Oops, Scientists May Have Severely Miscalculated How Many Humans Are on Earth

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While most estimates place the current human population at around 8.2 billion, a new study suggests we might be vastly underrepresenting rural areas.
By analyzing 300 rural dam projects across 35 countries, researchers from Aalto University in Finland found discrepancies among these independent population counts and other population data gathered between 1975 and 2010.
Such underreporting could have consequences in terms of resource allocation within a country, but other experts remain skeptical that decades of population counting could be off by such a wide margin.

Homo sapiens is the most successful mammalian species in Earth history, and it’s not even close. The species thrives on nearly every continent, in a variety of adverse conditions, and outnumbers the second-place contender—the rat—by at least a cool billion. However, a new study suggests that the impressive nature of humanity’s proliferation may have been vastly underreported.

Most estimates place Earth’s human population at around 8.2 billion, but Josias Láng-Ritter—a postdoctoral researcher at Aalto University in Finland and lead author of the study published in the journal Nature Communications—claims that these estimates could be underrepresenting rural areas by a significant margin.

“We were surprised to find that the actual population living in rural areas is much higher than the global population data indicates—depending on the dataset, rural populations have been underestimated by between 53 percent to 84 percent over the period studied,” Láng-Ritter said in a press statement. “The results are remarkable, as these datasets have been used in thousands of studies and extensively support decision-making, yet their accuracy has not been systematically evaluated.”

How exactly do you test the accuracy of global datasets used to derive population totals in the first place? Well, with a background in water resource management, Láng-Ritter looked at a different kind of population data gathered from rural dam projects—300 such projects across 35 countries, to be precise. This data focused on the years 1975 to 2010, and these population tallies provided a significant dataset to check against other population totals calculated by organizations like WorldPop, GWP, GRUMP, LandScan, and GHS-POP (which were also analyzed in this study).

“When dams are built, large areas are flooded and people need to be relocated,” Láng-Ritter said in a press statement. “The relocated population is usually counted precisely because dam companies pay compensation to those affected. Unlike global population datasets, such local impact statements provide comprehensive, on-the-ground population counts that are not skewed by administrative boundaries. We then combined these with spatial information from satellite imagery.”

Part of this discrepancy likely stems from the fact that many countries don’t have the resources for precise data collection, and difficulty traveling to far flung rural areas only exacerbates census-counting discrepancies. A widespread underrepresentation of rural populations across the world could have profound impacts on those communities, as censuses are central to figuring out how to divvy up resources.

However, not everyone is convinced by this research. Stuart Gietel-Basten from the Hong Kong University of Science and Technology told New Scientist that while increased investment in rural population data collection would be beneficial, the idea that Earth could contain a few billion more human inhabitants that we thought is extremely unlikely. “If we really are undercounting by that massive amount, it’s a massive news story and goes against all the years of thousands of other datasets.”

When trying to count such a massive population, a few hundred or maybe even a few thousand may slip through the cracks. But a few million or even billion would upend our understanding of human occupation on this planet. Scientists will need a bit more evidence before rethinking decades of dataset research.