Big thanks to our funders @gerda-henkel-stiftung.de, co-authors Jaafar Jotheri, @louiserayne.bsky.social, Nawrast Abdalwahab & @ericandrieux.bsky.social & all other contributors at Radboud University, @arcdurham.bsky.social, @newcastleuni.bsky.social & the universities of Al-Qadisiyah & Basrah.

While our work provides more details about this field system, it also opens many new questions which we hope to answer more fully in the future. Read more about these enigmatic features in our new paper published #OpenAccess in @antiquity.ac.uk today: doi.org/10.15184/aqy...

Climate change could have played a contributory role as any reduction in the amount of water flowing downstream in the Shatt al-Arab would have meant the tidal effects on the river would have been less pronounced, reducing the area that could be irrigated using this method.

The spread of plague in the 14th century, on the other hand, and the drop in population numbers this caused, may have impacted both the available workforce and the number of local consumers to such a degree that farming on this scale was no longer viable.

Possible explanations for the decline of this system might include the Mongol invasion of Iraq which caused significant disruption during the late 13th century.

While the ultimate origins of the system remain debatable, the ridges we sampled continued to accumulate between the 9th and 13th centuries meaning the surrounding area was farmed during this period.

Our results demonstrate that, while the ridges were likely there at the time of the slave revolt in the ninth century, the soil in the ridges continued to accumulate in the centuries that followed - so this agricultural system has a longer history than was previously assumed.

To provide more certainty, we retrieved samples from within the ridges themselves for analysis using ‘Optically Stimulated Luminescence’ methods. These date the last time individual grains in the soil were exposed to sunlight - when the earth was piled up to form the ridges.