The ancient ports of Rome revisited: a multiple proxy of environmental changes in relation to human occupation

Abstract

<p>The city of Rome neither have nor had natural bays in its vicinity working as ports. The navigable stretch of the Tiber River that extends from the sea to Rome compensated the lack of natural harbours along this part of the Tyrrhenian coast. The first marine port of Rome was the river dock of ancient Ostia that served Rome since the 4<sup>th</sup> cent. BC, well before the excavation of the imperial ports of Claudius and Trajan during the first and the second cent. AD in the Tiber delta.</p><p>The fate of the harbour system of Rome is closely linked to the fluvial dynamics of the Tiber river and the winter storms that characterise the Tyrrhenian sea even today. It is well known that during Imperial time, intense floods occurred and ships were lost or prevented to reach the harbours because of heavy storms. During the 9<sup>th</sup> century AD, when the entrance of Claudius harbour was silted up and the Trajan basin became a lake isolated from the sea, ships started to use again the Tiber river mouth at Ostia. The progradation of the Tiber delta is well explained by the present location of Claudius and Trajan basins, ca. 3.5 km far from the Tyrrhenian coast.</p><p>The palynological and ostracodological investigations integrated by other proxies in six chronologically framed sediment cores in the Tiber delta, close to ancient Ostia and Portus towns, provide a picture of complex environmental and historical changes for the last three millennia. Core dating was a challenge. AMS radiocarbon ages from terrestrial and marine plant macro-remains and sediment bulk, as well as historical events, archaeological pottery and palaeomagnetism have been used.</p><p>The six considered sediment cores record different periods of time, at times overlapping. Lagoon and freshwater conditions were reconstructed through ostracod and foraminifer analyses of the sediments, and pollen analyses described a plant landscape typical of a coastal deltaic environment before harbour activities, with increasing human impact related to the presence of Ostia and Portus and of medieval settlements. Imperial age floods are evidenced by ostracod assemblages, while a thick cover of Renaissance floods is spread on most of the Tiber delta area. Natural sedimentation continued only in the Trajan lake, and its sediments record the recent environmental and historical changes such as the reclamation works of the area during the first half of the last century, as well as the nuclear explosions occurred during the second half of the last century.</p>