The next mass extinction would not need an asteroid. It could unfold through ordinary decisions, repeated across millions of places, until the living world becomes something much poorer than the one we inherited.
A drained wetland. A forest broken into fragments. A river that still flows but supports less life. The disappearance of nature can look surprisingly undramatic when it happens a little at a time.
But how far has that process gone? Are we already in a sixth mass extinction, and what do the alarming numbers actually measure?
What counts as a mass extinction?
Extinction is part of the history of life. A mass extinction is a much larger disruption: the loss of roughly three-quarters or more of species within a geologically short interval. A 2011 review by Anthony Barnosky and colleagues in Nature describes five such major events over approximately the past 540 million years and finds modern extinction rates higher than the fossil record would lead us to expect.
Rate and total loss are different measurements. A dangerously elevated rate does not mean three-quarters of species have already disappeared. Equally, waiting for that threshold before treating losses as serious would turn a historical description into a disastrous decision rule.
The phrase “sixth mass extinction” is therefore often used for a process under way or a trajectory towards catastrophic losses. It should not be presented as a measured statement that 75% of today’s species are already gone.
Three losses that headlines can confuse
Population decline means fewer individuals in a particular population. Local extinction means a species disappears from a place while surviving elsewhere. Global extinction means the species no longer exists anywhere.
These outcomes matter at different scales. A bird can remain globally widespread while disappearing from the landscape where you grew up. A surviving species name in a database does not tell us how abundant it is, where it remains or which ecological roles it still performs.
The new wildlife index: what 73% actually means
Explore the evidence: View ZSL’s Living Planet Index and its 2026 findings · Read or download WWF’s Living Planet Report 2026.
On 7 October 2026, ZSL published its explanation of the 2026 Living Planet Index. It reports a 73% average decline in monitored populations of mammals, birds, fish, reptiles and amphibians between 1970 and 2022. The analysis draws on 35,803 population trends covering 5,790 species.
This does not mean 73% of all animals have vanished, or that 73% of species are extinct. It is an index of population trends, not a census of every animal. Its scope also does not encompass all plants, fungi and invertebrates.
ZSL reports that half of the monitored populations declined, while 7% were stable and 43% increased. Those figures can coexist with a strongly declining overall index: counting populations with positive or negative trends is different from measuring the magnitude of change.
The 2024 edition also reported a 73% decline, but covered a different period and dataset. ZSL cautions against comparing successive editions directly to infer that the rate of loss has stabilised.
A million threatened species are not a million completed extinctions
The 2019 IPBES Global Assessment estimated that around one million animal and plant species were threatened with extinction, many within decades. That was an assessment of risk, not a count of species already lost, and it should be dated rather than passed off as a new 2026 tally.
The assessment identified five leading direct pressures, in descending global order: changes in land and sea use; direct exploitation of organisms; climate change; pollution; and invasive alien species. Their relative importance varies between environments.
That matters because treating the biodiversity crisis as solely a climate problem leaves major causes unaddressed. Emissions reductions matter, but so do the ways we farm, fish, build, manage water and protect habitats.
What the UK evidence shows
The State of Nature 2023 report found that the abundance of 753 terrestrial and freshwater species studied across the UK had fallen by an average of 19% since 1970. Among 10,008 species assessed in Great Britain, 16% were threatened with extinction there.
That second figure concerns the risk of disappearing from Great Britain. It does not mean 16% of all British wildlife is globally threatened. Nor does the abundance result mean every species declined by 19%; some increased.
The report also emphasises that monitoring since 1970 follows centuries of habitat loss and other pressures. A modern baseline can already describe an impoverished landscape. Protecting only what we remember from childhood may set our ambitions too low.
Why the losses reach beyond wildlife
Nature is not simply scenery surrounding the economy. The IPBES assessment describes biodiversity as underpinning food security, livelihoods and quality of life. Damage to the systems on which people depend has consequences well beyond the disappearance of a familiar animal.
The moral question also extends beyond usefulness. A species need not supply a product or perform an easily priced service to make its disappearance matter. What value do we place on a living world that cannot simply be reconstructed after we have lost it?
The fossil record is a warning, not a timetable
Comparing ancient and modern extinctions is difficult. The Barnosky review explicitly examines differences between fossil and modern datasets. Preservation, sampling and the time intervals being compared affect what researchers can infer.
Uncertainty about the precise rate or future scale should encourage careful reporting. It does not erase documented declines, and it supplies no reliable countdown to human extinction.
We should also resist the reassuring phrase “life will recover” when it is used to dismiss losses now. The survival of life in some future form does not preserve a particular species, landscape or community today.
A recovery worth paying attention to
In October 2025, IUCN reported that the green sea turtle’s global status improved from Endangered to Least Concern. It attributed the recovery to sustained conservation, including protection of nesting females and eggs, reduced exploitation and measures to limit accidental capture in fishing gear.
The improvement did not mean every population was safe. IUCN highlighted continuing threats, depleted historical abundance and concerns for particular subpopulations. A global recovery can coexist with serious local problems.
In the same update, the slender-billed curlew moved to Extinct. It was last recorded in 1995. The assessment date was not the date of its disappearance—a reminder that recognising a loss can take decades.
These examples belong together. Some losses become final; others can still be prevented. Conservation works through specific, sustained changes, rather than optimism alone.
The next extinction is not a foregone conclusion
The useful question is what changes the outcome: protecting and restoring habitats, reducing damaging exploitation and pollution, tackling invasive species and limiting further warming. Those tasks require policy, funding, enforcement and the involvement of the people living alongside wildlife.
For individuals, recording local wildlife, supporting credible habitat projects and scrutinising land-use decisions can contribute. They work best alongside broader action, rather than being offered as substitutes for it.
We do not need to exaggerate the numbers to recognise the danger. The unsettling possibility is that the world can become quieter, emptier and less resilient while still looking normal enough for us to carry on.
Watch: what biodiversity means
WWF International’s What is Biodiversity? introduces the variety of life and its importance. Published in May 2019, it is background viewing rather than a presentation of the 2026 index or a measurement of how many species are extinct.
Watch “What is Biodiversity?” by WWF International on YouTube.
Sources and interpretation
Reviewed: 17 October 2026. Sources are linked throughout. The 2026 Living Planet Index, 2019 IPBES assessment, 2023 UK report and 2025 IUCN examples measure different things and cover different periods. None is presented as a complete real-time census of life on Earth.
Related: Thwaites Glacier: The Slow Disaster Behind the ‘Doomsday’ Name · Climate Change: What the Numbers Actually Tell Us.