How Have Wild Animal Populations Changed Over 10,000 Years?

It sounds like a question that ought to have a simple graph: how many wild animals lived on Earth before agriculture, and how many are left today?

The difficulty is not just missing historical records. It is also deciding what to measure. The number of animals, their combined weight, and an index of population change tell you different things. We have useful evidence for each part of the story—but no reliable global headcount stretching back 10,000 years.

Three Ways to Measure Wildlife

If you want to exclude insects and focus on mammals, birds, fish, reptiles and amphibians, you are mostly asking about vertebrates: animals with backbones.

Even for this narrower group, researchers cannot count every individual worldwide. Instead, they use several complementary measures.

A missing elephant matters enormously to biomass. A missing mouse matters equally to a headcount. Neither measure, on its own, tells you whether species and ecosystems are doing well.

There is no single defensible curve showing the total number of wild vertebrates over the past 10,000 years. There are several useful curves answering narrower questions.

What Can We Say About the Past 10,000 Years?

The longest view comes from wild-mammal biomass

One way to glimpse long-term change is to estimate the combined living weight of wild land mammals, excluding humans, livestock and marine mammals.

Approximate estimates presented by Our World in Data give this picture:

These estimates suggest a decline of roughly 80% in combined weight over 10,000 years.

But you should attach three qualifications:

• Weight is not headcount. Losing large mammals can reduce biomass disproportionately.
• These are mammals on land, not all wild animals.
• The estimates have substantial uncertainty, especially for the distant past.

The ancient estimate and the recent estimates also come from different reconstructions. They are useful landmarks, not evidence for a precisely shaped curve between them.

When does a more detailed time series begin?

A recent historical reconstruction estimates wild-mammal biomass from 1850 to 2020, on land and at sea. Historical records remain sparse, so this is a provisional reconstruction rather than a continuous global census.

For a broader range of animals—including birds, fish, reptiles and amphibians—the most widely used global trend measure begins in 1970: the Living Planet Index.

What the Living Planet Index Actually Measures

The Living Planet Index, or LPI, combines changes in monitored wildlife populations.

Here, a population means a species in a particular place: elephants in one protected area, for example, rather than every elephant worldwide.

Researchers collect repeated measurements of those populations. These may be counts, estimates of animals per unit area, or other measures of abundance. They then combine the proportional changes.

To keep the dates and methods consistent, the figures below use the 2024 Living Planet Report, covering 1970–2020. That edition used 34,836 monitored populations of 5,495 vertebrate species and reported a 73% decline in the global index. See the report’s technical supplement.

If you set the index to 100 in 1970, it ends at about 27 in 2020.

That does not mean 73% of all wild animals disappeared.

Why an index is not a headcount

Imagine two populations:

The combined headcount rises from 1,100 to 2,025. But one population has grown while the other has suffered a severe decline.

A simplified index combines their proportional changes using a geometric mean: an average suited to multiplying growth and decline factors.

In words: averaging a doubling and a fall to one-quarter in this way produces an index decline of about 29%, even though the total number of animals increased.

The real LPI is more elaborate. It combines annual trends across populations, species and geographic groupings, with weighting to address uneven coverage. But this example explains the essential distinction.

A 73% decline in the LPI does not mean:

• 73% of all individual animals have vanished;
• 73% of species have gone extinct;
• or 73% of monitored populations are declining.

It means the combined, weighted index of monitored population abundance has fallen by that amount.

Which Populations Have Declined Most?

Freshwater stands out

The 2024 report gives these habitat-specific changes:

These are separate indices, not shares of the global decline that you can add together.

Freshwater populations show the steepest indexed decline. Rivers, lakes and wetlands face several overlapping pressures: habitat loss, dams, disrupted water flows, pollution and exploitation.

A separate analysis of migratory freshwater fish—fish that move between habitats during their lives—reported an 81% index decline from 1970 to 2020. Blocked migration routes and loss of free-flowing rivers are important threats. That result describes a subgroup, not its numerical contribution to the global 73%.

Geography—and the starting date—matter

The steepest regional decline in the 2024 report was in Latin America and the Caribbean, at 95%.

But every regional result is measured against its own 1970 baseline. A smaller decline since then does not necessarily mean healthier wildlife today: substantial losses may already have happened before monitoring began.

This is a baseline problem. If you start measuring after much of the damage has occurred, the subsequent decline captures only the later part of the story.

Nor can you identify the biggest contributors to the global index merely by listing the populations with the largest percentage losses. Their influence also depends on how populations are grouped and weighted.

Why Are Wild Animals Declining If We Raise Livestock?

You might reasonably expect domesticated animals to have reduced pressure on wildlife. In many places, they have reduced dependence on hunting wild land animals.

But wild animals need more than protection from hunters. They need food, breeding sites, water, space and connections between habitats.

We have changed the competition, not ended it

Habitat loss and degradation—the removal of habitat or deterioration of its condition—are central pressures.

Forests become cropland or pasture. Wetlands are drained. Roads divide habitat into smaller pieces. Rivers are dammed or diverted.

Livestock production is part of this picture because it requires pasture and, often, cropland to grow feed. According to the global assessment by IPBES, the international body assessing biodiversity evidence, more than a third of the world’s land surface is devoted to crop or livestock production.

That does not mean farms contain no wildlife. It means large areas are managed primarily for human food production rather than for the ecological communities they previously supported.

We have partly replaced hunting wild animals with raising domestic ones, but we have not stopped competing with wildlife for land and resources.

Other major pressures include:

• Direct exploitation: catching, hunting or trapping animals. Fishing remains especially important in the oceans.
• Pollution: contamination that harms animals or their food supplies.
• Invasive alien species: organisms introduced beyond their native range that harm local wildlife.
• Climate change: shifts in temperature, rainfall and extreme events.
• Disease, sometimes interacting with the pressures above.

The IPBES global assessment identifies land- and sea-use change as the largest direct driver overall, followed by direct exploitation. The ranking differs by ecosystem; fishing is particularly important at sea.

How Much “Wild Forest” Remains?

“Wild forest” sounds straightforward, but several definitions answer different questions.

The first three figures come from the FAO’s 2025 forest assessment. The last comes from a separate intact-landscape assessment; it can include some non-forested land, so it is not directly interchangeable with forest-area figures.

Naturally regenerating forest declined by about 324 million hectares between 1990 and 2025, roughly 8%. Intact forest landscapes declined by about 15.2% between 2000 and 2025.

Why can wildlife decline faster than forest area?

First, the comparisons involve different periods and different things. The LPI includes animals in rivers, oceans and grasslands—not just forests.

Second, forest area is not forest quality:

• Logging can change habitat while leaving an area classified as forest.
• Roads can fragment a forest without removing many trees.
• Hunting can remove large animals from otherwise standing forest—sometimes called an “empty forest.”
• Losing a small area can be devastating if it contains much of a species’ remaining habitat.

You therefore cannot infer that each remaining hectare supports 73% fewer animals. Testing that would require matching animal populations with the amount and condition of their own habitats, over the same years.

Can You Inspect How the Index Is Calculated?

Yes. The LPI is open to substantial scrutiny, although exact reproduction from public data is not always possible.

You can access:

• Population records through the LPI data portal.
• Methods and technical supplements explaining trend estimation and weighting.
• Open-source calculation code, including ZSL’s rlpi package.

Some records remain confidential under agreements with data providers. The 2024 technical supplement listed 5,005 confidential time series among those used.

The magnitude of the result also depends partly on how extreme trends are handled. In one 2024 sensitivity test, removing the strongest-increasing 10% and strongest-decreasing 10% of population trends changed the reported decline from 73% to 61%. That is not a reason simply to discard those observations, but it shows why methodological checks matter.

Identifying exactly which populations pull the index down most requires a fresh analysis of their weighted contributions, not merely ranking their percentage declines.

The Most Honest Answer Is a Dashboard

If you want to understand wildlife change, use several measures together:

• Long-term mammal biomass reveals the broad historical loss of wild animal mass.
• The Living Planet Index tracks proportional changes across monitored vertebrate populations since 1970.
• Habitat area and condition help explain the pressures behind those changes.
• Species-level records reveal declines and recoveries hidden by global averages.

The overall evidence points to substantial human-driven reductions in wildlife. But precision matters: “wildlife has declined greatly” is well supported; “we have counted how many animals disappeared over 10,000 years” is not.