In a new study, to be published in the September 16 issue of the journal Science, Payne and his colleagues examined the association between extinction threat level and ecological traits such as body size for two major groups of marine animals – mollusks and vertebrates – over the past 500 years and compared it with the ancient past, stretching as far back as 445 million years ago and with a particular emphasis on the most recent 66 million years.
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The researchers considered four traits in particular – size (the animal’s length), habitat zone (whether it lived in open water or on the seafloor), motility (if it swims around or stays in one spot) and feeding (whether it is a predator or not).
There have been five cataclysmic events in our planet’s history-encroaching glaciers, volcanic eruptions, toxic oceans, and, perhaps most famously, a collision with a massive space rock-that almost wiped life from the face of the Earth.
“If we keep going at our current pace and keep our current ocean management practices, we are setting a course to create a sixth mass extinction-and what’s being seen on land will soon follow in the sea”, McCauley said. Now we might face the Sixth Extinction- and it might be our fault.
For the first time, body size appears to be a powerful predictor of extinction threat; as body size increases, so does the risk of extinction.
The danger is disproportionate to the percentage of threatened species, with the authors warning the loss of giants would “disrupt ecosystems for millions of years even at levels of taxonomic loss far below those of previous mass extinctions”.
Of all five past mass extinction, the Pernian one was one of the biggest, which occurred about 252 million years ago.
Larger marine animals are more at threat of extinction than smaller ones, scientists have said. It is a fact that every species’ extinction could potentially lead to the extinction of others and the change of biosphere is increasing.
A study found that larger-bodied animals are more likely to die out first than smaller ones.
“The proportion of species that are threatened increases enormously as body size increases”, Payne said. “These are the same kinds of environmental changes that we know are happening in the ocean today and that we anticipate for the future”. “To claim we’re in a sixth mass extinction is something very enormous”. However, the researchers have identified a new pattern that puts larger animals at greater risk of becoming extinct first.
There are still steps that humans could take to limit the damage.
Fish provide 17 percent of the animal protein consumed in the world, now home to more than seven billion people. “Studies of the fossil record indicate that this trend didn’t exist in the past – it’s a new development in today’s world”. Payne maintains hope, pointing to northern elephant seals, which had a population below 100 in the early 1900s. “We have the capacity to degrade the system, but there are hopeful examples that suggest if we change what we are doing, we can have a positive impact”.
“We’re really at a point where we need to make a decision”, Worm says, about whether we allow the destruction continue or reverse it. His research group recently found that large body size is strongly associated with higher extinction threat in living marine animals and that this pattern is distinct from extinction selectivity patterns in the marine fossil record.
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“I talked to a couple of people who said they found this a very discouraging result”, Payne says. “We have brought gray whales back from the brink of extinction and blue whales are coming back too”.
