‘Safe’ CO2 level may destroy the fishing industry, wreck reefs
September 23, 2008
An atmospheric carbon dioxide concentration of 450 parts-per-million (ppm) — a target level deemed safe by the United Nations Framework Convention on Climate Change (UNFCCC) — would be devastating to marine ecosystems warn scientists writing in the journal Geophysical Research Letters.
Modeling the impact of higher CO2 levels on ocean chemistry, Long Cao and Ken Caldeira of the Carnegie Institution's Department of Global Ecology concluded that absorption of CO2 by the world's oceans will reduce the availability of argonite, a mineral critical to corals and other marine organisms for growing their skeletons.
"Before the industrial revolution, over 98% of warm water coral reefs were surrounded by open ocean waters at least 3.5 times supersaturated with aragonite" said Cao. "But even if atmospheric CO2 stabilizes at the current level of 380 ppm, fewer than half of existing coral reef will remain in such an environment. If the levels stabilize at 450 ppm, fewer than 10% of reefs would be in waters with the kind of chemistry that has sustained coral reefs in the past."
Reefs would be greatly affected by the change, but in the long run, they won't disappear altogether. Other research has shown that some types of corals can persist in acidic oceans by utilizing non-argonite minerals pathways to build skeletons.
Nevetheless Cao and Caldeira say the biggest impacts may occur in the polar waters that are the base of the oceanic food chain. Die-offs in these regions could be catastrophic to marine fisheries.
"At atmospheric CO2 levels as low as 450 ppm, large parts of the Southern Ocean, the Arctic Ocean, and the North Pacific would experience a rise in acidity that would violate US Environmental Protection Agency water quality standards," said Cao, noting that under those conditions the shells of many marine organisms would dissolve.
"If current trends in CO2 emissions continue unabated in the next few decades, we will produce chemical conditions in the oceans that have not been seen for tens of millions of years," said Caldeira. "We are doing something very profound to our oceans. Ecosystems like coral reefs that have been around for many millions of years just won't be able to cope with the change."
"When you go to the seashore, the oceans seem huge. It's hard to imagine we could wreck it all. But if we want our children to enjoy a healthy ocean, we need to start cutting carbon emissions now."