A study recently published in Communications Earth & Environment has revealed that the current desert of Rub al-Jali in Arabia, one of the largest and driest in the world, was once a green and vibrant landscape, with lakes, rivers, and valleys formed by water.
This environmental change occurred during the wet periods of the so-called “Green Arabia”, between 11,000 and 5,500 years ago, according to the international and interdisciplinary team led by Dr. Abdallah Zaki, Professor Sébastien Castelltort (University of Geneva), and Professor Abdulkader Afifi (KAUST University).
A monumental lake and river networks in what is now the driest desert
The central finding of the study documents the existence of a 1,100 square kilometer lake, which reached its peak about 9,000 years ago and was up to 42 meters deep. This lake, located in Rub al-Jali, was formed by heavy monsoonal rains believed to originate from the African monsoon. These precipitations not only filled the lake but also, after overflowing, excavated a 150-kilometer-long valley, leaving a deep imprint on the desert floor.
Sediments analyzed by scientists allow tracking these rains along 1,100 kilometers, from the Asir mountains near the Red Sea. This discovery highlights that the region’s precipitations were not scarce but intense and capable of rapidly transforming the arid landscape.
Ecological transformation and human movements
Professor Michael Petraglia, from Griffith University, emphasized that the climatic change during these periods would have favored conditions of grasslands and savannas, attracting hunters, gatherers, and herding groups to this now inhospitable region. The abundance of archaeological evidence suggests that lake and river networks played a crucial role in the expansion and settlement of these human populations.
However, about 6,000 years ago, the landscape experienced a sharp decrease in precipitation, marking the beginning of the arid conditions that persist to this day. This climatic change forced human populations to migrate to more habitable areas and adapt their lifestyles to an increasingly hostile environment.
Importance of the study
This work not only highlights how past climate change radically transformed the environment but also how it affected human and ecological dynamics.
The Rub al-Jali desert, which now appears desolate, was once a vibrant environment, shaped by powerful monsoonal systems. These findings provide valuable context for understanding how extreme environmental changes impact ecosystems and human societies, also serving as a warning about the possible impacts of current climate change.
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