Earth is entering the sixth era of mass extinction! Scientists: An unprecedented crisis may come!

On June 16, 2020, a paper titled "Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction" was published in PNAS (Proceedings of the National Academy of Sciences). The sign of the sixth mass extinction), brought forward a conclusion that was expected, but still dare not face, we are in the whirlpool of the sixth mass extinction!

What are the signs of the sixth mass extinction?

The research team counted 29,400 terrestrial vertebrate species with less than 1,000 individuals, of which 94% of the 77 mammals and birds the team focused on are extinct. Assuming that all animals below 1,000 face this trend, then In total, more than 23,700 species have disappeared since the twentieth century, and the human-induced mass extinction is accelerating!

Tip: Why is less than 1000 extinct?

There is a 50/500 rule in the genetic world, which basically means that if a population is to thrive, there must be at least 50 or more individuals, preferably 500, but in fact, due to geographical separation, in many cases, even if the population is around 1000 , the local area will also be less than 50, so if there is no human intervention, it is inevitable to go to extinction.

Which species are going extinct?

The extinct species in the middle and late twentieth century include thylacine (Thylancinus cyanocephalus), ivory-billed woodpecker (Campephilus Principalis) and round island burrowing python (Bolyeria multocarinata), etc. Among them, thylacine is the famous Tasmanian tiger with stripes on its body. Much like tigers, the last thylacine was found in 1967.

The protagonists of the mass extinction in the past 2000 are amphibians. Hundreds of species of frogs and toads are rapidly disappearing. About one-fifth of amphibians are extinct or endangered. ), and the culprit is the chytrid fungus that is rapidly spreading due to human activities.

What factors caused the sixth mass extinction

The mass extinction of ancient creatures in the impression all happened in a vigorous manner. For example, the extinction of the dinosaurs 65 million years ago was caused by an asteroid hitting the earth, and a series of extinctions in the Permian and Triassic were caused by the Siberian shield volcano and Langley. caused by sub-supervolcanic eruptions.

The modern earth is safe and sound, where did the mass extinction of living things come from? Isn’t this unfounded worry? In fact, the vast majority of mass extinctions in history, except for asteroid impacts, occurred quietly, and what is even more worrying is that the current global state is very similar to the era of the rise of dinosaurs in the Permian!

234-232 million years ago, it took only 2 million years for dinosaurs to take over the world from birth. The reason was a million-year torrential rain, which made animals that had adapted to the continental arid climate to extinct one after another, and were used to warm and humid conditions. Dinosaurs succeeded in ascending, and it was the Langoria supervolcano in western Canada that caused this million-year torrential rain to change the earth's climate.

Geologists estimate that the Langoria supervolcano released more than 5 trillion tons of carbon dioxide into the atmosphere, leading the planet to an extreme greenhouse effect, with the climate changing from a dry to a warm and humid rainforest climate, while ocean temperatures soared in the equatorial regions To 40 ℃, it directly led to the biological exchange blood.

Since the Industrial Revolution, humans have released a total of about 280 billion tons of carbon dioxide into the atmosphere, causing a temperature rise of about 1.15 ° C, which seems not to be on the same level at all, but in fact, if the annual average emissions are considered, this rate is higher than that of Lan The eruption rate of Golia volcano is 1,000 times higher, and humans are artificially creating a mass extinction.

Another factor is human expansion

Since the last ice age, many large animals have become extinct, such as saber-toothed tigers and mammoths, and some have become extinct after human beings have historical records, such as the eaten dodo, the manatee, and the North American passenger pigeon. The effects of pesticides, such as DDT, which began to be abused in the 1940s, led to the extinction of numerous insects and birds.

Earth's ecological tipping point is fast approaching

On October 15, 2018, the world's second climate change conference put forward a "the earth's climate is approaching an irreversible tipping point", which is surprising, and the culprit is the uncontrolled pollution and greenhouse gas emissions of human beings.

On January 13, 2021, a paper from the Woodwell Climate Research Center at Northern Arizona University was published in Science Advances, and the Earth will reach a critical temperature tipping point in 20-30 years! The researchers say that the earth's current plants are absorbing more than 1/3 of carbon emissions, but the global temperature rise will cut this proportion in half. Therefore, carbon dioxide absorption will face a cliff-like decline in the future, and the result will be unbearable for human beings.

On April 21, 2021, "Scientific American" published an article "More than 97% of the earth's land is no longer ecologically complete." Andrew Plumptre, a conservation biologist at the University of Cambridge, pointed out that compared with 1500, the earth's The ecology has been greatly damaged by human beings, and more than 97% of the land no longer meets the standard of ecological integrity.

The only areas that remain intact are: the northern coniferous forests of Canada, large tracts of species-rich tropical rainforests such as the Amazon, Congo and Indonesia, the Great Siberia Ice Forest in northern Russia, etc.; the Serengeti grasslands in northwestern Tanzania etc., but there is no doubt that these regions will still suffer from the effects of global warming, and the last pure land of mankind is rapidly disappearing.

Earth's climate tipping point

Professor Tim Lenton, Director of the Global Systems Institute at the University of Exeter, explained that the Earth's climate cycle consists of several large systems, such as atmospheric and water cycles and the movement of global ocean currents, as well as cycles in various climate subsystems, but in these systems Has a "tipping point":

"Climate tipping points, or any tipping point in any complex system, are where small changes can make a big difference and change the state or fate of a system."

On April 20, 2021, a paper by University of Rhode Island researchers was published in the journal Communications Earth & Environment, saying that changes in the Atlantic Ocean Circulation (AMOC) will lead to major changes in the Earth's future climate in the medium and long term. , a professor of marine physics at the University of Potsdam, said that too much dilution of freshwater in the ocean affects this process.

AMOC

Another major impact is the collapse of the ice sheet on the west side of Antarctica, which can raise global sea levels by 3.3 meters. An analysis published in the journal Nature in 2018 showed that the rate of ice loss caused by the West Antarctic Ice Sheet (WAIS) increased from 1992-97. 2012-2017 increased from 53 billion tons per year to 159 billion tons per year in 2012-2017, a threefold increase.

There is also the demise of the Amazon rainforest. Professor Richard Bates, Chair of Climate Impact at the University of Exeter, said that the Amazon rainforest is undergoing unprecedented changes, with reduced rainfall and reduced transpiration (in response to increased carbon dioxide), and massive deforestation is making The rainforest is on its way to irreversible destruction.

In addition, the change of the southwest monsoon will make Africa into a doomed place. Professor Alexandra Giannini of Columbia University said that the southwest monsoon is easily affected by global warming, and most of Africa will fall into a long-term drought and exacerbate famine. It could take thousands of lives.

The most significant in the Northern Hemisphere are the loss of permafrost and the release of methane hydrates and the death of coral reefs and the transition of the Indian monsoon and the disintegration of the Greenland ice sheet. These events seem isolated but inseparable. These climate tipping points are one by one. collapse!

The tundra melts, the foundation sinks, and the bridge collapses

I believe that many friends think that climate tipping point and ecological tipping point are completely two concepts, but in fact there are many tipping points in the ecosystem and climate, many of which are interconnected. This means that the huge changes humans are causing will have many unintended consequences.

Of course, life on earth will not be extinct, and there will be new life to replace it, but human beings may not be in the plan!