When the desert was green: Grassland expansion during the early Holocene in northwestern Arabia

An early-to-mid Holocene lake in the north of the oasis of Tayma, northwestern Saudi Arabia, proved to be an excellent palynological archive. A shallow, probably brackish water body formed at about 9200 cal BP, with the dominance of goosefoot throughout the sequence indicating the persistence of desert vegetation. However, distinct vegetation changes are recorded during the early Holocene. Grasslands spread soon after 9000 cal BP and reached their maximal expansion ca 8600–8000 cal BP. At about 8000 cal BP these grasslands retreated abruptly and were replaced by more drought-resistant dwarf-shrublands, similar to the present-day ecosystems. The recorded early Holocene grassland expansion furnishes for the first time evidence of an additional and more favourable grazing resource, and thereby improved conditions for herders/hunters, during the Early Holocene in northwestern Arabia, which retreated abruptly due to aridification at about 8000 cal BP.