Of all the mysteries of ancient Rome, silphium is among the most intriguing. Romans loved the herb as much as we love chocolate. They used silphium as perfume, as medicine, as an aphrodisiac and turned it into a condiment, called laser, that they poured on to almost every dish. It was so valuable that Julius Caesar stashed more than half a tonne in his treasury.
Yet it became extinct less than a century later, by the time of Nero, and for nearly 2,000 years people have puzzled over the cause.
Researchers now believe it was the first victim of man-made climate change – and warn that we should heed the lesson of silphium or risk losing plants that are the basis of many modern flavours.
Paul Pollaro and Paul Robertson of the University of New Hampshire say their research, published in Frontiers in Conservation Science, shows that urban growth and accompanying deforestation changed the local microclimate where silphium grew.
“You’ll often see the narrative that it [became extinct] because of a mix of over-harvesting and also over-grazing – sheep were very fond of it and it made the meat more valuable,” Pollaro said. “Our argument is that regardless of how much was harvested, if the climate was changing, silphium was going to go extinct anyway.”
Silphium is believed to be a species of Ferula whose modern counterparts include fennel and asafoetida, a spice often used in Indian cooking. It was a bush that grew wild only in a strip of land 30 miles wide and 125 miles long in Cyrenaica, in what is now Libya.
The ancient Greeks, who colonised the north African territory in about 630BC, tried and failed for centuries to cultivate silphium. “They talked about the frustrations of trying to transplant it – ‘why doesn’t this stupid silphium plant grow’,” Robertson said. “It had these micro-climactic requirements and they couldn’t figure it out.”
Administrators in Cyrene ordered limits on how much silphium could be harvested, and fenced off areas where it grew, Pollaro said. “There’s evidence that they knew it was declining and they tried to preserve the plant. But all of these tactics were ultimately irrelevant, because they had changed the microclimate.”
Silphium grew along the drier, sea-facing side of Libya’s Jebel al-Akhdar plateau, a fertile, forested region. After harvesting, it was exported to Rome and beyond.
“It’s hard to overstate how important silphium was because the Romans in particular were absolutely obsessed with it,” Pollaro said. “They minted coins in ancient Libya that had silphium on the front of the coin and the god or the emperor’s face on the back.”
Herodotus, Theophrastus and Pliny the Elder wrote extensively about the plant and laser. Pliny extolled it as a cure for dog bites, snake venom and haemorrhoids. It could be used as a contraceptive and the plant itself was a prized vegetable.
Exports brought wealth, which meant expansion. The Greeks and the Romans, who took control of Cyrenaica about 90BC, cut down forests on the plateau to build bigger and better houses and to clear land for crops for the growing population.
Deforestation changed rainfall patterns, causing greater erosion on the hillsides where silphium grew, which Pollaro said was confirmed by excavations at Haua Fteah cave near Benghazi. Silphium’s microclimate was ruined and it disappeared quite rapidly.
“In a way, silphium’s value was the cause of its own decline,” Pollaro said. “Without silphium, Cyrene’s economy wouldn’t have grown so much.”
Modern climate change is having a similar impact. Asafoetida, a sap extracted from a herb that grows wild in parts of Afghanistan and neighbouring countries, is widely used in India. But its footprint is shrinking due to changes in the local climate.
Professor Monique Simmonds of Kew Gardens said coffee, carrots and rice were similarly at risk. “We rely on between 10 and 12 species for most of our food,” she said. Kew was collecting seeds of wild species for its millennium seed bank and this diversity was crucial, since modern varieties might prove vulnerable to changes in climate in ways that could not be foreseen.
“If we don’t do the research and collection of wild species, we won’t have the reserves of genetic material in banks to do crosses in the future,” Simmonds added.
