It’s a familiar trope that when humans move into a place, biodiversity suffers. And there’s some evidence supporting that view. For example, a number of massive mammals disappeared from the Americas around the time when humans are thought to have arrived, though the link is hotly debated.
More recently, people have remarked on the signs of nature rebounding when everyone was stuck in their houses at the height of the COVID pandemic—what’s become known as the “Anthropause.”
But a more devastating pandemic centuries ago suggests that the relationship between humans and biodiversity is more nuanced. A certain amount of human presence can be a boon for other species.
That’s the lesson emerging from pollen samples collected in Europe that span the disease-induced population crisis of the 14th century. Plant biodiversity fell dramatically after around the time the bubonic plague—also known as the Black Death—swept across the continent, killing every third person (or more), according to research published this month in Ecology Letters.
“Our work suggests that over 2,000 years of increasing European biodiversity was generated because of —not in spite of—humans,” wrote one of the paper’s authors, Jonathan Gordon from the University of York, and colleague Christopher Lyon at the University of Bath, in an essay for The Conversation.
The clues to this interplay between humans and the landscape are contained in tiny pollen grains encased in layers of sediment from bogs and lakes. These act like a timeline of changes in nearby vegetation, much like the rings in a tree trunk tell of year-to-year shifts in environmental conditions.
Gordon and his collaborators examined data derived from 109 different locations in Europe spanning the first 1850 years of the Common Era (We’re in 2026 of the Common Era, if you aren’t familiar with that terminology.). The data showed that in the 1300s, the diversity of species in the pollen samples plunged dramatically, bottoming out soon after the end of that century.
The drop coincides with a string of crises. First came the Great Famine lasting from 1315 to roughly 1317, when fierce weather that marked the start of the Little Ice Age caused widespread crop failures. That was followed by the Black Death in the middle of the century, when tens of millions of people perished—between 30 and 50% of the continent’s population. Large tracts of farmland were abandoned as the population shrank.
The scientists found additional evidence that this paired decline in human population and biodiversity wasn’t just a coincidence. The dramatic drop in the variety of plant pollens was greatest in samples that also showed a history of grain farming punctuated by a drop in cereal pollen around the 1300s.
“As farmland was abandoned, traditional land management practices ceased and forests spread,”’ said Gordon. “Rather than driving an increase in plant biodiversity, biodiversity plummeted. We only started to see a recovery once human populations rebounded and agricultural activity resumed – a process that took roughly 300 years to return to pre-plague levels.”
This might seem counterintuitive to people today, when industrial agriculture is linked to loss of biodiversity. But the authors point out that farming in medieval Europe was a far cry from the sprawling, pesticide-laden monocultures of the 21st century. In the 1300s, farms were a mix of natural and cultivated spaces—fields interspersed with hedgerows, marshes, and forest.
In a way, this link between plant biodiversity and low-intensity agriculture isn’t a surprise. Scientists have long appreciated the power of ecological disturbances—human or otherwise—to create room for a broader number of species.
Ecologists in the Pacific Northwest have, in recent years, touted the way fires, volcanic eruptions and even logging can be a boon for biodiversity by creating a mixture of habitats interspersed with old-growth forests. In Europe, scientists now warn that the decline of agriculture and the return of forests there poses a threat to meadow ecosystems once kept clear of trees by farming and grazing. And there’s a growing understanding of the roll Indigenous cultures around the world played in shaping the landscape in ways that promote a diversity of habitats.
This examination of the medieval era might hold lessons for today, as forests return to former farmland and pasture in parts of Europe, and some people campaign for policies of “rewilding” in which land is left untouched.
Rather than simply let the land go fallow, it might be worth taking a page from some of the places in Europe that still practice agriculture that doesn’t look very different from how it was done in the 1200s. Examples can be found in places as diverse as Hungary, the Iberian Peninsula, and Scandinavia, the authors note.
“Our work offers a more nuanced perspective on the relationship between humans and nature, indicating that biodiversity and human land use do not have to be in conflict,” said Chris Thomas, a co-author head of University of York program focused on biodiversity in the Anthropocene. “In many cases, they actually depend on one another.”
Gordon, J. D., B.Fagan, J.Finch, L.Gillson, N.Milner, and C. D.Thomas. 2026. “Black Death Land Abandonment Drove European Diversity Losses.” Ecology Letters 29, no. 3: e70325. https://doi.org/10.1111/ele.70325.
Image: ©Anthropocene Magazine
