Increase in coral reef bleaching attributed to climate change
By Michael Harper
Rising temperatures associated with climate change have already been shown to have an effect on a wide range of ecosystems and the creatures that reside within. Recent studies have now added coral reefs to the list of ecosystems that may be damaged as a result of climate change. Judging from new maps and models, the rising sea temperatures, which accompany climate change, could result in more frequent coral bleaching events, causing them to occur as often as once every year. Researchers have used different emissions scenarios to predict how prevalent these bleaching events will be on coral reefs around the world. A recent published study has now found 74 percent of the world’s coral reefs will begin experiencing annual bleaching events by 2045 if emissions rates remain unchanged.
These events occur whenever sea temperatures rise to higher-than-normal temperatures which kill off important algae. These algae, called “zooxanthellae,” live inside the coral and not only feed the corals, but give them their bright colors, as well. As sea temperatures climb, these algae become more sensitive to light, which either drives the algae away or kills it altogether. With the coral reef’s food source disturbed, they starve and eventually die. This lack of algae also turns the coral a bright white, making them appear they’ve been bleached. According to the Global Coral Reef Monitoring Network, (GCRMN) somewhere between 50 and 90 percent of the coral reefs in the Indian Ocean died during a bleaching event in 1998. In the same year, the Great Barrier Reef endured its first bleaching event, followed by other major events in 2002 and 2006.
If emissions remain, global bleaching events could begin occurring every year, affecting 74 percent of the world’s coral reefs. According to the GCRMN, such events not only threaten the extinction of certain types of coral, but could also leave coastal communities more vulnerable to storm and tsunami damage as well as erosion and loss of life.
To build this study, these researchers used models provided by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).
According to this data, a quarter of the world’s coral reefs may begin experiencing these annual bleaching events in 2035, five years before the rest of the world’s reefs begin experiencing these horrible events.
The researchers predict reefs in Australia, Papua, New Guinea, and some equatorial Pacific Islands like Tokelau may be the first to experience bleaching events. These events will require urgent attention.
“Coral reefs in parts of the western Indian Ocean, French Polynesia and the southern Great Barrier Reef, have been identified as temporary refugia from rising sea surface temperatures,” said Ruben van Hooidonk, PhD from the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) at the University of Miami, speaking in a statement.
“These locations are not projected to experience bleaching events annually until five or more years later than the median year of 2040, with one reef location in the Austral Islands of French Polynesia protected from the onset of annual coral bleaching conditions until 2056.”
Each of the researchers involved in this research believe these projections are accurate given current emission levels. An increase in emissions levels will hasten these bleaching events.