Coral Reefs: Are They Threatened by Robert Morris by Mass Extinction?
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GeoActiveGeoActive 507 OnlineOnline CORAL REEFS: ARE THEY THREATENED by Robert Morris BY MASS EXTINCTION? CHINA Key N CORAL REEFS ARE among the MYANMAR VIETNAM LAOS Coral Triangle region most biologically rich ecosystems Coral Triangle core Coral reefs on Earth. They are also one of THAILAND South Southern Islands, Singapore China CAMBODIA Bolinao Reef, Philippines the most threatened. They have Sea very high levels of biodiversity Kepulauan Seribu, Indonesia (a large number of species) with MALAYSIA Celebes about 5,000 species of fish and Sea Pacific Ocean 800 species of reef-building coral. INDONESIA They are also of huge economic Java Sea PAPUA NEW value, from fishing and as a GUINEA source of materials for jewellery manufacture and construction. Indian Ocean For these reasons, and because 0 1500 km of the effects of global warming, AUSTRALIA they are massively under threat. Figure 1: The Coral Triangle GeoActive Series 25 Issue 1 This unit deals with the threats to Fig 507_01 Mac/eps/illustrator v15 s/s Solomon Islands 97% coral reefs in the Coral Triangle NELSON THORNESProportion PUBLISHING of total national region (Figure 1) as this is where Artist: David Russell Illustration Timor-Leste 53% population within 10 km of the greatest concentration of coast and 30 km of reef reefs in the world is found. It Papua New Guinea 27% also looks at measures put into place to protect the reefs. More Malaysia 20% details on the formation and the Philippines 46% value of coral reefs can be found in GeoActive 392 ‘Caribbean Indonesia 26% Coral Reefs: an Ecosystem Under Threat’ (April 2008) – ask your 0102030405060 teacher for this. Millions Coral reefs in the Coral Figure 2: People in the Coral Triangle living near coral reefs, 2007 Triangle Source: World Resources Institute Spanning parts of Southeast Asia Over 80% of the reefs in Philippines account for a major and the western Pacific, the Coral this region are under threat, portion of these habitats. Triangle is recognised as the with 56% at high risk. The Local threats global centre of marine biological major threats toGeoActive reefs in the Series 25 Issue 1 There are a number of local diversity, with the highest coral Coral TriangleFig 507_02 are both Mac/eps/illustrator local v15 s/s diversity in the world (76% of (development of urban areas and threats affecting coral reefs all coral species) and the highest ports, overfishing,NELSON destructive THORNES within PUBLISHING the Coral Triangle. fishing practices, pollution, diversity of coral reef fishes (37% Artist: David Russell• Coastal Illustration development has generated of all species). The area within the sedimentation) and global a range of threats to nearby coral boundary of the Coral Triangle (coral bleaching and ocean reefs. Where space is limited, (shown on Figure 1) covers nearly acidification). More than 70% construction projects such as hotels 73,000 km2 of coral reefs (29% of the region’s people live are built upon reef communities. of the global total) and spans within the coastal zone (Figure Dredging of harbours and shipping parts of six countries: Indonesia, 2), putting pressure on nearby channels results in destruction of Malaysia, Papua New Guinea, the marine resources. Southeast these habitats. In many areas, coral Philippines, Solomon Islands, and Asia contains one-quarter of the is mined for limestone and sand Timor-Leste. world’s reefs. Indonesia and the to be made into cement. Shoreline Series 25 Autumn issue Unit 507 Coral Reefs: Are They Threatened by Mass Extinction? © 2013 Nelson Thornes GeoActive Online This page may be photocopied for use within the purchasing institution only. Page 1 of 4 turns white. Ultimately, weakened N corals may die. Bleaching is a SINGAPORE frequent symptom of pollution- induced stress, as well as a response to natural factors such as changes in water temperature, salinity levels, and ultraviolet light. During El Niño events, large areas of coral reef in the Coral Triangle are severely damaged by high Jurong Cyrene reefs Labrador Island beach Pulau Brani water temperatures, resulting in Sentosa coral bleaching. Scientific studies Pulau Busing Pulau Bukom have linked bleaching events to Pulau Tekukor Kusu Island temporary ‘hot spots’ – local areas Pulau Salu St John’s Island Pulau Hantu Pulau Jong Lazarus of unusually high temperatures Island Pulau Sudong The Sisters possibly caused by climate change. Pulau Pulau Sebarok Semakau • Ocean acidification – the oceans Key Pulau Pawai Pulau absorb about 25% of the carbon Land Semakau Fringing reefs Pulau landfill dioxide we release into the Pulau Biola Patch reefs (submerged at high tide, Senang 0 5 km atmosphere every year. As the exposed at low tide) carbon dioxide levels increase with Figure 3: Singapore’s coral reefs global warming, so do the levels in the ocean. Scientists originally Source: http://coralreef.nus.edu.sg/map.htmGeoActive Series 25 Issue 1 Fig 507_03 Mac/eps/illustrator v15 s/s focused on the benefits of the ocean removing this greenhouse construction disturbs sediments,NELSON THORNES PUBLISHINGinland can damage coral reefs Artist: David Russell Illustration gas from the atmosphere. which smother corals. Runoff when they are transported by However, research has shown from farming causes the growth of rivers into coastal waters. This that there is also a downside: the algae which interferes with coral results in the smothering of corals, carbon dioxide absorbed by the reproduction. Other threats include reducing light levels and affecting ocean is changing the chemistry of hot-water discharge from power growth, and over-nutrification of the seawater by becoming carbonic stations, mine runoff and toxic coral reefs. Pollution is a particular acid. This has affected corals and waste which poisons coral reefs. threat to coral reefs near the other crustaceans as they are then mouths of many smaller rivers, as unable to take calcium from the • Overfishing affects most of the the high volume of sediment and water to help them grow. world’s reefs. At a basic level, freshwater flow naturally inhibits overfishing results in changes coral growth. in fish size and reduction in the numbers of fish and of species • Deforestation can also affect the Case Studies within coral reefs. The removal of development of coral reefs. River certain species may have a serious basins cleared of their forests The following case studies impact on ecosystems and result in and other vegetation cover are illustrate the range of threats to wholesale changes as some species vulnerable to erosion and flooding. coral reefs in the Coral Triangle increase rapidly in numbers if they During flooding events, silt and and how, in some cases, they are have no natural predators. other pollutants within these basins being resolved. are carried out to sea, affecting the • Destructive fishing – fishing using offshore reefs. improvised explosives or using The Southern Islands, cyanide and other poisonous • Marine-based pollution – in Singapore chemicals, pounding reefs with comparison with the other stress factors, oil spills and the deliberate Most of Singapore’s reefs lie off weighted bags to scare fish out the Southern Islands in close of crevices and, in deeper waters, discharge of oily ballast water by proximity to Singapore city’s trawling, all damage corals. Large passing ships pose an unknown, marina (see Figure 3). This area numbers of other species, along but probably less significant, threat with undersized target species, to coral reefs. is home to nearly 200 species may be swept up in nets or killed of hard corals. It has a large by poisons or explosives in the Global threats tourist industry, as well as some process. Most of these methods are The two main global changes commercial and sport fishing. actually illegal but often cannot be affecting coral reefs are largely fully enforced by law enforcement driven by human development. The Southern Islands reefs lie agencies. As not all fishing methods within the port limits of the • Coral bleaching – when corals are destructive, this is a lesser world’s busiest harbour, while threat than overfishing. undergo certain kinds of stress, much of the zooxanthellae (the the islands themselves support • Impact from inland pollution and symbiotic algae that provide coral oil refineries and petrochemical erosion – sediment, pesticides, and polyps with nutrients) are expelled plants. Massive land reclamation pollution from human activities from the coral tissue and the coral programmes since the 1960s Series 25 Autumn issue Unit 507 Coral Reefs: Are They Threatened by Mass Extinction? © 2013 Nelson Thornes GeoActive Online Page 2 of 4 This page may be photocopied for use within the purchasing institution only. (resulting in nearly 1,700 fish numbers both seem to be washed up on local beaches. hectares of new land), along with increasing. Dynamite fishing, although regular dredging of shipping outlawed nationally since 1920, channels, has resulted in Despite this, the reef remains in still occurs, as well as heavy widespread sedimentation of the a critical state; coral bleaching ornamental fish collecting reefs. Underwater visibility was and ocean acidification remain and subsistence fishing. The reduced from 12 metres in the threats. Fish farming is also islands are under pressure from 1960s to 2 metres in 2000. The causing problems with pollution, developers seeking more tourism active growth zone of corals is water stagnation, and public and recreational facilities. There now confined to the topmost