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

A study by scientists at the Weizmann Institute of Science in Israel, published this month, concluded that the total weight of wild mammals alive today is 22 million tons. By comparison, humanity now weighs in at a total of 390m tonnes.

At the same time, our domesticated species, such as sheep and cattle, in addition to other hanger-ons such as urban rodents, add another 630m tonnes to the total group of organisms that compete with wild mammals for Earth’s resources. . Pigs alone have nearly double the biomass of all wild land mammals.

The statistics clearly show that humanity is now well on its way to converting the planet’s wilderness and natural habitats into massive global plantations – with devastating consequences for wildlife. As the study authors emphasize, the idea that Earth is a planet that still has vast plains and forests full of wild animals is now seriously out of touch with reality. The natural world and its wild animals are disappearing as humanity’s population of nearly eight billion people continues to grow.

Feeding fin whales in the Gulf of California. Studies have shown that this species has the highest biomass of marine organisms. Photo: Nature Picture Library/Image

“When you watch wildlife documentaries on television — for example, Wildebeest Basking — it’s easy to conclude that wild mammals are doing well,” said lead author Ron Milo. supervisor.

“But that intuition is wrong. These creatures are not doing well. Their total weight is about 22m tonnes which is less than 10% of the combined weight of humanity and the equivalent of only 6lb per capita of wild land mammals. And when you consider all our cattle, sheep and Add other livestock, it adds another 630m tonnes. That’s 30 times the total number of wild animals. It’s staggering. It’s a wake-up call for humanity.”

The study, The Global Biomass of Wild Mammals, also suggests that the best performers — such as white-tailed deer and wild boar in the U.S. — are those that find it easiest to adapt to the presence of people. Both species can be found near settlements and are sometimes kept as pets. “Even within the wild, the fingerprints of humanity are evident,” added Milo, whose team’s study is published in the American Journal of Medicine. Proceedings of the National Academy of Sciences.

As part of the paper, researchers Leor Greenspoon and Eyal Krieger collected biomass data on half of all known mammals and used machine-learning computational models on other animal samples to calculate the other half.

The alarming statistics for land mammals are matched by those found in the oceans. The total mass of marine mammals was calculated to be around 40m tonnes. Fin whales have the largest total biomass with sperm whales and humpbacks coming in second and third slots respectively.

Common domesticated species were also found to be major contributors to humanity’s planetary impact. Domestic dogs have a total biomass of about 20m tonnes, which is close to the combined biomass of all wild terrestrial mammals, while cats have a total biomass of about 2m tonnes, almost twice that of the African savannah elephant. “These domestic-wild mass ratios emphasize the active role that humans play in shaping the abundance of mammals on Earth,” the researchers explain 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, there are 1,200 species of bats, one-fifth of all land mammal species and two-thirds of all individual wild mammals based on head counts. However, they make up only 10% of the biomass of wild land mammals.

“Biomass complements species richness and other diversity metrics, and can serve as an indicator of the abundance and ecological footprint of wild mammals on a global scale,” the researchers said.

The team estimated two years ago that there were about 50 million tons of wild mammals on Earth. The new figures, calculated using a number of technologies including AI, indicate that the crisis facing the planet’s wildlife looks much worse than previously appreciated. Assessing how fast the decline of wild mammals is progressing is an urgent matter, they say, and is the focus of the next phase of the study, which will assess how much biomass has been lost over the past 100 years.


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