Medieval communities boosted biodiversity around Lake Constance

One of the major realizations of the Anthropocene era has been the importance of biodiversity for the functioning of the earth system, as well as for human societies. Recent trends show that human activities are driving biodiversity loss around the globe, but previous research has also shown an increase in biodiversity in Holocene Europe, showing that human societies can in fact support the health and resilience of their environments. The cultural phenomena that accompanied the increase in biodiversity, however, are less understood.

Now, a new study published in the Proceedings of the National Academy of Sciences integrates data from interdisciplinary datasets to examine the drivers of biodiversity change around Lake Constance in southwest Germany, then part of the Carolingian Empire. Researchers found a significant, sustained increase in plant diversity starting around 500 CE, culminating in a 4000-year “plant diversity optimum” around1000 CE. This increase, data shows, was driven by cultural innovations in agriculture, land management and trade in the formative period of medieval Europe.

“Our findings document a success story in human-environment interactions,” says Adam Izdebski of the Max Planck Institute of Geoanthropology. “Human communities can support biodiverse landscapes, and have done so for long periods of time in the past.”

“This study offers lessons for policy makers and conservationists,” adds Adam Spitzig of Stanford University. “Our data suggest that High Nature Value (HNV) farming systems and intermediate-disturbance, agro-ecological mosaics can effectively enhance plant diversity while simultaneously sustaining food production.”

To reach these findings, the researchers used palaeoecological and historical datasets from the Lake Constance region, a uniquely well-documented area. Analysis of fossil pollen from six sediment cores, combined with archaeobotanical evidence from hundreds of sites, allowed researchers to reconstruct the changes in plant diversity over the past 4000 years. By combining this data with historical documents from regional archives, including the Abbey Archives of St. Gall, they could uncover the agricultural, trade, and land management practices that enabled the increase in plant diversity.

As society progresses into the Anthropocene, the human era, stories of positive human-earth system interactions are increasingly important, reminding us that our societies can support biodiversity and healthy landscapes too. The researchers hope that future studies will continue to integrate long-term biodiversity estimates with detailed cultural contextualization, so that policy makers can implement the most effective biodiversity management policies.

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