Scientists reconstructed the location and history of Portus Pisanus, the ancient port of Pisa. This once important harbor fell into disuse when the sea inlet silted up and turned into an inland lake.
You probably know the Italian city mainly because of its leaning tower, but Pisa was once one of the most important port cities in the world. The old harbor – Portus Pisanus – is known, among other things, from the Roman Itinerarium Maritimum (the "Travel Guide to the Sea," comprising a list of locations and their distances) from the early sixth century, and from poems by the Roman writer Rutilius Namatianus from the early fifth century. Portus Pisanus was a thriving commercial port in a naturally sheltered sea bay, according to Rutilius' descriptions. But where exactly was that bay and what happened to the harbour? Until now, scientists have been unable to provide the exact answer to that question.
Sheltered
That has now changed. A team of French, English and Italian geologists and archaeologists reconstructed the environment and sea level in the area during the Holocene – from about 10,000 years ago to today. The harbor was about 20 kilometers south of present-day Pisa about 200 BC, as had already been shown from the writings and archaeological excavations. At the time, there was indeed a sheltered bay there with a good connection to the sea, the scientists now conclude.
After that, however, the environment changed under the influence of sea level rise and the accumulation of sediment in the delta. Around the year 1350 AD, the connection with the sea slowly but surely started to disappear due to the silting of sediment, after which the bay turned into a closed coastal lake around the year 1500. At the end of the sixteenth century, a new seaport was built in Livorno, which took over the task from Portus Pisanus (see box).
Combined
The Earth scientists combined several biological and geological research methods to arrive at their conclusions. From the analysis and radiocarbon dating of excavated sediments, pollen and plant remains, they learned when and where in the past there was a deep sea, a kind of Wadden Sea region, a freshwater lake or land, and they reconstructed the height of the sea level.
They also found charcoal fragments – often indicative of human activity – and remains of shipwrecks. By linking the findings to the ancient maps and writings, they were able to complete the reconstruction.
It is thorough research, says Sjoerd Kluiving, geo-archaeologist at VU University Amsterdam, who was not involved in it himself. “People knew roughly where the harbor used to be, but now it has become clearer where exactly and especially why.” He thinks the researchers have done their job well. “For example, the sea level reconstruction is based on measurements from 31 locations, which is quite a lot.”
In particular, the combination of data from the various disciplines – i.e. archaeology, geology and biology – makes the story of the port that fell into disuse plausible and complete, believes Kluiving.
The name Portus Pisan we find it for the first time in a travel poem by Rutilius Claudius Namatianus from the beginning of the fifth century. However, the city is much older than that:the Etruscans inhabited the settlement as early as the seventh century BC, when it was still directly on the coast. With the arrival of the Romans, the city turns into a military base and in the first century BC Pisa and the surrounding area is a veterans colony. Soldiers get a piece of land here after their military service.
When Rutilius describes the city, probably in the year 417, the city has grown into an important trade center. His experiences are reflected in the travel poem De reditu suo or "My Return" (to his native Gaul). He applauds the bustle and wealth of Portus Pisanus, which is surrounded by seaweed. In the wooded hills around the city, Rutilius goes on a wild boar hunt. The wood from these forests and the river clay serve as raw material for the firing of ceramics, one of the most important trade products in the region.
After the fall of the Roman Empire at the end of the fifth century and wars with Germanic tribes, Portus Pisanus went into a temporary great dip. Devastation, famine and epidemics ravage the city. But with the arrival of the Lombards a century later, the port city slowly blossoms again and trade increases. Pisa grew into one of the most important port cities in Italy in the Middle Ages, but the old port is already too far inland. Between 1300 and 1400 the Pisans built a fortified harbor in the west of the city, which is also called the port of Livorno.