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In Dead Water

Marine Pollution and Coastal Development

A major threat beyond overexploitation of fisheries and physical destruction of marine coastal habitats by unsustainable fishing practices is undoubtedly the strong increase in destruction of coastal habitats (Lotze et al., 2006) by coastal development and discharge of untreated sewage into the near-shore waters, resulting in enormous amounts of nutrients spreading into the sea and coastal zones (Burke et al., 2002; Wilkinson, 2002; Brown et al., 2006; UNEP, 2006).

Figure 23:Infrastructure development, intensive agricultural expansion, urbanisation and coastal development are increasing the flow of sediments and sewage into the ocean. The situation is most severe around Europe, the East coast of the United States, East of China and in Southeast Asia. These are also primary fishing grounds.

Around 60% of the waste water discharged into the Caspian Sea is untreated, in Latin America and the Caribbean the figure is close to 80%, and in large parts of Africa and the Indo-Pacific the proportion is as high as 80–90% (UNEP, 2006). An estimated US$ 56 billion is needed annually to address this enormous waste water problem. However, the costs to coral reefs, tourism and losses in fisheries and human health risks may be far more expensive. Waste water treatment is also one of the areas where least progress is being made globally. Many marine species, including cold-water corals like Lophelia sp., are highly sensitive to temperature changes and dissolved oxygen, making them highly vulnerable to climate change and pollution (Dodds et al., 2007). This, in turn, makes them vulnerable to diseases (Hall-Spencer et al., 2007). The poor management of sewage not only presents a dire threat to health and ecosystems services, it may also increase poverty, malnutrition and insecurity for over a billion people (UNEP, 2006).

Figure 24:Sewage treatment is low or absent in many parts of the World, leading to eutrophication of the coastal zone, (toxic) algae blooms and dramatically reduce the ability of coral to recover from bleaching events dramatically.

Marine pollution includes a range of threats including from land-based sources, oil spills, untreated sewage, heavy siltation, eutrophication (nutrient enrichment), invasive species, persistent organic pollutants (POP’s), heavy metals from mine tailings and other sources, acidification, radioactive substances, marine litter, overfishing and destruction of coastal and marine habitats (McCook 1999, Nyström et al 2000, Bellwood et al. 2004). Overall, good progress has been made on reducing persistent organic pollutants (POPs), with the exception of the Arctic. Oil inputs and spills to the Seas has been reduced by 63% compared to the mid-1980s. Oil releases from tanker accidents have gone down by 75%, from tanker operations by 90% and from industrial discharges by some 90%, a result partially obtained through the shift to double-hulled tankers (UNEP, 2006; Brown et al., 2006). Progress on reducing emissions of heavy metals is reported in some regions, while increased emissions are observed in others, including from electronic waste and mine tailings in Southeast Asia. Sedimentation has decreased in some areas due to reduced river flows as a result of terrestrial overuse for agricultural irrigation, while increasing in other regions as a result of coastal development and watershed deforestation as well as declines in mangroves (Burke et al., 2002; McCulloch et al., 2003; Brown et al., 2006; UNEP, 2006).

Figure 25:Dead zones (hypoxic i.e. oxygen deficient water) in the coastal zones are increasing, typically surrounding major industrial and agricultural centers.

Together with agricultural run-off to the sea or into major rivers and eventually into the ocean, nitrogen (mainly nitrate and ammonium) exports to the marine environment are projected to increase at least 14% globally by 2030 (UNEP, 2006). In Southeast Asia more than 600,000 tons of nitrogen are discharged annually from the major rivers. These numbers may become further exacerbated as coastal population densities are projected to increase from 77 people/km2 to 115 people per km2 in 2025. In Southeast Asia, the numbers are much higher and the situation more severe. Wetlands and mangroves are also declining rapidly, typically by 50–90% in most regions in the past 4 decades (UNEP, 2006). This, in turn, will severely exacerbate the effects of extreme weather, the ability of coral reefs to resist and recover from climate change and reduce the productivity of coastal ecosystems which supply livelihoods and basic food to the impoverished.