"Now we begin to see some of the consequences. For example, if the long-term trend continues, all fish and seafood species are projected to collapse within my lifetime -- by 2048." Worm is an assistant professor of marine conservation biology at Dalhousie University, Halifax, Canada.

In the paper "Impact of Biodiversity Loss on Ocean Ecosystem Services," an international team of ecologists and economists studied the role marine biodiversity plays in maintaining ecosystem services, which are those goods and functions that are essential for the growing human population.

"Worm and colleagues have provided the first comprehensive assessment of thestate of ecosystem services provided by the biodiversity of the world's oceans to humanity," said Science International Managing Editor Andrew Sugden. "The news is both bad and good.

"The strength of this paper lies in the breadth of the array of information the authors used for their analysis; they not only used new experimental data and recent data, they also delved into historical archives to assess the impact of humans on marine ecosystem overdecades and centuries," Sugden said.

"At this point," Worm said, "29 percent of fish and seafood species have collapsed -- that is their catch has declined by 90 percent. It is a very clear trend, and it is accelerating. We don't have to use models to understand this trend; it is based on all the available data."

Researchers also determined that the problem is much greater than losing a key source of food. Damage to the oceans impact not only fisheries, but the ocean ecosystem's overall productivity and stability. Specific services that have declined involve the maintenance of water quality by biological filtering, the provision of nursery habitats and the protection of shorelines by marine species. The loss of marine diversity also appeared to increase the risks of beach closures, harmful algal blooms (red tide, for example), oxygen depletion, fish kills and coastal flooding.

"The good news is that it is not too late to turn things around," Worm said. The scientists studied 48 areas worldwide that have been protected to improve marine biodiversity. "We see that diversity of species recovered dramatically, and with it the ecosystem's productivity and stability."

Researchers studied a variety of information in four meta-analyses, progressing from local to regional and global scales.

First, they analyzed 32 marine experiments that manipulated species diversity on small, local scales, and monitored the effects. Second, researchers tracked the 1,000-year-long history of change in species diversity and associated services across 12 coastal regions around the world. These included Chesapeake, Delaware, Massachusetts, Galveston, San Francisco Bay and Pamlico Sound (all U.S.), The Bay of Fundy and Gulf of St. Lawrence (Canada), The Adriatic, Baltic and North Seas (Europe), as well as Moreton Bay (Australia). Sources included archives, fishery records, sediment cores and archeological data.

Then, the team compiled global fisheries catch data from 64 large marine ecosystems to test for the effects of large-scale species loss on fisheries-related services. They used the fisheries database compiled by the United Nations Food and Agriculture Organization and the Sea Around Us Project at the Fisheries Centre, University of British Columbia. Finally, the scientists investigated how recovery of biodiversity in 48 marine protected areas -- reserves and fishery closures -- affected the recovery of services.

The researchers were surprised to find very similar relationships between biodiversity change and ecosystem services at scales ranging from small square-meter plots to entire ocean basins, Worm said. "This suggests that small-scale experiments can be used to predict large-scale ocean change.

"Through this research, it became clear to me that we hardly appreciate living on a blue planet," Worm said. "The oceans define our planet, and their fate may to a large extent determine our fate, now and in the future."

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