There is another somewhat unexpected threat to corals: ordinary sun-cream from holidaymakers swimming near reefs. The common sun-cream component of oxy-benzone (present in most sun-creams) is toxic to corals at only about 60 parts per trillion. Globally, an estimated 10,000 tonnes of sun-screen ends up in the oceans, near corals, every year. This has a noticeable negative impact on the reef.

Taken altogether, this quadruple whammy bodes ill for the world's coral reefs. When the reefs die, and sea level rises there will be nothing to stop sub-tropical waves eroding the very land that some Pacific Islanders live on. Even islands with higher elevations still have fringing reefs. They are all in trouble, because sea level rise and higher erosion rates will force a retreat from the coast (hopefully planned), with massive social, environmental and economic disruption. So yes, they are absolutely justified in getting agitated about reef degradation!