Dinosaurs, Insects, Soil, and the End of Epochs

Dinosaurs were majestic. Kings and queens of their jungles. Undisputed alphas of the animal kingdom. And then the impact came. About six miles wide, striking 66 million years ago, an asteroid (or was it a comet?) created a 90+-mile-wide crater called Chicxulub where the Yucatán Peninsula met the Caribbean Sea.

Close to the impact zone, death was likely instantaneous. Farther away—as far away as a New Jersey quarry—fossil evidence shows rapid die-off of many creatures within days, weeks, or months.

Worldwide, temperatures cooled as sulphur from vaporized rock and soot from fires filled the atmosphere. Unable to photosynthesize, plants died en masse, and the food chain crumbled, links dropping out like lights at bedtime. Eventually, about 75 percent of life on Earth—including all non-avian dinosaurs¹—was wiped out. The Cretaceous period had ended, and the Paleogene had begun.

What’s the relevance for humans in the 21st century?

We’re not facing imminent asteroid impact—at least, not that we know of. But many rungs in our food chain, from insects to mollusks to beneficial microbes, are wilting or even vanishing without fanfare or acknowledgment. If enough feedback loops kick in, this process may be irreversible and we may find ourselves, like the dinosaurs of the Cretaceous, wandering on a strange planet we hardly recognize, which has become inhospitable to us. 

Do we really live on a boundary between geologic periods, though? All human evolution has occurred in the current Quaternary period that started 2.58 million years ago (this handy chart is a good reference). Periods are divided into epochs. Early human evolution took place in the Pleistocene epoch, and modern societies arose in the Holocene epoch, which started about 12,000 years ago after the Ice Age.

A key thing to know about our Holocene epoch is that temperature has been unusually stable. This temperature stability coincided with the dawn of agriculture and the flourishing of humans across large parts of Earth. In contrast, earlier Pleistocene periods were characterized by more volatile and harsher temperature extremes.

The key question now is: have we begun to leave the Holocene behind?

That seems ominous.

Yeah. A true shift may not yet be baked in, but it’s under way. The last eight years have been the hottest eight years in recorded history. This has happened despite a La Niña weather pattern, which tends to cool temperatures, predominating for the last three years. Later this year, an El Niño weather pattern, which tends to warm temperatures, will take over.

We are not dinosaurs. The temperatures the dinosaurs faced weren’t the Holocene era’s human-friendly ones. The Cretaceous era was characterized by atmospheric CO2 levels “as high as about 2,000 ppmv, average temperatures were roughly [5 degrees to 10 degrees Celsius] higher than today, and sea levels were 50-100 meters higher.”

Ironically, dinosaurs might be more comfortable than humans in the world we’re rushing headlong toward. But they are gone, and we will have to deal with the fallout of destabilizing the Holocene. People sometimes use the term “Anthropocene” to describe the hotter, more extreme world we’re creating. Although “anthropocene” means “the period of time during which human activities have had an environmental impact on the Earth,” that world might ultimately lead to human obsolescence. 

Like dinosaurs?

Maybe more than we think. Dinosaurs likely died out when their food sources became scarce or went extinct. In our own era, climate change is affecting our smallest and most delicate lifeforms first. Take insects. Sure, some insects like cockroaches were around when T. rex still roamed and will probably be around when humans are dust. But, on the whole, Earth may have lost much of its insect biomass in just thirty or forty years.

One of the first studies came out in 2017: a 27-year assessment of 63 nature-protection areas in Germany showed a staggering 76% decline in flying insect biomass over the study period 1989-2016. Then a 2018 study of the El Yunque rainforest in Puerto Rico found an even more massive decline from 1976 to 2012. On the ground, catch traps in July 1976 collected 473 milligrams (mg) of insect biomass per trap, compared with 13 mg of insect biomass per trap in July 2012. And in the tree canopies, traps collected 37 mg of insect biomass per trap in July 1976 versus 5 mg per trap in July 2012. Unsurprisingly, frog and bird populations in that area also fell precipitously.

The data keeps accumulating. The good news about our insect-and-invertebrate apocalypse (snails and earthworms are also in trouble!) is that it’s not all because of climate change. Partially, we’re to blame for overusing pesticides and overrelying on modern till-agriculture methods that destroy the intricate web of life among roots, mycorrhizal fungi, beneficial bacteria, and critters in soil—and we can change those tactics at any time. The bad news is that climate change can also affect soil fertility, so like everything else, it’s a complex system.

There are, in fact, some nonprofits dedicated to invertebrate conservation. (Edit: if you’re interested in checking these out, they include the Xerces Society, Buglife, and Butterfly Conservation, among others.) Which is good, because although insects aren’t cuddly or publicity-friendly, they are keystones in the intricate ecosystems that keep us alive. Without bees, we starve. Without earthworms, soil structure and drainage decline. Every change in the web of life has second- and third-order effects, and those changes eventually shake our tree, too. It’s all interconnected.

So, what’s the goal for living in balance as part of nature?

It’s hard to even define a baseline for “wilderness” or “pristine nature” when we talk about ideas like rewilding, practicing regenerative agriculture, or living in harmony with the rest of our environment. That’s because humans have impacted nature throughout our time on this planet, and as more and more of us simultaneously live on Earth, our impact is ever greater. As J.B. MacKinnon wrote in his wonderful book The Once and Future World, “Research today considers new questions: How much balance is normal in nature, and how much change? At what point does change become damage? In what ways is natural change different from the changes wrought by human influence?”

Dinosaurs, for all their size and dominance, were part of the planet that supported them, occupying their own evolutionary niche alongside other creatures and plants, until the external shock of the asteroid displaced them. Humans, if we ever occupied such a harmonious niche, left it behind long ago, consuming and growing and extending our domain until it encompassed nearly the entire planet. Our impact is becoming the equivalent of an asteroid for other species—a destabilizing force that is shifting the planet away from the Holocene and toward a new and unknown era. 

If we don’t want to end up like the dinosaurs, diminished and eventually forgotten, we would do well to study the inherent patterns of nature and seek to bring the system back into balance, not to hit the gas pedal harder and accelerate our impact.

1. Birds are descended from avian dinosaurs. So have some respect for that sparrow giving you the side-eye on the patio.