The geological age of human activity’s impact on Earth is often referred to as the Anthropocene, even if not all scientists are using the term yet. The Geological Society of London has some stark figures on what we have done to the planet in our time on it: erosion caused by human activity now has an effect 24 times greater than the erosion caused by all the world’s rivers; the sea level, which had remained stable for 7,000 years, is now rising by 0.3 meters every century; and the oceans are now significantly more acidic than they used to be after millennia unchanged. Meanwhile, levels of carbon dioxide in the atmosphere are higher than at any point over the last four million years, and a million plant and animal species are threatened with extinction.
Amid this gloomy outlook, Ana María Alonso Zarza, 58, leads the Geological and Mining Institute of Spain (IGME) where time is usually measured by millennia rather than in days. In this interview, she warns that the influence of human activity on the planet could push humanity over the edge into a sixth extinction event.
Question. Why does the Anthropocene not yet exist in geology?
Answer. The Anthropocene does not exist as a formal term. I like to compare it to the Royal Spanish Academy [RAE, the body that oversees the use of the Spanish language]. There are many words that are used on a daily basis, and until the RAE decides to include them in the dictionary, we use them informally. The same happens with the Anthropocene in geology. It is a term that is widely used, but the equivalent of geology’s RAE has not yet included the term in its dictionary. But it exists, because the influence of mankind on nature suggests that it does. All the data indicate that human activity is modifying how the Earth functions and we are in an era in which our influence is very important for geology.
When it is said that our planet is in danger, that’s not quite it: our current way of life on the planet is in danger
Q. What characterizes the Anthropocene?
TO. There are many characteristics: the increase in greenhouse gases, in average temperatures, in the sea level, and the rate at which species are disappearing, which is enormous. Species also spread out more, and many species that were restricted to small areas have been able to reach the whole world.
Q. When did the Anthropocene begin?
TO. This is a sensitive issue and opinions vary among researchers. Human influence on Earth began with agriculture, about 11,000 years ago. Human influence then was not global, but it registered in some specific areas where agriculture was happening. There was a critical moment – the collision between the Old World and the New World. That had a significant impact and meant that fauna and flora moved between continents. Another possible key period for the Anthropocene was the Industrial Revolution, with the systematic use of fossil fuels. That also had an impact as, although it was initially local, especially in Europe, it gradually became global. This is recorded at the geological level in sediments. But it appears that the clearest signal is when nuclear detonations began in the mid-20th century and when chemicals such as pesticides started to be used systematically. Right now it seems that the most likely date to consider would be 1950.
Q. Why is Anthropocene still an informal term?
TO. That is still under discussion, although the use of the term Anthropocene is accepted in many disciplines. But in science, we have to be sure, and when there is a new concept being used, which in this case would be a new geological era, it has to be very clear that the signs of that era are going to persist in the geological record. It is difficult to explain because in geology we almost always look at what has already happened, at what has already remained recorded. It is a new paradigm within the sciences because we are not just looking backwards but rather considering whether something will remain in millions of years.
If you consider that the beginning of the Anthropocene is 1950, there have to be clear sediments and rocks left over from that time that are different from a previous era, which would be the Holocene, and all that has to be preserved for 100 million years . We cannot guarantee that [what we have now] is going to be preserved and that is the paradigm in which geology finds itself. The International Commission on Stratigraphy (ICS) has to validate the Anthropocene and logically it is still not clear, because we are projecting science into the future rather than into the past. That’s a paradigm shift.
Q. Will plastic be the most characteristic element of the Anthropocene?
TO. Remove possibly plastic will not be preserved because it will decompose. But the remains of concrete, cement, bricks, tiles, glass … all these synthetic materials that we have been creating and that are more durable and more likely to be preserved in the geological record.
All the data indicate that human activity is modifying how the Earth functions and we are in an era in which our influence is very important for geology
Q. Why is the concept of the Anthropocene important?
TO. It has a scientific connotation and we have to let science decide. It is like a medicine agency assessing the suitability of vaccines. This is the same kind of thing, we are going to let the working group of the International Stratigraphy Commission decide. But thinking about our future footprint on the planet should make us reflect that we are harming the Earth, and that we are changing some of its conditions. The planet has millions of years ahead to stabilize, bury what we have done and move on. Even if we are changing it right now, the planet will look for another state of equilibrium and will continue.
We have to consider what we are doing and who it really affects, which is us, humanity. We need so many resources that at some point are going to run out, and then what are we going to do? We are living in a moment where there are supposedly intelligent beings on Earth who realize that we are harming the planet and that we may be close to the so-called sixth extinction, and we may be involved in it. We have to contemplate it because we do not want to be the victims of the sixth extinction. We have to do something to avoid it. That is the important thing and it has to make us reflect on our life on the planet and in our world. Earth will survive, but our world will not.
We are only working with the most superficial part of our planet and the Earth will carry on at its own pace. The case most people understand is the extinction of the dinosaurs 66 million years ago, when a huge meteorite fell and generated a cloud of toxic dust that caused the extinction of about 80% of species, including the dinosaurs. That had an enormous impact in a short time. What happened? Well, the dinosaurs left their niche to the mammals and thanks to that we are here. In other words, each great extinction event, and there have been five and there is talk of ours being the sixth, causes some species to disappear and others to evolve and occupy their niche. The Earth passes to a different state of equilibrium, but it continues on. When it is said that our planet is in danger, that’s not quite it: our current way of life on the planet is in danger.
Q. And a change in our lifestyles would prevent it?
TO. Of course! If we consume fewer resources and burn fewer fossil fuels, we will reduce greenhouse gases and slow down sea-level rise. That’s why the geological perspective and distinguishing this moment is important. Now we are the ones in danger.