The world is experiencing a “biological annihilation” of its animal species because of humans' effect on the Earth, a new study has found.
Researchers mapped 27,600 species of birds, amphibians, mammals and reptiles — nearly half of known terrestrial vertebrate species — and concluded the planet's sixth mass extinction even was much worse than previously thought.
They found the number of individual animals that once lived alongside humans had now fallen by as much as 50 per cent, according to a paper in the journal Proceedings of the National Academy of Sciences.
The study’s authors, Rodolfo Dirzo and Paul Ehrlich from the Stanford Woods Institute for the Environment, and Gerardo Ceballos, of the National Autonomous University of Mexico, said this amounted to “a massive erosion of the greatest biological diversity in the history of the Earth”.
The authors argued that the world cannot wait to address damage to biodiversity and that the window of time for effective action was very short, “probably two or three decades at most”.
Mr Dirzo said the study’s results showed “a biological annihilation occurring globally, even if the species these populations belong to are still present somewhere on Earth”.
The research also found more that 30 per cent of vertebrate species were declining in size or territorial range.
Looking at 177 well-studied mammal species, the authors found that all had lost at least 30 per cent of the geographical area they used to inhabit between 1990 and 2015. And more than 40 per cent of these species had lost more than 80 per cent of their range.
The authors concluded that population extinction were more frequent than previously believed and a “prelude” to extinction .
“So Earth’s sixth mass extinction episode has proceeded further than most assume,” the study said.
About 41 per cent of all amphibians are threatened with extinction and 26 per cent of all mammals, according to the International Union for Conservation of Nature (IUCN), which keeps a list of threatened and extinct species.
In the study, the authors noted their findings were “conservative” since the drivers that cause extinction of species and populations loss were taking “increasing trajectories”.
This includes habitat loss, over-exploitation, invasive organisms, pollution, toxification, climate change and a potential large-scale nuclear war. The authors called for the growth in the human population to be curbed, over-consumption to be tackled, and for society to realise it must move away from “the fiction that perpetual growth can occur on a finite planet”.
The research’s lead author Mr Ceballos said the massive loss of populations and species “reflects our lack of empathy” towards wildlife.
"It is a prelude to the disappearance of many more species and the decline of natural systems that make civilisation possible,” he said.
Some of these species, for example, contribute to crop pollination, pest control and wetlands’ water purification.
The researcher also said the disappearance of species threatened to damage the broader, intricate ecological network of animals, plants and microorganisms which could cause ecosystems to become less resilient and affect species’ ability to survive in a rapidly changing world.
“When considering the frightening assault on the foundations of human civilisation, one must never forget that Earth’s capacity to support life, including human life, has been shaped by life itself,” the paper stated.
In 2015, another study co-authored by Mr Ehrlich concluded that the Earth had entered a sixth era of mass extinction. The last one was 66 million years ago when the dinosaurs died out along with more than 75 per cent of all life on the planet. While the current number of exctinctions has not reached that level, the rate is concerning scientists.
Commenting on the most recent findings, Mr Ehrlich said: “We are losing species at an extraordinarily rapid rate compared to the background rate in which we lost them between the previous five great extinctions —a couple of species a year disappearing. It turned out to be 10 to 100 times as fast as it happened in the past.”
Mr Ehrlich added that although the loss of species was “bad and largely irreversible”, losing individuals and groups was “equally important or more important” because it was “wrecking our life-support machinery”.
He cited the example of birds, bats and insects that control pests and help to maintain high-yield agriculture to feed the world’s 7.5 billion people.
Mike Barrett, director of science and policy at WWF-UK, said the study’s findings highlighted “the urgent need to take action to save the world’s wildlife”.
He added that WWF’s Living Planet Report had revealed that by the end of this decade wildlife populations will have fallen on average by a staggering 67 per cent from 1970 levels.
He said: “From the destruction of forests to the poaching of iconic species, we cannot ignore the impact that humanity is having on the world. We know how to stop this.
"It requires governments, businesses and every single one of us to rethink how we produce, consume and value the natural world. We must act now before it is too late.”
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