During the past 600 million years, scientists say, there have been five "global extinction events" in the ocean.
Now we're headed for another one unless we shrink our carbon footprint and quit overfishing now, not later, according to a group of world-class experts who gathered in Oxford, England this spring at a meeting organized by the International Programme on the State of the Ocean.
We're heard before that coral reefs are dying. We've heard of "dead zones" in the ocean, in some cases caused by oil spills and nutrient runoff from farming. We've heard that toxic algae blooms are invading healthy ocean ecologies, and species of valued food fish are being frighteningly depleted (63 percent of the world's assessed fish stocks are so overexploited that they may be headed for extinction). We've heard that the ocean is becoming acidic and that its capacity to contain carbon dioxide is likely strained.
What we've heard less often is that all these phenomena together threaten to overwhelm the ocean's ability to heal itself.
In 2007 the Intergovernmental Panel on Climate Change issued a report that included alarming projections about the effects of climate change on oceans and the resulting effects on people. An example is the prediction that "more than 1 million people will be directly affected [by rising sea levels] by 2050 in three megadeltas: the Ganges-Brahmaputra delta in Bangladesh, the Mekong delta in Vietnam and the Nile delta in Egypt. More than 50,000 people are likely to be directly impacted in each of a further 9 deltas [including the Mississippi Delta], and more than 5,000 in each of a further 12 deltas [including the Rhine, Niger and Volta deltas]." Other projections had to do with the rate of coral bleaching, of ocean acidification, of algae proliferation and many other processes affecting the health of the seas.
Of course, there was always the hope that the projections were pessimistic—that efforts to shrink the world's carbon footprint, or unforeseen mitigating factors, would slow the deterioration of the oceans.But according to the scientists at the IPSO meeting, developments over the last four years have been either on track with the 2007 projections, or more rapid.
A major reason the scientists think we are headed for a marine cataclysm is this: during the so-called End Permian mass extinction 251 million years ago, the ocean was taking in one to two billion tons of CO2 per year. During the Paleocene Eocene Thermal mass extinction, it was absorbing 2.2 billion tons a year. Today it's force-fed 30 billion tons a year, and "the uptake of CO2 into the oceans," warns marine biogeoscientist Dr. Jelle Bijma, "is outstripping [their] capacity to neutralize it." As the seas lose their capacity to absorb CO2, the land will be hotter, and in the meantime the survival of coral and plankton will be threatened.
Among the recommendations for restoring health to the oceans: immediate lowering of carbon dioxide emissions; an end to overfishing; international cooperation in protecting the health of international waters; and pollution control, including preventing toxic substances—from oil and fertilizers to plastics and pharmaceuticals—from entering the oceans by way of rivers and sewage systems.