One thousand years ago, people along Israelâs Mediterranean coast dug deeply enclosed plots in the sand, filled them with 80,000 tonnes of trash and used the fertile soil that formed for farming, allowing them to produce crops that would otherwise fail on such harsh ground.
This represents the oldest-known, large-scale plot-and-berm system that allows crop-growing in sand, putting it among multiple, less clearly dated sites across the globe. It might even be the origin of such oasis-like agricultural sites in deserts, some of which still exist today, says at Bar-Ilan University in Israel.
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âSand has no nutrients â all the water goes right through it,â he says. âAnd here they took this most inert substance, and they turned it into gardens, and amazing earthworks.â
In the 1940s, scientists discovered sandy mounds containing chipped pottery scattered in a chequerboard pattern that covered about 1.4 square kilometres in Caesarea, on the Mediterranean coast of northern Israel.
More than 30 years later, archaeologists started excavating the site and determined that it probably reflected an early Islamic farming system that included a guard tower, housing and storage facilities. By 2017, researchers had of the sediments to around 1140 AD.
In 2020, Roskin and his colleagues carried out in-depth excavations of the site, as well as two smaller but similar ones in nearby Yavneh and Ziqim.
The researchers discovered that the berms â sloping, sand-based barriers reinforced mainly with pebbles and broken pottery â enclosed plots where groundwater was only about 1 metre below the surface. They also found evidence of these plots being filled with charcoal, ash, bones, coins, glass, crushed pottery, burnt crop-making leftovers and other refuse, probably from city dumps and delivered by boat or wagons drawn by donkeys or camels. This was then supplemented with lime from limestone, produced onsite at kilns that have also been excavated.
Within years, that refuse, mingled with the sand and mixed with trapped rainwater and groundwater, would have created a from which farmers could probably have harvested fruit, vegetables, herbs or cotton, the researchers say.
âIt was probably a very sufficient way to get rid of and make use of garbage,â says team member at the Israel Antiquities Authority in Jerusalem.
Creating such an intensive agroecosystem would have required massive effortsâabout 1.7 million work-hours per square kilometre, the researchers say.
Despite the huge investment of effort required, which might have been motivated by tax breaks or Islamic religious convictions about reviving âdead landsâ, similar groundwater-harvesting techniques have also been discovered in sandy areas in the Americas, Iberia and other parts of the Middle East.
âIn Iran they have unique watermelons growing in the middle of the desert using this same technique,â says Roskin. The mostly abandoned plot-and-berm system could be revived to help modern populations grow food in arid or otherwise sandy regions that are increasingly affected by drought â provided there is shallow, unpolluted groundwater below, he says.
While at the University of Oklahoma calls the research âfascinatingâ, he questions whether the returns for such intense work would be worth it today. âThis is not to say I think they [older societies] have done it wrong,â he says. âItâs just that I ask myself, âhow could they ever plant something there that would recruit that level of investment?ââ
Applying such a system in modern times might thus prove complicated, especially since groundwater levels are dropping in much of the world. âOf course itâs a great [work] ethic,â says Pailes. âBut I imagine if you tried to sell this to local farmers today, they would say, âwhy donât I just buy a diesel pump and pump the water out of the ground and put it where I want it?ââ
Environmental Archaeology
