A team of environmental researchers made an estimated account of the biomass of all wild mammals and found that humans weighed much more combined.
The team, led by Ron Milo of the Weizmann Institute of Science in Rehovot, Israel, was trying to identify a metric that could be used to monitor conservation efforts on a global scale. “Estimating the number of a single organism is technically difficult even for a single species, due to issues such as detectability, inter-annual and seasonal variability, and a lack of standardization in measurement methods, especially for small-bodied species,” the team said in the paper. Measuring biomass allows us to compare species with very different body sizes, so biomass is complementary to species richness and other measures of diversity, and is an indicator of the abundance and ecological footprint of wild mammals on a global scale, a benchmark for tracking the temporal dynamics of the global wildlife situation, and conservation. It can serve as an intuitive data source for their efforts.”
The team first gathered current population estimates for specific species. They were able to come up with estimates for 392 land mammals, which is only about 6 percent of all wild land mammal species. The team used machine learning to make predictions for other species.
“We also obtained a combination of species-specific features that affect animal abundance for each wild land mammal,” the team says. we built a machine learning model.”
This model provided estimates for 4,805 mammal species. While the estimates generated are still less than the 6,400 species of land mammals thought to have lived, the team did not include animals for which the data was too scarce and said they believed the impact on overall biomass would be negligible anyway, given their rarity.
Total weight of wild mammals: 22 million tons!
The team estimates that the biomass of all wild mammal species is around 22 million tons. However, this biomass is not evenly distributed among species, with only 10 species accounting for about 40 percent.
White-tailed deer make up the most biomass of any species (excluding humans), with 2.7 million tonnes distributed over an estimated 45 million individuals. Wild boar with a weight of 1.9 million tons is next, followed by the African savannah elephant with a weight of 1.3 tons.
Humans, on the other hand, have a biomass of about 390 million tons, while cattle raised as livestock even outweigh humans at 420 million tons. However, these naturally do not belong to wild mammals.
The team summarizes their findings: “The global composition of mammalian biomass reflects anthropogenic pressures on wild mammal populations: increased human populations, increased global demand for animal-based products, and the consequent expansion of factory farms, for example, where domesticated mammals are now outnumbered by more than 30 wild land mammals. causes a result that outweighs by a percentage. While biomass is not a direct indicator of conservation status or anthropogenic pressures, we propose that the ratio between the biomass of wild and domesticated species provides further perspective on the phenomenal increase in humanity’s impact on our planet.”
The study has been published in the Proceedings of the National Academy of Sciences.
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