How Much Wild Forest Remains—and Why Trees Alone Don’t Tell You How Wildlife Is Doing

A forest can lose animals without losing many trees. A road may divide a breeding population, logging may remove essential nesting sites, or hunting may empty an otherwise green landscape. That is why answering “How much wild forest is left?” requires more than measuring tree cover.

There are good global statistics—but they measure different things. To understand what those numbers mean for wildlife, you need to distinguish forest area, forest condition, and animal abundance.

What counts as a “wild forest”?

“Wild forest” is an everyday expression, not a single scientific category. You might mean any forest that grew naturally, an old forest with little visible human disturbance, or a vast landscape uninterrupted by roads.

Each interpretation leads to a different estimate.

The UN Food and Agriculture Organization’s 2025 Global Forest Resources Assessment provides several useful measures:

A hectare is 10,000 square metres—roughly the area of a large sports field. These estimates therefore describe enormous areas, but they are not interchangeable measures of wilderness.

In particular, naturally regenerating does not mean untouched. A forest can regrow naturally after logging and still belong in that category.

Primary forest is closer to what many people imagine as “wild,” but even that label is not a guarantee that every animal population remains healthy.

Source: FAO’s 2025 global assessment summary.

A different question: how much remains intact?

Intact forest landscapes measure something different: large, connected natural landscapes within forest regions, without signs of significant human activity.

An intact landscape can contain wetlands, natural grasslands and other non-forested areas. Consequently, its area cannot simply be compared with—or subtracted from—the FAO forest totals.

The Intact Forest Landscapes assessment for 2000–2025 estimates about 1.09 billion hectares remaining, following a loss of approximately 195 million hectares, or 15.2%, over that period.

Forest area asks how much forest remains. Intactness asks how much remains connected and relatively undisturbed.

For wildlife, both questions matter.

How quickly is natural forest disappearing?

According to FAO, naturally regenerating forest declined by about 324 million hectares between 1990 and 2025—approximately 8%.

That gives the following broad comparison:

The 1990 figure is reconstructed from the reported current area and cumulative loss.

An 8% decline is substantial. But the global total conceals two important complications.

First, net change is the balance between losses and gains. Forest recovery in one place can partly offset clearing elsewhere in the global arithmetic. It does not necessarily replace the habitat lost by the animals living in the cleared forest.

Second, an area can remain classified as forest while becoming much less suitable for particular species.

These modern assessments offer a much firmer picture of the last few decades than of the full 10,000 years since agriculture began spreading. They should not be mistaken for an equally detailed historical record stretching back that far.

Why animal populations can decline faster than forest area

Imagine measuring a city’s ability to support people only by its residential land area. That would miss whether its homes still have water, whether roads connect neighbourhoods, and whether essential services remain accessible.

Forest area is similarly incomplete as a measure of animal habitat.

1. Remaining forest can lose important features

Habitat means the environment that supplies an organism’s needs: food, shelter, breeding sites and suitable physical conditions.

Selective logging may leave much of a forest standing while removing large trees that provide nesting cavities. Other disturbances can alter the canopy, undergrowth or local conditions.

The result may still look like forest on a map, but it no longer supports the same animals—or the same numbers of them.

Researchers use forest integrity to describe how closely a forest retains its natural composition, structure and ecological functioning. A study of tropical vertebrates found that integrity provided information about extinction risk and population decline beyond forest cover alone.

2. Connected forest can become isolated patches

Fragmentation is the division of continuous habitat into smaller, separated pieces.

A road may remove relatively little tree cover yet create a major obstacle for an animal reluctant or unable to cross it. Isolated populations can lose access to feeding grounds, seasonal resources or potential mates.

Fragmentation also creates more forest edges, where conditions differ from those in the interior.

For some species, therefore, losing a narrow strip of forest can matter much more than its area suggests.

3. Animals can disappear while trees remain

Hunting can severely reduce mammals and birds in otherwise forested places. This is sometimes called the “empty forest” problem: the vegetation remains, but important parts of the animal community have been depleted.

This illustrates a separate pressure from habitat loss: direct exploitation, meaning the removal of organisms through activities such as hunting, fishing or harvesting.

The IPBES global biodiversity assessment ranks changes in land and sea use as the largest direct driver of biodiversity loss overall, followed by direct exploitation. The relative importance varies among environments; direct exploitation is especially important in the ocean.

These pressures can also interact. A new road may both fragment habitat and make hunting easier.

4. Location matters as much as area

A small global percentage can conceal a devastating local loss.

If a species lives only in one valley, clearing much of that valley may threaten its survival while barely changing the world’s forest total. Conversely, forest expansion elsewhere does not restore that species’ home.

An animal population responds to the amount and condition of its own habitat, not to the global forest balance sheet.

Why the Living Planet Index is not a forest-loss statistic

A common puzzle arises when you compare a modest-looking percentage decline in forest area with a much larger reported decline in wildlife populations.

The most familiar wildlife headline comes from the Living Planet Index, or LPI. This index tracks changes in monitored populations of vertebrates—animals with backbones, including fish, amphibians, reptiles, birds and mammals.

For a clearly documented reference point, the 2024 Living Planet Report reported a 73% decline in the index between 1970 and 2020, using 34,836 population time series covering 5,495 species. A time series is a sequence of observations collected over time.

That does not mean:

• 73% of all individual wild animals disappeared;
• 73% of species became extinct;
• every monitored population declined by 73%;
• or forests now contain 73% fewer animals.

It describes a combined measure of proportional population change.

What does “proportional change” mean?

A population falling from 100 animals to 50 has halved. So has one falling from 100,000 to 50,000.

Those changes have the same proportional size, despite very different numbers of animals lost. The LPI combines population trends through successive levels of aggregation and weighting rather than adding all animals into one global headcount.

Its calculation uses a geometric mean, a way of averaging multiplicative changes. As a simple illustration, a halving and a doubling balance each other multiplicatively. They do not imply that the same absolute number of animals was lost and gained.

The official calculation is more elaborate because populations are grouped into species and broader categories, with adjustments for uneven monitoring.

It covers much more than forests

The 2024 report’s habitat indices showed:

These are separate indices, not contributions that can be added together.

Freshwater populations showed the steepest decline. A forest-area chart cannot capture pressures such as dams blocking fish migration or changes in river flow.

Nor is the terrestrial index a forest-only index: it also includes populations in grasslands and other land environments.

The comparison with forest loss therefore differs in what is measured, where it is measured, and which years are covered.

Sources: Living Planet Report 2024 and its technical supplement.

Can you inspect what drives the wildlife index?

Yes—much of the underlying evidence and calculation method is available.

The LPI data portal provides public population records. Technical documentation explains the calculations, and the open-source R package rlpi supplies code for constructing indices.

However, publicly inspectable does not necessarily mean exactly reproducible. Some records remain confidential under agreements with data providers. The 2024 technical supplement identified 5,005 confidential time series among those used in that edition.

Which populations pull the index down most?

You cannot answer that simply by ranking percentage declines. Populations have different roles in the aggregation, and multiple populations may represent the same species.

A rigorous analysis would examine the weighted contributions and recalculate the index with selected groups excluded. Using only public records, that would test a public-data reconstruction, not necessarily reproduce the official result exactly.

Extreme trends matter, too. A sensitivity test in the 2024 technical supplement removed the 10% most strongly increasing and 10% most strongly decreasing population trends. The estimated decline changed from 73% to 61%.

That does not show that the excluded observations were wrong. It shows that the headline’s magnitude is influenced by very large changes—and that understanding an index requires more than reading its headline.

Finally, the LPI measures what happened, not automatically why. Establishing causes requires additional evidence about habitat change, exploitation, pollution, invasive species, climate and disease.

The most useful way to read the numbers

To understand forest wildlife, keep three questions separate:

1. How much habitat remains?
   Look at forest area and where losses occur.

2. What condition is it in?
   Examine fragmentation, disturbance and the features animals need.

3. How are the animals responding?
   Track populations in those same places over comparable periods.

The world still has vast forests. Yet “still forested” is not the same as “still functioning as the same habitat.”

That is the central reason wildlife can decline even when the forest-area chart appears to change slowly: animals need more than trees on a map—they need a place where they can continue to live and reproduce.