Today is Wildlife Conservation Day
Nature documentaries and conservation campaigns paint an image of Earth teeming with wildlife, but the numbers tell a different story. A February 2023 study, published in PNAS, quantified the biomass of the world’s mammals and revealed an ecosystem heavily dominated by humanity and its livestock.
A few striking figures from the study:
🐕 The biomass of domestic dogs (20 million metric tons) nearly equals that of all wild land mammals combined.
🐈⬛ Domestic cats (2 million metric tons) have nearly double the biomass of African savanna elephants.
🧍 Humans outweigh wild land mammals nearly 20 to 1, with a combined biomass of 390 million metric tons.
🐄 Livestock (630 million metric tons) surpasses wild marine mammals (40 million metric tons) and wild land mammals (20 million metric tons) by orders of magnitude.
🐖 Even pigs outweigh all wild land mammals combined.
Wildlife, it seems, is rare today. For every kilogram of wild land mammal, there are over 50 kilograms of humans and their domesticated counterparts.
“The dazzling diversity of various mammal species may obscure the dramatic changes affecting our planet,” noted Ron Milo, the study’s lead researcher. His team employed machine learning and ecological data to estimate biomass for thousands of species. The findings underscore the profound imbalance between humanity and nature.
Large herbivores, such as white-tailed deer and wild boars, dominate wild land mammal biomass, often thriving due to human activity. In the seas, baleen whales alone account for more than half the biomass of marine mammals. Yet even these giants are dwarfed by domesticated species. Cattle alone weigh 20 times more than all wild terrestrial mammals.
The study provides a stark benchmark for understanding humanity’s impact. As Milo observed, “Our research shows, in quantifiable terms, the magnitude of our influence.”
It is worth noting the study focused solely on mammals, a fraction of Earth’s biodiversity. Insects, birds, reptiles, and other creatures collectively outweigh mammals, but they, too, face growing threats from human expansion and climate change.
Wildlife Conservation Day serves as a reminder of nature’s diminished state. While the biomass of wild mammals may seem small compared to the weight of humanity, their role in ecosystems—and our planet’s future—remains immense.
🔬 L. Greenspoon, E. Krieger, R. Sender, Y. Rosenberg, Y.M. Bar-On, U. Moran, T. Antman, S. Meiri, U. Roll, E. Noor, R. Milo (2023), The global biomass of wild mammals, PNAS 120 (10) e2204892120, doi:10.1073/pnas.2204892120
