Note the astonishing headline and the interesting fact that domestic dogs weigh 20 times more than pet cats. Ants do well too! Livestock kept by humans and mammals that would not exist but for livestock such as rats have a combined weight of 630 million tonnes worldwide.
The information comes from Prof Ron Milo (and colleagues) of the Weizmann Institute of Science in Israel, the lead author of the study: The global biomass of wild mammals. published in the National Academy of Sciences of the United States [link: https://doi.org/10.1073/pnas.2204892120].
Prof Milo said:
“These domesticated to wild mass ratios emphasise the active role humans play in shaping the abundance of mammals.”
The authors of the study compiled estimates of the total abundance of several hundred mammal species from available data to estimate the overall global biomass of wild mammals. They found a total wet biomass of approximately 20 million tonnes (Mt) for all terrestrial wild mammals, which is equivalent to approximately 3 kilograms per person on earth. The primary contributors to the biomass of wild land mammals are large herbivores such as the white-tailed deer, wild boar, and African elephant. Even-hoofed mammals, such as deer and boars, represent about half of the combined mass of terrestrial wild mammals.
The authors also estimated the total biomass of wild marine mammals at approximately 40 Mt, with baleen whales comprising more than half of this mass. In comparison, the total mammal biomass is overwhelmingly dominated by livestock (approximately 630 Mt) and humans (approximately 390 Mt).
This study provides a provisional census of wild mammal biomass on Earth and can serve as a benchmark for understanding human impacts on the natural world. It highlights the importance of conserving wild mammals, particularly large herbivores, for maintaining the balance of ecosystems and the health of the planet.
Cutting down rainforests because less rain to fall
Separately, another scientific study claimed that the more you cut down rainforests the more likelihood there is of less rain. In fact, they said that for every percentage point of forest cover lost, rainfall declined by 0.6% in the wet season and 0.2% at the rest of the time.
Taking the Congo as an example, if you project a 40% decline in forest cover during the next 80 years, they expect the region to see a 10% drop in rainfall. This creates a negative cycle because less rainfall means that the forest suffers.
