Higher in the mountains: Dynamics of agro-pastoral practices in a low-latitude mountain system (Karkas Mountains, central Iran) during the Mediaeval Warm Period and the Little Ice Age

Little is known about the impact of the Mediaeval Warm Period (MWP: 950-1250 CE) and the Little Ice Age (LIA: 1250-1850 CE) on high-altitude agro-pastoral practices and the vertical mobility of human communities in the mountain regions of interior Southwest Asia. Although the area experienced significant socio-political changes during the last millennium, the socio-environmental interactions during these climatic periods remain poorly understood. This study presents a geochronologically well-constrained, multi-proxy geochemical and palaeoecological record from a high-altitude (2500 m) wetland in the Karkas Mountains, located on the central Iranian desert plateau. All proxies, including bioindicators (pollen, non-pollen palynomorphs, fossil insects) and sedimentological and geochemical data (X-ray fluorescence intensity variations, Isothermal Remanent Magnetization measurements, and lithological changes), reveal two contrasting patterns of hydroclimatic conditions and agropastoral practices during the MWP and the LIA. Pollen and non-pollen palynomorphs show that the MWP was characterised by intensive cereal cultivation (mainly wheat) and the establishment of permanent agricultural communities, while the LIA was characterised by intensified grazing pressure on montane steppe vegetation, suggesting a shift towards a more mobile pastoral lifestyle-one that persisted into the 20th century. Interestingly, this shift coincides with the Mongol invasion of the Iranian plateau. Variations in lithology, XRF intensities, magnetic field as well as the insect faunal assemblages further provide insights into the wetland hydrological variations and erosional episodes related to land-use and hydroclimatic changes during the MWP and LIA. Based on the Gahak wetland record and regional palaeoclimatic data, we conclude that the MWP in the mountainous areas of central Iran was marked by milder winters and possibly shorter summer droughts, in contrast to the LIA, which had harsher winters and longer-lasting snow cover. Results of the spectral analysis on Gahak record compared to well-known solar cycles, suggest that the climate of the central Iranian highlands is highly sensitive to the variations in solar irradiance. Our findings highlight the significant role of high-altitude agro-pastoral communities in supplying food to the lowland urban centres of mediaeval Persia, at least during the MWP. Although socio-political changes (e.g. Mongol invasion) could affect the mediaeval societies, the impact of climatic shifts on socio-economic changes should not be underestimated.