It is not too late to stop mass extinction in the ocean

It is not too late to stop mass extinction in the ocean

Two hundred and fifty million years ago on planet Earth things were not going well, to put it mildly. At the time, the planet was in the midst of the worst mass extinction event in its history, far more serious than the one that wiped out non-avian dinosaurs 66 million years ago. During this event, known as the Permian-Triassic Mass Extinction, about seventy percent of Earth's species met their end. Greenhouse gases emitted by volcanic eruptions in Siberia reached the sky, warming the Earth and generating acid rain that poured onto the soil. The scenario was so severe that paleontologists have dubbed this mass extinction the Great Dying.

In the oceans, the situation was even worse. Temperatures around the tropics rose 10 degrees Celsius and deep sea currents slowed, depriving the oceans of oxygen. Less than five percent of marine species managed to survive the Great Dying. It would take tens of millions of years for life in the ocean to bounce back to previous levels of biodiversity. The trilobites, a large group of underwater creatures that have populated the oceans for more than 250 million years, were completely wiped out. On land, the listrosaurus, a bizarre-looking vertebrate, quickly spread to the barren new planet.

According to oceanographers Curtis Deutsch and Justin Penn, the Great Death can tell us a lot about our planet's possible future in the event where we couldn't manage climate change.

"These environmental changes are also occurring in modern oceans," says Penn, an associate researcher in the Department of Geosciences at Princeton University and co-author of a new paper published in the journal Science. In the ocean, the overall oxygen content has already decreased by about two percent since the mid-twentieth century. This led Deutsch and Penn to ask a simple question: If greenhouse gas emissions accelerated ocean extinctions in our distant past, what level of extinction could climate change cause?

Two conflicting scenarios To understand this, scientists looked at two scenarios relating to future emissions. In one, fossil fuel-related emissions are rising rapidly - well beyond current estimates - triggering a rise in temperatures of approximately 4.9 degrees Celsius by 2100. In the other scenario, the lower levels of emissions keep rising emissions. temperatures just below two degrees by the end of the century. It should be emphasized that the first projection represents the unlikely worst-case scenario, and would require huge increases in the use of coal to materialize, which however peaked in 2013. If the countries of the world continued in the current trend, we would more likely go towards a increase by 2.7 degrees, while in the event that the commitments made at COP26 are kept, humanity may be able to keep global warming below two degrees Celsius.

WiredLeaks, how to send us a report anonymous "There is still an enormous variety of possible futures - says Deutsch -. We wanted to best represent the range of plausible futures without being extreme in one direction or the other".

Scientists have used these two scenarios to estimate what would be the repercussions on the demand and supply of oxygen in the ocean. Like humans, marine animals also need oxygen to survive. Rising temperatures, however, reduce the amount of oxygen that seawater is able to contain and slow down the currents that usually allow it to circulate between the surface and the depths of the ocean. At the same time, higher temperatures mean that marine creatures need more oxygen to carry out their activities. Increased demand and decreased oxygen availability are thought to be a major reason why the Permian-Triassic extinction caused the disappearance of so many marine species.

When Deutsch and Penn performed the simulations to discover what the response of the species in the two scenarios would have been, ended up with two clearly divergent visions on the future of the planet. In the scenario where emissions were greatest, the predicted mass extinction reached severity levels in line with the five great extinctions of the past, including that of the Permian-Triassic and the one that wiped out the dinosaurs. If, on the other hand, global warming traces the levels estimated in the second scenario, the loss of species caused by climate change should remain similar to the current levels.

Different impacts In the future, these possible extinctions will not occur uniformly over the whole planet. The models by Deutsch and Penn predicted that as the oceans warm, marine species in the tropics will likely move further north and south, while species already living near the poles are at greater risk of becoming extinct. The signs of these movements are already visible in today's oceans, explains Louise Rutterford of the University of Bristol. Rutterford is the co-author of a 2020 study examining the distribution of marine species in the oceans and which found that a species' abundance tended to increase near the poles and decrease near the equator, an indication that the Warming of the seas was forcing these animals away from the equator. Species that already live near the poles are less likely to find a place to relocate when the oceans begin to warm. This is why in the Deutsch and Penn model species near the poles tend to become extinct, while tropical ones are more likely to move away from the area.

What we can do Although scientists are aware of the fact that this shift is already underway, it is difficult to establish how serious the situation is at the moment. To begin with, we don't have a precise idea of ​​what's going on in our oceans. Much of the most reliable data on fish abundance comes from studies of commercially important fish species, such as tuna and pollock, while data on tropical species is much more scarce. “If we really want to find out what's going on at the equator, we need studies at the equator,” explains Rutterford.

See more Choose the newsletters you want to receive and sign up! Weekly news and commentary on conflicts in the digital world, sustainability or gender equality. The best of innovation every day. It's our new newsletters: innovation just a click away.

Arrow "Silent extinctions are almost certainly occurring in the oceans right now that go undetected. This wave will become a tsunami if we allow climate change to advance "says McCauley.

Even if we manage to manage climate change, humans are still putting enormous pressure on the oceans due to fishing and marine habitat changes. In 2008, the International Union for Conservation of Nature reported that 22 percent of marine species assessed were at risk of extinction, including 17 percent of sharks and their close relatives. One of the ways that governments and NGOs have agreed to protect the oceans is the establishment of large marine protected areas, the ocean equivalent of national parks.

"Marine protected areas are the best protection, as they give us a chance to catch our breath in the face of the unknown, ”explains Katrina Davis, a conservation biologist at the University of Oxford. In October, the members of the United Nations Convention on Biological Diversity will meet to define the objectives for the protection of biodiversity on the planet. Among the main proposals, there is a plan to transform at least thirty percent of land and sea areas into protected areas. Protecting coastal areas is particularly important, says Davis, as they are one of the main areas where humans and marine species come into conflict.

If we allow climate change to get out of our control, however, the Marine protected areas will only be a patch, says McCauley: "It is undesirable to try to resolve threats to diversity locally and let climate change defeat everything in the future," he adds. A return of the Great Moria is far from inevitable, but averting even fraction of a degree of temperature increase allows to mitigate the severity of ocean extinctions. "The main finding [of our study, ed.] Says that the extent of future extinctions depends on CO 2 emissions from here on out - explains Penn -. This story has yet to be written."

This article is originally featured on UK.

Powered by Blogger.