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Monday, July 13, 2020

Explained: What is the ongoing sixth mass extinction?

Researchers have described the sixth mass extinction, or the Anthropocene extinction, as the “most serious environmental problem”, since the loss of species here will be permanent.

By: Explained Desk | New Delhi | Published: June 2, 2020 7:13:58 pm
sixth mass extinction, Anthropocene extinction, what is the sixth mass extinction, wolves in Yellowstone park, reasons for sixth mass extinction, sixth mass extinction species impacted, express explained, indian express When wolves in Yellowstone Park in California, US, were hunted to near extinction by the 1930s, it had a cascading effect on the ecosystem. The reintroduction of wolves has stabilised the food chain. (Photo courtesy: yellowstonepark.com/NPS Barry O’Neill)

The ongoing sixth mass extinction may be one of the most serious environmental threats to the persistence of civilisation, according to new research published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

The research claims that this extinction is human-caused and is more immediate than climate destruction. “Even though only an estimated 2% of all of the species that ever lived are alive today, the absolute number of species is greater now than ever before. It was into such a biologically diverse world that we humans evolved, and such a world that we are destroying,” the study says.

What is the mass extinction of species?

Mass extinction refers to a substantial increase in the degree of extinction or when the Earth loses more than three-quarters of its species in a geologically short period of time. So far, during the entire history of the Earth, there have been five mass extinctions. The sixth, which is ongoing, is referred to as the Anthropocene extinction.

The five mass extinctions that took place in the last 450 million years have led to the destruction of 70-95 per cent of the species of plants, animals and microorganisms that existed earlier.

These extinctions were caused by “catastrophic alterations” to the environment, such as massive volcanic eruptions, depletion of oceanic oxygen or collision with an asteroid. After each of these extinctions, it took millions of years to regain species comparable to those that existed before the event.

So what is the sixth mass extinction then?

Researchers have described it as the “most serious environmental problem” since the loss of species will be permanent.

The study analysed 29,400 species of terrestrial vertebrates and determined which of these are on the brink of extinction because they have fewer than 1,000 individuals. Out of the studied species, they concluded that over 515 of them are near extinction, and that the current loss of species, which is based on the disappearance of their component populations, has been occurring since the 1800s.

Most of these 515 species are from South America (30 per cent), followed by Oceania (21 per cent), Asia (21 percent) and Africa (16 percent) among others.

Further, attributing this mass extinction to humans, they said that one of the reasons that humanity is an “unprecedented threat” to many living organisms is because of their growing numbers. The loss of species has been occurring since human ancestors developed agriculture over 11,000 years ago. Since then, the human population has increased from about 1 million to 7.7 billion.

The study notes that more than 400 vertebrate species went extinct in the last century, extinctions that would have taken over 10,000 years in the normal course of evolution. In a sample of 177 species of large mammals, most lost more than 80 per cent of their geographic range in the last 100 years, and as per a 2017 study published in the same journal, 32 per cent of over 27,000 vertebrate species have declining populations.

Significantly, the study calls for a complete ban on wildlife trade as many of the species currently endangered or on the brink of extinction are being decimated by legal and illegal wildlife trade.

Researchers point out that the current COVID-19 pandemic, while not fully understood, is also linked to the wildlife trade. “There is no doubt, for example, that there will be more pandemics if we continue destroying habitats and trading wildlife for human consumption as food and traditional medicines.”

What happens when species go extinct?

According to the Center for Biological Diversity, when species go extinct, the impact can be tangible such as in the form of a loss in crop pollination and water purification. Further, if a species has a specific function in an ecosystem, the loss can lead to consequences for other species by impacting the food chain.

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For instance, an example referenced by Columbia University’s Earth Institute states that when the wolves in Yellowstone Park in California, US, were hunted to near extinction by the 1930s, the deer and elk they preyed upon thrived, as a result of which their grazing decimated the streamside willows and aspens, which provided habitat for songbirds.

This also left the stream susceptible to erosion and a decline in the songbirds allowed mosquitoes and other insects that the birds would have eaten to multiply.

Subsequently, the wolves were reintroduced into the park in 1995, after which they preyed on the elks and deer once again, the plant life returned and so did the songbirds.

The study warns that the effects of extinction will worsen in the coming decades as the resulting genetic and cultural variability will change entire ecosystems. “When the number of individuals in a population or species drops too low, its contributions to ecosystem functions and services become unimportant, its genetic variability and resilience is reduced, and its contribution to human welfare may be lost.” the study says.

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