Human biomass movement 40x greater than all land animals combined

A medium-sized, grey bird that weighs just 100 g travels from pole to pole each year, covering 90,000 km back and forth. Thus the Arctic tern, with its distinct forked tail, undertakes the longest journey of any of the planet’s wild animals. Every year two million of these birds travel from the Arctic to Antarctica. But being so light, their total biomass is only 0.016 gigatonnes (gt) per km per year.

Biomass movement of a given species is defined by its total biomass times the distance it actively travels per year. For instance, the grey wolf that moves longer distances than most land mammals has a biomass movement of around 0.03 gt/km/yr. The migration of over a million blue wildebeest, gazelles, and zebras of the Serengeti constitutes an annual biomass movement 20x larger than that of the grey wolf.

“Putting it in a human perspective, it is similar to the biomass movement associated with international human gatherings such as … the the FIFA World Cup,” a paper published recently in Nature Ecology & Evolution said.

This study has now reported that the biomass movement of humans is 4,000 gt/km/yr, “over 40-times greater than our best estimate for all wild land mammals, arthropods, and birds combined, and over six-times greater than the upper estimate for the biomass movement of all land animals combined.”

“As animals and humans move, they shape ecosystems in myriad ways, from transporting nutrients and organisms to trophic effects and physical ecosystem engineering,” per the paper. “Mobility can thus serve as a concrete and direct comparison between humans and animals.”

Humans move longer average distances of around 30 km per day, the study said, most of it with the use of “motorised vehicles, with ~65% in cars and motorcycles, ~10% in airplanes and ~5% in trains and subways. Two-thirds of all motorised mobility occurs in high-income and upper-middle-income countries.”

Even has humans’ movement has exploded, that of marine animals, which the study estimated to be “the living world’s largest,” has halved since 1850 thanks to industrial fishing and whaling in the Anthropocene epoch.

Curiously, the biomass movement of domesticated animals was found to be of the same order of magnitude as humans and the locomotion of non-dairy cattle corresponds to most of this biomass movement, the authors added.

The combined biomass movement of all wild land mammals (excluding bats) was estimated at 30 gt/km/yr, and that of large-bodied animals, which travel more, declined the most.