An aerial handout picture of a construction site surrounded by Caribbean seawater at the Yucatan resort of Cancun, May 27, 2008. Local environmental problems like sewage, farm runoff and overfishing could kill off much of the world's reefs decades before global warming does, according to an expert near Cancun.

Coral reefs like Chitales, near the northern tip of a Caribbean reef chain stretching from Mexico to Honduras, are dying around the world as people and cities put more stress on the environment.

Climate change alone could trigger a global coral die-off by 2100 because carbon emissions warm oceans and make them more acidic, according to a study published in December.

But local environmental problems like sewage, farm runoff and overfishing could kill off much of the world’s reefs decades before global warming does, said Roberto Iglesias, a biologist from UNAM university’s marine sciences station near Cancun.

“The net effect of pollution is as bad or maybe worse than the effects of global warming,” said Iglesias, a co-author of the study in the journal Science on how climate change affects reefs.

Human waste like that from Cancun’s hotels and night spots aggravates threats to coral worldwide like overzealous fishing which hurts stocks of fish that eat reef-damaging algae.

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