Rome’s unique skyline scattered with steeping basilica domes, ancient forum ruins and the infamous Colosseum would not be complete without the silhouette of an Italian Stone Pine.

Also known as Umbrella pines, parasol pines, pignolia nut pines, or by its botanical name Pinus Pinea, these beloved trees are a staple along Rome’s villas, parks and highways. However several key developments indicate an uncertain future for their existence within Italy’s Capital.

While the trees are native to the Meditteranean region, they have also naturalized in parts of North Africa, the Canary Islands, South Africa and New South Wales. Cultivated throughout these regions millennia ago, it is practically indistinguishable from being native beyond its generic range.

• The trees of Rome 
• Protecting Rome from falling trees

The species has been harvested at least 6,000 years for its edible pine nuts, a historically traded resource and sustenance. The pine nut seeds in nearly all of Italy have since been destroyed due to the introduction of the western conifer seed bug (Leptoglossus occidentalis).

Accidentally imported with timber from the western United States to northern Italy in the late 1990s, the invasive pest species feeds on the sap of developing conifer cones, causing the seeds to wither and misdevelop. Coined the Dry Cone Syndrome, the decrease of pine nut yield in Italy threatens the natural reproduction of new pine trees, which is further concerning considering the species relatively young life span.

Romans armies included pine nuts in their diets, however these impressive trees individually have an average longevity of between 50 and 150 years. This means that the rows of Stone pines planted by Mussolini, now infected with pests, will begin to fall without seeding a forest of heirs. These pines have already begun to wreak havoc across the city during major storms, inspiring statements by mayor Viriginia Raggi. She believes that while the “the city’s ancient pines are part of the city's panorama”, government funds must be allocated for cutting down dangerous aging trees before they fall on properties or main roads.

Environmental factors are now accelerating these trees’ decay, as irregular temperatures have provoked a generalized dieback and decay, lack of regeneration, and stimulated the preferred living conditions of invasive pests. A shift on vegetation has been observed, as P. Pinea are being displaced by Juniperus thurifera and Quercus ilex, which are better adapted to the new conditions.

Harsher coastal conditions have strained the role of Stone pines in protecting inland areas from salty winds and preventing further cliff erosion. Remaining pines have been awarded high legal conservation status, but the long term solution to this pressing issue remains unclear.