Hydroclimate variability and human influence in southern Yemen over the past 1100 years: Insights from subfossil midge (Diptera: Chironomidae, Ceratopogonidae) assemblages from paleolake Gayal el Bazal

We present the first subfossil chironomid record from the Arabian Peninsula from a sediment core from Lake Gayal el Bazal, southeastern Yemen, providing insights into hydrological changes over the last ~1100 years. Shallow-water chironomid morphotypes, Dicrotendipes nervosus-type and Polypedilum nubeculosum-type, indicating low lake levels and productive habitats with abundant macrophyte cover, suggest two dry intervals between ca. 1575 and 1670 CE and 1770–1930 CE. These periods fall within the Little Ice Age (LIA), suggesting a link between lower global temperatures and weakened monsoonal activity. Since ca. 1930 CE, Tanytarsus cf. formosanus-type Bazal is dominant, indicating higher lake levels and lower productivity. This is supported by rising Ti/Al values, suggesting enhanced runoff and increased precipitation. A rise in Ceratopogonidae Dasyhelea-type during the last three decades suggests a decrease in lake size, likely reflecting anthropogenic water withdrawal since ca. 1989. Our findings support the notion of a dry LIA, affecting parts of Eastern Africa, southwestern Saudi Arabia, and extending to other latitudes such as the Tibetan Plateau. This points to large-scale weakening of the boreal summer monsoons and latitudinal southwards shifts of the Intertropical Convergence Zone. A pluvial period during the 17th century could be connected to a positive Indian Ocean Dipole event. Reconstructed increasing moisture during the pre-industrial era, which contrasts modern-day precipitation measurements, could be explained by seasonal variability with moisture increase during the early summer and autumn. Overall, our record emphasizes the interplay of climate variability and anthropogenic activities in shaping water resources and their sustainability in extremely dry low-latitude regions such as the Arabian Peninsula.