Sedimentary faecal biomarkers in European lakes: tracing land-use activity during the medieval agricultural revolution

Present-day biodiversity and landscapes in Europe reflect millennia of human influence. Particularly, the ‘medieval agricultural revolution’ marked large-scale movements of people, plants, and livestock, and major shifts in agricultural practices, coinciding with the Medieval Climate Anomaly. Understanding how this biodiversity emerged, and how it contributes to the resilience of socio-ecological systems is critical for future climate-adaptive land-use planning and management. Existing human-ecodynamic reconstructions are largely based on archaeological sites and mires, and therefore often lack the spatial representativeness beyond an individual site, continuous depositional archives, or the temporal resolution and ecological breadth needed to assess biodiversity, land-use history, and species vulnerability in detail.

The ERC synergy project “MEMELAND – Molecular Ecology of Medieval European Landscapes” addresses these gaps through an interdisciplinary multi-lake, multiproxy framework. As part of this project, we will investigate lake sediment records from 50 lake pairs across a latitudinal gradient in Europe. Each pair consists of one lake located near a high-status (elite) site and one “control” lake from a nearby area lacking direct archaeological evidence for medieval elite activity. Such baselines from nearby “pristine” lakes are rarely established but are essential for disentangling natural from anthropogenic drivers of change.

Here we present our faecal biomarker framework to reconstruct grazing and manuring intensity during the medieval period using sterols, stanols, and bile acids measured as concentrations and depositional fluxes. To improve source attribution, we are developing a diet-controlled livestock reference library that characterizes sterol/stanol and bile-acid fingerprints and diagnostic ratios under historically plausible feeding regimes. We further leverage MEMELAND’s sedaDNA component to benchmark biomarker-derived livestock inputs against taxonomically resolved signals of domestic animals and land-use indicators. In this complementary approach, faecal biomarkers constrain the magnitude of livestock input, while sedaDNA refines the source and ecological context.

We ask which faecal biomarkers and diagnostic ratios are most robust across heterogeneous European lake systems, whether paired-lake comparisons reveal consistent spatio-temporal contrasts in land use during the medieval period, and whether eutrophication trajectories track enhanced nutrient loading associated with grazing and manuring. Besides the sedaDNA data, biomarker results are further integrated with palynological proxies, hyperspectral imaging, geochemistry (µXRF), and chronostratigraphic approaches to identify and contextualize land-use signatures in sediment archives.

On our poster, we present an overview of this biomarker contribution to MEMELAND and look forward to discussing it with you.