Thirty trillion tons. That’s how much debris and disturbed land people have left behind across Earth’s surface, according to a new study. It’s a jumble of everything from plowed-up fields to ancient Roman ruins, plastic bags and those earbuds you lost last week.
And these findings amount to more than just trash talk. Poeple have created an entire new geologic layer, explains study leader Jan Zalasiewicz. He is a geologist at the University of Leicester in England. Plants and animals constantly re-use nutrients and wastes. But people aren’t so good at that, he observes. While we may recycle some materials, Zalasiewicz notes that most of our junk keeps piling up. “We don’t recycle like the biosphere does.”
The human-trash-laden layer atop Earth’s surface has a name: the technosphere. Scientists came up with that name around 2013. But this study is the first attempt to estimate its mass. Zalasiewicz and his colleagues used satellite images, maps and geological knowledge, such as topography (the shape of the Earth’s surface, for instance, or how deep mines extend) to come up with a very rough tally.
People appear to have deposited 30 trillion tons of this “stuff” on Earth’s surface. That’s spread over about 80 million square kilometers (31 million square miles). “It’s very approximate,” Zalasiewicz says of his team’s estimate. “But it’s a start.” Such a large amount surprised him, he says: “It’s about 100,000 times the weight of all [living] humans.” Zalasiewicz and colleagues published their estimates November 28 in Anthropocene Review.
The scientists did more than examine the size of the technosphere. They also estimated how many types of things this vast debris pile already includes. It’s similar to how biologists add up species of life. In biology, that's called diversity.
The technosphere’s “stuff,” too, is diverse. There are more types of these materials than there are species of life, the researchers have concluded . Take cell phones. Think of cell phones as a family, akin to the role people share in the family Hominidae. “Smartphones may be a subfamily within that," Zalasiewicz explains. A brand of cell phones might be a genus. "And a particular make of that brand, a little different in shape than the others, will be a species,” he says. Accounting that way for all types of litter and trash makes for a lot of different kinds of stuff.
Just another layer
Over time, the technosphere may become sedimentary rock. That’s the type that forms when sediments, such as sand or mud, become buried by newer sediments. Eventually, pressure and heat hardens those layers into rock. Much of Earth’s complex, 4.6-billion-year history is recorded in such rock. The oldest rocks lay on the bottom and the youngest at the top. Like chapters in a book, each layer tells a story. The clues they contain — such as fossils, ancient beach deposits or ash from long-extinct volcanoes — reveal something about the geologic time in which they were deposited.
Gradually, the technosphere is becoming just another layer with its own stories to tell. Like older rocks, it is also associated with a period of geologic time. That time is called the Anthropocene. This age includes all the years that people have been altering Earth’s surface. Exactly when the Anthropocene started is still under debate.
“The term ‘Anthropocene’ is a concept,” explains Lucy Edwards. A geologist at the U.S. Geological Survey in Reston, Va., she helps name geologic features. Naming our time the Anthropocene, she says, “recognizes that humans are really changing the environment — and to a large extent.” The technosphere is a good way to describe the physical effects of that, she says. And even if Zalasiewicz’s estimate of the technosphere’s mass is “just in ballpark,” Edwards says it makes a good point for discussinghumanity’s impacts.
Today, the technosphere is mostly a loose mix of everything from garbage, roads and buildings to churned-up soil. But that will change in the distant future as it turns into a geologic layer. “Far-future geologists will have a huge set of puzzles on their hands,” Zalasiewicz predicts.
Bricks, plastic and concrete will provide evidence that people were here, long after they have vanished, Zalasiewicz’s team imagines. Food waste tossed into landfills will have turned to black carbon. There will be mine shafts, layers of iron where metal has rusted to dust, maybe even a few smudges from petrified ball point pens. Former cities will be a confusion of concrete chunks, building parts and countless odds and ends.
Some clues will make unraveling this geologic puzzle a little easier. For starters, there will be plenty of techno-fossils. “All those things that people make end up in the ground, just like fossils,” says Pat Holroyd. As a paleontologist at the University of California Museum of Paleontology in Berkeley, she studies fossil animals.
Even in places where there are no buildings, roads or landfills, humans have left their mark. For example, she notes, farms and factories leave a chemical signature of humans' impacts.
World War II created an especially clear layer that marks the middle of the 20th century. For example, in Berlin, Germany, rubble from bombed buildings was pushed into mounds. Fourteen of those mounds still persist, Zalasiewicz’s team notes. The biggest, a hill named Teufelsberg (TOY-fels-burg), is now a pile of debris. It measures up to 80 meters (262 feet) thick and covers an area equivalent to 200 football fields.
The technosphere continues to grow. And everyone contributes to it. A plastic water bottle, the old socks you finally tossed, a broken cell phone. “All the stuff we make is evolving fast and piling up fast,” notes Zalasiewicz.
Geologists of the future will also find plenty of index fossils in the technosphere. Past ones are from organisms that were widespread but only existed for a very short time. Geologists use index fossils to figure out the age of the rocks in which they are found. A nail might not make a very good index fossil in the technosphere, since nails have been in use for centuries. But a smashed iPhone 7 would pin the date of some layer down to 2016 or later.
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Anthropocene Term coined by scientists to describe the age in which humans have been the strongest force of change on the planet. It is generally believed to date from at least the dawn of the Nuclear Age (in the middle 1940s), and possibly even earlier — from the beginning of the Industrial Revolution in the early 1800s.
ash (in geology) Small, lightweight fragments of rock and glass spewed by volcanic eruptions.
biology The study of living things. The scientists who study them are known as biologists.
black carbon Particles of carbon that are released as fossil fuels, wood or other carbon-based materials burn.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
cell The smallest structural and functional unit of an organism. Typically too small to see with the naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere from thousands to trillions of cells, depending on their size. Some organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.
colleague Someone who works with another; a co-worker or team member.
concrete To be solid and real. (in construction) A simple, two-part building material. One part is made of sand or ground-up bits of rock. The other is made of cement, which hardens and helps bind the grains of material together.
debris Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.
diversity (in biology) A range of different life forms.
environment The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.
extinct An adjective that describes a species for which there are no living members.family A taxonomic group consisting of at least one genus of organisms.
football field The field on which athletes play American football. Owing to its size and familiarity, many people use this field as a measure of how big something is. A regulation field (including its end zones) runs 360 feet (almost 110 meters) long and 160 feet (almost 49 meters) wide.
fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
genus (plural: genera) A group of closely related species. For example, the genus Canis — which is Latin for “dog” — includes all domestic breeds of dog and their closest wild relatives, including wolves, coyotes, jackals and dingoes.
geological Adjective to describe things related to Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists.
iron A metallic element which is common in minerals of the Earth’s crust and in its hot core. This metal is also found in cosmic dust, and in many meteorites that fall to Earth from space.
landfill A site where trash is dumped and then covered with dirt to reduce smells. If they are not lined with impermeable materials, rains washing through these waste sites can leach out toxic materials and carry them downstream or into groundwater. Because trash in these facilities is covered by dirt, the wastes do not get ready access to sunlight and microbes to aid in their breakdown. As a result, even newspaper sent to landfill may resist breakdown for many decades.
nutrient A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
organism Any living thing, from elephants and plants to bacteria and other types of single-celled life.
paleontology The branch of science concerned with ancient, fossilized animals and plants. The scientists who study them are known as paleontologists.
physical (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
plastic Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.
pressure Force applied uniformly over a surface, measured as force per unit of area.
recycle To find new uses for something — or parts of something — that might otherwise be discarded, or treated as waste.
remnant Something that is leftover — from another piece of something, from another time or even some features from an earlier species.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
sediment Material (such as stones and sand) deposited by water, wind or glaciers.
sedimentary rock A type of rock that forms from accumulated material that has been eroded from other rocks. It often forms from mud, sand, or clay gathered at the bottom of an ocean, lake, or river.
smartphone A cell (or mobile) phone that can perform a host of functions, including search for information on the internet.
solid Firm and stable in shape; not liquid or gaseous.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
trillion A number representing a million million — or 1,000,000,000,000 — of something.
technosphere The accumulation of human-created and altered materials, debris and other visible alterations to Earth's surface.
U.S. Geological Survey (or USGS) This is the largest nonmilitary U.S. agency charged with mapping water, Earth and biological resources. It collects information to help monitor the health of ecosystems, natural resources and natural hazards. It also studies the impacts of climate and land-use changes. A part of the U.S. Department of the Interior, USGS is headquartered in Reston, Va.
waste Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.