The transformation of natural landscapes due to human activities is a significant concern in the Anthropocene. While large-scale deforestation is a contemporary issue, human impact on ecosystems stretches back millennia. In Europe, the Neolithic Revolution and subsequent intensification of agriculture during the Medieval Age caused critical transitions in pristine ecosystems, including forests and wetlands. This study focuses on the impact of a specific medieval society – the Joannites (Knights Hospitaller) – on the landscape surrounding Łagów, Poland. The Joannites' arrival and economic expansion offer a unique opportunity to examine the influence of a specific socio-economic system on long-term ecological changes. The research question centers on how the Joannites' economic practices led to deforestation and altered wetland function. The hypothesis is that the economic transformation associated with the Joannites' arrival in Łagów caused irreversible modifications in the forest structure and cascading consequences for the nearby peatland ecosystem. This study contributes to our understanding of long-term human-environment interactions, particularly the role of socio-economic systems in driving critical transitions in ecosystems and the emergence of novel anthroecosystems. Understanding these historical changes provides insights into contemporary challenges of deforestation and biodiversity loss, particularly in the context of rapid economic development.

Previous research highlights the long history of human impact on European ecosystems, dating back thousands of years. Studies employing multi-proxy approaches, using paleoecological archives like lake and peat sediments, have revealed varying degrees of disturbance in different ecosystems, including wetlands. In Medieval Europe, the accelerating development of economies led to considerable land-use change that significantly impacted forests and wetlands. While some studies have examined the effects of monastic orders or other large-scale entities on the environment, there is a lack of high-resolution evidence illustrating how changes in economy and forest loss affected wetland ecosystems on a long timescale. Furthermore, studies on the forest-wetland interface have been limited in resolution. This study addresses this gap by utilizing a densely-dated multi-proxy record from a peatland in Poland, providing a high-resolution view of the long-term effects of the Joannites’ economy on the surrounding ecosystem. The researchers acknowledge that the perception of wetlands as pristine is often inaccurate, as wetlands are sensitive to even subtle changes in their catchment, including those indirectly caused by human activities like deforestation.

The study used a multi-proxy approach analyzing a 5-meter peat core from Pawski Ług, an ombrotrophic *Sphagnum*-dominated peatland located in western Poland near the town of Łagów. Due to the soft nature of the upper meter of the peat, analyses were conducted on the section between 100 and 500 cm. The core was sampled for various proxies at different resolutions: pollen, microscopic and macroscopic charcoal, and testate amoebae every 5 cm, and plant macrofossils every 1 cm. A total of 29 ¹⁴C dates were used to establish a high-quality age-depth model, which was constructed using OxCal 4.3 software, employing the IntCal13 atmospheric curve for calibration. Palynological analysis followed standard procedures, counting pollen, cryptogam spores, and non-pollen palynomorphs (NPPs) to a minimum pollen sum of 500. Microscopic charcoal particle counts were conducted on the same slides, with calculations of microscopic charcoal accumulation rates (MIC). Macroscopic charcoal analysis involved bleaching and wet sieving, and macroscopic charcoal influx (MAC) was calculated. Plant macrofossil analysis involved sieving through a 125 µm mesh, identifying, and estimating volume percentages. Testate amoebae (TA) analysis involved washing peat samples and analyzing under a microscope to reconstruct depth-to-water table (DWT). Nonmetric Multidimensional Scaling (NMDS) was used to analyze the trajectories of vegetation changes over time in relation to environmental variables. Data analysis was conducted using R version 3.6.2.

The study identified three main stages of land-use change: (1) Pre-Joannites (500-1350 CE): This period showed wet conditions in the mire, an open water environment, and a dense forest with local fires, likely caused by the local Slavic population with a mixed economy. The intensity of fires increased, possibly due to population growth and land clearance in association with the formation of the Polish state. (2) Joannites (1350-1812 CE): The arrival of the Joannites marked a critical transition, with increasing cereal pollen indicating agricultural expansion and deforestation. Local fires ceased, likely due to reduced fuel availability, while regional fires increased, suggesting regional wood use. The wetland transitioned to an acidic, drier *Sphagnum*-dominated peatland. The rapid deforestation was associated with the Joannites' colonization and economic modernization, which led to the implementation of the Stadt-Landkolonisation model. (3) Post-Joannites (1812-1950 CE): After the Joannites' dissolution, there was a period of forest regeneration with beech and the decline of intensive agriculture. The study strongly suggests a direct relationship between the deforestation associated with the Joannites' agricultural expansion and the transformation of the mire’s hydrology and chemistry from a mesotrophic fen to an ombrotrophic bog.

The findings highlight the profound and rapid impact of the Joannites' economy on the landscape. The study demonstrates a direct link between the intensification of agriculture, deforestation, and significant alteration of the wetland ecosystem. The disappearance of the forest and the transformation of the mire occurred within a relatively short period, emphasizing the rapid pace of ecological change associated with human activity. The transition from mesotrophic to oligotrophic conditions in the wetland, indicated by the invasion of *Sphagnum*, was likely triggered by the decrease in forest cover and the subsequent changes in soil and water chemistry, specifically the increase of humic acids from eroded soils. This study provides a high-resolution example of how economic systems can trigger rapid and irreversible changes in ecosystems, leading to the creation of anthroecosystems. The results have implications for understanding the long-term effects of human activity on landscapes and the resilience of ecosystems to disturbance.

This study provides a compelling example of how the economic practices of a medieval society dramatically altered a landscape within a relatively short timeframe. The Joannites' intensified agriculture, driven by economic modernization, resulted in the rapid deforestation of the region and an abrupt shift in wetland ecology. This research emphasizes the lasting legacy of historical land-use changes on ecosystem structure and function. Further research could explore similar historical transformations in other regions and examine the long-term consequences of past land-use practices on biodiversity and ecosystem services.

The study focuses on a single peatland, limiting the generalizability of findings to other regions. While the high-resolution data provides excellent temporal detail, the spatial extent of the Joannites' impact remains a limitation. Future work could expand the spatial scope of the analysis to include more sites, providing a more comprehensive understanding of the Joannites' impact on the regional landscape.