Using sedimentary ancient DNA to identify past ecosystem engineering in rivers

Before humans took on a dominant role in modifying streams and floodplains, native species were the primary agents of ecosystem engineering and surface change within river-floodplain systems. These natural, pre-human condition of European rivers and their floodplains remains poorly understood. In periods when human activity became a major driver of river and floodplain evolution, it is often difficult to distinguish between human and faunal impacts, especially in the absence of clear physical evidence. In this pilot study, we aim to reconstruct the pre-human environmental conditions of low-order streams and their floodplains in central Europe. We also develop a methodology to identify the dominant ecosystem engineers at specific riparian sites. Three research sites in central Europe were selected, where we reconstruct palaeo-environmental conditions using a combination of sedimentary ancient DNA (sedaDNA), botanical macroremain analysis, and chrono-stratigraphy to detect the presence or absence of key wetland plant species. Additionally, we investigate the presence of key animal ecosystem engineers which are now globally or locally extinct but were once critical to the functioning of sustainable riparian ecosystems. Identifying when and where these species were present will not only enhance our understanding of natural, resilient riparian conditions but also provide a baseline for interpreting subsequent human-environment interactions.