Corals decline where humans thrive, according to a study to be published in the Proceedings of the Royal Society B: Biological Sciences.
The study by Camilo Mora of Dalhousie Uiversity in Canada, used a large-scale database on the status of coral reef communities in the Caribbean (consisting of 322 sites in 13 countries) and statistically analysed it in combination with a comprehensive set of socioeconomic and environmental databases to identify the drivers of change in coral reef communities.
The author found that an increase in human population is positively related to macroalgae abundance and coral mortality, and negatively related to the biomass of herbivorous and carnivorous fishes.
The main effect of coastal development is to negatively impact the biomass of carnivorous fishes and increase mortality of corals, whereas the main effect of increasing area of cultivated land near the reefs is to increase macroalgae abundance.
The author concludes: Human settlements have been inevitably accompanied by the changes in land use and exploitation of natural resources which have caused widespread and profound changes in the structure of coral reef communities.
The increasing production of greenhouse gases to supply an increasing demand for energy is also leading to increases in temperature...which causes bleaching and coral mortality and indirectly threatens other reef organisms as the coral reef matrix becomes degraded.
The expected increase in human population from six billion people today to nine billion for the year 2050...and a probable 1.8-4C temperature increase over the same time period...suggest that coral reefs are likely to witness a significant ecological crisis in the coming half century. Fortunately, the solutions are already available, which include the use of enforced no-take MPAs definitely complemented with strategies to regulate the effects of land use and international commitment to reduce the emission of greenhouse gases, and finally the implementation of strategies to reduce or stabilize the ultimate cause of all these stressors, the world's human population.
For more information, see the paper: Mora, C (2008) A clear human footprint in the coral reefs of the Caribbean. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2007.1472