An international scientific review gathered evidence from five continents showing how human activity has left measurable marks on the planet’s geological records, especially from the mid-20th century onward. Even stalagmites in remote caves preserve signs of industrialization and nuclear weapons tests, fueling the debate over the Anthropocene.
Published in the journal Nature Reviews Earth & Environment, the study gathered evidence from 12 sites across five continents, drawing on natural records such as lake sediments and deep-sea sediments, ice cores, peatlands, coral reefs, and cave formations. The researchers identified indicators associated with human activity, including radioactive waste from nuclear weapons tests, byproducts of fossil fuel combustion, and changes in the carbon and nitrogen cycles. Although human influence on the environment dates back thousands of years, the signals recorded in these archives become stronger and more widespread from the 1950s onward, during the rapid post-war industrial and economic expansion.
Andrea Borsato, associate professor at the University of Newcastle and the only researcher from an Australian institution among the 29 authors of the review, contributed stalagmite data from the Grotta di Ernesto cave in the Italian Alps. These calcite formations grow slowly as carbonate-rich water drips from the cave ceiling, preserving information about environmental conditions over time.
Through dating techniques and geochemical analysis, the team identified signals associated with industrial activity and nuclear tests. Unlike lake sediments and ice cores, cave records do not directly capture atmospheric signals: soil acts as a natural filter, potentially delaying or attenuating some of these traces. Nevertheless, stalagmites allow the identification of significant environmental changes related to human activity.
The conclusions contribute to the Anthropocene debate, the concept used to describe human influence on a planetary scale. Since 2009, the Anthropocene Working Group has evaluated the possibility of formally recognizing this phase as a new epoch on the geologic time scale, distinct from the Holocene.
The proposal was rejected in 2024, but the scientific discussion continues. For Borsato, a formal definition would help distinguish the long-term human influence on local environments from the more recent global changes, now clearly identifiable in the geological records. The University of Newcastle’s investigation continues in caves of the Pacific, including the Cook Islands, Tonga, and French Polynesia, to better understand how these environments preserve signals of environmental changes.
