Are We Witnessing a Mass Extinction?

^{Australian sea lion pups. In the period from 1977 to 2019, their number decreased by 64%.}

Some scientists warn that we are on the verge of a mass extinction. Others argue that it has already begun.

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Own Subjective Impressions

I well remember that when I was a child, the winters in my region were snowy and frosty. Arriving in the village for Christmas, we could not leave the house in the morning because of the large amount of snow. I walked along the paths, like tunnels.

The last ten years have had very mild winters. If last winter there was a little snow and several frosty days, the previous two were completely snow-free and warm. The current winter is also warm so far. For example, it is now +8 degrees Celsius outside the window.

If I remember my conversations with my grandmother, the current winters are not at all like those that previous generations talk about. But this does not allow me to claim that the climate has changed. It is quite possible that this is a temporary warming.

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What Does Science Say?

Many groups of scientists are working on modeling climate change. All of them have different prognostic results. On average, it is believed that by the end of the century, the temperature on Earth may rise by 4.4 degrees Celsius.

^{Barbary Lion. Considered extinct since the 1960s..}

Climate scientist Kunio Kaiho from Tohoku University in Japan attempted to quantify the relationship between the Earth's average temperature and the planet's biodiversity. The obtained result shows that the more the temperature changes, the stronger it affects biodiversity. And according to his data, extinction begins if the temperature drops by 7 degrees Celsius or rises by 9 degrees. At the same time, the scientist tried to reassure society that we are not threatened with mass extinction in the near future.

But still, it is not only the increase in temperature that leads to extinction, but also the speed with which it occurs. The most massive extinction on Earth, which occurred 250 million years ago, led to the disappearance of 95% of species and lasted more than 60 thousand years. However, current warming is occurring much faster.

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Mass Extinctions

The history of our planet counts five or six periods, during which mass extinctions of various biological species occurred. A mass extinction is a relatively short period of time in which the planet loses most of its species diversity. Among the largest extinctions:

• 2.4-2.0 billion years ago, an Oxygen catastrophe occurred, as a result of which anaerobic life forms became extinct;
• 440 million years ago, more than 60% of marine invertebrate species disappeared;
• 364 million years ago, the number of species of marine organisms decreased by 50%;
• 251.4 million years ago, the most massive extinction occurred, when more than 95% of living species disappeared;
• 199.6 million years ago, half of the known species that lived on Earth at that time became extinct;
• 66 million years ago, the last mass extinction occurred, which destroyed 70% of all species, in particular, dinosaurs.

Current Mass Extinction

When we expect a mass extinction, a picture pops up in our mind, when everything living around suddenly dies. But it is not so. Extinction can last 60 thousand years and be imperceptible to humans.

^{Bramble Cay melomys. Considered extinct since 2016..}

More and more scientists are arguing that we are now witnessing a mass extinction. They assure that it is already underway. According to their data, the Earth's wildlife population has declined by 69% in less than 50 years. In particular, Latin America and the Caribbean, including the Amazon, experienced the steepest decline in average wildlife populations, with a 94% drop in 48 years.

The reduction of wildlife populations in other regions amounted to:

• Africa - 66%;
• Asia and the Pacific region - 55%;
• North America - 20%;
• Europe and Central Asia - 18%.

Another group of scientists, led by Giovanni Strawn and Corey Bradshaw, created a "virtual Earth" with all its biodiversity and cataclysms. For this, they used a supercomputer. More than 15,000 food chains were entered into the computer database. As a result, the machine concluded that the sixth (or maybe the seventh) mass extinction has begun. The computer model showed that after 28 years, 10% of all species of fauna and flora will disappear. And by 2100, the reduction of biodiversity will amount to 27%.

Sources:

• Daily Mail.
• The Guardian.
• Biological Reviews.
• Science Alert.