Land-use change is hurting bird diversity far more than we realized

Researchers have conducted the world’s most extensive bird diversity survey across Colombia. They recorded 971 species from forests and pasturelands over more than a decade.

The survey accounted for nearly 10% of all bird species worldwide, but the findings went far beyond bird counts.

Combining fieldwork with species data, the researchers discovered that biodiversity loss from clearing forests for pasture is 60% worse than earlier local estimates suggested. This is not just a local concern – it is a national alarm.

Local surveys miss bird diversity

Until now, most biodiversity assessments relied on small local surveys. These studies ignore what happens when forests are lost across entire regions.

“When people want to understand the wider impact of deforestation on biodiversity, they tend to do a local survey and extrapolate the results,” said Professor David Edwards from the University of Cambridge.

“But the problem is that tree clearance is occurring at massive spatial scales, across all sorts of different habitats and elevations.”

By studying 13 different eco-regions, the team revealed that single-region estimates miss the mark badly. The real biodiversity loss becomes visible only when you zoom out to a national scale.

Birds vanish with deforestation

Tropical forests are not just rich in species. They are also rich in species turnover, what scientists call beta-diversity. That means two nearby forests can host very different bird communities.

When forests are cleared and replaced with pasture, many species with small ranges vanish. In contrast, a few wide-ranging species adapt and spread.

The result is what researchers call biotic homogenization, where different areas end up with the same handful of generalist species. This makes large-scale biodiversity damage invisible at the local level.

In Colombia, some regions like the Caquetá and Napo moist forests, with dense and specialized bird populations, showed the greatest losses. Meanwhile, pasture areas, regardless of location, often hosted the same disturbance-tolerant birds.

Bird diversity tracked by sound

The team used sound recordings across Colombia’s forests, mountains, and pasturelands. In 80% of cases, birds were heard but not seen.

These recordings allowed the researchers to identify species and predict which others shared the habitat.

Data was analyzed from over 24,000 detections and modeled occupancy for 1,614 bird species using habitat, range, and trait data. This enabled the team to estimate how each species responds to forest conversion with high spatial detail.

Many regions show bird losses

The study revealed that sampling just one or two eco-regions is not enough. It takes data from at least six or seven biogeographic zones to get within 5% of the true, national-scale biodiversity impact.

In fact, when looking at highly sensitive species, those in the 75th percentile of conversion impact, national losses were 67% higher than local estimates. These species are often rare, specialized, and cannot adapt to pasture.

Most pastures are harmful

The researchers studied traditional cattle pastures with scattered trees and hedgerows. These low-productivity pastures dominate Colombia’s agricultural land.

Even with scattered forest remnants, these areas showed major declines in species richness and diversity.

Silvopastoral systems, pastures combined with trees, can reduce damage, but they still do not support forest-dependent species. Thus, agriculture-friendly designs alone will not save biodiversity.

Bird diversity declines across regions

Some areas like Santa Marta appeared less sensitive to forest loss, but appearances can be deceiving. This region includes 24 bird species found nowhere else. So, even a small reduction in forest there risks wiping out irreplaceable species.

Beta-diversity also explained why losses soared at scale. In forests, bird communities change greatly across space and elevation.

In pastures, these differences collapse. Over 200 kilometers [124 miles], pasture communities barely differ, showing how homogenized they become.

Lessons for conservation and policy

The study warns against relying on global meta-analyses based on local data. Most deforestation studies still ignore regional variation in biodiversity. This leads to dangerously low estimates of environmental cost.

“The food we eat comes with a much great environmental cost than we thought,” said Edwards. “We need policy makers to think much more about the larger scale biodiversity impact of deforestation.”

The authors call for regionally structured monitoring systems, better land-use planning, and policies that prioritize biodiversity across elevation and habitat types.

Every forest patch counts

The research changes the way we understand birds and biodiversity loss. The message is clear. Protecting one forest patch is not enough. Protecting whole regions matters.

Colombia’s birds tell a simple story. When forests fall, many voices go silent – especially those that once sang from the shadows, highlands, and far corners of this rich tropical land.

The study is published in the journal Nature Ecology & Evolution.

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