The weight distribution is also skewed: 40% global biomass of wild land mammals is concentrated in only 10 species
The population of wild mammals is shrinking despite conservation efforts and the extent of this crisis is visible in a new report that compares the biomass of wild and domesticated mammals and human beings.
Total mass of humans is 10 times that of all the world’s wild mammals combined, the report published in Proceedings of the National Academy of Sciences journal showed.
Wild mammals comprise some of the heaviest animals of the planet — the elephants, bears, bisons and whales. The total weight of wild land mammals and marine mammals is around 22 million tonnes and 40 million tonnes respectively.
Humans, by contrast, weigh 390 million metric tonnes and domesticated mammals around 630 million metric tonnes, according to the findings.
“Many domesticated mammal species outweigh the top wild mammal biomass contributors by 10 to 1,000 fold,” the researchers wrote in the report.
The total mass of domestic cats is more than that of all of the world’s African savanna elephants combined. The total weight of dogs is similar to that of all the terrestrial mammals put together.
The interest and activity of human beings play a big role in this imbalance, the data indicated.
“The most significant mammal biomass contributors are cattle (420 million tonnes), humans and other livestock species most commonly reared for meat or dairy (including buffaloes, pigs, sheep and goats),” according to the authors.
Domesticated pigs alone weigh 40 million tonnes, almost double the combined mass of all terrestrial wild mammals. These are followed by pack animals (horses, camels and donkeys).
For thousands of years, the rise of civilisation has spelled doom for wild mammalian species, the authors highlighted. “The blue whale, for example, which currently contributes a tenth of the total wild marine-mammal biomass, is estimated to have been more than 10-fold more abundant prior to industrial whaling.”
Moreover, about 30 per cent of terrestrial wild mammals live in both human-dominated and natural habitats, the reports noted. A section of them are hunted down as pests, hurting their overall population, the researchers wrote.
“The distribution of biomass across wild land mammal orders and species reveals that about 40 per cent of the global biomass of wild land mammals is concentrated in only 10 species,” the report stated.
The total biomass of the three elephant species in the world, for instance, is similar to that of all the 1,200 bat species combined, the authors said.
The comprehensive analysis of the biomass distribution of wild mammals. The authors hope that the findings will inspire more detailed ecological research that will strengthen conservation efforts.
ITAI RAVEH / WEIZMANN INSTITUTE OF SCIENCE
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