Species are currently going extinct somewhere between 100 and 1,000 times faster than what the fossil record suggests is normal, depending on which baseline estimate researchers use and which group of organisms they examine. That range is not vague hand-waving; it reflects a genuine scientific disagreement about what “normal” even means when you’re measuring disappearances across millions of years of geological time. The gap between the lowest and highest credible estimates still points in the same direction, though, and what that direction tells us about the state of life on Earth is worth understanding in some detail.
What Counts as a Normal Extinction Rate
Every species that has ever existed will eventually go extinct. Roughly 99 percent of all species that have lived on Earth are already gone. Extinction is not just normal; it is the default outcome over long enough time spans. The question is how fast that turnover happens during the stretches of geological time between catastrophic events like asteroid impacts or massive volcanic episodes. Scientists call this the “background rate,” and pinning it down is surprisingly contentious.
The background rate is usually expressed as extinctions per million species-years, abbreviated E/MSY. One widely used estimate, drawn from fossil data on mammals, puts the background rate at about 2 E/MSY, meaning roughly two species per 10,000 would be expected to disappear every century under normal conditions. A more recent analysis, however, concluded that typical background extinction rates are closer to 0.1 E/MSY, roughly twenty times lower than that older figure.1PubMed. Estimating the normal background rate of species extinction The difference matters enormously when you start calculating how far above normal the current rate sits. If the background rate is 2 E/MSY, today’s losses are perhaps 100 times worse than expected. If it is 0.1 E/MSY, the multiplier jumps to around 1,000.
Why can’t researchers agree? The fossil record is incomplete and biased toward organisms with hard shells, bones, or teeth that preserve well. Soft-bodied creatures, small insects, and tropical species leave fewer traces. The time resolution of the fossil record is also coarse: a “moment” in deep time might span tens of thousands of years, smoothing over short-lived spikes in extinction that would be invisible to a paleontologist but devastating to the species involved. Different methods of reading that record yield different baselines, and the honest answer is that the true background rate is somewhere in the range between those two estimates, with increasing evidence favoring the lower end.
How Today’s Rate Compares
Even when researchers deliberately stack their assumptions to minimize the apparent severity of modern extinctions, the numbers are stark. A 2015 analysis used the higher background rate of 2 E/MSY as its benchmark and still found that the average rate of vertebrate species loss over the past century was up to 100 times greater than that baseline. Under that conservative framing, the vertebrate species confirmed extinct in the last hundred years would have taken between 800 and 10,000 years to vanish at normal rates, depending on the group examined.2PubMed Central. Accelerated modern human-induced species losses: Entering the sixth mass extinction
When the lower and arguably more accurate background estimate of 0.1 E/MSY is used instead, current extinction rates come out at about 1,000 times above normal, with projections suggesting future rates could reach 10,000 times higher.3PubMed. Estimating the normal background rate of species extinction A separate review in Science reached a similar conclusion, placing current rates at roughly 1,000 times the likely background.4PubMed. The biodiversity of species and their rates of extinction, distribution, and protection These figures have led many biologists to describe the present moment as the onset of Earth’s sixth mass extinction, following the five major die-offs visible in the geological record, the most recent being the asteroid-driven event that ended the age of dinosaurs about 66 million years ago.
For context, the worst mass extinction on record, at the end of the Permian period around 252 million years ago, wiped out an estimated 81 percent of marine species, though that figure is lower than the 90 to 96 percent often cited in popular accounts. Those higher numbers were based on calculations that incorrectly lumped together two separate Permian extinction pulses.5PubMed Central. Estimates of the magnitudes of major marine mass extinctions in earth history Even with the corrected figures, that event was catastrophic. The concern is not that we are there yet, but that the trajectory of current loss rates, if sustained or accelerated, puts us on a path toward comparable devastation over the coming centuries.
Why Counting Extinctions Is Harder Than It Sounds
Declaring a species extinct requires a high burden of proof. You have to demonstrate, essentially, that it no longer exists anywhere on Earth, and proving a negative is inherently difficult. The International Union for Conservation of Nature requires exhaustive surveys over appropriate time frames before listing a species as extinct, and many scientists are understandably reluctant to make that call for species that might just be hiding in some unsurveyed patch of forest or reef. Each year, two or three species previously thought to be extinct are rediscovered.6PubMed. Extinct or still out there? Disentangling influences on extinction and rediscovery helps to clarify the fate of species on the edge Even in well-studied groups like mammals, species with long gaps in their sighting records are sometimes found alive.7PubMed Central. Correlates of rediscovery and the detectability of extinction in mammals
This detection problem cuts in both directions. Rediscoveries make the official count of confirmed extinctions slightly lower than reality, but a far larger effect works in the opposite direction: the vast majority of species on Earth have never been formally described by science at all. We know of about 1.5 to 2 million named species, but estimates of total species range from 8 million to over 10 million. Species can go extinct before anyone realizes they existed. The confirmed extinction tally is, by every serious estimate, a floor, not a ceiling.
Researchers also grapple with time lags. When a forest is fragmented into isolated patches, some species may persist in those patches for years or decades before their populations finally collapse. This phenomenon, known as extinction debt, means that habitat destruction today locks in future species losses that have not yet been tallied.8PubMed Central. Habitat fragmentation causes immediate and time-delayed biodiversity loss at different trophic levels The species are still there to be counted, but their fate is already sealed. Any snapshot of current extinction numbers misses this slow-motion wave still working its way through fragmented ecosystems.
One common shortcut for estimating extinction is the species-area relationship, a mathematical pattern that links the area of habitat to the number of species it supports. But how well this works depends heavily on context. When remaining habitat drops below roughly 20 percent of the original landscape and what remains is highly fragmented, the standard approach tends to underestimate the number of species headed for extinction.9PubMed. Species-area relationships and extinctions caused by habitat loss and fragmentation In other words, the tools scientists use to project future losses may themselves be too optimistic in the most degraded landscapes.
Which Species Are Most Vulnerable
Extinction does not hit all organisms equally. Amphibians are in the worst shape of any well-studied vertebrate group. About a third or more of the world’s roughly 8,000 known amphibian species are threatened with extinction, and that fraction is expected to grow because most amphibians live in the tropics with small geographic ranges.10PubMed Central. Are we in the midst of the sixth mass extinction? A view from the world of amphibians A single disease, the chytrid fungus Batrachochytrium dendrobatidis, has driven the decline of at least 501 amphibian species over the past half-century, with 90 of those presumed extinct.11PubMed. Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity Some of these disappearances happened inside protected areas, where habitat loss was not the issue. The golden toad of Costa Rica, famously, vanished from an intact cloud forest reserve.12PubMed Central. Coincident mass extirpation of neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis
Island species have been disproportionately destroyed. Since 1500, 95 percent of recorded bird and terrestrial mammal extinctions have occurred on islands. Only six continental bird species and three continental mammal species were recorded as going extinct over that period, compared to 123 bird species and 58 mammal species on islands.13Diversity and Distributions. Historical bird and terrestrial mammal extinction rates and causes Island species evolved without the predators and competitors that mainlanders face, leaving them catastrophically naive when rats, cats, or humans arrived.
Insects present a different kind of problem. They are the most species-rich group of organisms on the planet, but our knowledge of them is riddled with gaps. Monitoring data is geographically patchy, concentrated mainly in parts of Europe, and taxonomic effort skews toward showy groups like butterflies and beetles. The accelerated loss of insect species likely outpaces the rate at which new species are being described, meaning the extinction ledger is deeply incomplete.14Ecological Entomology. Geographical, temporal and taxonomic biases in insect GBIF data on biodiversity and extinction We are almost certainly losing insect species we have never named, and because insects underpin pollination, decomposition, and food webs, those losses carry outsized consequences.
What Is Driving the Acceleration
Habitat destruction is the dominant cause of modern extinction by a wide margin. An analysis of over 20,000 threatened species found that about 88 percent were affected by habitat destruction, and for more than 71 percent of those species, it was the single most important factor pushing them toward extinction. Overexploitation (hunting, fishing, harvesting) was the primary threat for about 7 percent, invasive species for about 7 percent, pollution for about 5 percent, and climate change for under 2 percent.15Conservation Science and Practice. The greatest threats to species
That last number surprises people, and it needs context. Climate change’s contribution to confirmed extinctions is small so far, but it is projected to become enormous. A recent meta-analysis found that extinctions will accelerate rapidly if global temperatures exceed 1.5°C above pre-industrial levels, and the highest-emission scenarios could threaten roughly a third of all species.16PubMed. Climate change extinctions The 2-percent figure reflects where we have been; the projections describe where we are heading. Climate change also interacts with habitat loss in ways that amplify both: a species trapped in a small fragment of forest cannot migrate to track its preferred temperature range.
Habitat conversion is also not random. People tend to clear land in the most productive, species-rich areas first, which means habitat loss is spatially concentrated in exactly the places where it does the most damage. This nonrandom pattern causes species losses to exceed what simple area-based models predict.17PubMed Central. Extinction rates under nonrandom patterns of habitat loss Tropical lowland forests, coastal wetlands, and fertile river valleys are the first to go. The biodiversity-poor landscapes that humans leave behind are not a representative sample of what was there.
When Species Loss Cascades
Counting extinct species, one by one, understates what is actually happening ecologically. When a species vanishes, it takes its relationships with it. Parasites, pollinators, seed dispersers, and prey all depend on specific partners, and the loss of one can trigger the loss of others. Models suggest that this kind of cascading disappearance, called coextinction, may be the most common form of biodiversity loss overall.18PubMed Central. The sixth mass coextinction: are most endangered species parasites and mutualists? A fig tree goes extinct, and with it the specialist wasp that pollinated it, the birds that ate its fruit, and the parasites that lived on those birds. None of those secondary losses may be formally tallied as extinctions for years.
Researchers have found that the loss of ecological interactions, the relationships between species, often outpaces the loss of the species themselves. A pollinator and a plant might both survive in a degraded landscape but no longer encounter each other often enough to sustain their mutualism. The species persist on paper, but the function they performed together has already vanished.19Functional Ecology. Beyond species loss: the extinction of ecological interactions in a changing world This means that ecosystem services like pollination, seed dispersal, and pest control can erode well before the species providing them officially disappear. Extinction rates, as usually measured, capture only the most extreme endpoint of a long degradation process.
What Conservation Has Actually Achieved
In the face of these numbers, it is worth asking whether conservation efforts make any difference. The evidence says they do, and substantially. A study of birds and mammals estimated that targeted conservation action prevented between 28 and 48 extinctions since 1993. Without those interventions, the extinction rate for those two groups would have been roughly three to four times higher than what was actually observed.20Conservation Letters. How many bird and mammal extinctions has recent conservation action prevented? The species that were saved include some dramatic recoveries, from captive-breeding programs for the California condor to predator-control campaigns on remote island nesting grounds.
A broader meta-analysis of 186 conservation studies across diverse taxa and ecosystems found that in two-thirds of cases, conservation either improved the state of biodiversity or at least slowed its decline compared to doing nothing. Interventions aimed directly at species and ecosystems, such as controlling invasive species, reducing habitat loss, restoring degraded areas, and establishing protected zones, consistently showed large positive effects.21PubMed. The positive impact of conservation action The caveat is scale. Conservation works where it is applied, but the scope of current efforts is far short of what global biodiversity targets would require. International targets set under the Convention on Biological Diversity have repeatedly been missed; a mid-term assessment of the 2011-2020 targets found that despite accelerating policy responses, improvements in actual biodiversity trends were unlikely to materialize by the target date.22Science. A mid-term analysis of progress toward international biodiversity targets
The gap between what conservation can do and what it is being funded to do is enormous. Protected areas cover about 17 percent of land and around 8 percent of ocean, but many of those protected areas are inadequately managed or located in places with relatively low biodiversity. The 2022 Kunming-Montreal Global Biodiversity Framework set a target of protecting 30 percent of land and sea by 2030, but meeting that goal will require an unprecedented expansion of both protected area coverage and enforcement.
New Tools for Finding and Restoring Lost Species
Technology is changing what is possible on both ends of the extinction problem. On the detection side, environmental DNA, or eDNA, allows researchers to find traces of species in water, soil, or air samples without ever seeing the animal itself. A species might be too rare or too elusive for traditional surveys, but it sheds DNA into its environment, and that DNA can be picked up with sensitive molecular techniques.23PubMed Central. Robust detection of rare species using environmental DNA: the importance of primer specificity This has already helped rediscover species thought to be locally extinct and is becoming a standard tool for monitoring biodiversity in rivers, lakes, and marine environments. It is especially useful for species that live in places where visual surveys are impractical, like deep-water fish or burrowing amphibians.
On the more speculative end, de-extinction technologies are being developed to bring back species that are already gone or to restore lost ecological functions to degraded ecosystems. These efforts use gene-editing tools to modify the genomes of closely related living species, essentially engineering a proxy for an extinct one. The primary motivation is ecological: restoring the role an extinct species played in its ecosystem, such as seed dispersal or grazing, rather than simply resurrecting a charismatic animal for its own sake.24Journal of Heredity. De-extinction technology and its application to conservation The same gene-editing technologies can be applied to living endangered species in a different way, introducing genetic diversity into small, inbred populations or conferring resistance to diseases that are currently driving declines. Whether any of this will work at scale remains to be seen, but the toolkit available to conservation biologists is expanding rapidly.
The tension in the field, though, is that de-extinction and high-tech monitoring risk becoming attractive distractions from the unglamorous work that actually prevents extinction: protecting habitat, controlling invasive species, and enforcing harvest limits. Every dollar spent engineering a woolly mammoth proxy is a dollar not spent keeping the last population of some unremarkable freshwater mussel alive. The species quietly going extinct right now are not the ones likely to be resurrected by a biotech startup. They are small-ranged tropical invertebrates, unnamed fungi, plants in a forest fragment being cleared for agriculture. The extinction rate will be determined mostly by decisions about land use, not by the sophistication of the tools we use to count or resurrect what we have lost.