Huge loss of wild mammals weighs heavily on Earth

New study reveals how the biomass of marine and terrestrial mammals has plunged since 1850

- By Don Pinnock

The number of wild creatures is dwindling as the ones we have domesticated grow... and grow. A new study by scientists at Israel's Weizmann Institute of Science, published in the journal Nature, has taken on an extraordinary challenge: to weigh all the mammals on Earth not individually, of course, but in terms of biomass, the total mass of living matter.

By tracing this back to the year 1850, the researchers have shown just how profoundly humanity has reshaped the animal world.

Their results are both fascinating and sobering. In 1850, the total biomass of wild mammals everything from whales to elephants and mice was estimated to be roughly equal to that of humans and our domesticated animals combined. Since then, whereas humans' weight on the planet has multiplied many times over, the collective mass of wild mammals has more than halved. Today, humans and our livestock outweigh all wild mammals by about 10 to one.

A new way of seeing life

When we talk about the loss of wildlife, it's usually in terms of species extinctions. However, extinction statistics can hide the scale of ecological change. Losing a single rare species equates to losing millions of individuals from a common species. Biomass offers a more holistic picture: not just who's alive, but how much life exists.

The researchers, led by Lior Greenspoon, Elad Noor and Ron Milo, used a vast range of historical data, models and population records to construct a timeline of mammal biomass from 1850 to the present the first global attempt to do so at this level of detail.

What they found was a story of human expansion, industrialisation and unintended consequences for the rest of the animal kingdom.