We often speak of tipping points when it comes to global warming: here's what happens if exceed 1.5 degrees Celsius, 2 degrees ...you get the picture.
But there is another critical tipping point. One which illustrates humanity's enormous impact on our planet using precise metrics, down to the gigaton: the mass of human-made material on Earth.
Researchers have been collecting data on the mass of human-made materials on Earth for a little more than a century. By comparing how this mass stacks up to the natural biomass, a new study published Wednesday in the journal Nature reveals a potentially deadly environmental imbalance.
Why it matters — It seems we are at a cross-roads in the history of our time on Earth. In 1900, human-made objects equaled just 3 percent of Earth's total biomass. But skip forward a mere 120 years — a blip in the 4.5-billion-year-old Earth's lifetime — and human-made objects now outweigh living biomass by 100 billion tons.
Overall, human-made objects clock in at 1.1 teratons, the study finds, while the rest of life is estimated to weigh 1 teraton.
Inverse reached out to the research team for comment but did not hear back by the time of publication.
How they did it — Biomass in this study refers specifically to the combined weight of all the bacteria, animals, fungi, and plants in the world.
The researchers weighed life on Earth by calculating averages across different models of vegetation, finding that plant biomass constitutes some 90 percent of all the Earth's living biomass. Since 1900, human activity has cut the plant biomass in half — from 2 teratons to 1 teraton, the study finds.
Each teraton is 1,000,000,000,000 metric tons. That is almost 8000 times the weight of the island of Manhattan. Human-made objects are now exceeding this, the study finds.
The researchers looked at the production of specific materials to calculate the anthropogenic mass on Earth — concrete, bricks, aggregates (like gravel), asphalt, metals, and 'other' components, like wood used for paper and industry, glass, and plastic. They calculate that, since 1900, the production of these materials has followed a Moore's Law-like pattern, with the mass of these materials on Earth doubling every 20 years.
What's new — We know humans are driving significant changes to the Earth. But this study offers jaw-dropping data to quantify just how much we are affecting our planet.
The study finds current human-made mass production is now more than 30 gigatons per year — in other words, the mass of anthropogenic material produced every week now outweighs all 7.8 billion humans on the planet.
The data reveal shifts in our production of materials around economic crises or global wars. Naturally, these human-made materials skyrocketed in the immediate aftermath after World War II, with human-made mass peaking at just over 5 percent increase in a single year.
If we continue on this trajectory, we will likely exceed the dry biomass on Earth three times over by 2040, surpassing a whopping three teratons in human-made mass.
Digging into the details — Depending on how you look at the data, we may have already surpassed this tipping point a few years ago.
If waste products — mass that has been "demolished or taken out of service" — is included in the calculation, then human products surpassed the "dry" living biomass in 2013.
The study focuses on 'dry' biomass, but even if you include water in the equation, human-made mass will still exceed the estimated 2.2 teratons this constitutes by a point in the 2030s.
It is important to note the margins of error for such monumental masses is relatively large — some plus or minus 16 percent for biomass and plus or minus 6 percent for anthropogenic mass.
But, on the whole, the researchers state if we have not already surpassed the living biomass, we will in the next two decades.
The Inverse Analysis — When we talk about climate change, it's daunting to think about the carbon emissions we have generated since the Industrial Revolution.
But, perhaps equally terrifying is the idea that we humans — and our buildings, roads, and machines — have come to weigh more than the sum of the parts of the 4.5-billion-year-old Earth.
In this paper, the researchers argue we are at the dawn of a new human-made era, one which vastly reshapes the planet and which deserves its own name — similar to periods in the past, such as the Jurassic and Cretaceous — the Anthropocene.
"The impacts of these activities have been so abrupt and considerable that it has been proposed that the current geological epoch be renamed the Anthropocene."
Abstract: Humanity has become a dominant force in shaping the face of Earth1–9. An emerging question is how the overall material output of human activities compares to the overall natural biomass. Here we quantify the human-made mass, referred to as ‘anthropogenic mass’, and compare it to the overall living biomass on Earth, which currently equals approximately 1.1 teratonnes10,11. We find that Earth is exactly at the crossover point; in the year 2020 (± 6), the anthropogenic mass, which has recently doubled roughly every 20 years, will surpass all global living biomass. On average, for each person on the globe, anthropogenic mass equal to more than his or her body weight is produced every week. This quantification of the human enterprise gives a mass-based quantitative and symbolic characterization of the human-induced epoch of the Anthropocene.