RIYADH: The Empty Quarter, a vast desert on the Arabian Peninsula, was not always barren — a study by King Abdullah University of Science and Technology, the University of Geneva, Griffith University, California Institute of Technology, the University of Texas, and the University of the Fraser Valley reveals that this region once had a lake and river system.

These favorable conditions supported grasslands and savannahs, enabling human migration until droughts forced populations to move, according to a study published in the Communications Earth & Environment scientific journal.

The study was led by KAUST Professor Abdulkader M. Afifi, with researchers Antoine Delaunay and Guillaume Baby from KAUST, and Abdallah Zaki from the University of Geneva. It highlights the impact of climate cycles on landscapes and human societies.

The Empty Quarter, or Rub Al-Khali, is one of the world’s largest deserts, covering nearly 650,000 sq. km, mostly in Saudi Arabia, with dunes reaching 250 meters. However, it was once much more hospitable.

“Beneath Rub Al-Khali’s desolate sands lies a vibrant past of lakes and rivers,” Delaunay said. “Our study highlights the transformative power of climate on Arabian landscapes and human occupation; further research is essential to understanding these complex interactions.”

These water sites emerged during the “Green Arabia” period, from 11,000 to 5,500 years ago, at the end of the Quaternary era. The lake, covering 1,100 sq. km and up to 42 meters deep, eventually overflowed, carving a 150 km-long valley in the desert.

Based on sediments and landforms traced over 1,000 km, scientists suggest that rains from the northward expansion of the African and Indian monsoons fed these ancient waterholes. These wet phases varied in duration, favoring grasslands and savannahs, which enabled human expansion across the Arabian Peninsula.

This study is part of KAUST’s broader effort to understand climate, landscape, environment and human habitation in the region. KAUST Professor Frans Van Buchem leads another team studying ancient lakes in Wadi Al-Dawasir and their impact on human occupation near Al-Faw, a UNESCO World Heritage site.

‘‘The formation of lake and river landscapes, along with grasslands and savannahs, would have facilitated the expansion of hunting, gathering, and pastoral groups into what is now a dry, barren desert,’’ said Michael Petraglia, a professor of archaeology at Griffith University’s Australian Research Center for Human Evolution. ‘‘This is confirmed by abundant archaeological evidence found in the Empty Quarter and along its ancient lake and river systems,’’ he said.

About 6,000 years ago, a sharp decline in rainfall resulted in arid conditions that forced nomadic populations to migrate to more hospitable areas.

These findings highlight the role of the African monsoon in transforming the Arabian Peninsula’s desert landscape and shaping human migration. This narrative of climate change and human movement is crucial to understanding the potential impacts of current climate change.