LIFE SCIENCE

Wild mammal biomass is pitifully small


Which wild mammal walks the most on land? Not elephants, not wild mice. A global study of total mass of mammal species estimates that the heavyweight champion is the white-tailed deer, which accounts for almost 10% of the total biomass of wild land mammals. The study used artificial intelligence to optimize the data and found that the total biomass of currently alive wild land mammals is 22 million tons, and the total biomass of marine mammals is 40 million tons. The results of the study were published in the Proceedings of the National Academy of Sciences on February 27.

White-tailed deer have more biomass than all other wild mammals. IMAGE CREDIT: JASPER DOEST/MINDEN

This figure may seem insignificant compared to the 12 million tonnes of total biomass of ants. But what the study hopes to draw attention to is that humans collectively weigh about 390 million tons, while other accessory animals such as livestock and city mice weigh 630 million tons. Researchers say this is clear evidence that nature is being overwhelmed.

“I hope this will be a wake-up call for humanity that we should do everything we can to protect wild mammals.” Ron Milo, a quantitative biologist at the Weizmann Institute of Science in Israel, said corresponding author of the study.

Milo has always believed that numbers can “provide a sixth sense of the world.” In 2018, they made headlines for estimating the weight of all life worldwide. Two years later, they estimated the weight of all man-made objects and infrastructure around the world, from cars to buildings. Shahid Naeem, a biodiversity ecologist at Columbia University in the United States, recalls that Milo’s team also roughly estimated the weight of wild mammals at 14 million tons — a fraction of the mass of life on Earth, which is very shocking. Since then, the team has been working to improve estimates of this data.

The researchers found detailed data on the populations, weights, range of motion and other metrics of 382 wild mammal species, and to predict the total mass of the less-studied mammals, they used data from half of the 382 species to train the machine learning system. The researchers tested and refined the model until it could accurately predict the other half of the biomass of these known species. Any data that could be found — range, size, abundance, diet — was then fed into a model of about 4,800 mammal species to estimate their biomass and abundance.

On land, most of the biomass of wild mammals is concentrated in a few larger species, including wild boar, elephants, kangaroos and several species of deer. The research team reports that the top 10 species account for 8.8 million tonnes, or 40% of the estimated biomass of global wild land mammals. Rodents (excluding rats and mice associated with humans) accounted for 7% of the total, and carnivores 3%. Among marine mammals, baleen whales make up more than half of the biomass. But in terms of numbers alone, despite accounting for only 7% of the total number of land mammals, bats “rule” the mammalian world – accounting for 2/3 of the total number of wild mammals.

By comparison, the study said, in domestication, cattle weigh 420 million tons, and dogs weigh as much as all wild mammals. Domestic cats have about twice the biomass of African elephants and four times as much as moose.

Renata Ivanek, a veterinary and epidemiologist at Cornell University, said: “There is a lot of uncertainty in the estimated biomass, but this is a start. Ece Bulut, a food scientist at Cornell University, says the results change his view of the seemingly omnipresent nature of wildlife and provide insight into the extent to which human activities affect the world. (Source: China Science News Xin Yu)

Related paper information:https://doi.org/10.1073/pnas.2204892120



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