How many dead canaries does it take? The warning indicators of an impending ecological collapse keep piling up. Forests get most of the headlines, but in many ways the oceans are the lungs of the planet. And they’ve been smoking 30 a day for too long. The effects are becoming clear:
Plankton, base of ocean food web, in big decline
Despite their tiny size, plant plankton found in the world’s oceans are crucial to much of life on Earth. They are the foundation of the bountiful marine food web, produce half the world’s oxygen and suck up harmful carbon dioxide.
And they are declining sharply.
Worldwide phytoplankton levels are down 40 percent since the 1950s, according to a study published Wednesday in the journal Nature. The likely cause is global warming, which makes it hard for the plant plankton to get vital nutrients, researchers say.
The numbers are both staggering and disturbing, say the Canadian scientists who did the study and a top U.S. government scientist. “It’s concerning because phytoplankton is the basic currency for everything going on in the ocean,” said Dalhousie University biology professor Boris Worm, a study co-author. “It’s almost like a recession … that has been going on for decades.”
Half a million datapoints dating to 1899 show that plant plankton levels in nearly all of the world’s oceans started to drop in the 1950s. The biggest changes are in the Arctic, southern and equatorial Atlantic and equatorial Pacific oceans.
Plant plankton â€” some of it visible, some microscopic â€” help keep Earth cool. They take carbon dioxide â€” the key greenhouse gas â€” out of the air to keep the world from getting even warmer, Boyce said.
Worm said when the surface of the ocean gets warmer, the warm water at the top doesn’t mix as easily with the cooler water below. That makes it tougher for the plant plankton which are light and often live near the ocean surface to get nutrients in deeper, cooler water. It also matches other global warming trends, with the biggest effects at the poles and around the equator.
Combine this with the evidence of increasing acidification of oceans and the message is clear. The lungs of the planet are giving out on us.
[Update: From comments – â€˜best evidence yet’ of rising long-term global temperatures]