When Deutsche and Penn ran their models of how species would respond to very high- and low-emission conditions, they found two dramatically different perspectives on the future of the planet. In extremely high-emission conditions, projected mass extinction rivals the intensity of previous “Big Five” extinctions in the Earth’s past – including the Permian-Triassic extinction and the one that wiped out dinosaurs. But if temperatures are approximate in low-emission conditions, the species loss due to climate change should be close to its current level.
Douglas McCauley, a marine biologist at the University of California, Santa Barbara, said: Science On paper, however, there is a possibility of mass extinction along that hill, he said.
These potential future extinctions will not happen equally on the planet. Deutsche and Penn’s models predict that tropical marine species are likely to move further north and south due to warmer oceans, while species living near the poles are at risk of extinction. “We are already seeing signs of this movement in the oceans today,” said Lewis Rutherford of the University of Bristol in the United Kingdom. In 2020, Rutherford co-authored an analysis that looked at where marine species could be found in the ocean. He observed that the abundance of a species tends to increase along its range which was closest to the poles and decreased near the equator, suggesting that warming seas are forcing these creatures to move away from the equator.
Species that already live near the poles are less likely to move anywhere when the oceans begin to warm up. This is why in the Deutsche and Penn models, the Polward species tends to become completely extinct while the tropical species are more likely to move away from the tropics. “You’ve got the chance to change this guard,” Rutherford said.
Scientists know that this movement is happening today, but it is difficult to identify how bad things are at the moment. For a start, we have no idea what is going on in the ocean. Much better information on fish abundance comes from research on commercially important fish species such as tuna and pollock, while data on tropical species are much less. “If you really want to find out what’s going on at the equator, we have to study the equator,” Rutherford said.
“There is a quiet extinction that is almost certainly happening at sea that is not going to be detected right now. And if climate change is allowed to continue, the wave of unknown extinction is going to turn into a tsunami,” McCully said.
Even if we can get a handle on climate change, people are still putting the oceans under extreme pressure due to changes in fishing and marine habitat. In 2008, the International Union for Conservation of Nature reported that 22 percent of the assessed marine species were at risk of extinction, including 17 percent sharks and their close relatives. One of the ways governments and NGOs have agreed to protect the oceans is to turn a large part of them into marine protected areas – an ocean equivalent to a national park.