Extinction is forever. Once the last individual of an animal, plant, or other living species dies, that entire species is gone and will not evolve in the exact same form again. The popular image of extinction is one of disastrous, sudden death—dinosaurs wiped out by an asteroid, say, or rainforest creatures plowed under along with their precious habitat. But extinction can also be a slower, subtler process. Many species disappear without any fanfare at all, and though extinction may be a common end for most, if not all, species, how that end comes varies.

A Brief History of Extinction

In the early history of Western science, the concept of extinction could be a controversial or scandalous idea. That the Christian God would have allowed whole kinds of creatures to die out was, to some, blasphemy against the perfection of His plan. After all, even when humanity was punished by the Biblical flood in the Genesis story of Noah, all the animals and a few lucky humans were allowed on his ark. Indigenous people have found evidence of large extinct animals for millennia, and when scientists started to collect and study fossils, it was hard to avoid the conclusion that at least some species had existed, and then had not.

In 1758, Carl Linnaeus published the tenth edition of his life’s work, the Systema Naturae. Before Linnaeus, “species” was used to describe not only kinds of life, but kinds of anything. A seventeenth-century writer would be as likely to talk about species of storms or desks as of birds. Linnaeus didn’t invent the words species, genus, family, and so on, but he did popularize them, giving scientists the vocabulary to describe the life they saw—and that had already disappeared.

Even as extinction gained traction as a scientific theory, resistance to it by many Christian leaders limited its broader acceptance. One way to relieve this pressure between doctrine and growing evidence was to question whether these creatures were extinct at all. In 1790, a farm worker employed by Reverend Robert Annan unearthed a largely intact skeleton of a what would come be called a mastodon, an extinct relative of the elephant, in New York. With so much of North America still out of reach of European colonists, he thought these huge creatures might still be found alive, somewhere out west. In a paper addressed to the American Academy of Arts and Sciences, he wondered if he should

… suppose the species to be extinct over the face of the globe? If so, what could be the cause? It is next to incredible, that the remains of this animal could have lain there since the flood. May there not be some of the kind surviving, in some of the interior parts of the continent? Comparatively little of it has been explored.

One discovery in particular made widespread extinction all but impossible to ignore or deny. In 1824, William Buckland stood before his peers in the Geological Society of London and described a 40-foot reptile he called Megalosaurus, or “great lizard.” It was the first formal scientific description of a group of creatures that would fascinate the world for centuries: the dinosaurs. Although some may have dreamed of an island or other sanctuary where these giants still roamed, as new finds piled up, it became clear that they had once been common over large areas of the world. This wasn’t a case of a few remnants missing Noah’s boat. Extinction had taken place, and it had wiped out a large variety of species.

Some early scientists may have seen extinction as a thing of the past, a disaster that befell dinosaurs and mastodons, in a period before humanity roamed the Earth. But it didn’t take long before humans started to record extinctions in the present tense: the Great Auk in 1844, the Labrador Duck in 1875, and the Falkland Islands wolf a year later. And then there’s the loss of the dodo—the era’s most famous extinction object lesson; modern researchers now posit it went extinct at least 150 years before it was reported to have done.

Local Extinction, the Slow Drip of the Biodiversity Crisis

The extinction wave that followed European expansion and colonialism tended to have a common theme. Most of the species snuffed out in that period, at least the ones that were recorded, inhabited islands or other small territories. Human populations were growing but had not yet exploded into the billions. A wide-ranging species could still stand a chance of avoiding humanity. But these species were declining too, just less conspicuously than the island ones, and their wide ranges would only protect them for so long.

In 1924, a road crew recorded the last verified sighting of a grizzly bear in California. For a century, the symbol of the state, emblazoned on its flag, has been missing. The Golden State has lost its golden bears. Grizzlies are a subspecies of the brown bear, Ursus arctos, and brown bears are still relatively common in some parts of their range, such as Alaska, Canada and Russian Kamchatka, and still dwell in Yellowstone National Park and other regions of North America. Their disappearance from California is an example of local extinction, known by scientists as extirpation. For many species, extinction is not a sudden bang, but a slow whimper of one local extinction after another, often occurring so lethargically that we fail to notice it until it’s too late. Local extinctions can be especially hard to diagnose. From a single local perspective, a species disappearing could mean a lot of things. Their migratory pattern could have changed, or they could have simply moved to a more favorable habitat.

The Carolina parakeet once graced the skies over half of the continental United States. Our only native parrot, they nested in large colonies with a range stretching from New England to the Gulf of Mexico and west to the Rocky Mountains. But as European settlers spread west, large swaths of forest were felled to build the new towns and cities of the Midwest. The parakeet probably disappeared from its namesake Carolinas first, holding on in some of its northern and western range a little longer, until those forests finally met the ax and saw. The last sighting of a Carolina parakeet in the wild was in 1910. The final captive bird died eight years later.

Other birds, such as the sparrow-like dickcissel and the ruffed grouse, experienced similar extirpations, but held on in refuge areas, spared from complete extinction. Birds were not unique victims of this wave of extinctions, but they were probably the creatures whose loss we noticed first. Humans have always watched and followed birds, and it took time to realize that while we were recording the ends of these colorful and visible species, others were disappearing right before our eyes.

Tiny Extinctions Everywhere

As time went on, it became clearer that the extinctions we were seeing—the birds, mammals, and reptiles we had lost over the previous few centuries—were just the tip of the proverbial iceberg. Most species live in relatively small, isolated habitats. Not just on literal islands, like the homes of the dodo and Falklands wolf, but on islands of rainforest, coral reef, mountaintop, and more. Tropical rainforests, for example, cover only 6% of the Earth’s surface but house more than half of terrestrial plant and animal species. Scientists began to see the world as a patchwork of small habitats. These were homes to a few large, visible species, but also to large numbers of insects, plants, and other organisms that, though beautiful when examined closely, are easy to ignore or miss altogether.

By the 1910s, several countries, including the United States and Germany, had established government offices for the sole purpose of cataloging and preserving native plants. In 1913, A. R. Horwood of the Leicester Museum sounded the alarm that a similar agency was needed in the United Kingdom. Already, plant extinction was on the world’s radar.

By mid-century, we were starting to see extinction where we had mostly thought it to be impossible, even in modern times: the oceans. Again, the “charismatic megafauna”—in this case, whales—attracted more media attention, but fish, marine invertebrates, and others were also endangered. In 1968, British geographer David R. Stoddart published a scathing article in the journal Geography, laying out the damage human activities were having on coral atolls in the Pacific, with species both above and below the water threatened with extinction within decades.

“The number of atolls which have not, over the past century, had their biota significantly changed by conversion to agriculture is now small,” he wrote. “Where further large-scale development is envisaged on such atolls, adequate scientific studies and conservation measures must be planned in advance.”

For most of modern history, our relationship with insects was one of ignorance at best, but more often a state of outright war. The twentieth century brought new advances in the age-old conflict between humans and the insects that had plagued crops and killed humans by transmitting diseases to them. Malaria alone, spread by mosquitoes, kills over a million people a year. But as soon as we had rolled out new, wildly effective chemicals like DDT, we started seeing the effects on species other than the ones we had targeted. Our new tools were far too effective at their job, and in seeking to control the few species of insect that caused damage, humans laid waste to the thousands of species that did us no harm at all. In many cases, we killed the insects that pollinated our crops along with the ones that ate them. Rachel Carson’s landmark book Silent Spring brought attention to the DDT crisis, but not before the chemical had been applied to huge percentages of the world’s agricultural and residential land.

The extent of the modern insect apocalypse is only now becoming clear. In 2005, only seventy insect extinctions had been recorded by scientists, but University of Tennessee biologist Robert Dunn estimated that thousands more had occurred without us even taking note.

“Anecdotal evidence and recent simulations suggest that many insect extinctions may have already occurred,” he writes. “To neglect such extinctions is to ignore the majority of species that are or were in need of conservation.”

Dead (and Dying) on Arrival

Scientists have described and named about 2 million species of living things, according to the International Union for Conservation of Nature (IUCN). But even after centuries of effort, our records are woefully incomplete. By some estimates, only about 25 percent of species in the world have been formally described. Other studies say it is far less. Whatever the number, scientists are adding thousands of species to our formal tree of life every year. Many of those added in recent years are rare, endemic species, often already endangered by the time they are described. Then there’s the most invisible kind of extinction, so-called “dark extinction,” which occurs when a species becomes extinct before it is even named and its existence recorded.

The popular image of species discovery has us imagine a scientist sweating their way through a tropical forest, searching tirelessly and following hints until finally—Eureka!—finding and describing a new form of life. But just as often, this kind of work takes place in a museum. Collections, even from decades or centuries ago, still hold thousands of undescribed species, and the farther back the collection dates, the more likely that the “new” species and its entire ecosystem may already be altered or gone.

In recent decades, as if mass extinction wasn’t enough on its own, a new kind of loss has arisen that threatens to blind us even further to the scope of the crisis. Taxonomists, those scientists who describe and classify species, are themselves endangered. In the 1992 Rio de Janeiro Earth Summit, the first Convention of Biological Diversity was signed, and, along with its historic statements on extinction and species endangerment, it included a short note on the lack of both taxonomists and taxonomic resources. This gap has become known as the “taxonomic impediment.” Ironically, just when we most need new Linnaeuses to catalog life before it disappears, potential contributors are themselves disappearing, not due to a lack of habitat, but its academic equivalent, the lack of funding. Environmentalist Aldo Leopold famously said about conservation and wildlife management that “to keep every cog and wheel is the first rule of intelligent tinkering.” Not only are we losing wheels and cogs every day, but we’re also losing the science and scientists needed to count them.

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