Since the 1850s, two per cent of marine mammal species have gone extinct. But if we look at the biomass—if we add up everything that makes up whales, dolphins, seals, sea lions, dugongs, manatees, and sea otters—then the amount of these wild animals has dropped by 70 per cent, according to a new study published in Nature Communications.
Most of this decline is due to whaling, while the amount of seals and sea lions is estimated to have remained steady. Estimates are all we have: these numbers are good guesses based on limited catch records and population surveys.
Over the same time, the biomass of humans increased by 700 per cent. That’s partly because the numbers of humans soared, and partly because humans have become individually larger. Scientists are a lot more certain about this estimate, as humans are easier to count (and weigh) than whales.
