For thirty-eight minutes on January 13, fear of an incoming nuclear ballistic missile gripped the people of Hawaii. While the warning turned out to be in error, the terror it engendered was very real. For people who grew up during Cold War, it revived memories of fallout shelters, warning siren tests, and “duck-and-cover.”
The end of the Cold War and the fall of the Soviet Union pushed the potential horror of nuclear war out of our thoughts. It did not end our fascination with world-ending devastation. Post-apocalyptic fiction remains a fixture of our cultural landscape, whether in books such as Margaret Atwood’s MaddAddam trilogy or in movies like the Mad Max series. Although climate change or disease have replaced nuclear war as the agent of destruction, the underlying cause is still the capability of humans to destroy themselves. What this fiction generally overlooks is that these catastrophes will be just as devastating for the living things that share the planet with us as it would be for humanity. Fictional or not, the ability of the natural world to survive and recover from an environmental disaster would be critical for our own survival. It is essential to understand what happens to the biosphere when global environmental catastrophes occur. And no one understands this better than paleontologists.
The recognition that extinctions happen is paleontology’s great contribution to human thought, dating back to 18th century when Georges Cuvier proved that mastodons no longer walked the Earth. Not long after, as paleontologists documented the history of life on Earth, they recognized that extinctions came in waves, the mass extinctions, with the largest episodes killing most of the species on Earth.
How many mass extinctions, how large they were, and what caused them is actively debated. What is clear is that the underlying causes were dramatic changes in the physical environment. The largest mass extinction, the one at the end of the Permian, some 250 million years ago, wiped out more than three-quarters of all species, on both land and in the sea. A growing consensus is that massive volcanism in Siberia triggered unprecedented changes in the Earth’s oceans and atmosphere, including huge outpourings of carbon dioxide and abrupt increases in temperature. The collapse of ecosystems and the resulting extinction took less than 60,000 years, an eye blink in geological terms.
The iconic mass extinction, because it claimed the dinosaurs (except the ancestors of modern birds) occurred 66 million years ago at the end of the Cretaceous. It was again a period of environmental stress due to volcanic eruptions, this time in what is now India. But this coincided with the now famous asteroid impact in the Yucatan. The result again was massive environmental disruptions and a very rapid major drop in life’s diversity.
What are the implications of the paleontologist’s perspective on past biosphere disruptions for our understanding of potential future changes? First, rapid changes in the chemistry and temperatures of the air and water could lead to the demise of numerous species in a relatively brief amount of time. Second, that although life is resilient, it may still take millions of year for ecosystems to return to some resemblance of pre-existing conditions. Third, the past is at best an incomplete model for the future. Human produced stresses on animals and plants, such as hunting, invasive species, and habitat destruction, are unprecedented in the history of life. The modern extinction, aka the Sixth Extinction, takes the biosphere into unknown territory.
Admittedly, we are far from a mass extinction. Estimates by Anthony Barnosky and colleagues suggest that we are centuries away from reaching the level of loss associated with the major mass extinctions in the fossil record. So there is still time to act and save what we still have. Unfortunately, the recent history of action on climate change and conservation gives only limited grounds for optimism.
We can only plan for a future of environmental disruptions, both fast and slow, it we understand when has happened before. Paleontologists, because of their intimate knowledge of the history of environmental catastrophes, should be active participants in this planning.