Dale C. S. Destin |
The highest coral bleaching alert level is forecast for Antigua and Barbuda and much of the Caribbean as a part of the third ever global coral bleaching event. Alert level 2 has been issued for our coral reefs. This means that our coral reefs are expected to undergo widespread bleaching with a significant amount possibly dying.
Credit: NOAA Coral Reef Watch
The bleaching in our neck of the woods is due mainly to the warming of the Atlantic Ocean which was brought on by persistent light winds or negative North Atlantic Oscillation. Meanwhile, the Pacific bleaching is largely due to El Nino. Global warming is most likely playing an underlying role.
Corals start to bleach when the sea surface temperature (SST) exceeds the maximum monthly mean SST by 1 °C (1.8 °F). This cause corals to spew their algae, which they need to feed themselves. For our area, the bleaching threshold is 30.0 °C (86 °F). Currently, SST around Antigua is about 30.0 °C (86 °F) and rising.
Credit: NOAA Coral Reef Watch – http://coralreefwatch.noaa.gov
In the future, climate change, force by global warming, is expected to play a lead role in coral bleaching. According to the Inter-governmental Panel on Climate Change, warming in the top 100 metres of the ocean will rise a further 0.6 to 2 °C by the end of the 21st century. Greater warming is anticipated at the surface of the ocean. This could result in mass bleaching events becoming common place.
These images, taken in American Samoa, show the devastation caused by coral bleaching between December 2014 and February 2015 (Credit: XL Catlin Seaview Survey)
The bleaching has negative implications for our tourism industry. Coral reefs are a major source of sand for tropical beaches such as our 365 white sandy beaches, which are our main tourism drawing card. Degraded coral reefs could result in a decline in the replenishment of sand on our beaches and eventually reduce our islands’ attractiveness to tourists.
Additionally, many persons come to our shores to snorkel and enjoy the spectacular underwater beauty provided by coral reefs and the sea life they attract. Every coral bleached or killed reduces our drawing power of those tourists interested in this kind of scenery.
The bleaching also has negative implications for our food security, livelihoods, coastal protection, ocean acidification and climate change.
According to Professor Ove Hoegh-Guldberg of the University of Queensland, who was quoted in a recent BBC news article, “just like in 1998 and 2010, we’re observing bleaching on a global scale, which will cause massive loss of corals. With people relying on fisheries and reefs for sustenance, the repercussions could be potentially disastrous.”
Coral reefs are vitally important to Antigua and Barbuda and the rest of the world. They perform a long list of functions for us all. Chief among them is the role they play in the food chain. Corals serve as sanctuary for countless different species of fish. These reefs serve as homes for fish, without which they would be homeless with no place to safely have their babies.
The role played by coral reefs contributes in no small way to reef fish and mollusc, feeding as many as 40 million people annually.
Another important role coral reefs play is that of protecting our coastlines. For regions like ours that are visited by tropical cyclones (the generic term for tropical depressions, tropical storms and hurricanes) on an annual basis, coral reefs serve as a natural and vital protection against storm surge, strong currents and large waves by slowing down the water before it reaches the coastlines.
Coral reefs also play a very important role in the carbon cycle. They convert carbon dioxide (CO2) into limestone shell. Their absence would result in a rapid increase in CO2, which would eventually affect all living things on earth.
Generally, bleached corals end up dying. If they survive, their recovery can be very slow, taking decades.
The truth is, there isn’t a lot that we can do to mitigate a given bleaching event. However, systems could be put in place to keep our corals as healthy as possible by reducing pollution, coastal runoff and over fishing. Such measures would raise and keep corals at optimal health, which would improve their chances of surviving bleaching.
In the final analysis, if we are to continue to enjoy the products and services of our coral reefs, the world would have to make better than ambitious cuts to their CO2 emissions, the main cause of global warming and climate change. So far, the proposed cuts to emissions are still very far from what is required to keep global surface temperature below the level that will perhaps prevent the extinction of corals and dangerous climate change.
We will continue to follow this issue over the upcoming months and keep you informed.