The statistic seemed to pop up everywhere. Versions were cited at UN negotiations, on protest banners, in 186 peer-reviewed scientific papers – even by the filmmaker James Cameronwhile promoting his Avatar films. The exact wording varied, but the claim was this: that 80% of the world’s remaining biodiversity is protected by indigenous peoples.
However, when scientists investigated its origin, they found nothing. In September the scientific journal Nature reported that the much-cited claim was “an unsubstantiated statistic,” unsupported by any real data, and could jeopardize the very indigenous-led conservation efforts it was cited in support of. Indigenous communities play “vital roles” in biodiversity conservation, the commentary says, but the 80% claim is simply “wrong” and risks undermining their credibility.
The carefully worded article, written by 13 authors, including three indigenous scientists, was about five years in the making. But it raised other questions: including how a baseless fact gained so much traction — and what other inaccuracies circulated.
“There have been policy reports that use it. There were scientific reports. It has been cited in more than 180 scientific publications,” says Álvaro Fernández-Llamazares, an ethnobiologist at the Universitat Autònoma de Barcelona and one of the authors of the article. It has been verified as “true” by a devotee fact-checking organizationand quoted by numerous news organizations (including the Guardian). Fernández-Llamazares stressed they do not blame those who used the figure. Instead, he said, “What we are questioning is: how is it that this figure has gone unchallenged for so many years?”
To verify the claim, the scientists searched decades of literature and citations. They found nothing that looked like an actual calculation. Instead, reports by the UN and the World Bank from the early 2000s seem to have popularized it. They in turn cited an encyclopedia article on eco-regions that by Indigenous peoplesand research that found that some indigenous tribes in the Philippines “retain more than 80% of the original high-biodiversity forest cover”.
However, perhaps the statistic should have raised eyebrows from the start. Despite recent advances in measurability, biodiversity as a concept is still difficult to define, let alone quantify and count. Millions of species are not even described or their status as a species is debated. “The 80% claim is based on two assumptions: that biodiversity can be divided into countable units, and that it can be mapped spatially on a global scale. Neither achievement is possible,” the Nature authors wrote.
On the face of it, the biodiversity field is very numbers-driven. But the appearance of mathematical precision can be misleading, in a field concerned with measuring understudied species, changing ecosystems and data black spots.
“We are not honest with ourselves within our own ranks,” says Matthias Glaubrecht, a professor at the Leibniz Institute for the Analysis of Biodiversity Change in Hamburg. “Biology is, so to speak, a dirty science: numbers here are an auxiliary construction to prove a case, but always accompanied by a big question mark.”
Elephants in Africa, for example, are often used as a symbol of mass extinction. Discourse surrounding African elephants often focuses on a dramatic decline in the 20th century. Popular data platform Our World in Data reported that there were once 26 million elephants in Africa, which dropped to 10 million in 1900, to half a million today. The same figures are widely used by NGOs and the press.
But 26 million elephants would mean almost one elephant for every square kilometer across the entire African continent, with its wide variations in habitat – a figure that emphasizes plausibility.
The number comes from A PhD thesis in the early 1990s by Oxford biologist Eleanor Jane Milner-Gulland. Debates about a ban on the ivory trade were high at the time, and Milner-Gulland tried to estimate the influence of poaching on population sizes. Because there were no robust elephant counts until well into the 1900s, she built a statistical model, which took recent counts of areas populated by elephants and extrapolated them across the continent to areas where elephants could have lived. She arrived at an estimate of between 13.5 million and 26.9 million elephants for the early 19th century.
“The assumption of the study is wrong,” says Chris Thouless, research director for Save the Elephants in Kenya: “It was written with the idea that almost no people lived in Africa.”
Thouless says an unsurprising range would be “a few million – rather than tens of millions”. There is no doubt that elephant populations have suffered. But their decline is a more complicated story than the sudden apocalypse that is sometimes painted. After the Guardian approached him about the veracity of historical elephant data, Our World in Data removed the figures.
Statistical modeling of a world we may have lost is common in the field. But it’s hard to do. “Historic land-use reconstruction is a very messy business, especially on a global scale,” says Erle Ellis of the University of Maryland. Ellis works with these types of models, which date back 12,000 years. A single parameter based on an archaeological find can change an entire region. “There are many models – for example about habitat loss and what it does to a given species. But is there a good model that does this? I don’t think so,” says Ellis.
Despite the importance of robust data in environmental crises, calling out bad statistics is sometimes seen as an attack on conservation itself. The Nature article on the 80% was five years in the making, says one of the authors, because the subject is so sensitive and can be politically abused. In the article they write that “the 80% claim can undermine [more] rigorous studies – as well as effective efforts to conserve biodiversity by indigenous peoples on the ground”. After its publication, however, the authors faced intense criticism.
“The feedback here in Mexico is strong … is rude. Someone told me it was a call to war,” says Yesenia H Márquez, a co-author of the article and member of the expert group on indigenous and local knowledge at the UN’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (Yes). “But I think it’s not a problem to promote the paper,” she says. “We know our territories. We know all the biodiversity we have.”
Tin Fischer is a data journalist based in Berlin, and author of a book about how political allegiance can change perception of data.
