"Whereas those systems that still had a full portfolio of species or had large species diversity to begin with were more robust, better buffered against change."
In a telephone briefing with reporters, Worm added that he and his colleagues were "really surprised, to some extent shocked, by the consistency of the result."
Worm told National Geographic News that the tight-knit connections between ocean communities and their habitats might explain why species diversity affects ecosystem services so closely.
He likened the relationship to a house of cards: Remove one species or habitat type in the system, and the whole thing comes tumbling down.
But Donald Boesch at the University of Maryland Center for Environmental Science in Cambridge is not convinced.
In a Science news article on the study, he said "it falls short of demonstrating that biodiversity losses are the primary drivers of why the services have declined."
For example, excessive fertilizer runoff into the Chesapeake Bay is most likely behind the decline in water quality there, not loss of biodiversity, he says.
Reversing the Trend
But the finding that areas do recover if managed is a major bright spot to the otherwise dark study, Worm says.
"This can be done. It's not beyond our reach at all," he said.
The study recommends an ecosystem management approach that sets aside some zones completely off-limits to any human activity while opening others to certain uses, such as recreation, research, and fishing.
"It's exactly what we do on land, and we've been doing it for a long time," Worm said.
Jane Lubchenco, a marine biologist at Oregon State University in Corvallis, praised the study for presenting compelling evidence that ecosystems can recover if appropriate action is taken.
"That said, their first conclusion about the downward spiral [of biodiversity] suggests that the rate of implementation of those recovery tools needs to be sped up quite significantly," she said. But "just making recommendations doesn't make things happen, unfortunately."
However, she points to several promising developments, including a proactive movement toward marine reserves and protected areas off the coast of California and Australia's Great Barrier Reef. (Related: "Giant Marine Reserve Created in South Pacific" [March 29, 2006].)
She also promotes "catch shares" fisheries management, in which commercial fishers have a stake in maintaining healthy fish populations because they are granted a percentage of the total allowable catch. As more fish are available, the fishers get a larger share.
"The whole idea is to align fishing and conservation interests so there is incentive for fishermen to conserve stocks so we have something to catch in the future," she said.
On the individual level, Worm says, people need to pay attention to what they eat.
"All of these species end up in our bellies somewhere, so of course we have a lot of control over what is caught and how it is caught," he said. "We need to make informed choices on the fish we eat."
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES