Steppe sustainability in a changing world – STEPABILITY

The arid steppe ecosystems characteristic of the Arid Circum-Caspian Zone (ACC) are favoured by current and future climate change. It is therefore essential to better understand the ecosystem services that they are able to provide on a sustainable basis, in particular for human societies, particularly nomadic or semi-nomadic and pastoral. This interdisciplinary project consists in testing, depending on several types of agrarian, cultural and societal developments, the vulnerability or resilience of steppe ecosystems with a view to sustainable exploitation. To do this, the interaction between researchers from two different disciplinary fields (archaeology and paleoecology / paleoclimatology) is necessary. Several study areas are targeted: Caucasus countries, Uzbekistan, and Turkmenistan. In these workshop zones, the history of domestication, of the agro-pastoral impact and then of intensive livestock farming will made it possible to establish a scale of impact of agro-pastoral practices on the resilience of steppe ecosystems since the Bronze Age.

We propose to develop modern calibrations on recent markers to improve the reliability of palaeoenvironmental reconstructions in the ACC. This region is so far very poorly documented. We will follow an interdisciplinary approach to combine 1) multi-marker analyses from sedimentary archives to reconstruct the links between past vegetation (represented by pollen), climate (pollen and molecular biomarkers such as branched Dialkyl Glycerols Tetra-ethers, brGDGTs), lake-level variations (paleoshorelines, ostracods), anthropic impact (non-pollen palynomorphs; Anthropogenic Pollen Indicators ; fires, macro-charcoal), soil ecology (brGDGTs) and erosion (X-ray fluorescence, XRF; Magnetic Susceptibility, MS), and 2) bioarchaeological analyses of plant species replacement rates and past population dynamics (Summed Probability Distribution of C14 datation; SPD) based on published contexts and new excavations from ongoing partner projects in these study areas. These results will be compared and interpreted using (1) ecological statistical tools (pollen ratio, biodiversity, evenness and turnover estimates from pollen, NPPs and archaeobotany) (2) modelling tools (REVEALS, Anthropogenic land cover change), and (3) cross-correlation and geographical Information System to evidence time-lagged and geo-spatial relationships between pressure and response of steppe ecosystems.