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Biomass study finds that humans extinguish wild mammals



  • A team of scientists has dismantled previous studies for estimating the total mass of carbon in each group of organisms on Earth as a way to measure relative biomass.
  • Plants harbor about 450 gigatons of 550 gigatons – or about 80 gigatons Humans find only 15 percent of the Earth's entire life form, and another 15 percent are bacteria.
  • Humans represent only one hundredth of the Earth's biomass, but we have pushed back biomass from terrestrial animals by 85 percent and marine mammals by about 80 percent since the beginning of the last great extinction around 50,000 years ago.

Humans have had a massive impact on other life forms that far outweigh how little biomass we represent According to a recent study

"It's striking, our disproportionate place on earth," said Ron Milo, an environmental scientist on Israeli Weizmann Institute of Science, Guardian Newspaper 659005] Milo and his colleagues have conducted previous studies for estimates of the total mass of carbon in each group of organisms on Earth as a way of measuring relative biomass. They published their results May 21 in the journal Proceedings of the National Academy of Sciences

A spiny tail iguana in Panama. Image by Rhett A. Butler / Mongabay

Previous research on the uncovering of life distribution has examined the number of species present. Others have looked at the weights of organisms without the water they contain, known as "dry weight". But so far no one has put together a biosphere-wide census of the distribution of biomass based on carbon, the central element for all living things, and it has brought new revelations about the construction of life on the planet and our role in shaping it.

By far the biomass heavyweights are the plants that harbor 450 gigatons of the total 550 gigatons of carbon living on Earth, the team found. They also calculated that humans only hold one-hundredth percent of that carbon. But this tiny fraction says little about how much we have shaped our environment.

For example, humans have falsified species by decaying animals into our orbit since the beginning of domestication. Today, wild mammals account for just over 4 percent of mammalian biomass on Earth. In contrast, the livestock biomass, most of which are cattle and pigs, is more than 14 times that of their wild cousins.

"When I make a puzzle with my daughters, an elephant is usually next to a giraffe next to a rhinoceros," Milo said in the Guardian article. "But if I tried to give them a more realistic feel for the world, it would be a cow next to a cow next to a cow and then a chicken."

Ubiquitous bacteria account for 15 percent of global biomass. But other groups with a reputation for widespread dominance, such as the millions of species that make up the class of arthropods we call insects, hold a "tiny" share of carbon, the researchers found.

Elephants at a waterhole in South Africa. Picture by Rhett A. Butler / Mongabay

Also surprising is the proportion of biomass that can be found in the countryside compared to the world's oceans. Although they cover almost three-quarters of the Earth's surface, the world's oceans contain only a fraction – about 1.2 percent – of the biomass that is found on land.

In both environments, people in our relatively short 200,000 have made a great impact on years on this planet. The biomass of wild land mammals has dropped by 85 percent since the last large extinction of large animals began about 50,000 years ago, write the authors. And whaling and other hunting methods have reduced marine mammal biomass by about 80 percent over the same period.

"Humans have culled and in some cases eradicated wild mammals for food or pleasure on nearly every continent." The biological oceanographer of Rutgers University Paul Falkowski, who was not involved in the research, told the Guardian.

The results of the study show that "humans are extremely efficient in exploiting natural resources," Falkowski added. Cattle in Colombia is by Rhett A. Butler / Mongabay.

Quote

Bar-On, YM, Phillips, R. & Milo, R. (2018). The biomass distribution on the earth. Proceedings of the National Academy of Sciences 201711842.

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Agriculture, Animals, Biodiversity, Biodiversity crisis, Cattle, Livestock, Conservation, Environment, Extinction, Fungi, Hunting, Livestock, Mammals, Marine mammals, Plants, Species from extinction, 6. Mass extinction, Wildlife, Wildlife conservation


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