Mass extinctions throughout history have altered the structure of life in the seas, with dominant creatures being toppled and others rushing in to take their place, creating a whole new ecosystem.
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Mass extinctions in the past have altered the structure of life in the seas.
"It would be unwise to assume that any large number of species can be lost today without forever altering the basic biological character of Earth's oceans," John Alroy of Macquarie University in Sydney, Australia, wrote in his study, published this week in the journal Science.
Human activity such as fishing, agriculture and logging have greatly accelerated the rate at which species go extinct. As of last year, one in eight birds, one third of amphibians and almost a quarter of mammals were threatened with extinction, according to the International Union for Conservation of Nature.
Alroy's study looked at 100,000 fossil collections spanning hundreds of millions of years, with a strong focus on marine life. He found that dominant creatures can be dramatically affected by large extinctions.
One example is the brachiopods family of creatures, which are similar to clams and were among the dominant life forms in the ocean for nearly 300 million years. Then they were hit with a mass extinction event about 250 million years ago. This "reset the clock on diversification and overturned the balance of groups," according to the study.
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Now, the brachiopods are rare marine creatures, with low levels of diversity. Today's rate of extinction may be as great as 100 times the historic norm, according to LiveScience. Some scientists even say that we're entering a new phase in the Earth's history, called the Anthropocene Epoch.
This rapid change in biodiversity makes it difficult to predict how life on the planet will change, the researchers say.
"The main implication is that we're really rolling the dice," Alroy told LiveScience.