The totality of stuff made by humans and currently in-use, from forks to cars to buildings, is likely to now outweigh all of the plants, animals, bacteria, and other living things on Earth. According to researcher from Israel's Weizmann Institute of Science published in the journal Nature, "In the year 2020 (±6), the anthropogenic mass, which has recently doubled roughly every 20 years, will surpass all global living biomass." From Scientific American:
The implications of these findings, published on Wednesday in Nature, are staggering. The world's plastics alone now weigh twice as much as the planet's marine and terrestrial animals. Buildings and infrastructure outweigh trees and shrubs. "We cannot hide behind the feeling that we're just a small species, one out of many," says study co-author Ron Milo, who researches plant and environmental sciences at the Weizmann Institute of Science in Israel. These numbers should be a wake-up call, he adds. They tell us "something about the responsibility that we have, given that we have become a dominant force," Milo says […]
The researchers chose to focus only on living biomass and anthropogenic objects that are in use—not waste. With waste, anthropogenic mass began outweighing biomass in 2013, plus or minus five years. And the crossover point is slightly later if water weight is included in the biomass calculations. The wet weight of the biomass on Earth is currently 2.2 trillion metric tons, and humans are on track to outproduce that figure in 2031 (including waste) or 2037 (without it).
About half of the world's current human-made mass is concrete, with aggregates such as gravel making up much of the rest. Bricks, asphalt, metals, plastic and other materials make up about 19 percent of the total.
"Human-Made Stuff Now Outweighs All Life on Earth" (Scientific American)