If marine fossils could talk, they'd probably tell us to pack our bags. Because what the foraminifera of the ocean floor are revealing doesn't leave much room for optimism. These single-celled organisms, which have survived no less than five mass extinctions, have recorded in their calcareous shells a climate history that makes our worst ecological nightmares look like Sunday strolls.
And do you know what the most worrying fact is? We are repeating the same mistakes of the past, but at an accelerated speed. As if nature had pressed the fast-forward button on a horror movie already seen too many times.
The invisible guardians of the earth's memory
When you look at a handful of sea sand, you probably don't think you're holding one of the most detailed historical archives on the planet. Yet those grains could contain thousands of fossil foraminifera, tiny protozoa that for over 500 million years have documented every single climate change on Earth. Planktonic foraminifera are unicellular marine organisms with calcitic shells that live in the surface part of the oceans., recording in their shells the chemical-physical conditions of the waters in which they develop.
Their importance is such that paleoclimatologists consider them “living thermometers” of ancient oceans. Each time a foraminifer dies, its shell is deposited on the seafloor, creating layer after layer of a continuous record of the temperatures, salinity, and even oxygen levels of the oceans of the past. As highlighted by recent studies, these calcareous nannofossils allow us to reconstruct the climate of specific areas of the Earth going back as far as 200 million years.
Marine Fossils: Professional Survivors of the Apocalypse
What makes foraminifera so valuable to climate science is their extraordinary ability to survive. They survived the extinction that wiped out the dinosaurs 66 million years ago unscathed., when an asteroid (or were there two?) hit the Earth creating conditions that wiped out 75% of living species. Evidence of this catastrophic event It was found right here in Italy, in the Bottaccione gorge in Umbria, where marine fossils have documented the moment of impact with millimetric precision.
But the asteroid wasn't the only enemy they had to face. Foraminifera have recorded every single mass extinction, including episodes of extreme global warming such as the PETM (Paleocene-Eocene Thermal Maximum), which occurred 56 million years ago. An international study coordinated by the Max Planck Institute analyzed these microfossils to understand how the oceans responded to a temperature increase of 5 degrees Celsius in geologically rapid time.
The alarm of the present
What worries researchers most is the speed of current change. During the PETM, ecosystems took more than 100.000 years to recover to their pre-event state. Today, changes in ecosystems are occurring at an extremely rapid rate.. A study published in Nature demonstrated that current marine plankton assemblages are markedly different from those of pre-industrial times, confirming that marine ecosystems have now entered the Anthropocene.
Globigerinella warm , caught in the southwestern Indian Ocean with a plankton net in 2009. The tentacles it uses for feeding and movement are clearly visible, and extend a significant distance from the shell.
The data is unequivocal: Foraminifera abundance has declined by 25% in the last 80 years. As we have pointed out in this article on the archaeological discoveries of 2023, the fossil record is showing us how quickly planetary balances can change.
Marine Fossils, the Message from the Past
Foraminifera aren’t just telling us about the past; they’re giving us the tools to understand the future. The message emerging from the world’s ocean floors is as clear as it is urgent. We are replicating the conditions that led to mass extinctions in the past, but at a rate unprecedented in Earth's history..
These tiny witnesses of time remind us that the Earth knows how to survive extreme changes. The real questions are different: will we be able to do it? And above all, will we be able to learn from their testimonies before it is too late? After all, foraminifera are offering us their 500 million year diary. It would be a shame not to read it.
