Study: Human activity affecting oceans NEW YORK, March 1 (UPI) -- Earth's oceans may be turning acidic faster from human carbon emissions than during four major extinctions in the last 300 million years, U.S. researchers say. A study by scientists at Columbia University is the first to survey the geologic record for evidence of ocean acidification and life extinctions over such a vast time period, a Columbia release reported Thursday. It compared human-caused emissions to natural pulses of carbon that have sent global temperatures soaring in Earth's past. "What we're doing today really stands out," Barbel Honisch, a paleoceanographer at Columbia's Lamont-Doherty Earth Observatory, said. We know that life during past ocean acidification events was not wiped out -- new species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care about -- coral reefs, oysters, salmon. Oceans absorb excess carbon dioxide from the air that reacts with seawater to form carbonic acid, but if CO2 goes into the oceans too quickly, it can deplete carbonate ions that corals, mollusks and some plankton need for reef and shell-building, the researchers said. It may take decades before ocean acidification's effect on marine life shows itself, but the study highlights the extreme effect human activity has had on marine chemistry, experts said. "These studies give you a sense of the timing involved in past ocean acidification events -- they did not happen quickly," Richard Feely, an oceanographer at the National Oceanic and Atmospheric Administration who was not involved in the study, said. The decisions we make over the next few decades could have significant implications on a geologic timescale.