Roughly 900 documented species have gone extinct since the year 1500, and around 1 million more are currently threatened with extinction, largely because of human activity. That 900 figure sounds modest until you consider that scientists have formally assessed less than 5% of all described species on Earth. The true number of human-caused extinctions is almost certainly far higher, and the rate at which species are disappearing is between 100 and 1,000 times faster than what would happen naturally.
What the Documented Record Shows
The IUCN Red List, the most comprehensive global tracker of species survival, has recorded roughly 900 confirmed extinctions since 1500 AD. Of those, 86% were animals and 14% were mostly flowering plants along with a few ferns and mosses. That works out to an average pace of about 180 extinctions per century, or nearly two species lost every year for the past five centuries.
These numbers are conservative. They only count species that scientists formally described, monitored, and then confirmed as gone. Countless species, particularly insects, fungi, and deep-sea organisms, have likely vanished before anyone documented them. The IUCN itself cautions that because less than 5% of the world’s known species have been evaluated for extinction risk, no precise global percentage is possible from documented records alone.
How Fast Humans Are Accelerating Extinction
To understand the scale of human impact, scientists compare today’s extinction rate to the “background rate,” the normal pace at which species disappear through natural processes like competition, disease, and climate shifts. That natural baseline is estimated at roughly 0.1 to 1 extinction per million species per year. A mammal species, for instance, typically persists for about a million years before going extinct naturally. Marine invertebrates last even longer, around 10 million years on average.
Against that baseline, human-driven extinction is dramatically faster. A 2015 study published in Science Advances found that vertebrate species have been disappearing at 22 to 53 times the expected background rate since 1900, depending on how you count species that are likely extinct but not yet confirmed. Using the most generous estimates for natural extinction, the rate is up to 100 times higher than normal. Broader analyses that include all taxonomic groups put the current rate at 1,000 times the background level, with projections suggesting it could reach 10,000 times higher in the coming decades.
To put that in concrete terms: the vertebrate extinctions recorded over the past century would have taken 800 to 10,000 years to occur under natural conditions.
How Many Species Are Threatened Right Now
The picture becomes more alarming when you look beyond confirmed extinctions to species that are sliding toward the edge. The 2019 IPBES Global Assessment, the largest scientific review of biodiversity ever conducted, estimated that around 1 million animal and plant species are now threatened with extinction, many within decades. Across terrestrial, freshwater, and marine groups that have been studied in sufficient detail, about 25% of species face extinction risk.
The IUCN Red List currently classifies more than 48,600 species as threatened, representing 28% of all species assessed so far. The breakdown by group reveals how unevenly the damage falls:
- Reef-building corals: 44% threatened
- Amphibians: 41% threatened
- Mammals: 26% threatened
- Birds: 11% threatened
Amphibians have been hit especially hard by a combination of habitat destruction, pollution, climate change, and a devastating fungal disease that spread partly through global trade. Reef corals face warming oceans and acidification, threats that are intensifying with each passing decade.
The Ocean’s Hidden Losses
Marine species are harder to monitor than land animals, which means the true scale of ocean biodiversity loss is poorly understood. The IUCN lists 25% of marine mammals (32 of 128 known species) as threatened with extinction. But modeling work published in the Proceedings of the National Academy of Sciences suggests the real figure is closer to 37%, because the conservation status of nearly 40% of marine mammals remains unknown due to insufficient data. Sharks, rays, and many fish populations face intense pressure from overfishing, bycatch, and habitat degradation, though firm global percentages for these groups are still being assembled.
Population Collapse, Not Just Extinction
Extinction counts alone understate what’s happening. A species doesn’t have to vanish entirely for ecosystems to unravel. The 2024 Living Planet Index, based on the largest wildlife monitoring dataset ever compiled, found that monitored vertebrate populations declined by an average of 73% between 1970 and 2020. That means the typical population of mammals, birds, fish, reptiles, and amphibians being tracked is less than a third the size it was just 50 years ago.
This kind of population collapse, sometimes called “biological annihilation,” erodes the ecological functions that species perform long before the last individual dies. Pollination networks thin out, predator-prey relationships destabilize, and ecosystems become less resilient to shocks like drought or disease. By the time a species is formally declared extinct, its ecological role has often been empty for years.
Why Islands Tell the Sharpest Story
A disproportionate share of recorded extinctions has occurred on islands. Island species evolved in isolation, often without large predators, which left them especially vulnerable when humans arrived with rats, cats, goats, and diseases. The dodo on Mauritius is the most famous example, but the pattern repeated across the Pacific, Caribbean, and Indian Ocean islands for centuries. Research on late Quaternary extinctions (the past 50,000 years or so) shows that islands suffered massive human-driven species losses well before the modern industrial era, as early human colonizers hunted large animals and transformed landscapes.
These island losses also distort our understanding of natural evolutionary patterns. Studies have found that basic biological rules, like the tendency for species on islands to evolve toward different body sizes, only become clear once you account for the hundreds of species humans wiped out before scientists could study them.
Putting the Percentage in Perspective
So what is the actual percentage of species humans have driven extinct? The honest answer is that we don’t have a single clean number, and anyone who gives you one is oversimplifying. The documented figure (around 900 species since 1500) represents a tiny fraction of estimated global biodiversity, which ranges from 8 to 10 million species depending on the estimate. That would put confirmed extinctions below 0.01% of all species. But this figure is misleadingly low because the vast majority of species have never been assessed.
The more meaningful numbers are the rates and trajectories. Extinction is running 100 to 1,000 times faster than the natural pace. One in four assessed species is threatened. Vertebrate populations have dropped by nearly three-quarters in half a century. Scientists who study mass extinctions in the fossil record note that the current pace, if sustained, would qualify as the sixth mass extinction in Earth’s 4.5-billion-year history. The five previous ones were caused by asteroid impacts, volcanic eruptions, and rapid climate shifts. This one is caused by land conversion, overexploitation, pollution, invasive species, and climate change, all driven by a single species.