Humans just 0.01% of all life but have destroyed 83% of wild mammals – study
Groundbreaking assessment of all life on Earth reveals humanity’s surprisingly tiny part in it as well as our disproportionate impact
Humankind is revealed as simultaneously insignificant and utterly dominant in the grand scheme of life on Earth by a groundbreaking new assessment of all life on the planet.
The world’s 7.6 billion people represent just 0.01% of all living things, according to the study. Yet since the dawn of civilisation, humanity has caused the loss of 83% of all wild mammals and half of plants, while livestock kept by humans abounds.
The new work is the first comprehensive estimate of the weight of every class of living creature and overturns some long-held assumptions. Bacteria are indeed a major life form – 13% of everything – but plants overshadow everything, representing 82% of all living matter. All other creatures, from insects to fungi, to fish and animals, make up just 5% of the world’s biomass.
Another surprise is that the teeming life revealed in the oceans by the recent BBC television series Blue Planet II turns out to represent just 1% of all biomass. The vast majority of life is land-based and a large chunk – an eighth – is bacteria buried deep below the surface.
“I was shocked to find there wasn’t already a comprehensive, holistic estimate of all the different components of biomass,” said Prof Ron Milo, at the Weizmann Institute of Science in Israel, who led the work, published in the Proceedings of the National Academy of Sciences.
“I would hope this gives people a perspective on the very dominant role that humanity now plays on Earth,” he said, adding that he now chooses to eat less meat due to the huge environmental impact of livestock.
The transformation of the planet by human activity has led scientists to the brink of declaring a new geological era – the Anthropocene. One suggested marker for this change are the bones of the domestic chicken, now ubiquitous across the globe.
The new work reveals that farmed poultry today makes up 70% of all birds on the planet, with just 30% being wild. The picture is even more stark for mammals – 60% of all mammals on Earth are livestock, mostly cattle and pigs, 36% are human and just 4% are wild animals.
“It is pretty staggering,” said Milo. “In wildlife films, we see flocks of birds, of every kind, in vast amounts, and then when we did the analysis we found there are [far] more domesticated birds.”
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