Wildlife

Humans just 0.01% of all life but have destroyed 83% of wild mammals – study

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.

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. A cattle farm in Mato Grosso, Brazil. 60% of all mammals on Earth are livestock.

The destruction of wild habitat for farming, logging and development has resulted in the start of what many scientists consider the sixth mass extinction of life to occur in the Earth’s four billion year history. About half the Earth’s animals are thought to have been lost in the last 50 years.

But comparison of the new estimates with those for the time before humans became farmers and the industrial revolution began reveal the full extent of the huge decline. Just one-sixth of wild mammals, from mice to elephants, remain, surprising even the scientists. In the oceans, three centuries of whaling has left just a fifth of marine mammals in the oceans.