Extinctions and Optimism

11/13/25 - What a recent study says and doesn't say about extinctions

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Hello everyone:

As always, please remember to scroll past the end of the essay to read some curated Anthropocene news.

Now on to this week’s writing:

What happened

If recent political news reminds us how easily we, at the voting booth, can forget the dark forces that have shaped recent human history - fascism, profit-driven dictatorship, racism, misogyny, corruption, and religious nationalism, to name a few - it should also serve as a reminder that we are nearly blind to the vastness of Earth history. I’m not referring, as I often do, to what we’ve forgotten about the intricacies of nature and the balm of a deeper relationship with it. I’m referring literally to the history of the Earth, the deep, deep span of time we can scarcely conceive of, much less inhabit.

Tell me, for example, what 220 million years means to you. Or what meaning can we make, in our mayfly-like little lives, of the Paleozoic?

The few shamans among us who are capable of thinking in terms of eons are known as geologists. But because they are story-telling humans like us, they define the timeline of Earth history not as a continuous flow of life in all its myriad forms but as episodes marked by the violence and loss of major transitions in that flow. That is, what distinguishes one eon, era, or epoch from the next in our geologic time scale is often the disappearance of particular species in the fossil record. Sometimes those markers are the extraordinary disappearance of much of life on Earth.

The most severe punctuation between eras are what we call mass extinctions, defined variously as the loss of 50% or 75% of all species in less than a million years. There have been five so far: the End-Ordovician (86% of species going extinct), Late Devonian (75%), End-Permian (96%), End-Triassic (80%), and End-Cretaceous (76%). (See the graphic above for details, and at the graphic below for the entire geological time scale.) These catastrophic events were, respectively, 444 million years ago (mya), 360 mya, 250 mya, 200 mya, and 65 mya. That last one, the End-Cretaceous, is the one we know best, because we’ve popularized the tale of an asteroid killing off the dinosaurs and allowing - after millions of years - the rise of mammals, including us.

You’ll find no better source on the story of these cataclysms in Earth history than The Ends of the World by Peter Brannen. I highly recommend it. He guides us with good humor, thoughtful conversation, and deep research through each of the Earth’s mass extinctions and then, finally, into a discussion of how this Anthropocene moment you and I occupy does - and does not - resemble those vast erasures of life on Earth.

“The five worst episodes in earth history have all been associated with violent changes to the planet’s carbon cycle,” he writes, somewhat ominously. But, he explains,

Though we’ve proven to be a destructive species, we have not produced anything even close to the levels of wanton destruction and carnage seen in previous planetary cataclysms.

Crossing that line would mean not merely devastation in the human moment, but deep into a future that exists on an entirely inhuman scale. As I wrote in an early Field Guide essay, “It’s About Time,” Brannen teaches us that a mass extinction event

will take hundreds of thousands of years to balance out the carbon cycle, a hundred thousand years for the oceans to de-acidify, and millions to tens of millions of years to correct for the crash in biodiversity.

In re-examining the “Big Five” extinction graphic above, I find myself focusing not on the big five but on the many smaller but still devastating spikes scattered between them, and then on the question mark above the dotted possibilities of increasing human impacts on the far right. How does this story end?

The common wisdom about biodiversity in the Anthropocene is that it is in steep decline and that the losses are piling up. The normal extinction rate for life on Earth has been accelerated by human population growth and our resource-extracting behaviors. This is part of the story I tell in the Field Guide.

But according to a new study, “Unpacking the extinction crisis: rates, patterns and causes of recent extinctions in plants and animals,” that story is much more nuanced than anyone has understood.

What didn’t happen

The study’s authors are the first to look comprehensively and quantitatively at the full history of known extinctions over the last 500 years. In addition, they examined the long list of species currently listed in the IUCN “red list” as endangered and threatened. What they found surprised them.

Humans have accelerated the natural extinction rate in recent centuries, but the data suggest that extinctions have actually declined a bit in the last century. What this suggests is that, so far, “peak extinction” in this human epoch is not now. It was about a hundred years ago.

Many of the extinctions at that peak occurred on islands full of endemic species (living only on those islands), who were overrun by invasive species (introduced by us) that either ate, outcompeted, or displaced them. Another large cluster of erased species were in freshwater habitats, victims of the brutal mix of habitat loss, exploitation, invasives, and pollution we still face today. Our understanding of exactly what drove each of these extinctions is spotty, but the authors estimate that habitat loss and invasives accounted for more than two thirds of all disappearances.

A warming climate over the last two centuries was found, surprisingly, not to have increased extinctions. Not yet, anyway. And this brings me to the authors’ main point: Not only have we not properly understood what was happening with the extinction rate, but what we do know suggests that we cannot extrapolate the earlier increase in extinctions to understand the threats to biodiversity now.

The lead author phrased it this way: “To our surprise, past extinctions are weak and unreliable predictors of the current risk that any given group of animals or plants is facing.” As a review of the study in Phys.org put it,

The paper argues that claims of a current mass extinction may rest on shaky assumptions when projecting data from past extinctions into the future, ignoring differences in factors driving extinctions in the past, the present and the future.

How should we read this? Have we turned the tide on extinctions? Or have we merely stemmed the previous impacts through good conservation work while much larger threats (based on population, exploitation technology, pollution, and habitat loss) continue to gather steam?

The study’s authors have been at pains to explain that their conclusions are not cause for blind optimism. Climate change (i.e. disturbing the planetary carbon cycle) is still a threat to the stability of life everywhere, and the current rate of biodiversity loss is still a crisis. The authors have done the hard work of data analysis to paint a realistic portrait of the fate of life on Earth, because until now we have relied on short-term impressions and fear. As the lead author said,

If we’re saying that what is happening right now is like an asteroid hitting Earth, then the problem becomes insurmountable... By looking at the data in this way, we hope that our study helps inform our overall understanding of biodiversity loss and how we can come up with better ways to address it.

In interview after interview, the authors emphasize what their report does not conclude: “we do not downplay the current extinction crisis or future risks to biodiversity.” What “Unpacking the Extinction Crisis” does, instead, is explain in great detail that the crisis and those risks “might be very different from these patterns of past extinctions over the last 500 years.”

map of Pangaea (supercontinent from 200-300 million years ago), with modern borders written in / credit: Massimo Pietrobon, via Visual Capitalist

What is happening

Homo sapiens are a recent Pleistocene/Holocene blip in terms of our time on Earth, but in a geological nanosecond our population and culture have metasticized into something like a CO2-spewing supervolcano. Looked at another way, the impacts of our species have not arrived as quickly as those from the End-Cretaceous Manhattan-sized asteroid, but they’re certainly occurring faster than the millennia of volcanic purges that led to other mass extinctions. We’re neither asteroid nor supervolcano, of course, but we are consciously exhibiting symptoms of both. For now.

As Brannen explained, we are not in a mass extinction event, not by a long shot, but despite the slight decline in the Anthropocene extinction rate over the last hundred years, we are on the path to one. How far down that path we travel, and what size spike in the extinction chart we create, is up to us.

If the new normal of Homo sapiens impacts on Earth’s fabric of life now has a newer normal - global heat and habitat loss rather than island invaders, say - then we must pay very close attention to those species and habitats that are most threatened.

There’s a lot to pay attention to. Unique in Earth history, we’ve created a de facto Pangaea by stitching the continents back together through the mass exploitation of supplying stuff for 8.2 billion humans through international trade. Each landmass, to different degrees, is comprehensively altered by human activity. The oceans too are rapidly warming, acidifying, and deoxygenating, and ocean currents essential to a stable climate are already slowing down.

Habitat loss means species loss. When less than half of native grassland in the Americas remain, when 64% of the Earth’s wetlands have been erased, when tropical and northern forests burn, when most of the world’s rivers are dammed, etc., the innumerable species (from mammals to microbes) who have evolved together in extraordinary ways are pushed to the brink. Most have nowhere else to go. Grassland birds and freshwater mussels may not be gone, but they exist in fragments that a hotter world may not sustain.

The good news is that we are paying attention. In fact, the care and attention we now offer threatened species and their habitats may be the primary reason the extinction rate has declined in the last century. Conservation is working, across the Earth. Every day there are heartening stories of threatened species brought back from the brink or given safe haven. A quick glance at recent reports finds good news for American crocodiles in Florida, bumblebees in the UK, Darwin’s frog in Chile, green sea turtles around the world, and many more.

And as

Amanda Royal

pointed out recently, this isn’t simply happening. This is people doing the good hard slow work of conservation biology and habitat restoration. It’s active success, not passive recovery. These people are role models for a better Anthropocene.

But those recovered populations are almost always well below historic levels. Some exist only as a handful of survivors being nurtured heroically toward an uncertain future. It is worth noting that the recovery of green sea turtles has allowed the IUCN to improve their listing from Endangered to Least Concern even though their population is still a fraction of what it once was. The same is true of, say, Western Meadowlarks and Tree Swallows, both of which are listed as Low Concern despite having lost a third of their population in the last half century.

We must remain aware that survival is not the same as resilient abundance. When the lead author of the extinction study says that “Biodiversity loss is a huge problem right now, and I think we have not yet seen the kinds of effects that it might have,” I think it’s reasonable to assess our current relationship to the extinction rate this way: We have the compassion and capacity to rescue species and preserve habitats, and continue to do admirable work against the tide of our impacts to the natural world, but even as small bulwarks for frogs, bees, lemurs, and corals are maintained, whole continents and oceans are still being transformed. Despite extraordinary progress on many fronts, we are still fragmenting and thinning nature down to the nub.

The extinction rate is not what we thought it was, but the future remains unclear.

bee in solar farm meadow / credit: Dr. Hollie Blaydes, source

What might happen

Through four and a half years of writing the Field Guide, I’ve had to be careful about falling into the trap of a declensionist narrative - everything is getting worse - while being as honest as I can about what the world really looks like. I struggle to balance a handful of Darwin’s frogs rescued from chytrid fungus against, say, ocean acidification and a climate-caused tipping point for coral bleaching. Do I focus on pollinators thriving in solar farm meadows, or on dark taxa, the millions of unknown species that may be lost before being known and protected? Do I worry aloud about reports that untouched tropical forests are already losing insects in a warming world or hail reports that show tropical deforestation is on the decline?

But the world is still beautiful, and I try to attach both types of stories to that fundamental truth.

I don’t write much about hope, because it means very different things to different people. But in preparing this essay, I came across two formulations that I think are relevant here.

Julie Gabrielli

writes in “Functional Hope Tempers Despair” that “Hope is a holy force that flows through all of life, whether we’re aware of it or not.” And

Rhett Ayers Butler

writes in “A Final Reflection on Jane Goodall” that for Goodall “hope was the bridge between knowledge and action, and she practiced it with the rigor of a scientist.” And this:

Jane measured [hope] in perseverance. She knew that visible wins, however small, sustain people through slow, grinding work. Clean a polluted stream and you see the fish return. Restore a forest and you feel the air cool. These are feedback loops of hope—tangible reminders that action changes outcomes.

This new study on biodiversity loss and the extinction rate highlights the tension between optimism (extinctions have declined) and clear-eyed concern (we’re transforming the Earth faster than much of life can adjust). The image I keep coming back to is of those smaller spikes in the mass extinction graphic. In between our optimism that a better Anthropocene has arrived and our fear that we’re headed for a mass extinction is the more likely possibility that isn’t often discussed: A sizable disruption and erasure of life that doesn’t reach the “mass extinction” definition.

I wish we would talk about “mass extinctions” the way we talk about “mass shootings” (mostly here in the U.S.), as truly horrifying events even if the slaughter of innocents is, say, 2% or 5% of the crowd rather than 75%. Each extinction, whether mussel or moa, sedge or sequoia, wasp or worm, unravels millions of years of evolution and an as-yet-unmapped suite of relationships that encircled each species.

Extinction, as they say, is forever, and most of us are unequipped to think about forever.

I have a softball-sized, 220 million-year-old Glossopteris seed fern fossil from Antarctica on my shelf here. It’s a window into an era in which the now-frozen continent was near enough to the equator that trees grew cheerfully under a younger sun. All Glossopteris species went extinct in the End-Permian cataclysm. By the time I found the fossil, it was isolated on an Antarctic nunatak and had been polished by wind-driven sand for thousands of years. It’s my talisman for conjuring up the vastness of Earth history, though there’s only so far my mind can travel in that direction.

But the fossil is a reminder that we live in relationship with deep time, and that even in our mayfly-like little lives, we get to decide what that relationship will be.

author photo

Thanks for sticking with me.

In other Anthropocene news:

The newest book by Peter Brannen is The Story of CO2 is the Story of Everything, and though I haven’t read it yet I’m willing to bet that it is as astonishing and necessary as The Ends of the Earth. Here’s climate scientist Kate Marvel’s effusive quote about it:

What a brilliant and epic book this is! From the magical transformation of CO2 into the first life to our current flailing attempts to pump less of it into our atmosphere, Brannen gives us a sweeping history of the planet in a single molecule. I study this stuff for a living and still learned so much—how coal nearly froze the planet, why the rocks beneath our feet allow us to breathe, and the origins of our modern industrial world. This book is a collection of wonderful things woven together into a fascinating, terrifying whole.

From the always-astonishing Maria Popova at The Marginalian, “How to be a Lichen,” an eloquent evocation of all the lessons that these miracles of evolution can teach us, with references to space travel, Beatrix Potter, and poet Elizabeth Bishop along the way.

From Current Affairs, “There are Many Threats to Humanity: A Low Birth Rate Isn’t One of Them,” an essay from earlier this year dismantling much of the pronatalist nonsense that has become increasingly common on both the hard right and the left. The author makes the mistake of describing current threats to biodiversity a mass extinction event, but otherwise does well in describing the world as it is, and in what ways it might improve with a declining human population.

From Reasons to be Cheerful, “In Goats We Trust,” a beautiful and fascinating story about the new age in conservation work, using tiny transmitters on wildlife to transmit via satellite an incredible trove of data. This new technology deepens our relationship with the natural world by allowing us real-time observations far beyond what we can see with our eyes:

“Biologists,” he adds, “now want to understand the vast wealth of invisible knowledge animals have that emerges only when we analyze their interactions with each other and with their environment.”

From Frontiers in Ecology and the Environment, an illustration from a study on the role of the arts in conservation biology (hat tip to

Michelle Nijhuis

and her latest excellent Conservation Works post for the link):

credit: J Malumbres-Olarte

Finally, from Guest Editions, The Anthropocene Illusion, a large-format book of photography by Zed Nelson highlighting how “humans immerse ourselves in increasingly simulated environments to mask our destructive divorce from the natural world.” CNN has a review as well:

credit: Zed Nelson/Institute