Land mammals are not only our closest relatives, they are often among the best-studied animal species in the world. However, it was not previously clear how large the biomass of terrestrial and marine mammals on our planet is. The comprehensive balance sheet now shows that the biomass of all terrestrial and non-domesticated mammals is 22 million tons, and that of marine mammals is 39 million tons. This means that human biomass exceeds that of all terrestrial mammals by a factor of nearly 20 and that of all marine mammals by a factor of ten. However, the largest biomass is in our livestock and domestic animals: its mass is about 630 million tons, the researchers report.
In view of the rapid loss of species, it is extremely important to know as much as possible which species exist and also to monitor their number and share in the Earth’s ecosystems. But there are huge gaps in our knowledge of the animal world on our planet. Even for mammals, which are some of the best-studied and best-known animals, the data is incomplete. Numerous studies have examined the distribution, diversity and number of species of terrestrial and marine mammals. To date, however, there have only been very rough estimates of mammalian biomass. “But biomass is a good complement to species richness and other biodiversity indicators,” explain Lior Grinspoon of the Weizmann Institute of Science in Israel and colleagues. Because biomass also provides information about ecological footprint and abundance on a global scale.
Deer, wild boar and elephant are among the top three
That’s why Grinspoon and his team have now created a comprehensive list of all the land mammals on our planet. To do this, they used data from nearly 400 mammalian species for which detailed information on abundance and biomass is available. Using an algorithm, they then determined the biomass of the remaining 4,800 land mammal species based on estimated body weight and distribution. The assessment showed that the biomass of all land mammal species on Earth is about 22 million tons. Compared to the biomass of our own species, this is minuscule: at about 390 million tons, we humans outnumber our fellow land mammals by about 20 times. The contrast with livestock and domestic animals was even more stark: Their biomass is 630 million tons—nearly 30 times more than that of wild land mammals, the researchers reported. With a total of 20 million tons, our domestic dogs alone have roughly the same biomass as all land mammal species combined. At 40 million tons, the pigs we keep weigh twice as much as the researchers calculated.
Of the ten largest wild land mammals, three species are in the lead: the white-tailed deer (Odocoileus virginianus), common in North America, with a weight of 2.7 million tons, the wild boar with a weight of 1.9 million tons, and the African elephant with about 1.3 million. tons. tons. “Forty percent of the biomass of wild wild mammals is concentrated in just 10 species,” say Grinspoon and colleagues. Seven of them are even-toed ungulates, including five species of deer. Native red deer and fallow deer are seventh and eighth in the top ten. On the other hand, rodents, bats and other groups of animals that are far ahead in terms of the number of species and individuals make up only a small proportion of the biomass. “Although more than 95 percent of all mammals belong to these small species with a body mass of less than one kilogram, they make up less than a fifth of the total biomass,” the biologists explain. “Bats, for example, account for one-fifth and two-thirds of all mammalian species, but they contribute less than a tenth of the total biomass of wild wild mammals.”
Whales dominate the biomass in the sea
Some large species also make up the majority of marine mammal biomass. Of the total 39 million tons of biomass from all marine mammals, 23 million tons — about 60 percent — are represented by whales, Grinspoon and colleagues determined. The top three are fin whales at eight, sperm whales at seven and humpback whales at four million tons. The largest mammal on Earth, the blue whale, shares fourth place with the southern minke whale, both weighing three million tons. “Our study sheds light on the distribution of terrestrial mammal biomass on our planet,” the scientists wrote. “The results are important for understanding the global status of mammals and for comparing different groups and species.”
Source: Lior Grinspoon (Weizmann Institute of Science, Rehovot) et al., Proceedings of the National Academy of Sciences, Available here. doi: 10.1073/pnas.2204892120)
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