Whatever we call this era, people are changing the planet. Here’s how.
After almost fifteen years of consultation, a statement by geologists on Tuesday feels almost anticlimactic: Our species has not changed our world so radically that a new chapter in its history has begun, at least not yet, a scientific panel decided.
But even though the era of the “Anthropocene” is not described in textbooks and research articles, earth scientists have no doubt that humans are changing the planet. When deciding whether or not to adjust the geological timeline to reflect this, they took into account a variety of human-induced changes that will be marked in the rocks for a long time to come.
Ultimately, several scientists who voted on the question of the Anthropocene said that humanity had left too many different types of imprints in nature, over too broad a time frame, to be neatly captured in a single premise, which is what geological timekeeping requires.
Here are some of the planet-wide changes they considered.
Nuclear fallout
An important part of the case that some scientists made to explain the beginning of the Anthropocene Epoch was the pulse of radioactive isotopes that spread hundreds of nuclear detonations across the Earth in the mid-20th century. There is no doubt that humans are responsible for these particles, even if they end up in different places at slightly different times.
However, some scholars have raised concerns about whether using weapons of mass destruction to mark humanity’s transformation of the planet would send the wrong message about our times.
Biodiversity is changing
Fossilized life tells scientists a lot about what the Earth was like in its deep past, and that will undoubtedly remain the case as future researchers try to study our time. Not only are we losing species at a rapid rate, we have also upended the places where they live and thrive (or not thrive), both by destroying their habitats and by domesticating them for agriculture and companionship.
Shifting ground
Our civilization moves and changes the ground beneath us in very direct ways. We flatten hills to build cities and grow crops. We excavate the land to extract raw materials or bury waste. We dam rivers, so they can no longer transport mud and soil from the continents to the seas. Worldwide, according to one estimatethe total amount of sediment humans move each year is now more than 24 times the amount transported by rivers.
Fossil fuels
The burning of fossil fuels adds enormous amounts of carbon dioxide and methane to the atmosphere, which together warm the Earth’s surface and oceans. Temperatures are now rapidly diverging from their relatively stable levels during the current geological epoch, the Holocene. That’s the period that began 11,700 years ago, when the melting of glaciers made many parts of the planet habitable for humans.
But industrial activity also leaves another kind of lasting legacy: ash from the combustion of coal and fuel oil finds its way into lakes, sediments and the seabed.
Plastic and other pollution
Industrial ash is not the only type of matter that will remain in mineral history as a distinctive feature of our time. There are also pesticides, plastics, heavy metals, concrete and fertilizers, not to mention all kinds of waste from landfills.