
Overall vulnerability
  Sea surface temperature Solar radiation Ocean chemistry Cyclones storms Rainfall patterns Sea level Nutrients
Mangroves 2035 Very low Low Very low Moderate Low High Low
2050 Very low Low Very low Moderate Moderate Very high Low
2100 Very low Low Very low Moderate Moderate Very high Low
Sea grasses 2035 Moderate Moderate Very low Moderate Moderate Low Low
2050 Moderate Moderate Very low Moderate Moderate Moderate Low
2100 High High Very low High High Moderate Moderate
14
Projected habitat change

• Loss of habitat area

Year Mangrove area () Mangrove area () Seagrass area () Seagrass area ()
2035 -10 to -30 lt -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