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The levels of biodiversity in the world’s oceans have remained largely unchanged for hundreds of millions of years, according to a new study published in Science.
The conclusion that marine biodiversity has been stable over time and has not multiplied over the past 200 million years challenges existing assumptions that there has been a constant diversification of species, the study authors say.
“Our article rejects past hypotheses that current marine diversity is higher than ever, due to sustained increases in the past 200 million years. Rather, we find that today’s levels of diversity are probably not so different from levels from hundreds of millions of years ago, “Lead author Dr. Richard Close, a paleobiologist at the University of Birmingham in the UK, said Newsweek.
“This may have implications for the way we understand modern biodiversity and conservation.”
According to Close, the assumption that biodiversity levels increase at least partially is due to a methodological error: the global fossil record on which it is based is not really global. It is more fractured than its name suggests, varying in geographic scope and continuity, leading to biased results.
“The fact that the ‘global’ fossil record is not truly global has not been widely recognized until now,” Close said. But new computer models capable of identifying patterns in diversity on a regional scale have allowed Close and his team to analyze changes in biodiversity levels in time and space since the start of the Cambrian Explosion, approximately 540 million years ago. years, to this day.
The results suggest that global biodiversity levels did not increase steadily for prolonged periods of time. Rather, it remained stable. However, the team noted differences in levels on a regional scale, with coral reefs historically displaying some of the largest varieties of species, as they do today.
“When you look at these individual animal groups, you can see fluctuations in diversity that are often substantial. But taken together, these patterns add up to one of restricted diversity,” Close said in a statement.
“Some groups may benefit from the misfortune of others, but the overall levels of diversity we see have been fairly stable for hundreds of millions of years.”
According to Close, understanding how biodiversity came to exist over time provides an important context for biodiversity today, as well as how it may change in the future.
This may be particularly relevant today given a series of recent studies suggesting that marine biodiversity is under serious threat, from the disappearance of coral reefs to the acceleration of species extinction rates. According to a study recently published in A land, more than a quarter of the world’s oceans must be protected to preserve marine biodiversity.
If current trends continue, would Close expect to see marked declines in biodiversity in the fossil record, or do you think it would be followed by a subsequent boom in biodiversity levels?
Points close to the Cretaceous period 66 million years ago, when an extinction event wiped out about half of all plant and animal species (especially non-avian dinosaurs). The study suggests that it was followed by a dramatic change in biodiversity levels, with an expanding list of new species, and gastropods in particular, taking advantage of the space left behind.
“We found a rapid recovery in diversity levels after the last mass extinction 66 million years ago, in fact, to levels even higher than before (although the temporal resolution of our study is quite low),” Close said. “Previous work has suggested that biodiversity would recover from anthropogenic extinction in a few million years.
“Long after we are gone, biodiversity is likely to recover to levels seen for tens to hundreds of millions of years. But it will take hundreds of thousands to millions of years, and it depends on how badly we ruin the natural environment ” “
WILLIAM WEST / AFP / Getty
