This study investigates the impact of the Joannites' economic activity on the primeval forest and wetland ecosystems in medieval Central Europe. Using a high-resolution multi-proxy analysis of a peatland in western Poland, the researchers reconstruct environmental changes over the last 1500 years. The findings reveal a rapid and significant land-use transition in the late Middle Ages, correlating with the Joannites' economic expansion and resulting in widespread deforestation. This transition led to a shift in the wetland ecosystem from an alkaline fen to an acidic, *Sphagnum*-dominated peatland. The study highlights the surprisingly fast rate at which feudal economies could eliminate pristine nature and create novel anthroecosystems.

Mariusz Lamentowicz, Katarzyna Marcisz, Piotr Guzowski, Mariusz Gałka, Andrei-Cosmin Diaconu, Piotr Kołaczek