total weight of wild mammals less than 10% of that of humanity

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The total weight of Earth’s wild land mammals – from elephants to bison and deer to tigers – is now less than 10% of the combined tonnage of men, women and children living on the planet.

A study by scientists from the Weizmann Institute of Science in Israel, published this month, concludes that wild land mammals alive today have a total mass of 22 million tons. By comparison, humanity now weighs a total of about 390 million tons.

At the same time, the species that we have domesticated, such as sheep and cattle, in addition to other pests such as urban rodents, add another 630 million tons to the total mass of creatures that now compete with wild mammals for the Earth’s resources. . The biomass of pigs alone is almost double that of all wild land mammals.

The numbers clearly demonstrate that humanity’s transformation of the planet’s wilderness and natural habitats into a vast global plantation is now well underway – with devastating consequences for its wild creatures. As the authors of the study point out, the idea that Earth is a planet that still has great plains and jungles teeming with wild animals is now seriously out of step with reality. The natural world and its wild animals are disappearing as the human population of nearly eight billion people continues to grow.

Fin whales feeding on the Gulf of California. The study found that the species had the highest biomass of ocean creatures. Photograph: Nature Image Library/Alamy

“When you watch wildlife documentaries on television – for example about the wildebeest migration – it’s easy to conclude that wild mammals are doing quite well,” said lead author Ron Milo. Observer.

“But this intuition is wrong. These creatures are not well at all. Their total mass is about 22 million tons, less than 10% of the combined weight of mankind and only about 6 pounds of wild land mammals per person. And when you add all of our cattle, sheep and other livestock, that adds another 630 million tonnes. That’s 30 times the total for wild animals. It’s amazing. This is a wake-up call for humanity. »

The study, The Global Biomass of Wild Mammals, also finds that the ones that fare best – like white-tailed deer in the United States and wild boars – are the ones that adapt most easily to human presence. Both species can be found near colonies and are sometimes treated as pets. “Even in nature, humanity’s fingerprints are evident,” added Milo, whose team’s study is published in the American journal Proceedings of the National Academy of Sciences.

As part of the paper, researchers Lior Greenspoon and Eyal Krieger collected biomass data on about half of all known mammals and used machine learning computer models on other zoological samples to calculate the other half.

The grim figures of terrestrial mammals matched those found in the oceans. The total mass of marine mammals has been estimated at around 40 million tonnes. Fin whales have the largest total biomass, with sperm whales and humpback whales falling into the second and third slots respectively.

Domesticated/wild mass ratios highlight the active role humans play in shaping the abundance of mammals on Earth


Common pet species have also proven to be major contributors to humanity’s planetary impact. Domestic dogs have a total mass of around 20 million tonnes, a figure close to the combined biomass of all wild land mammals, while cats have a total biomass of around 2 million tonnes, almost double that of that of the African savannah elephant. “These domesticated-to-wild mass ratios underscore the active role humans play in shaping the abundance of mammals on Earth,” the researchers state in their paper.

Biomass studies are not the only way to quantify the animal world. The number of species is also revealing. As an example, it has been discovered that there are 1,200 species of bats which represent one fifth of all terrestrial mammal species and two thirds of all individual wild mammals by number of heads. However, they represent only 10% of the biomass of wild terrestrial mammals.

“Biomass is complementary to species richness and other diversity parameters, and can serve as an indicator of the abundance and ecological footprint of wild mammals on a global scale,” the researchers say.

Estimates made two years ago by the team suggested there were around 50 million tonnes of wild mammals on Earth. The new figure, calculated using a host of techniques including AI, indicates that the crisis facing the planet’s wildlife appears to be far worse than first believed. appreciated. How quickly the depletion of wild mammals is now proceeding needs to be assessed urgently, they say, and is the focus of the next phase of the study which will assess how much biomass loss has occurred over the past 100 last years.

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