The 73% You Haven't Heard About

In 1995, a marine biologist named Daniel Pauly published a short paper introducing a concept he called “shifting baseline syndrome.”¹ The idea was simple: each generation of scientists accepts the state of the environment they first encounter as normal. What looks like a healthy fishery to a young researcher would have looked depleted to their predecessor. The baseline shifts, and the loss becomes invisible not because it didn’t happen, but because nobody remembers what was there before.

Pauly was writing about fish stocks. The concept has since been confirmed across 73 case studies worldwide, covering everything from coral reefs to songbird populations to the size of trophy fish in old photographs.² It is one of the most thoroughly documented cognitive biases in environmental science. And it helps explain something that would otherwise be baffling: how the most severe ecological crisis in modern history has managed to unfold in broad daylight while attracting a fraction of the public attention given to climate change.

The Living Planet Index, published by the World Wildlife Fund and the Zoological Society of London, tracks monitored populations of vertebrate species around the world. Its 2024 report found that those populations have declined, on average, by 73 percent since 1970.³ That is not a projection. It is not a model output. It is a measurement of what has already happened.

The number is so large that it resists comprehension. Three-quarters of monitored wildlife, gone in a single human lifetime.

The scale of what is happening

The IUCN Red List, the most comprehensive inventory of species conservation status on Earth, assessed over 163,000 species as of October 2025. Of those, 48,646 are classified as threatened with extinction.⁴ That number has increased every year the list has been updated.

But the Red List itself understates the problem, because most species on Earth have never been assessed. Scientists have described roughly 2.1 million species. Estimates of total species diversity range from 8 million to over 10 million. For most of these organisms, we have no population data, no trend lines, no conservation status. They exist in a vast informational blind spot.

Among the groups where data does exist, the picture is unambiguous. Freshwater species have declined by 85 percent since 1970, making rivers, lakes, and wetlands the most devastated ecosystems on the planet.⁵ Insect populations, which underpin pollination, decomposition, and the base of countless food webs, have been declining at rates between one and two percent per year across studied regions. Amphibians are experiencing what researchers have called the worst mass extinction since the dinosaurs, driven by a combination of habitat loss, disease, and climate disruption.

This is not a collection of isolated problems. It is a pattern, and the pattern has a direction.

The machinery of loss

Biodiversity decline is not mysterious. The drivers are well documented and, for the most part, well understood.

Habitat destruction and degradation account for the largest share. Agriculture, urbanization, logging, and infrastructure convert ecosystems into something else. The conversion is often irreversible on any human timescale. A tropical forest cleared for cattle ranching does not return to tropical forest when the cattle are removed. The soil structure has changed. The seed bank is gone. The mycorrhizal networks are severed. The species that depended on that specific assemblage of conditions have either relocated or died.

Overexploitation is the second driver. This includes overfishing, bushmeat hunting, wildlife trade, and the harvest of species faster than they can reproduce. It also includes less obvious forms of exploitation, like the industrial harvest of horseshoe crabs for biomedical testing, which has contributed to declines in shorebird species that depend on their eggs during migration.

Invasive species, introduced through global trade, shipping, and deliberate importation, disrupt ecosystems by outcompeting, predating, or parasitizing native species. The brown tree snake eliminated most of Guam’s native forest birds within decades of its accidental introduction. Chytrid fungus, spread partly through the international amphibian trade, has caused population declines in over 500 amphibian species and is implicated in 90 extinctions.

Pollution, in forms ranging from pesticides to light to noise to microplastics, degrades habitat quality even where habitat quantity remains intact. A forest fragment surrounded by agricultural fields sprayed with neonicotinoids is not the same as a forest fragment embedded in a larger landscape of native vegetation, even if both appear green from the air.

And increasingly, climate change acts as an accelerant, shifting the ranges of species faster than many can track, disrupting the timing of ecological events like flowering and migration, and creating novel conditions that have no analog in evolutionary history.

None of this is new to scientists. The mechanisms have been described for decades. What is new, or at least newly measurable, is the cumulative scale.

The perception gap

Here is what makes biodiversity loss unusual as a crisis: the severity of the problem and the level of public concern about it are not merely mismatched. They are almost inversely related.

Climate change, by comparison, has an institutional architecture purpose-built for public communication. The Intergovernmental Panel on Climate Change was established in 1988.⁶ It produces regular assessment reports that are covered extensively by international media. It has a single, intuitive metric, global average temperature change, that can be expressed in a number anyone understands. When scientists say “1.5 degrees,” the phrase carries meaning even for people who have never read a climate paper.

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, or IPBES, is the biodiversity equivalent of the IPCC. It was not established until 2012.⁷ That 24-year institutional lag matters. It means that for nearly a quarter century, climate change had a dedicated international body producing synthesized assessments, building relationships with media, and establishing itself as the authoritative voice on an environmental issue, while biodiversity had no comparable structure.

The lag has consequences that compound over time. The IPCC has produced six assessment cycles. Its reports are anticipated events in international media. Journalists have developed expertise in covering them. Editors understand that they are newsworthy. IPBES has produced important assessments, its 2019 Global Assessment on Biodiversity and Ecosystem Services was a landmark document, but it operates with a fraction of the recognition, a fraction of the media infrastructure, and a fraction of the public awareness.

The media coverage disparity is quantifiable. Studies of major international news outlets have found an approximately 8:1 ratio in coverage of climate change versus biodiversity loss.⁸ For every eight stories about climate, one mentions biodiversity. This is not because journalists have evaluated both crises and concluded that climate is eight times more important. It is because climate has a communication infrastructure that biodiversity does not.

The metric problem

Climate change benefits from a single, powerful metric. CO2 concentrations in the atmosphere can be measured precisely, expressed simply, and tracked over time. The Keeling Curve, showing the relentless rise of atmospheric carbon dioxide since 1958, is one of the most famous graphs in science. It tells a clear story with a clear direction.

Biodiversity has no equivalent.

There are, as of recent counts, 573 different biodiversity metrics in active use across the scientific literature.⁹ These include species richness, functional diversity, phylogenetic diversity, the Living Planet Index, the Biodiversity Intactness Index, the Red List Index, Mean Species Abundance, the Species Habitat Index, and hundreds of others. Each measures something different. Each has strengths and limitations. None has achieved anything close to the cultural penetration of global temperature or atmospheric CO2 concentration.

This is not a trivial communication problem. It is a structural one. When 573 metrics compete for attention, the result is not a richer understanding. The result is metric paralysis, a situation where the abundance of measurement actually undermines the clarity of the message. A policymaker who asks “how is biodiversity doing?” can receive 573 different answers, each technically correct and each telling a slightly different story. The effect is not illumination but fog.

Compare this with the climate communication landscape. When the IPCC says the planet has warmed by 1.1 degrees Celsius above pre-industrial levels, there is no ambiguity. The number can be debated at the margins, but its meaning is clear. Biodiversity science has no comparable moment of clarity. The 73 percent figure from the Living Planet Index is the closest thing to one, but even it requires explanation, it measures population declines in monitored vertebrate populations, not total species loss, and it does not mean that 73 percent of animals are gone.

The distinction matters, and the need to explain it every time the number is cited reduces its rhetorical force. Climate science had the luxury of a metric that was both accurate and intuitively understandable. Biodiversity science has not yet found that combination.

What we see and what we don’t

There is another layer to the invisibility problem, and it operates at the level of cognition rather than communication.

Humans are not equally attentive to all forms of life. The term “plant blindness,” coined by botanists James Wandersee and Elisabeth Schussler in 1998,¹⁰ describes the well-documented tendency of humans to overlook plants in their environment, to treat them as a backdrop rather than as organisms. The phenomenon extends more broadly: people are more aware of large mammals than of insects, more aware of colorful birds than of soil fungi, more concerned about creatures that resemble themselves than about creatures that do not.

This cognitive bias has measurable consequences for conservation funding. Mammals receive approximately 40 percent of conservation spending despite representing less than one percent of threatened species.¹¹ Insects, which include more threatened species than all vertebrate groups combined, receive a negligible share. The allocation of concern follows the allocation of attention, not the allocation of need.

The bias also shapes public perception of what biodiversity loss looks like. When most people think about extinction, they think about charismatic megafauna: elephants, tigers, rhinos, polar bears. These species are genuinely threatened, and their conservation matters. But they are not representative of the crisis. The crisis is overwhelmingly a crisis of organisms that most people have never seen, cannot name, and would not recognize: beetles, nematodes, freshwater mussels, epiphytic orchids, mycorrhizal fungi, deep-sea invertebrates.

The gap between what is threatened and what is noticed is not a minor distortion. It is a fundamental one. It means that the public understanding of biodiversity loss is shaped by a tiny, unrepresentative sample of the species actually at risk. The crisis that people imagine and the crisis that is actually occurring occupy different worlds.

The economic blind spot

One of the more persistent obstacles to biodiversity policy is the perception that biodiversity conservation is an economic cost, something that constrains development, limits resource extraction, and requires trade-offs with growth. This framing is not merely incomplete. On its own terms, it is incoherent.

The World Economic Forum estimated that $58 trillion of global GDP, more than half the world’s economic output, is moderately or highly dependent on functioning ecosystems.¹² This includes agriculture, forestry, fisheries, and the ecosystem services that underpin them: pollination, water filtration, soil formation, flood regulation, pest control.

These are not abstract benefits. They are inputs to economic production. When pollinator populations decline, crop yields decline or crop production costs increase. When wetlands are drained, water treatment costs rise. When fisheries collapse, coastal economies lose their primary industry. The costs are real and they are already being incurred. They are simply not appearing on the balance sheets of the industries that cause them.

This is the externality problem applied at planetary scale. The market price of a product reflects the costs that someone had to pay to produce it. It does not reflect the costs that were transferred to someone else, deferred to the future, or imposed on systems that cannot send invoices. Biodiversity loss is, among other things, a massive exercise in cost transfer.

The economic case for biodiversity conservation is not that nature has intrinsic value, though it does. The economic case is that the systems we depend on for economic production are themselves dependent on biological diversity, and their degradation represents a form of capital consumption that accounting conventions are not designed to capture.

Why invisibility accelerates loss

The perception gap around biodiversity is not just a communication failure. It is itself a driver of continued decline.

Policy responds to public concern. Public concern responds to media coverage. Media coverage responds to narrative clarity and institutional signals. Biodiversity loss, as described above, suffers from deficits in all of these. The result is a feedback loop: low public salience leads to low political priority, which leads to underfunded conservation, which leads to continued decline, which fails to register because the institutions that would communicate it are themselves underfunded and understaffed.

Consider the funding landscape. Global biodiversity finance, the total amount spent on biodiversity conservation worldwide, was estimated at $143 billion per year in 2022. The estimated funding gap, the difference between what is spent and what is needed to halt biodiversity loss, is between $598 billion and $824 billion per year. That gap is not closing.

Meanwhile, subsidies that directly harm biodiversity, primarily in agriculture, fisheries, and fossil fuels, total approximately $1.8 trillion per year. The world spends roughly twelve times as much actively destroying biodiversity as it does trying to protect it.

This is not a problem that can be solved by making people feel guilty or by producing more alarming statistics. The statistics are already alarming. The problem is structural. The institutions, metrics, media incentives, cognitive biases, and funding mechanisms that shape public understanding of environmental issues were not designed with biodiversity in mind, and they are not serving it well.

The shifting baseline, revisited

Daniel Pauly’s original insight about shifting baselines was about fish. But the phenomenon operates at every scale of the biodiversity crisis.

A child growing up today in most of the developed world has never experienced a night sky dense with insects around every light source. They have never seen the rivers thick with salmon that were normal a century ago. They have never walked through a forest with the density of birdsong that ornithological recordings from the mid-20th century document. They do not know what has been lost, because they never saw what was there.

This is not ignorance. It is the normal functioning of human memory and experience. People calibrate their expectations to the world they encounter. If the world they encounter has already lost 73 percent of its monitored wildlife, that diminished world becomes the baseline against which future change is measured.

The practical consequence is that each generation tolerates a lower level of biological richness than the one before, not because they value nature less, but because they have less to compare it to. Restoration targets are set based on recent baselines rather than historical ones. Conservation “success” is defined as slowing the rate of decline rather than rebuilding what was lost. The ratchet turns only in one direction.

Shifting baseline syndrome has been confirmed in studies of fishers, divers, hikers, birdwatchers, and the general public across dozens of countries. It is not a hypothesis. It is a measured feature of how humans relate to ecological change, and it reliably produces the same outcome: the normalization of degradation.

What the numbers describe

It is worth pausing on what the 73 percent figure actually represents, because the abstraction of the number conceals the specificity of what is happening.

A 73 percent decline in monitored wildlife populations means that where there were once four animals, there is now roughly one. It means breeding colonies that once numbered in the hundreds of thousands now number in the tens of thousands. It means migratory routes that once carried billions of individuals now carry a fraction of that. It means the intricate, evolved relationships between species, predator and prey, pollinator and plant, parasite and host, are being simplified and degraded at a pace that has no precedent in the human record.

The 85 percent decline in freshwater species is not a number about rivers in the abstract. It is about specific rivers where specific fish, amphibians, mollusks, and insects that existed fifty years ago no longer do. It is about the people who fished those rivers, the ecosystems that were sustained by those species, and the cascading effects that propagate through food webs when foundational species disappear.

The 48,646 species on the IUCN Red List that are classified as threatened are not a statistic. They are 48,646 distinct lineages, each with millions of years of evolutionary history, each occupying a unique niche, each connected to other species in ways that are often poorly understood. When one disappears, the consequences ripple outward, sometimes immediately and sometimes across decades, reshaping the systems it was part of.

This is the nature of biodiversity loss. It is not one event. It is millions of events, happening simultaneously, across every continent and every ocean, most of them unrecorded and many of them irreversible. The aggregate statistics are staggering, but they are summaries of individual tragedies that no aggregate can fully capture.

The structural deficit

The core argument of this piece is not that biodiversity loss is severe. That has been established beyond reasonable dispute. The argument is that the severity is inadequately perceived, and that the inadequacy of perception is not random. It is the product of specific, identifiable structural factors.

The 24-year institutional lag behind climate science. The absence of a single, intuitive metric. The 573 competing indicators that fragment the message. The 8:1 media coverage disparity. The cognitive biases that direct attention toward mammals and away from the organisms that constitute most of life on Earth. The shifting baselines that normalize each generation’s diminished experience. The economic frameworks that treat ecosystem destruction as an externality rather than a cost.

Each of these factors is individually significant. Together, they form a communication environment in which the largest ongoing ecological catastrophe in human history fails to register with the urgency it demands.

This is not a call for better marketing. It is an observation that the systems through which democratic societies identify, prioritize, and respond to threats are failing to identify, prioritize, or respond to this one. And because those systems are failing, the policy response is failing. And because the policy response is failing, the loss continues. And because the loss is gradual, dispersed, and affects organisms most people cannot name, the failure of the systems is not itself perceived as a crisis.

The loop is self-reinforcing. The invisibility produces inaction. The inaction produces further loss. The further loss is invisible for the same reasons the original loss was invisible. The baseline shifts again.

A direction

Breaking this cycle does not require a single dramatic intervention. It requires sustained work on several fronts simultaneously.

It requires the biodiversity science community to converge on a small number of headline metrics that can perform for biodiversity what global temperature does for climate, not replacing the 573 measures in use, but establishing a common language for public communication.

It requires IPBES to be funded and staffed at a level commensurate with the importance of its mandate, rather than operating as a smaller and less visible sibling of the IPCC.

It requires media organizations to develop biodiversity as a beat, with dedicated reporters who build expertise over time, rather than treating it as an occasional feature story when a photogenic species is declared extinct.

It requires economic institutions to incorporate natural capital accounting into standard economic metrics, so that the destruction of ecosystem services registers as the cost it actually is rather than disappearing into the category of externalities.

And it requires educational systems to address shifting baseline syndrome directly, teaching young people not only about the current state of biodiversity but about the historical baselines against which current conditions should be measured.

None of these changes is sufficient on its own. All of them are necessary. The biodiversity crisis is not going to solve itself, and it is not going to be solved by a public that cannot see it. Making it visible is not the whole solution. But it is the precondition for every other part of the solution.

The 73 percent has already happened. What happens next depends, in large part, on whether the systems we rely on for understanding the world can be made to register what is already underway.