Reacción a "Reactions to the proposal of Crawford Lake in Canada as a geological reference site for the Anthropocene "

Using a lake-bottom probe as a possible GSSP for the Anthropocene is a wise decision. Sedimentary records from lake environments are excellent tools (proxies) to analyse recent environmental changes with a high temporal resolution, as a new layer of sediment is deposited on lake bottoms every year and continuously for centuries or millennia. This makes it possible to give a precise age to the main geochemical indicator considered as a possible start of the Anthropocene, the radioactive Pb signal from atomic testing. Furthermore, having this record of human-induced environmental variations from one year to the next facilitates the correlation of geological records from around the world with a precision never before achieved in geology. 

However, lake probes can have certain limitations. Lakes are very sensitive to environmental and climatic changes, recording not only global scale variations, but also local or regional scale variations, such as nearby fires, intentional modifications of water systems or human-induced alterations of fauna and flora. For this reason, it is necessary to have other possible secondary reference sections to identify, characterise and give a precise age to the changes that have occurred at a global scale, in order to separate their signals and evidence from local alterations. 

This international meeting takes the geological discussion on the possible definition of the Anthropocene as a new temporal division of the Earth's history a step further. But its ratification is only a scientific matter. On a social level, it should serve as the presentation of new, solid and rigorous scientific evidence that humans are capable of altering the natural biogeochemical cycles of our planet through our actions, which are marked in sediments all over the world. Even if, for the time being, we are still living in the Upper Holocene.