Remember the time when rhinos used to walk the Earth? Glistening in their body armour, horns intact and wielding a disproportionate influence in the savannas. When numbers were their strength, and when this keystone species and mega-herbivore held together entire grassland ecosystems.

It is 2050. We have lost all our rhinos. At the beginning of the 20th century, there were 500,000, in 2015, there were 29,000 in the wild, and now there are none. Plant species that populated the grasslands are no longer extant, and the large, natural carbon sinks too have disappeared. Like in the Pleistocene period (or the Ice Age extinction), when megafaunal species such as the wooly mammoth and mastodon died out and forests replaced grasslands, the extinction of the rhino has wrought devastating changes to land. The ecosystem is completely off-kilter in the absence of the apex consumer. Say hello to the sixth phase of mass extinction.

A recent paper, published in Sciencemag in June 2015, titled ‘Accelerated modern human-induced species losses: Entering the sixth mass extinction’ reveals that mass extinction, perhaps the deadliest so far, is underway. An examination of this paper and an earlier 2014 research ‘The biodiversity of species and their rates of extinction, distribution and protection’, also published in Sciencemag , confirms the sixth mass extinction event, at a rate 1000 times faster than seen before. “It took four years to finalise (the findings),” says lead author of the 2015 paper Dr Gerardo Ceballos, speaking from Spain, and quelling reports that the study is just further evidence and not a confirmation.

Red List

In 2014, the International Union for Conservation of Nature (IUCN) Red List, which classifies species based on threat level, assessed 71,576 terrestrial and freshwater species – 860 species were extinct, 21,286 species were threatened. Thirteen per cent of birds, 41 per cent of amphibians, 23 per cent of mammals and fishes, and 39 per cent of reptiles are threatened. The 2015 paper says, “In tropical Oceania, up to 1,800 species of birds are estimated to have gone extinct in (nearly) 2,000 years of human colonization.” One-fifth of plant species are threatened; 29 per cent species of conifers, found in all types of forests, are facing extinction.

One in four mammals, one in eight birds, one in three amphibians, and half of all tortoises and freshwater turtles face extinction in the near future. According to the 2014 study, on an average, 52 of nearly 22,000 species move “one Red List category closer to extinction each year.” Nearly 132 plant and animal species in India are listed as critically endangered in the Red List.

The problem is compounded further as less than three per cent of the 1.9 million species known to us have been assessed by the IUCN. To add to this staggering math, more than 10 million species are yet to be described and discovered.

Death race

In the previous five mass extinction events, species were wiped out in massive numbers. For instance, the Permian extinction, nicknamed ‘The Great Dying’ saw 96 per cent of all life going extinct and in the Late Devonian extinction, three-quarters of all species died out. So what if we are in the middle of a much faster sixth extinction? Won’t ecosystems and species diversify? Won’t the human remain largely immune to such changes?

Most evidence for the current extinction event points to human involvement as the primary reason for the accelerated rates. “The overarching driver of species extinction is human population growth and increasing per capita consumption,” write the authors of the 2014 study. Habitat modification, change of land use, pollution and introduced species are major contributors to extinction.

Extinction rate (or the death rate) is shown as fractions of species going extinct over time, ie, extinctions per million species-years (E/MSY). Both papers calculate the death rate on the basis of the “background rate of extinction”, which is calculated in the absence of human activity. Since 1900, on the background rate of 2 E/MSY (two extinctions per 100 per 10,000 species, a highly conservative estimate), the extinction rate should’ve been 9 E/MSY. But Ceballos’s study notes that, in 114 years, 468 more vertebrates have gone extinct, including 69 mammal species, 80 bird species, 24 reptiles, 146 amphibians and 158 fish, with rates eight to 100 times higher than the background rate.

Brick in the wall

It’s not yet 2050 and rhinos are still around (despite the alarming figure of one rhino poached every five hours). Despite not being apex predators, they are keystone species, vital to an ecosystem’s survival. “Think of it as a brick wall. One by one, bricks are being removed. When a keystone species goes, the wall crumbles. In time, it will collapse and so will humanity,” says Dr Ceballos. Or if the current rate of extinction continues, in just three human lifetimes, we will have lost our biodiversity. Environmental agencies estimate the value of ecosystems at $33 trillion per year, twice that of production from human activities.

In the debate of nature versus development, Dr Ceballos says, “there is no conflict”, one can’t be pitted against the other. “What should be examined is the relation between poverty and environment.”

Extinction, in many cases and on small and large scales, is a natural process, but never before has a single species – ours – been solely responsible for such mass events. What would the Western Ghats be without the hundreds of amphibian species, the Himalayan subalpine conifer forests without pine trees and the floodplains of Assam without its rhinos?

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