Projected Changes to Coastal Habitats in Solomon Islands - Coral Reefs, Mangroves, Seagrasses

Projected changes to coral reefs, mangroves and seagrasses Solomon Islands Government

Based on......

Outline Coastal habitats: roles and values Requirements for good coral growth Recent stresses on coral reefs Projected effects of climate change on: coral reefs mangroves seagrasses Key management measures

Requirements for good coral growth Warm water temperatures Shallow well-lit waters Low sediment and nutrients Right ocean chemistry Coral reefs grow in the warmest parts of oceans & have a narrow temperature range

Corals must build skeletons fast enough to withstand natural forces of erosion cyclones & storms waves bleaching predators coral eaters

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

Stresses higher water temperatures Stressed corals lose algae (and their pigments) Coral bleaching Corals living only ~1-2oC below upper thermal limit Too much freshwater can also cause bleaching Stressed - bleached Healthy - unbleached Recently dead

Stresses ocean acidification 30% extra CO2entered ocean Changes ocean chemistry Harder to form skeletons Greater coral erosion

Ocean acidification: natural laboratory High CO2volcanic seeps, PNG Winners = massive corals Losers = branching, tabulate corals Reduced coral diversity Much simpler reef with lower pH Lower pH = 2100 Mid pH = 2050 Normal pH = now Fabricius et al 2011

Projected effects of climate change

Projected climate change 1980 1999 average 2035 A2 2050 A2 2100 A2 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 (%) +5 to +20 +10 to +20 +10 to +20 n/a Rainfall: subtropics (%) -5 to -20 -5 to -20 -5 to -20 +6a Sea level (cm) +20 to +30 +70 to +110 +90 to +140 Ocean pH (units) 8.1 -0.1 -0.2 -0.3 Number of cyclones/storms may decrease but likely to be more intense Cyclones & storms 9 a = since 1960

Warmer water temperatures Reefs very high vulnerability Increased bleaching, ~1% loss per year by 2035

More acidic ocean Reefs have high vulnerability Weaker reef frameworks

Stronger storms and heavier rainfall Moderate vulnerability of reefs More disturbances = less time to recover

Higher sea level Some corals may keep up Loss of deeper corals

Opportunities for interventions Anthony & Maynard 2011

What climate change means for reefs More bleaching and diseases Weaker skeletons Physical destruction Less time to recover between disturbances Healthy reefs better able to cope Coral reefs will not disappear entirely BUT likely to be MUCH SIMPLER ECOSYSTEMS

Mangroves: role

Vulnerability of mangroves http://awsassets.panda.org/img/mangroves_borneo_34180_349602.jpg Most vulnerable to: sea-level rise increasing storm intensity Ability to adapt by migrating landward as sea-level rises but human barriers may constrain movement Overall moderate-high vulnerability to climate change

Overall vulnerability of mangroves Sea surface temperature Solar radiation Ocean chemistry Cyclones & storms Rainfall patterns Sea level Nutrients Mangroves 2035 A2 Very low Low Very low Moderate Low High Low 2050 A2 Very low Low Very low Moderate Moderate Very high Low 2100 A2 Very low Low Very low Moderate Moderate Very high Low

Projected loss of mangroves in Solomon Islands From 525 km2 today: Year Mangrove area (%) 2035 -10 2050 -50 2100 -60 Unlikely Somewhat likely Likely Very likely Likelihood 0% 29% 66% 90% 100% Very low Low Medium High Very high Unlikely Somewhat likely Likely Very likely Confidence Likelihood 0% 29% 66% 90% 100% 0% 5% 33% 66% 100% 95% Very low Low Medium High Very high Confidence 0% 5% 33% 66% 100% 95%

Vulnerability of seagrasses Most vulnerable to: Warmer waters Increased rainfall (turbidity) Increasing storm intensity Reduced light Limited ability to adapt Overall moderate vulnerability to climate change

Overall vulnerability of seagrasses Sea surface temperature Solar radiation Ocean chemistry Cyclones & storms Rainfall patterns Sea level Nutrients Seagrasses 2035 A2 Moderate Moderate Very low Moderate Moderate Low Low Moderate Moderate 2050 A2 Very low Moderate Moderate Low Low High High 2100 A2 Very low High High Moderate Moderate

Projected loss of seagrass in Solomon Islands From 66 km2 today: Year Seagrass area (%) 2035 -5 to -20 2050 -5 to -30 2100 -10 to -35 Unlikely Somewhat likely Likely Very likely Likelihood 0% 29% 66% 90% 100% Very low Low Medium High Very high Unlikely Somewhat likely Likely Very likely Confidence Likelihood 0% 29% 66% 90% 100% 0% 5% 33% 66% 100% 95% Very low Low Medium High Very high Confidence 0% 5% 33% 66% 100% 95%

Key management measures 1. Build health of coral reefs, mangroves and seagrass by addressing existing threats: Integrated catchment management Foster the care of coastal fish habitats Manage and restore coastal vegetation 2. New measures to allow future adaptation of mangroves: Provide for landward migration

Conclusions Coral reefs, mangroves and seagrasses in Solomon Islands 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

Thank you j.johnson@c2o.net.au