Impacts of Climate Change on Coral Reefs and the Marine Environment

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It is estimated that 70 per cent of the Earth's surface area is made up of oceans, (1) the most productive habitat, comprising 75 per cent of all known species. This unique environment, which remains generally unexplored and hidden from the world, plays an important role in regulating global temperature and is the primary producer of oxygen. Coral reefs, which comprise only about 0.5 per cent of the ocean floor, are complex three-dimensional structures built up over thousands of years as a result of the deposition of calcium carbonate skeletons of the reef building coral species. These reefs are often referred to as the "rainforest of the sea". This allegory underestimates the complexity of coral reefs, which have a greater diversity of animal and plant life than rainforests, circulate nutrients through the intricate food web and provide food at all levels of the food chain.



Historically, the sea has served as a major transportation network, a source of food and a favourite recreational area. Most major cities were developed along the coast as trading areas. The growth of these cities is manifested today in the percentage of the world's population (approximately 80 per cent) who live within 100 kilometres of the coast and depend on the sea for their livelihood (approximately 3.5 billion people). (2) In fact, the survival of the world's poorest people depends on their close relationship with the sea. The economic importance of the sea is evidenced in the ecosystem services provided by way of fisheries, tourism, coastal protection, and in its role as a source of raw materials. This dependency on the sea is now threatened by environmental conditions brought on by global climate change.


The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2007) (2) presented strong evidence that global warming over the last century was largely a result of human activity, such as the burning of fossil fuel, deforestation and the conversion of lands for agricultural use. Temperature records from as far back as 1850 show that the globe has on average warmed by 0.8 [degrees]C, and further analysis has shown that since the 1970s each decade has been warmer. Global concentrations of carbon dioxide (C[O.sub.2]) have also shown increased levels from an average of 280 parts per million (ppm) in the mid-nineteenth century, at the beginning of the industrial revolution, to approximately 388 ppm at the beginning of the twenty-first century. The global warming trend is expected to continue, as IPCC estimates that the global average temperature will be 2.5-4.7[degrees]C higher in 2100 when compared to pre-industrial levels. (4)


In order to assess the impact of climate change on coral reefs and the marine environment, we need to examine the predicted environmental changes and evaluate the capacity of the marine organisms to adapt to these changes. (5) Climate models indicate that the sea surface temperature is expected to rise by 1 to 3[degrees]C, while the sea level is expected to rise by 0.18 to 0.79 metres. Regional weather patterns are likely to change, resulting in an increase in the severity and frequency of storm events, particularly cyclones. In addition, ocean circulation patterns are expected to be modified and pH is expected to decline as a result of the absorption of CO,. (6)


Despite having taken millions of years to evolve, marine organisms, under today's conditions, must adapt very quickly to new conditions. Marine organisms will be affected by changes in two main aspects of their environs, namely, by changes in the natural habitat and food supply, and changes in ocean chemistry. Marine plants, mainly phytoplankton, are primary producers that form the base of the food chain. …