A groundbreaking new assessment of life on the planet reveals that humanity is both insignificant and utterly dominant in the grand scheme of life on Earth.
According to the study, the 7.6 billion inhabitants of the planet represent only 0.01% of all living beings. However, since the dawn of civilization, mankind has caused the loss of 83% of all wild mammals and half of all plants, while human-raised livestock 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 an important life form – 13% of everything – but plants eclipse everything, accounting for 82% of all living matter. All other creatures, from insects and fungi to fish and animals, make up only 5% of the world’s biomass.
Another surprise, the abundant ocean life revealed by the BBC’s recent Blue Planet II TV series turns out to be only 1% of all biomass. The vast majority of life is on land, and much of it – one-eighth – is made up of bacteria deep below the surface.
“I was surprised to see that there was no overall estimate of all biomass componentssaid Professor Ron Milo of the Weizmann Institute of Science in Israel, who led the work, published in the Proceedings of the National Academy of Sciences.
“I hope this gives people an idea of the dominant role humanity now plays on Earth.“, he said, adding that he now chooses to eat less meat because of the huge environmental impact of livestock.
The transformation of the planet by human activity has led scientists to declare a new geological era: the Anthropocene. One indicator of this change is the bones of domesticated chickens, now ubiquitous around the world.
The new work reveals that farmed poultry now make up 70% of all birds on the planet, while only 30% are wild. The picture is even bleaker in the case of mammals: 60% of all mammals on Earth are farm animals, particularly cattle and pigs, 36% are humans and only 4% are wild animals.
“It’s amazingMilo said. “In animal films, we see flocks of birds, of all kinds, in large numbers, and when we did the analysis we found that there were [mucho] more domestic birds“.
The destruction of wildlife habitat for agriculture, logging and development has triggered what many scientists consider to be the sixth mass extinction of life in the Earth’s four billion year history. It is believed that over the past 50 years, about half of the animals on Earth have been lost.
But comparing the new estimates with those from the period before humans entered agriculture and the start of the Industrial Revolution reveals the full extent of the huge decline. Only one-sixth of wild mammals remain, from mice to elephants, which surprises even scientists. In the oceans, three centuries of whaling have left only a fifth of marine mammals in the oceans.
“Our disproportionate place on Earth is definitely striking,” Milo said. “When I do a puzzle with my girls, there’s usually an elephant next to a giraffe next to a rhino. But if I wanted to give you a more realistic idea of the world, it would be a cow next to a cow then a hen.“.
Despite the supremacy of humanity, in terms of weight, Homo sapiens is insignificant. Viruses alone have a combined weight three times that of humans, as do worms. Fish are 12 times larger than humans and mushrooms 200 times larger.
Plants make up 82% of all biomass on the planet, 7,500 times more than humans.
But our impact on the natural world remains immense, Milo said, particularly in what we choose to eat: “Our food choices have a huge effect on the habitats of animals, plants and other organisms“.
“I wish people would take that [trabajo] as part of their worldview on how they consume“, mentioned. “I haven’t become a vegetarian myself, but I consider the environmental impact when making decisions, so it helps me to think about whether I want to go with beef or poultry, or whether I prefer to use tofu“.
Researchers have calculated biomass estimates from data from hundreds of studies, often using modern techniques such as satellite remote sensing, which can scan large areas, and genetic sequencing, which can unravel the myriad of microscopic organisms of the world.
They started by estimating the biomass of a class of organisms, then determined what environments that life might live in around the world to create a world total. They used carbon as a key measure and found that all life contains 550 billion tons of this element. The researchers acknowledge that significant uncertainties remain in some estimates, particularly for subterranean bacteria, but say the work presents useful insight.
Paul Falkowski, from Rutgers University (USA) and who is not part of the research team, says: “The study is, in my opinion, the best to date: “The study is, to my knowledge, the first comprehensive analysis of the biomass distribution of all organisms – including viruses – on Earth.“.
“Two important conclusions emerge from this work.“, mentioned. “First, humans are extremely efficient at exploiting natural resources. Humans have killed, and in some cases eradicated, wild mammals for food or entertainment on virtually every continent. Second, terrestrial plant biomass overwhelmingly dominates globally, and most of this biomass is in the form of wood.“.