Imagine if all the world’s corn, rice, and wheat crops began failing catastrophically. Lose those food staples, and global starvation isn’t far behind.

That’s akin to what’s happening in the world’s oceans, according to a new study published in the July 29 edition of Nature (see article and news story).

Researchers found that phytoplankton, the underlying fabric of the ocean’s food web, has declined 40 percent since the 1950s. The likely cause? Global warming, which has heated the upper water column around the globe — slowing the circulation of nutrients from colder depths toward the surface, where phytoplankton live.

“It’s concerning because phytoplankton is the basic currency for everything going on in the ocean,” Dalhousie University biology professor and study co-author Boris Worm told the Associated Press in a story published July 28. “It’s almost like a recession … that has been going on for decades.”

Not only are phytoplankton a key food source in the ocean, they also help keep the Earth cooler than it otherwise would be by taking in carbon dioxide from the atmosphere above, wrote AP science writer Seth Borenstein in the story.

Increased greenhouse gases heat the upper oceans, which depresses populations of phytoplankton, which reduces their natural ability to absorb greenhouse gases from the atmosphere. Sounds like a textbook definition of a climate feedback.

Care About Phytoplankton?  You Should …

Think “So What?” about a few plankton? Think again. Better yet, take a look at the opening paragraphs of Chapter 4 — “Reading the Vital Signs: Metabolism” — from Canadian science journalist Alanna Mitchell’s award-winning 2009 book Sea Sick:

Plankton are the nonchalant wanderers of the ocean. They go with the flow. And one of the toughest, least understood questions about the changing global ocean is where plankton will go next. “Go” in the geographical sense as well as the evolutionary, biological, chemical and even metaphysical.

Does it matter where they go?

Resoundingly, yes. Impossible as it seems, this question — unimagined by most of us — may be the most important question humans will ever grapple with.

Plankton — a group of tiny organisms that range from microscopic marine viruses and bacteria to single-celled plants with fabulously ornate shells to miniscule plant-eating animals — are the lynchpin on which life itself depends. Not only do they produce half of the planet’s oxygen but they are also responsible for a host of different, invisible and interlocked parts of the metabolism of the planet.”

Why worry about the fate of plankton? Now you know. They matter, matter a lot.