- New research carried out in Colombia by the University of Cambridge suggests that local surveys assessing the effect of land clearances on biodiversity may be underestimating the impact by as much as 60%.
- To fully understand the effects of clearing forests for pastureland, much surveys of a much larger scale are required to reflect the different levels of biodiversity in regions and habitats and their resilience to change.
- More accurate species surveys, the authors say, could also support future programs such as biodiversity offsetting schemes as well as influencing farming policies.
A survey of Colombian birdlife, which evolved over more than a decade into the world’s largest-ever ornithological study, has found that clearing forests to create new pastures is causing as much as 60% more damage to biodiversity than previously thought.
Until now, research into the impact on biodiversity of land use change has generally involved small-scale, local surveys. But this approach does not accurately represent the larger-scale damage caused to nature, says study co-author David Edwards, a professor of plant ecology at the University of Cambridge.
When forests are converted to pasture, some species win and others lose, he explains, and measuring the biodiversity loss at a local scale does not capture the larger-scale effect of these land clearances, which are occurring across the ranges of many different species.
“When people want to understand the wider impact of deforestation on biodiversity, they tend to do a local survey and extrapolate the results,” Edwards tells Mongabay in a phone interview. “But the problem is that tree clearance is occurring at massive spatial scales, across all sorts of different habitats and elevations.” By focusing on isolated sites, researchers were missing how these effects accumulate across regions, he says.
In 2024, Colombia lost 113,608 hectares (about 280,700 acres) of forest, a 43% increase compared with 2023, when deforestation had dropped to its lowest level in more than two decades. But while organized crime, ongoing armed conflict and wildfires have been partially blamed for the spike, land use change for cattle ranching remains a huge driver of deforestation.
David Wilcove, a professor of ecology and evolutionary biology at Princeton University, says the study, published in Nature Ecology and Evolution, makes an important point about how future surveys should be conducted. “If we want to truly understand the extent to which deforestation and other types of land-cover change affect biodiversity, we need to undertake studies across the full range of ecosystems in a given country or region,” he tells Mongabay via email. “Estimates of biodiversity loss based solely on local studies can miss the full extent of species disappearance.”
“Conservation scientists have known for quite some time that understanding the impact of land-use change on biodiversity requires large-scale research, covering many ecosystems and elevations,” Wilcove, who was not involved in the study, writes. “What this study does … is quantify the degree to which local studies underestimate species loss by undertaking a heroic number of surveys of birds in intact and altered ecosystems across the most species-rich nation on earth.”
Edwards began the study in Colombia’s Western Cordillera mountains in 2012, framing his ideas as he drove across vast areas of central Colombia that had been cleared for cattle farming. As he crossed the landscape, he was struck that the birds he saw were limited to a few common species. But while the likes of the Andean lapwing (Vanellus resplendens), the tropical kingbird (Tyrannus melancholicus) and the great thrush (Turdus fuscater) dominated the cattle fields, he assumed that the birds in the forests he could see in the distance were clearly going to be different — therefore, across several different regions, the amount of biodiversity loss would be far higher.
He explains that the concept hinges around beta diversity, the change of biodiversity over space and the fact that there can be a sharp turnover of species between different but adjacent habitats. The study found that birds that thrived in the cattle fields were generalist, competitive species often with large ranges. In the forest, however, there was hyper-diversity, with much smaller specialist communities of animals, with far more limited ranges. If their corner of the forest is cleared, they may be unable to adjust and die out.
Edwards and his research team spent the next 13 years obtaining 24,981 detections of 971 different bird species, with fieldwork that analyzed 848 forest and cattle pastures points, across 13 different biogeographic regions.
They found huge differences in species sensitivity depending on the type of habitat being converted to pasture. The montane forests of the Central and Eastern Cordilleras, along with the moist forests of Napo and Caquetá, showed the greatest sensitivity to habitat conversion. In these areas, he explains, there was clear evidence of “species packing,” a concept that refers to many different species coexisting within one ecosystem, each one evolving to use different elements of that environment. But because these habitats have been largely undisturbed by farming or logging, species there have a low tolerance to disruption and can be particularly badly hit by a change in land use.
In contrast, in areas such as the Magdalena dry forests and the Llanos and Andean páramos, species are not as diverse. “These habitats will have more changeable environmental conditions embedded within them … [and] therefore, species occurring there are likely to be less sensitive to disturbance, which means when you convert the forest, more of the species will persist,” Edwards says.
Diego Martínez-Revelo, another co-author of the study and doctoral student at the Universidad del Valle in Cali, Colombia, tells Mongabay in an email: “It became clear that not all regions are equally affected [by deforestation]. … In places like the Amazon and the montane forests of the Andes, the losses were striking, many specialized species simply disappeared.
“Other regions appeared more resilient,” Martínez -Revelo adds. “But once we combined the data, the message was undeniable: the total biodiversity loss, at a near-country scale, was far greater than we would have guessed from any single region alone.”
Jose Manuel Ochoa-Quintero is the manager of the Center for Socioecological Studies and Global Change at the Alexander von Humboldt Biological Resources Research Institute, which advises the Colombian government on environmental policy. The center supplied field and logistical support to the researchers, as well as help with site selection and introductions to landowners.
He says the report is important as it provides “a standardized method that allows us to make comparative analysis within the same region” and could help to develop policies around agriculture and deforestation. In a mega-diverse country such as Colombia, he says, you can’t adopt a one-size-fits-all approach. So, while the Global Biodiversity Framework talks about conserving 30% of a landscape, he explains, this is not something one can apply homogeneously across a country like Colombia.
“In regions when the sensitivity of the species to land use change is higher, probably you will need [a] higher number … of protected areas to be able to maintain biodiversity in the long term,” he says.
The resilience of an ecosystem is also governed by land sharing, Edwards says, when the amount of land dedicated to food production is minimized through intensification, maximizing yields of the fields, while leaving larger areas of forest and other natural habitat untouched.
Cattle farming in Colombia is fraught with economic inequalities, Ochoa-Quintero says, with larger, wealthier intensive farms close to cities on one side and smaller rural ranches on the other. And this is where deforestation occurs, he explains.
Small farmers can’t afford to intensively manage their cattle, he says, and have little money for artificial inputs such as fertilizers, so their pastures often become degraded and can no longer support their herd. This forces them to buy up small pockets of cheap land so the farm can expand, at the same time increasing deforestation.
Ochoa-Quintero says he believes the research provides important evidence showing the environmental benefits that well-managed intensive farming can bring, which could influence government policy toward helping small farmers convert to more intensive techniques, reducing the need to cut down more forests.
Edwards says that more accurate future species surveys will be important to biodiversity offsetting schemes, which aim to compensate for the loss of species caused by development in one place with boosting biodiversity in another.
While he says his research methods are more arduous and time-consuming than traditional, small-scale surveys, he hopes a new generation of ecologists will use the research as the basis for quantifying biodiversity loss over a much greater scale.
You need “plans to protect biodiversity that transcends biogeographic regions. That allow us to protect sufficient of each habitat,” Edwards says. “You have to think about this holistically.”
“Looking at one region in isolation isn’t enough. We need to monitor biodiversity and guide decisions with a broader, country-level perspective, one that captures both regional variation and the cumulative impact across landscapes,” Martinez-Revelo adds. “Only then can we respond meaningfully to the scale of the challenges we face in a world where ecological pressures are intensifying.”
Citation:
Socolar, J. B., Mills, S. C., Gilroy, J. J., Martínez-Revelo, D. E., Medina-Uribe, C. A., Parra-Sanchez, E., … Edwards, D. P. (2025). Tropical biodiversity loss from land-use change is severely underestimated by local-scale assessments. Nature Ecology & Evolution, 9(9), 1643-1655. doi:10.1038/s41559-025-02779-4
Banner image: The plate-billed mountain-toucan is native to a portion of Colombia’s Nariño department. Cattle grazing is one of the main threats to its habitat and survival. Image by Ben Tavener via Flickr (CC BY 2.0).
FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.