The Black Death killed more than a third of Europe's population in the 14th century, and new research shows that as farmland was abandoned, plant biodiversity plummeted by about 40 percent. But the loss was temporary: within 150 years, as populations recovered and human disturbances returned, biodiversity climbed back to slightly above pre-plague levels. The study, published in Ecology Letters, reveals that medieval farming practices, far from being uniformly harmful, created patchwork landscapes that sustained a rich variety of plants.
A team led by paleoecologist Jonathan Gordon of the University of York's Leverhulme Centre for Anthropocene Biodiversity examined more than 100 European pollen records spanning roughly 4,600 sediment samples across France, the United Kingdom and the Swiss Alps.
"We found a decline in biodiversity overall, but the decline overall was driven by those landscapes that declined in agricultural production," Gordon told Live Science. In those areas, biodiversity fell by roughly 40 percent. Only when populations began to recover more than a century later did the landscape, disturbed once again by people, support higher species numbers.
The findings challenge a simple narrative of pre-human nature as pristine and human activity as only destructive. "Many people think there was a stable and pristine world in which the entry of people has only one result: net loss of species and homogenization," said Erle Ellis, an agroecologist at the University of Maryland, Baltimore County, who was not involved in the research. "The paleoecologists have always known the story is far more complicated."
Medieval agriculture, the study notes, was a mosaic of small fields interwoven with patches of woodland, heath, ponds and secondary forest. "In that landscape, you had lots of natural features that remained from the Middle or Early Holocene," Gordon said. "It was all interlaced with these agricultural mosaics, and that led to raised biodiversity because there were more habitats for different plant species to exploit."
Modern farming, by contrast, relies on large-scale monocultures that replace these varied habitats with a single crop. "Rather than the monoculture, plantations, or uniform changes to landscapes we see in the 20th and 21st centuries, emphasis was placed on maintaining 'mosaics,'" said Patrick Roberts of the Max Planck Institute for Geoanthropology, who was not involved in the research.
Gordon cautioned that the study measured only species richness, not what he termed "functional diversity" -- the different roles plants play in an ecosystem. "There may be a hundred types of plants in a landscape, but if they do the same thing, you have low functional diversity," he said. Understanding that is "super important for how ecosystems adapt to changes in climate and how resilient they are, which is something we need for future-proofing our agricultural system."
The research is part of a growing body of evidence that, until the industrial era, human land management often enhanced rather than diminished biodiversity, and it offers lessons for designing agricultural landscapes that support both food production and a healthy environment.
Analysis
Why This Matters
- The study challenges the assumption that human activity always degrades nature: traditional mosaic farming sustained higher biodiversity than either abandoned land or modern monocultures.
- The findings could help shape agricultural policy to reverse the 11% decline in global biodiversity seen during the 20th century by encouraging mixed, diverse land-use practices.
- Understanding how ecosystems recovered after a catastrophic human die-off can inform conservation strategies and climate-change adaptation.
Background
The Black Death was a bubonic plague pandemic that swept Europe between 1346 and 1353, killing an estimated 30-50% of the population. It followed a period of agricultural crisis and famine that had already put pressure on land use. The sudden loss of life led to the abandonment of large areas of farmland, which reverted to scrub and secondary woodland. Pollen preserved in lake and bog sediments provides a natural archive of vegetation change, and this study uses that archive to track plant biodiversity over time.
Key Perspectives
[Study authors, led by Jonathan Gordon]: A drop in plant diversity of about 40% occurred where agriculture was abandoned, but recovery began after roughly 150 years as human disturbance returned and created new habitats. The key insight is that medieval farming, with its patchwork of different land uses, sustained more species than either pristine woodland or modern uniform fields.
[Erle Ellis, agroecologist at University of Maryland, Baltimore County (not involved)]: The work confirms what paleoecologists have long understood: human-shaped landscapes are not uniformly destructive. "The story is far more complicated," and long-term cultural land management often produces diverse habitats.
[Patrick Roberts, Max Planck Institute for Geoanthropology (not involved)]: The contrast between medieval mosaic maintenance and the monocultures of the 20th and 21st centuries is striking. The research shows that until recently, people actively used landscapes while preserving mixed ecosystem functions.
[Critics/Skeptics]: Gordon himself notes that the study only looks at species counts, not functional diversity. A landscape may be rich in species that all fill the same ecological role, offering less resilience than one with fewer but more diverse roles. Further work is needed to determine whether medieval practices can be scaled to modern food production without sacrificing yield.
What to Watch
- New research on functional diversity in historical and modern agricultural systems.
- Policy discussions on agroecology and incentives for mixed-use farming in Europe and elsewhere.
- Integration of paleoecological data into national biodiversity targets and land-use planning.