We humans have been shaping the world around us for millennia, using resources from a seemingly infinitely large natural world. Yet, we know this not to be the case. From climate change to habitat destruction, the toll our activity has taken on Earth is coming into view at an ever-increasing rate. While we often focus on the effects of our choices, we seldom consider the actual weight of our footprint. Physically, how large of a mark are we leaving on the planet? This is the question Ron Milo and colleagues at the Weizmann Institute set out to answer in their latest paper published in Nature.

The researchers calculated human-made mass, or anthropogenic mass, from 1900 to current day using data on the global stock and flow of materials in six categories: concrete, aggregates, brick, asphalt, metals, and other (such as plastic). They then compared these values against the global biomass, the total global mass of biological organisms. They found that anthropogenic mass has been increasing exponentially, doubling about every 20 years, and has reached a total of 30 Gigatons per year. This value is equivalent to each person producing their own body weight’s worth of mass per week.

Though anthropogenic mass has been growing at an alarming rate, global biomass has remained largely stable, with plants accounting for most of it. Thus, while in 1900, human-made objects were equivalent only to 3% of global biomass, in 2020, the mass of these materials has overtaken that of all biological organisms, reaching a total of 1.1 teratonnes. If these trends continue, anthropogenic mass is projected to triple global biomass by 2040. The scientists’ results showed that most anthropogenic mass was made up of building materials, and at 1100 gigatonnes, buildings and infrastructure exceeded the mass of all tree and shrubs, which measured at 900 gigatonnes. On the other hand, plastic made up less than 1% of the mass of infrastructure, yet still doubled the mass of all animals on Earth.

Highlighting the great impact human activity has had in such a short period of time, the authors called for the current time period to be renamed the Anthropocene, and cautioned that the use of geological materials for human use had far ranging consequences for the planet, from causing habitat and biodiversity loss to altering climactic and biogeochemical cycles.

The lead author Emily Elhacham is a graduate student in the Milo Group at the Weizmann Institute in Israel. Ron Milo, the corresponding author of the Nature paper, is a professor in the Department of Plant and Environmental Sciences at the institute. His group uses computational and experimental synthetic biology tools to address the grand challenges of sustainability and quantitatively uncover the nature of the central carbon metabolism.

Managing correspondent: Melis Tekant

Original article: Global human-made mass exceeds all living biomassNature

Media coverage: Human-made materials now outweigh Earth’s entire biomass – studyThe Guardian
Human-Made Stuff Now Outweighs All Life on EarthScientific American

Image credit: Sam Valadi, via Wikimedia Commons

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