A new study has found that that climate change and over-fishing, rather than pollution, were responsible for destroying coral reefs in the Caribbean.The paper, by researchers from the Washington-based US Wildlife Conservation Society, Columbia University and the University of Maryland, examined the effects of two of the most common pollutants: phosphorus and nitrogen.
They concluded that nitrogen is the more damaging of the two, but its effects are mostly felt after a reef is dead or dying, “because it stimulates the growth of microscopic green algae that break down the calcium carbonate skeleton of the coral”.
The team concluded that the massive die-offs of Caribbean corals in recent decades “stemmed mostly from warming ocean temperatures and declines in fish and invertebrates that protect reefs by feeding on the algae”.
Tim McClanahan, a senior conservation zoologist with the Wildlife Conservation Society, said the study helps explain why coral reefs were struggling across the globe.
“Pollution has been seen as one of the major culprits in the loss of coral reefs around the world,” said McClanahan, the lead author of the study.
“But our study indicates that it cannot explain the widespread changes we are seeing, which leave climate change and over-fishing as the major culprits.
“This helps us further pinpoint the causes of coral loss. But neither climate change nor fishing are easy problems to solve.”
McClanahan said, however, that pollution still matters, because, once global warming or over-fishing damages corals, “their skeleton will erode away faster in the presence of pollution”.
Meantime, another study released Tuesday by Dr. Amilo Mora, a marine ecologist at Dalhousie University, Halifax, Canada, found that humans have caused profound changes in Caribbean coral reefs.
“The continuing degradation of coral reefs may be soon beyond repair, if threats are not identified and rapidly controlled,” Mora said, noting that his study moves from the traditional localised study of threats to a region-wide scale, while, simultaneously, analysing contrasting socioeconomic and environmental variables.
The study monitored coral reefs, including corals, fishes and macroalgae, in 322 sites across 13 countries throughout the Caribbean.
The study was complemented with a comprehensive set of socioeconomic databases on human population density, coastal development, agricultural land use and environmental and ecological databases, which included temperature, hurricanes, productivity, coral diseases and richness of corals.
“The human expansion in coastal areas inevitably poses severe risks to the maintenance of complex ecosystems such as coral reefs,” Mora said.
“The future of coral reefs in the Caribbean and the services they provide to a growing human population depend on how soon countries in the region become seriously committed to regulating human threats.
“Although coral reefs will experience benefits of controlling fishing, agricultural expansion, sewage or ocean warming, it is clear that underlying all these threats is the human population.”
Mora said the expected increase of the world’s human population, from six billion to 9 billion by 2050, suggests that coral reefs are “likely to witness a significant ecological crisis in the coming half century, if effective conservation strategies, including policies on population planning, are not implemented soon”.
Last month, a United States study said Caribbean coral reefs could be among the first casualties of increasingly acidic oceans