The idea that ants collectively outweigh humans is a common myth; in reality, humans outweigh all ants by about five to one in total biomass. To compare life on Earth fairly, we must look at biomass across all kingdoms and consider not just wet mass but carbon content, which reflects the flow of energy through the biosphere.
Humans account for roughly 350 million metric tons of biomass, while Antarctic krill reach about 379 million tons and cattle, the most numerous domesticated animal, about 650 million tons. However, when measured by carbon mass—a better indicator of ecological impact—all animal life totals only about 2 billion tons of carbon, far less than the 450 billion tons of carbon stored in plants.
Among individual species, the black spruce (Picea mariana) of boreal forests dominates, with over 11 billion tons of biomass in Canada alone and additional growth in the United States; its wood is about 51% carbon, giving this single species nearly 5.6 billion tons of carbon, almost three times the carbon found in all animals combined. A similar scale is suggested for the Dahurian larch in Russia, which may hold at least 8.4 billion tons of biomass.