Human disruption has caused the total biomass of wild animals to plummet by 90 percent

If you stand on a busy city street, it’s obvious that humans are in charge. What’s not as obvious, however, is what the world was like before humans took control of the planet from other mammals. New research shows just how completely humankind has taken over and dominated the living world.

In a pair of studies, scientists looked at the total weight, or “biomass,” of mammals on Earth. Since 1850, wild land and marine mammals have lost most of their mass, while humans and our livestock have exploded in number

The team also created a new way to measure how much life “moves” around the planet. Since the Industrial Revolution, human movement has skyrocketed while the movement of marine animals has dropped sharply.

The results of this unsettling research come from collaborations between the Caltech laboratory of Rob Phillips, and Ron Milo, professor of systems biology at the Weizmann Institute of Science in Israel.

“Centuries of work by naturalists have made it abundantly clear that living organisms are connected in giant webs of interactions,” says Phillips.

“But this is not just a vague idea; it is instead an idea that can be rendered quantitatively. These two papers make huge steps toward turning those intuitive ideas into concrete and quantitative time series.”

Humans, mammals, movement

The first study centers on the Weizmann Institute of Science in Israel, led by Dr. Yuval Rosenberg, and asks a blunt question: How much motion do people add to the planet compared with animals that still roam free?

Human movement today is about 40 times greater than the combined movement of all wild animal species – including land mammals, birds, and arthropods.

The team defined biomass movement (the total mass of a group multiplied by the distance it travels in a year) to compare humans and animals on the same scale.

That single yardstick connects walkers, cars, flocks, herds, and ocean life without mixing apples and oranges.

Humans now account for far more motion than land wildlife because there are billions of us and we travel daily. On average, each person covers about 19 miles per day by foot, bike, road, rail, or air.

About 65 percent of human biomass movement happens in cars or motorbikes, 10 percent in airplanes, 5 percent on trains, and 20 percent on foot or bicycles.

Even walking alone now exceeds the combined movement of wild land mammals, birds, and arthropods by roughly six to one.

Why animal movement matters

Animal movement spreads nutrients, seeds, energy, and genes across landscapes. When that flow weakens, ecosystems lose the quiet services that keep them stable and productive.

Human activity alters how animals move, how far they go, and when they travel. A global assessment shows widespread disruption of animal movement across birds, mammals, reptiles, amphibians, fish, and arthropods.

Reduced movement can lower survival, shrink ranges, and isolate populations. It also weakens natural processes that keep soils, rivers, and food webs functioning.

Energy costs and machine weight

Movement takes energy, and for many mammals the cost per pound per mile is modest. Humans on foot are efficient movers, but the machines we ride are heavy and energy hungry.

Counting only the passenger’s mass makes motor travel look efficient, yet the vehicle mass and fuel make the true energy bill high. That energy bill scales up across billions of trips and adds to the overall pressure on ecosystems.

“We often marvel at the power of nature compared to how small we are,” said Ron Milo, a professor at the Weizmann Institute. His point is simple, the everyday movement of people can now overshadow iconic migrations.

The numbers offer a way to compare that is concrete and testable. They also help track progress if policies or technologies change travel patterns.

Humans, mammals, biomass

A companion analysis, led by Weizmann graduate student Lior Greenspoon, reconstructs mammal biomass since 1850 and shows a sharp pivot. The total weight of wild mammals on Earth has crashed while humans and our farm animals have surged.

Researchers calculated the biomass – the combined weight – of every mammal species over this period. They found that wild land and marine mammals together have dropped by about 70 percent, from around 200 million tons to just 60 million tons.

At the same time, human biomass has shot up by about 700 percent, and the biomass of domesticated animals has risen by about 400 percent. Today, humans and our livestock together weigh about 1.1 billion tons.

“It is important to establish quantitative historical baselines of wild animal populations so that we can avoid the shifting baseline syndrome – a gradual change in the accepted norms for the condition of the natural environment,” says Greenspoon. “This study helps establish such a global baseline.”

Ocean biomass, movement collapse

The collapse is especially severe in the oceans. Marine mammals like whales now have only about 30 percent of the total biomass they had in 1850, mostly because of industrial hunting and fishing.

“To get a sense of the consequences of these changes in the mass distributions of mammals over time, I find it both fun and interesting to compare the total fertilizer used across the entire planet to the amount of missing whale poop per year due to the missing 3 million whales killed during the 20th century,” says Phillips. “Perhaps people will be surprised to find that those two numbers are comparable.”

That missing whale poop once helped fertilize the oceans and support marine life. So this isn’t just a story about numbers – it’s about how deeply we’ve changed basic natural cycles that used to run without us.

Humans, mammals, and the future

To sum it all up, when you step back from all the numbers, the lessons learned here are disturbing and hard to ignore.

Humans have taken over the planet – not just in how much we weigh, but in how far and how fast we move – while wild animals have shrunk and slowed down across land and sea.

On the other hand, optimists can say that these studies give us something solid to work with – a clear starting point to measure how much we’ve changed the living world and how much we’re still changing it.

What we choose to do next – how we build our cities, run our farms, travel, and protect wild places – will decide nothing less than the future of this beautiful planet that both humans and animals call home.

The study is published in the journal Nature Ecology & Evolution.

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