Marine Atlas: Maximizing Benefits for Solomon Islands

REEFS AT RISK: REEF RISK LEVEL

Solomon Islands’ reefs are at risk. The direct and indirect impacts of climate change are exacerbating the pressures reefs face, jeopardizing marine values worth billions of dollars.

As shown in the previous maps, coral bleach- ing is the silent reef killer, caused by rising sea levels as well as ocean acidification. There is little information on coral bleaching in Solo- mon Islands, with the earliest coral bleaching recorded during a 1965 Royal Society expe- dition, which found dead coral in the shallow waters of several locations around Honiara, Tete Island and the Sandfly Passage of the Nggela Islands (Reefbase). This mortality is thought to have been the result of a bleaching event, due to high SSTs several months before the expedition. Confirmed coral bleaching was observed in 2000 around Ghizo Island and by 2002 had spread around much of the Solo- mon Islands (Sulu et al., 2002). In addition to bleaching, coral reefs face sev- eral other natural threats, including cyclones, tsunamis and earthquakes. In April 2007, an earthquake and subsequent tsunami dam- aged Solomon Islands’ coral reefs. In one case, reef flats were uplifted, exposing the coral to the air (Wilkinson, 2008). Maintaining healthy coral communities helps build their resilience against many natural threats. Human disturbances are another threat to coral reefs in Solomon Islands and in- clude overfishing, pollution, sedimentation,

eutrophication and coastal development (Wilkinson, 2008). Prevalent widespread log- ging is also having a major impact on lagoons and coral reefs, such as the Marovo Lagoon, by causing huge sediment discharges from rivers draining the logged catchments (Sulu et al., 2002). Plans for land-based human activities, such as forestry, agriculture, aqua- culture and mining, must therefore take into account their downstream impacts on coast- al habitats in order to maintain the resilience of coral reef communities. This interaction shows the cumulative impact of climate change and local human activities on Solomon Islands reefs; threats that will increase over time. The risk of these threats is shown on the map of Solomon Is- lands’ reefs, classified by estimated present threat from local human activities, according to the Reefs at Risk integrated local threat index. Threats considered in the index include coastal development, including coastal engineering, landfilling, run-off from coastal construction, sewage discharge (see also chapter “The dose makes the poison”), and impacts from unsustainable tourism (see also chapter “Beyond the beach”); watershed-based pollution, focusing on erosion and nutrient fertilizer run-off from agriculture entering coastal waters via rivers; marine-based pollution and damage, includ- ing solid waste, nutrients, toxins from oil and gas installations and shipping, and physical damage from anchors and ship groundings (see also chapter “Full speed ahead”); and overfishing and destructive fishing, including unsustainable harvesting of fish or inverte- brates, and damaging fishing practices such as the use of explosives or poisons (see also chapters “Fishing in the dark” and “Small fish, big importance”).

Acropora coral field in Solomon Islands exposed to multiple impacts, including a crown-of-thorns outbreak and cyclone damage.

nutrient loads into coastal waters. Certain types of fishing practices can also damage coral reefs, which will subsequently affect the productivity of these fisheries. Luckily, there are many initiatives aiming to facilitate the changes needed. The Cor- al Triangle Initiative is helping Solomon Islands develop its capacity to manage coral reefs. Integrated approaches to coral reef conservation should consider land–sea connections and require an understanding of how and where terrestrial conservation actions influence reefs. Klein et al. (2012)

examined the impact and cost effectiveness of protecting forests as a reef conservation measure. Their analysis found that relative coral reef condition could be improved by between 8 and 58 per cent if all remnant forest was protected rather than deforested (Klein et al., 2012).

the threat index indicates that 31.3 per cent of the reef area is classified as facing a low level of risk, 40.3 per cent a medium risk, 22.8 per cent a high risk and 5.6 per cent a very high risk. The areas of very high risk (red) are found on many of the main islands’ coasts, particularly around populated loca- tions, such as Guadalcanal. The reefs are important to the local communities’ econo- mies, especially for subsistence and coastal protection. Land-based activities, including logging, farming and aquaculture, can affect coastal habitats, such as coral reefs, due to the release of increased sediment and

Crown-of-thorns starfish damage Solomon Islands’ reefs. Outbreaks often occur when their natural predators are overfished.

This multitude of man-made threats leaves Solomon Islands’ reefs at risk. Analysis of

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

CLIMATE CHANGE THREATS

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