"Long before it's in the papers"
January 27, 2015


Caribbean coral reefs disappearing, study says

July 2, 2014
Courtesy of the International Union for 
Conservation of Nature
and World Science staff

With only about one-sixth of the orig­i­nal cor­al cov­er left, most Car­ib­be­an cor­al reefs may dis­ap­pear in the next 20 years, ac­cord­ing to a re­port.

The study in­di­cates that glob­al warm­ing alone is­n’t to blame for a pre­cip­i­tous de­cline in cor­al area—the main prob­lem is a loss of graz­ing fish, which eat the al­gae on the reefs.

A parrotfish caught in a net. (Credit: Aya­na John­son)

“The rate at which the Car­ib­be­an cor­als have been de­clin­ing is truly alarm­ing,” said Carl Gus­taf Lundin, Di­rec­tor of Glob­al Ma­rine and Po­lar Pro­gramme for the In­tern­ati­onal Un­ion for Con­serv­ati­on of Na­ture, which con­tri­but­ed to the re­port. But “the fate of Car­ib­be­an cor­als is not be­yond our con­trol and there are some very con­crete steps that we can take to help them recov­er.”

“Even if we could some­how make cli­mate change dis­ap­pear to­mor­row, these reefs would con­tin­ue their de­cline,” added Jer­e­my Jack­son, lead au­thor of the re­port and the un­ion’s sen­ior ad­vi­sor on cor­al reefs. “We must im­me­di­ately ad­dress the graz­ing prob­lem for the reefs to stand any chance of sur­viv­ing fu­ture cli­mate shifts.”

Car­ib­be­an cor­als have de­clined by more than 50 per­cent since the 1970s, the study found, but re­stor­ing par­rot­fish popul­ati­ons and im­prov­ing oth­er man­age­ment strate­gies, such as protecti­on from over­fish­ing and ex­ces­sive coast­al polluti­on, could help the reefs recov­er.

The re­port is the re­sult of the work of 90 ex­perts over three years. It con­tains the anal­y­sis of more than 35,000 sur­veys con­ducted at 90 Car­ib­be­an loc­ati­ons since 1970, in­clud­ing stud­ies of cor­als, sea­weeds, graz­ing sea ur­chins and fish.

The re­port, Sta­tus and Trends of Car­ib­be­an Cor­al Reefs: 1970-2012, from the Glob­al Cor­al Reef Mon­i­tor­ing Net­work, the In­tern­ati­onal Un­ion and the Un­ited N­ati­ons En­vi­ron­ment Pro­gramme, was re­leased July 2 in Gland, Switz­er­land.

Cli­mate change has long been thought to be the main cul­prit in cor­al de­grad­ati­on. While it does pose a se­ri­ous threat by mak­ing oceans more acid­ic and caus­ing cor­al “bleach­ing,” the re­port says that the loss of par­rot­fish and sea ur­chin – the area’s two main “graz­ers” – has been a worse prob­lem. 

An un­iden­ti­fied dis­ease led to a mass death of the sea ur­chin in 1983 and ex­treme fish­ing through­out the 20th cen­tu­ry has brought the par­rot­fish popul­ati­on to the brink of extincti­on in some regi­ons, the re­port added. The loss of these spe­cies breaks the del­i­cate bal­ance of cor­al ecosys­tems and al­lows al­gae, on which they feed, to smoth­er the reefs.

Reefs pro­tected from over­fish­ing, as well as oth­er threats such as ex­ces­sive coast­al polluti­on, tour­ism and coast­al de­vel­op­ment, are more re­sil­ient to pres­sures from cli­mate change, ac­cord­ing to the au­thors.

* * *

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With only about one-sixth of the original coral cover left, most Caribbean coral reefs may disappear in the next 20 years, according to a report. The study indicates that global warming alone isn’t to blame for a precipitous decline in coral area—the main problem is a loss of grazing fish, which eat the algae on the reefs. “The rate at which the Caribbean corals have been declining is truly alarming,” said Carl Gustaf Lundin, Director of Global Marine and Polar Programme for the International Union for Conservation of Nature, which contributed to the report. But “the fate of Caribbean corals is not beyond our control and there are some very concrete steps that we can take to help them recover.” “Even if we could somehow make climate change disappear tomorrow, these reefs would continue their decline,” added Jeremy Jackson, lead author of the report and the union’s senior advisor on coral reefs. “We must immediately address the grazing problem for the reefs to stand any chance of surviving future climate shifts.” Caribbean corals have declined by more than 50% since the 1970s, the study found, but restoring parrotfish populations and improving other management strategies, such as protection from overfishing and excessive coastal pollution, could help the reefs recover. The report is the result of the work of 90 experts over three years. It contains the analysis of more than 35,000 surveys conducted at 90 Caribbean locations since 1970, including studies of corals, seaweeds, grazing sea urchins and fish. The report, Status and Trends of Caribbean Coral Reefs: 1970-2012, from the Global Coral Reef Monitoring Network, the International Union for Conservation of Nature and the United Nations Environment Programme, was released July 2 in Gland, Switzerland. Climate change has long been thought to be the main culprit in coral degradation. While it does pose a serious threat by making oceans more acidic and causing coral bleaching, the report shows that the loss of parrotfish and sea urchin – the area’s two main “grazers” – has been the key driver of coral decline. An unidentified disease led to a mass mortality of the sea urchin in 1983 and extreme fishing throughout the 20th century has brought the parrotfish population to the brink of extinction in some regions, the report added. The loss of these species breaks the delicate balance of coral ecosystems and allows algae, on which they feed, to smother the reefs. Reefs protected from overfishing, as well as other threats such as excessive coastal pollution, tourism and coastal development, are more resilient to pressures from climate change, according to the authors.