Sick water?

these net benefits by an estimated US$350–870 million a year (Burke and Maidens, 2004).

exposure to the herbicide toxins which then had toxicological effects on other highly valued marine ecosystems such as the reefs and lagoons of the Great Barrier Reef (Duke et al , 2005). Another example of transfer of terrestrial pathogens to marine mammals concerns Toxoplasma gondii, a pathogen of marine mammals commonly found in domestic cats and terrestrial wild mammals. It is believed that the oocysts from cat faeces are washed into seawater where they remain a source of infec- tion for up to two years, depending on the water temperature (Lindsay and Dubey, 2009) Coastal regions and Small Island Developing States (SIDS) rep- resent an area of particular concern as they contain some of the most productive ecosystems. It is here that human popu- lations concentrate – they are the most densely populated on the planet, and yet the most productive. This zone where land and sea meet has historically been a strategic location for hu- man communities, with good positioning for trade and secu- rity, productive land and water providing access to food and energy sources. Twenty-one of the world’s 33 megacities are on the coast (Martínez et al , 2007). By 2015, the coastal population is expected to reach approximately 1.6 billion people, nearly 22.2% of the global total (Manson, 2005). This increasing pressure from changing climate and growing populations threatens the continued provision of vital services, in particular where economies are highly dependent on coastal resources. In Zanzibar, a Tanzanian island off the east coast of Africa, for example, marine ecosystem services account for 30 per cent of GDP, 77 per cent of investment, and a large amount of foreign exchange and employment. The value of tourism alone in 2007 accounted for 25 per cent of GDP, five times greater than the combined value of all the other ecosystem val- ues and dependent on a healthy marine environment. How- ever uncontrolled release of wastewater from Zanzibar town into the coastal zone is a particular threat to water quality and ecosystem integrity impacting the two main economic activi- ties – fisheries and tourism – a risk for the very assets that tour- ists pay to come and see (Lange and Jiddawi, 2009). In Carib- bean SIDS, the economies of some states are almost entirely dependent on the health of their reefs for tourism, fisheries and shoreline protection. Degradation of the reefs could reduce

Desalination of sea water is often the only viable option for providing safe drinking water in many arid, coastal regions or isolated locations such as small islands, An established tech- nology since the 1950s, by 2006 approximately 24.5 million m 3 of water were being produced per day for drinking water, tour- ism, industry and agriculture (58 per cent of all desalinated wa- ter produced) (UNEP, 2008; Lattemann, and Hoepner, 2008). Production is expected to increase to 98 million m 3 a day by 2015 (UNEP 2008). It is not however without consequences both in terms of high economic cost, energy requirements (Bleninger and Jirka, 2008; Lattemann, and Hoepner,2008; von Medeazza GLM 2005; Sadhwani et al , 2005; UNEP, 2008), environmental and social implications (Lattemann, and Ho- epner,2008). There is scope to improve the sustainability of the desalination process. The process results in the discharge of a concentrated brine into the receiving waters. Temperature and salinity are two factors that determine the composition and distribution of species in the marine environment affecting water density and causing stratification (Miri and Chouikhi ,2005;Lattemann and Hoepner,2008) changes to primary production and turbidity. Changes in these parameters over sustained periods could lead to local ecological changes, resulting in shifts in species diversity, opening the potential for the colonization of exotic and potentially invasive species, and changing ecosystem function. The process requires the use of descaling and anti- fouling products, which can contain heavy metals and toxic chemicals, although the impact of these can be managed with good practice and plant maintenance. Desalination and impacts on the marine and coastal environment Healthy, functioning ecosystems provide a wide array of valu- able services to human security and wellbeing. Coastal eco- systems provide global services estimated at US$25 billion a year (Martínez et al , 2007) – contributing food security, shore- line protection, tourism, carbon sequestration through blue

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