Abrupt climate change could hurt marine life for thousands of years, according to a new study of the ocean floors. Even if global warming were immediately halted, millennia would pass before the ocean ecosystem could recover from the effects of human civilization.
The study examined ocean fossils off the coast of California to understand the impact of climate change at the end of the last ice age. At that time, polar ice caps melted and ocean zones with low oxygen became more common. This process only took about a century to transpire.
After inspecting more than 5,400 invertebrate fossils, including clams and sea urchins, researchers determined that these animals nearly went extinct from a lack of oxygen.
A similar series of climatic events is unfolding once again around the world — driven by the release of greenhouse gases from factories and vehicles. Scientists believe a similar development of oxygen-poor regions could occur in oceans over the course of a century. It would take thousands of years to dissipate — much like the pattern seen during the last major deglaciation, when the climate abruptly warmed, polar ice caps melted, and low-oxygen zones in the ocean expanded.
A sediment core of fossils dating back between 3,400 and 16,100 years ago provided a snapshot of marine life before and after the end of the last ice age. Researchers wanted to gather information on deglaciation from invertebrate fossils gathered from the core drilled from the ocean floor.
"After the initial sampling at sea, I took the entire core, which was about 30 feet long. I cut it up like a cake, and I sampled the whole thing. Because of that, I had the whole record," said Sarah Moffitt from the UC Davis Bodega Marine Laboratory and Coastal and Marine Sciences Institute.
Analysis reveals that the invertebrate life was rich with a diverse range of species prior to the end of the ice age. That was followed by a rise in ocean dead zones, which drove extinction. Oxygen levels fell by between 0.5 and 1.5 mL/L over a period of less than 100 years, scientists found, which shows that "relatively minor changes in oxygen levels could result in dramatic changes and reorganizations for seafloor communities."
Climatologists previously estimated that it might take just a century for oceans to recover from the effects of global climate change. The new study shows that the recovery period could be 10 times longer than believed.
"There's not a recovery we have to look forward to in my lifetime or my grandchildren's lifetime. It's a gritty reality we need to face as scientists and people who care about the natural world and who make decisions about the natural world," Moffitt said.
The study was published in the early edition of the journal PNAS, Proceedings of the National Academy of Sciences of the United States of America.
Photo: Michael Gras M.Ed. | Flickr