Serious consequences for the marine ecosystems
Uncontrolled fishing practices have given rise to a new trend that places larger animals at greater risk of extinction than smaller ones, according to scientists from Stanford University.
“We’ve found that extinction threat in the modern oceans is very strongly associated with larger body size. This is most likely due to people targeting larger species for consumption first,” said Jonathan Payne, Associate Professor of Geological Sciences at Stanford School of Earth, Energy & Environmental Sciences.
In a study recently published in the Science journal, Payne and his colleagues examined the relationship between the risk of extinction and characteristics such as body size for two major groups of marine animals – molluscs and vertebrates – in the last 500 years. They then compared their results with data from the last 445 million years, emphasising the last 66 million years.
“We used the fossil record to show, in a concrete, convincing way, that what is happening in the modern oceans is really different from what has happened in the past,” said co-author Noel Heim, a postdoctoral researcher.
“What our analysis shows is that for every factor of 10 increase in body mass, the odds of being threatened by extinction go up by a factor of 13 or so. The bigger you are, the more likely you are to be facing extinction,” added Payne.
Based on studies of fossil records, this is a new trend that did not exist in the earth’s history.
This selective extinction of large animals has actually occurred in the recent past, as our ancestors killed off mammoths and other megafauna around the world. “We see this over and over again. Humans enter a new ecosystem, and the largest animals are killed off first. Marine systems have been spared up to now, because until relatively recently, humans were restricted to coastal areas and didn't have the technology to fish in the deep sea on an industrial scale,” said Heim.
If this selective extinction scenario does take place in the oceans, it may lead to serious consequences for the marine ecosystems, as the large marine animals are at the top of the food chain. Their movement in the water column and seafloor help to distribute nutrients in the oceans.
However, there is still hope for the large marine animals – if people change their behaviour and fishing practices now. “We can’t do much to quickly reverse the trends of ocean warming or ocean acidification, which are both real threats that must be addressed. But we can change treaties related to how we hunt and fish. Fish populations also have the potential to recover much more quickly than climate or ocean chemistry,” said Payne.
More information: news.stanford.edu
Link to study: science.sciencemag.org/content/353/6305/1284