When a civilization is barreling towards its demise, garbage collectors tend to stop picking up the trash.
At least, that might have been the case for the Byzantine settlement of Elusa (also known as Halutza) in Israel’s Negev Desert, according to a study published today in the journal PNAS. Though the collapse of cities like Elusa is often linked to the Islamic conquests of the seventh century, a new analysis of garbage heaps near the ancient settlement indicates that organized trash removal might have come to a halt up to a century prior. These findings hint at a controversial idea: that the region’s decline was actually brought on by the far-reaching repercussions of a small ice age that took root around the year 540 CE, long before foreign forces invaded.
“This is a wonderful example of a thoughtful, well-grounded archaeological study,” says Melinda Zeder, an archaeologist and curator emeritus at the National Museum of Natural History who edited the paper for publication. “It brings climate back into the discussion of this particular societal collapse in the Byzantine Empire, especially in this area of the Negev.”
Though refuse ultimately became the piéce de rèsistance of his team’s work, study author Guy Bar-Oz, an archaeologist at the University of Haifa in Israel, didn’t plan on dumpster diving when he began excavations at the Byzantine ruins swaddled in the sands of the Negev Desert.
Upon arriving in Elusa, Bar-Oz and his colleagues sought out the highest point of elevation they could find to survey the site: a loamy knoll protruding nearly 17 feet out of the ground. It was only once they’d reached its crest that the researchers realized their makeshift platform was actually a heap studded with charred seeds, pottery, and bones—a pile of 1,500-year-old garbage crunching beneath their shoes.
The trash in this mound, and three others like it, turned out to be an archaeological gold mine. Much of it was domestic: olive pits, pieces of pottery, ashes cleaned out from ovens, the bones of sheep, goats, and fish whose meat might have fed the masses. Other debris included discarded building blocks from the city itself, such as excess rubble from construction, and lumps of mud-based mortar.
But Bar-Oz was most struck by the scraps that signaled a Negev Desert specialty: hundreds of grape seeds, presumably byproducts of fermentation of the region’s famous and highly sought-after export of Gaza wine (which Bar-Oz hopes to someday recreate). “We immediately knew these were important—there were just so many, and you could see the diversity of them with the naked eye,” he says.
By chemically dating the debris, the researchers discovered that the trash was stratified into distinct chronological layers, each likely representing a separate dumping event. In general, the bottoms of the piles held the oldest artifacts, dating as far back as the third century BCE, when Elusa supposedly had its urban beginnings. It’s probable that dedicated garbage men were regularly amassing trash within Elusa’s borders and discarding it into these mounds at a rate of around 6,000 cubic meters per year, Bar-Oz says—a hefty yield for a population that numbered in the tens of thousands (Bar-Oz estimates that this is about three orders of magnitude less than what an urban landfill in a developing country would yield today).
And it turns out the dirtiest parts of Elusa’s history are a pretty good indicator of the city’s intricate social infrastructure: These mounds appear to be the products of highly organized, meticulously monitored waste management, Bar-Oz says. Which might mean that pinpointing the dissolution of this sophisticated system could reveal when things started to go south in Elusa as a whole.
Elusa’s untimely end has often been attributed to the arrival of Islamic forces, which ultimately wrested the region from Byzantine control in the middle of the seventh century. But very little of the trash that had accumulated in the city’s garbage heaps seemed to date beyond around the mid-sixth century. Other studies have noted that, from this point on, waste in nearby settlements appeared primarily in the form of little piles in and around households within city borders, Bar-Oz says. This suggests that something else upended formal garbage collection in Elusa decades before its residents were ousted by foreign armies.
The end of organized trash removal might seem minor, but it could actually be a bellwether of more severe changes to come, Zeder says. Such an elaborate system would have required diligent oversight, and could have easily fallen by the wayside in the event of serious social upheaval, she says.
Others, however, are more cautious about bookending the rise and fall of garbage collection in Elusa. “This is suggestive, but I don’t know if you can reach a definitive conclusion,” says Jodi Magness, an archaeologist at the University of North Carolina at Chapel Hill who specializes in the Byzantine and early Islamic periods and was not involved in the study. The age of many artifacts, including certain types of pottery and coins, can only denote the approximate dates they were made—not when they were taken out of circulation or disposed of, she says. It’s still possible that these dumping grounds were created later than the researchers theorize.
Still, the simplest explanation for the paucity of post-sixth-century artifacts in the heaps is that some dramatic change occurred in Elusa around this time, Bar-Oz argues. But in the mid-500s, no one was yet encroaching on Byzantine borders. So what, then, could have collapsed trash collection in Elusa?
That’s still an open question. For Bar-Oz, though, the frontrunner theory is something perhaps unexpected: climate change—in the form of a large-scale cooling event known as the Late Antique Little Ice Age.
Triggered by a series of three massive volcanic eruptions beginning in 536 CE, this mini ice age ushered in a prolonged period of cooling across much of Europe and Asia. A decades-long cold spell might have contracted growing seasons and hastened the spread of infectious diseases like the Justinian plague in parts of Europe, says Ulf Büntgen, a geologist not involved in the new study whose 2016 work characterized the timeline of this climatic event. The ensuing turmoil could have then spilled over into other parts of the world, like Elusa, that depended on European markets for trade and commerce.
For now, it’s hard to know if the toll of this economic strain would have been enough to push Elusa over the edge, cautions Matthew Jones, a quaternary scientist and paleoclimate expert at the University of Nottingham in the United Kingdom who was not involved in the study. Jones, who praises the work, adds that “the answer will never be definitive, but we can get towards an answer by getting data from both archaeological and paleoclimate perspectives.”
One important next step will be to continue gatherine information about other settlements in the Negev, Magness says. If the failure of foreign markets was the impetus for Elusa’s societal downturn, she says, the same trajectory could be expected its neighbors, like Shivta and Nessana (or Nitzana). There’s evidence that a few Negev cities were occupied well into the seventh century—but then again, that story could shift the next time someone digs through their garbage.
Regardless of how the situation shakes out for other settlements, the case of Elusa suggests just how sensitive cities can be to the consequences of climatic perturbations. Elusa might not have collapsed directly at the hands of climate change itself, Zeder says, but there’s a good case to be made for it feeling the reverberating effects of chaos abroad.
All this speaks to the interconnectedness of economic and social networks with climate, even from afar, Büntgen says. Humans don’t have to be subject to—or even within eyeshot of—the immediate effects of climate change to suffer its impacts.
“This is a parable from the past that has incredible resonance for today,” Zeder says. “People should take changes like climate change extremely seriously…we need better resilience to combat what are going to be major changes.”
Part of that will be leveraging the major advantages we have over civilizations of late antiquity. “The folks in the Byzantine had no idea there were going to be volcanic explosions and climate change,” Zeder says. “But we don’t have the same excuse. We know how our systems work, and we can predict it.”