The next mass extinction: how it will happen and who will suffer

It is hot, there is no oxygen, and there is nowhere to go from this - marine species can face such conditions on

around the world due to climate change. The end result is a mass extinction.

What is happening to the ocean?

Changes are already underway.Carbon dioxide dissolves in the ocean to form carbonic acid. As a result, the pH of the ocean has already decreased by 0.1 compared to the pre-industrial era. Perhaps by 2100 it will fall another 0.5. Climate experts believe that by 2100 the global average temperature will increase by 2.1-4.4°C, according to the "moderate" scenario. All this is due to anthropogenic climate change.

It is expected that in the coming decades, globaltemperatures will become even higher, the authors of the new work said. Therefore, researchers are wondering how these changes will affect life on Earth - and especially in the seas. But the oceans have experienced major crises before, with at least five mass extinctions. If you study these events, you can understand what awaits us in the future.

What did the authors of the new work find out?

To better understand what trends shouldAs expected, Princeton University oceanographers Justin Penn and Curtis Deutsch used a scientific model that they used to predict the extent of mass extinctions in the past. The authors wanted to assess the consequences of today's global warming.

According to their research published inAccording to Science magazine, if humanity cannot reduce emissions from burning fossil fuels, then within the next 300 years, another mass extinction will occur in the Earth's oceans.

This potential catastrophe will have different consequences depending on different factors. The response of species at the North and South Poles will be different from what happens in the tropics.

How is the predicted extinction similar to those that have occurred before?

The authors of the new work first studied the mosta terrible mass extinction that occurred about 250 million years ago, at the end of the Permian period. Then there was a powerful volcanic eruption, which led to environmental changes and mass extinction. It wiped out approximately 95% of known marine species.

Penn and his colleagues found that during this time, oxygen levels decreased, the climate changed, and together with other factors, this destroyed suitable habitats for many marine species.

“The same environmental changes are taking place in the oceans today,” says Penn, “so we wanted to quantify the magnitude of a possible extinction that is following a similar path.

Penn and Deutsch considered the implications of severalscenarios. When global warming persists but minimal change occurs, and up to high emission scenarios with abrupt warming.

What will happen to the ocean?

The researchers found that at worstoption, the extinction in the oceans will be similar to the five that occurred earlier on Earth. In all cases, the organisms struggled to find a suitable habitat in the elevated temperature and lack of oxygen.

Ecosystems where the level of oxygen in the water is alreadylow, such as those in the tropical seas of the Indo-Pacific, are likely to be hit particularly hard. Seawater may lack the oxygen needed to sustain life for all creatures. Organisms that are closer to the poles will suffer as well, as the water becomes too warm for species that are accustomed to the cold.

“Tropical species are already adapted to a certain environment,” says Penn, “and polar organisms will have nowhere to go in search of shelter.”

Did scientists previously know that extinction was about to happen?

Perhaps they guessed, but, according to the authors of the new work, their assessment differs from the previous ones.

“Many previous biologists' work suggested thatthat marine life has a large habitat, and the marine systems themselves are very inert, so climate change is unlikely to cause serious consequences, ”says David Lazarus, a paleontologist at the Museum of Natural History. He did not participate in the new study.

Although the oceans are vast and diverse ecosystems with many species, the worst-case global warming scenarios will severely impact them.

According to Lazarus, the new study hassome limitations - it does not take into account other factors that affect ocean biodiversity - overfishing and pollution. The authors also need to collect more information about the metabolic requirements of different organisms.

However, the study is convincingproves that many marine species cannot simply move to another place, and changes in ocean temperature worsen the survival of different species, notes Lazarus.

What will happen next?

Looking a hundred years into the future, the authorsstudies underline that now is the time to prevent the worst consequences that await the ocean. The global climate is expected to warm by about 3.6°C by 2100. If emissions are limited, and warming is kept at this minimum, then mass extinction can be avoided.

“We found that the volume of the mass extinctiondepends on the amount of CO2 we emit,” says Penn. He notes that according to the results of the work, there are two possible scenarios. Emissions from fossil fuels will continue and this will lead to one of the worst biological crises on Earth. But if the amount of emissions is reduced, then there is hope that the ecosystems and biodiversity of the ocean will be preserved.

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