Building Resilience through Territorial Planning: Water Management Infrastructure and Settlement Design in the Coastal Wetlands of Northern Apulia (Salpia vetus-Salapia) from the Hellenistic Period to Late Antiquity

Abstract

This Gulf of Manfredonia has, for millennia, been the primary water feature of the coastal wetland of Northern Apulia, Italy, although modern reclamation works make writing its long-term history challenging. Our recent paleoenvironmental research has reconstructed the evolution of the southern half of this lagoon since the Neolithic period. Here, we write a history of water management and environmental change in this landscape from the perspective of two key urban sites: pre-Roman Salpia vetus and Roman Salapia. The Roman architectural historian Vitruvius recounts the abandonment of Salpia vetus and the refoundation of Salapia. We employ his narrative as a frame for a more complex environmental history, starting from a historiography of this landscape’s study and a summary of our interdisciplinary research agenda, which unifies environmental, topographical, remote sensing, and archaeological approaches. Resilience in this changeable wetland environment was only possible through an integrated and intentional management of water among rivers, the lagoon, and the Adriatic Sea. While Salpia vetus exploited this wetland and thrived for centuries, the settlement eventually collapsed due to human and environmentally impelled factors. Roman Salapia subsequently emerged with a different approach, new infrastructure, and a new location. This blueprint would sustain urban life in this wetland for six centuries and lay the groundwork for the Medieval town.

1. Introduction

Resilience is a theme richly explored when considering how ancient cities confronted environmental change and challenges. This assertion is further strengthened when those cities were situated in wetland environments, prone to sometimes radical and deleterious changes resulting from natural trends and human activities. In coastal Apulia, in southeastern Italy, the histories of pre-Roman Salpia vetus and Roman Salapia were already known in antiquity, a cautionary tale and colonial success story, respectively, employed by the architectural theorist and urban planner Vitruvius.

In his treatise De Architectura, Vitruvius dedicated part of his first book to choosing the most salubrious place for the foundation of a new city (Vitr. 1, 4, 11–12)1 [1]. He recalls how, unlike Altinum, Ravenna, and Aquileia, the oppidum vetus of Salpia was built near a stagnant marsh (palus). This location was the cause of pestilential vapors that led the exasperated inhabitants to entrust Hostilius, probably the patronus of the community, with the task of finding a more suitable site to relocate the settlement. After thoroughly surveying the surrounding area, Hostilius purchased more salubrious land four miles from the old town (oppidum vetus), not far from the sea, on the shores of a coastal lacus, now called the Salpi Lagoon. There, he refounded Salapia. Finally, to preserve the salubriousness of the area and avoid new swamping, Hostilius opened the basin of the coastal lagoon toward the sea, transforming it into a port to serve the new city.

The leading players in this history, more complex than his narrative divulges, were multiple: the oppidum vetus of Salpia, a site in severe urban decline; the refounded city of Salapia, a town in ascent due to favorable, even if heavily managed, circumstances; and the coastal wetland, with which the two Salapia related over centuries and whose evolution affected the settlement choices of local communities.

We start with a definition of resilience in a literal sense, based on its Latin root, the ability of a community to “bounce back” when faced with environmental stress and disturbance, both naturally conditioned and human-impelled [2,3]. The ecological systems model of Hollings and Gunderson provides a useful baseline, acknowledging the cyclicality of changes while not presuming that all occur at the same pace or involving the same variables in all contexts [4,5]. However, this theory poses some problems and encourages questions. Past and recent theorizing has often presumed the static location of settlements or systems that enable a clear path to tracking adaptability and transformations. Even the short-scale movement seen in the wetland under investigation here must be interrogated: do they maintain the function, structure, and identity required of the panarchy model [5,6,7]?

Additionally, treating systems as internally homogenous [8,9] allows little flexibility in interpreting the multi-variate, political, economic, and social character of human interactions, presupposing a predetermined narrative or “rationality” to problem-solving [2,10]. Indeed, what would balance be when seen from a distinctly political, economic, or social perspective? And balance for whom? Can imbalances exist in one arena but not in others and still produce stability? The challenges of charting a model in a wetland context become increasingly apparent because it is predicated on seasonal, annual, and even longer changes. The marsh is not necessarily consistent from day to day, let alone year-to-year or century-to-century.

Our focus on the relationship of human settlements around the Salpi Lagoon to water makes this slipperiness ever more apparent (no pun intended!). This was not just a negotiation with the lagoon itself. Our context being permeable, this marsh was impacted by relationships to rivers, their outflows, and the sea. In his model of climate change archaeology, Van der Noort encourages us to delve into the study of local contexts to chart the strategies of communities to confront this changeability [10,11]. Marshlands can be risky environments: they bring great opportunities to inhabitants and ruinous stresses. However, the weight of each over time can be complex and not easily predicted. Resilience is highly contextual, in other words.

To chart the resilience of these towns over nearly one thousand years, a multidisciplinary team of archaeologists, bioarchaeologists, geomorphologists, and palynologists, coordinated by the Department of Humanities of the University of Foggia and McGill University in Montreal, has been reconstructing the long-term, co-evolutionary processes shared between these anthropic settlements and the environment in the coastal plain of northern Apulia (Figure 1). With the resurrection of myriad variables and tracking patterns over centuries, we have written this complex history that was not linear and surely not predetermined. Indeed, wetlands can be highly productive, meaningful contexts for urban development. While Vitruvius and his evocative story of settlement transition in a wetland are the starting point for this exploration, environmental and material data must be studied and interpreted to flesh out more fully the complexities of change through time, the waxing and waning and waxing again of urban life along and around the Salpi Lagoon. In this study, we chart what might be considered a single “adaptive cycle”: the growth, floruit, decline, and demise of pre-Roman Salpia vetus that led to the growth and floruit of Roman Salapia. These stories were spatially proximate, and resilience was communicated and imparted environmentally and materially.

First, we present a contextualization of the Salapia lagoon landscape, from a geographical, historical, and archaeological point of view. What did we already know about it before our research project began? What are the already available sources for its study? How had previous historical and archaeological research addressed the reconstruction of this habitat? From there, we present the research agenda designed by our group to resurrect the history of this wetland, whose past boundaries and character have been obscured by 19th and 20th century reclamations works. Finally, we evaluate the relationship of Salpia vetus and Salapia with the surrounding wetlands and how water management strategies were crucially important to both sites.

2. The Study Area and Background

The coastal plain of Northern Apulia (Figure 2), in southeastern Italy, has long been defined by the presence of a wide lagoon. Prior research has registered diachronic evolution prompted by climatic changes, sea level fluctuations, river floods, and adaptation/containment/exploitation strategies influenced by local communities and their everyday activities over centuries [12,13]. At the beginning of the 20th century, the growing demand for cultivable land and the progressive degeneration of human health in this zone pushed the State to reclaim most of the coastal wetlands and lagoons spread along this gulf [14]. Alluvial deposits, purposefully transported, obliterated almost every trace of the ancient morphology of the shoreline, saving only two derivations of the original coastal lagoon: the Palude Frattarolo, near Manfredonia, and a part of the Lago di Salpi, which was transformed into saltpans, and are still in use. Therefore, the modern image of this lagoon is likely radically different from its ancient form and appearance.

Ancient textual sources have helped to write part of this history or at least provide glimmers of past engagement with this coastal context. The most ancient source on the presence of a lake or lagoon along the Adriatic coast of Northern Apulia is a passage of the Alexandra of Lychóphron (Lyc. Alex. 1126–1140), dated to the end of the 4th century BCE. In his words, a temple dedicated to Cassandra was built by the local inhabitants (the Dauni) on the shores of a limne near Salpe. Two centuries later, Strabo, in his description of coastal Daunia (Strabo 6, 3, 9), presented Salapía as the epíneion of Arpi, 140 stadia from Sipontum, situated near to a navigable river and a stomalímne megale where the grain coming from Arpi and Sipontum was traded. Even if some doubts remain about the meaning of the term stomalímne (a lagoon? an estuary? an estuary flowing into a lagoon?), we have more certainty in identifying Strabo’s Salapía with the settlement identified by Giulio Schmiedt in 1964 in the area of Lupara-Torretta dei Monaci (see infra), a site with phases of occupation dating back to the 10th–9th centuries BCE. That was the site directly involved in the Hannibalic War (Liv. 24, 20, 16; 26, 38, 6; 27, 28, 3–13) and also active in the Social War until 89 BCE, the year of its conquest and destruction (App. BC. 1, 52).

A few decades later, in 63 BCE, in his oration against the Agrarian Law of Servilius Rullus, Cicero evoked an image of the pestilential nature of the land inhabited by the Salapini (Cic. leg. agr. 2, 71). This is a testimony of great importance: on the one hand, it allows us to understand the difficulties in which the inhabitants of the lagoon city lived at that time; on the other hand, it foreshadows the event that, shortly afterward, would be described by Vitruvius [1]: the founding of the ‘second’ Salapia and the migration of the local community from the oppidum vetus to the new one.

The available written sources of the Roman period do not mention the Salapia lagoon. Even in medieval and late medieval documents, it is barely mentioned. The Pantanum Salparum is cited rarely in documents of the 12th and 13th centuries CE [14]. In these texts, there is no reference to topographic features, only a precise listing of landholdings, rural houses, or churches in the territory of the medieval town of Salpi, whose buildings occupied part of the area of the pre-existing Roman city (see infra). The meaning of pantanum evokes an image of a stagnant, unhealthy place unsuited to settlement, but we cannot exclude the possibility that the term might have been used in a more “neutral” way, to indicate portions of closed water. Also, immediately adjacent to the Pantanum Salparum was the probable location of one of the most important domus solatiorum constructed by Frederick II in Northern Apulia. Thus, in the mid-13th century, the area was still an accessible place, productive, and not lacking natural appeal [14] (p. 96).

If, as it seems possible from a few notations, the Pantanum Salparum was full of water, rich in fish still in the late 15th–16th century [15,16], we are confronted with a very different picture than that recorded in travel narratives of the 17th–18th century and in some official documents written between the 19th and the beginnings of the 20th century, in which the Salpi Lagoon is described as an unproductive marsh, in an area deserted by people because of its pestilential nature [17] (pp. 23–24).

Writing the history of this wetland has posed considerable challenges, as until recently, information from written sources, historical cartography, and historical aerial photographs were the only sources available to reconstruct this coastline and changes through time. Historical maps visually represent the Pantanum Salparum/Salpi Lagoon and the coast from the 15th century to the 1950s. Depending on the scale adopted, they can provide precious details and are very descriptive, offering images of landscapes that have completely disappeared or have been radically transformed (Figure 3). However, the high complexity inherent in coastal environments, subject to profound and sometimes rapid changes over time, does not allow wholesale or even piecemeal retrojection of this information without a critical approach. Instead, these maps visually represent the more recent evolution of the territorial context under examination.

Aerial photographs are predominantly vertical photos taken by the Italian Military Geographic Institute (IGM-Instituto Geografico Militare) in 1954–1955, which captured how the area looked before the development of intensive agriculture, which has played a commanding role in changing local morphology (Figure 4).

Using the IGM 1954–1955 photos, Giulio Schmiedt first hypothesized the setting and limits of the urban centers of Salpa vetus, Salapia, and Salpi, and of the areas allegedly covered by the recently reclaimed lagoon system [18,19,20]. Thanks to a complex network of cropmarks and damp marks, he suggested a series of hypotheses, identifying correspondences with descriptions in the ancient literary sources.

First, he identified the center of Salpia vetus with the widespread settlement located in Torretta dei Monaci-Lupara, 8 km from the coast (Figure 5 and Figure 6). As suggested by the photo interpretation, the settlement rose up on slightly elevated mounds (the so-called penisole), and it was reached via multiple roads from the countryside, visible as cropmarks and grassmarks; a semi-circular ditch also protected the city. Excavations conducted in the area between 1967 and 1979, by Fernanda Tinè Bertocchi, proved this theory and dated the occupation of the settlement from the 10th–9th century BCE to at least the end of the 2nd century BCE [21].

Second, Schmiedt identified the plateau where the new Salapia was founded, along the present-day saltpans of Margherita di Savoia, approximately 6 km (the 4 Roman miles mentioned by Vitruvius) from the oppidum vetus located at Lupara-Torretta dei Monaci. He also recognized the Monte di Salpi, at that time 10–12 m above sea level and still surrounded by a defensive moat, as the site of the medieval city of Salpi. Moreover, he identified many roads originating from and leading to both the Roman and Medieval towns, connecting them to other main centers of the coast and the hinterland (Figure 7).

Third, thanks to dumpmarks, Schmiedt designed the ancient lagoon extent, stretching from the foothills of the Gargano Mountain to the Ofanto River. The Bronze Age settlement of Coppa Nevigata [22], the pre-Roman site of Sipontum (Masseria Cupola) [23], the Roman and medieval city of Sipontum [24], Salpia vetus (Torretta dei Monaci-Lupara), Salapia, and Salpi (Monte di Salpi) were therefore located on its shores, defining the limits of the water basin.

Schmiedt identified the sites and demonstrated why an in-depth analysis of the area was necessary, as ancient landscapes were affected by the drastic changes to local geomorphology, to reconstruct the history of Daunia. Nevertheless, he stretched the data to confirm the ancient sources. Geoarchaeological analyses would not adequately support his coastal environmental reconstruction. In the early 2000s, the first integrated program of geoarchaeological and paleoenvironmental analyses was conducted by a team of geologists and geomorphologists of the University of Bari, focused on the northern part of the ancient wetlands, near the Neolithic and Bronze Age site of Coppa Nevigata [22]. Such evidence had been lacking for the southern portion of the lagoon until our research campaign.

Therefore, at the start of our research on the Salpi Lagoon, we had a few certainties and many questions: how did this coastal wetland evolve from the Neolithic period to the Middle Ages in relation to interior watersheds and the sea? What trends can we reconstruct in the environmental history of this wetland? How has this transitional landscape been organized and managed over the centuries, particularly throughout the long period from the emergence of Salpia vetus (9th–8th c. BCE) to the abandonment of medieval Salpi (15th c. CE)?

3. Materials and Methods

To address these questions, the research project Life on the Lagoon: Reconstructing the Biography of Human-Landscape Dynamics on the Salpi Lagoon, Italy defined and tested a set of best practices for a wetLandscape archaeology. The research program, from the macro to microscale, included the following:

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Dedicated off-site coring: our project gathered and analyzed sedimentological, palynological, and micropaleontological data coming from a total of 10 drilled boreholes (depth between 9 and 16 m), collected in the area between the sites of Salpia vetus, Salapia, and Salpi (Figure 8). Accelerator Mass Spectrometry ¹⁴C dates were obtained from selected charcoals, ostracod shells, and organic sediments (processed by Beta Analytic Radiocarbon Dating—Miami, FL, USA) [13] (in part. pp. 40–41 for details on the calibration methods used). Calibrated ages have been obtained from SAL3, SAM5, SAM6, SAM7, and SAM9 cores, from which datable material was recovered. Apart from the SAM9 core, the relative scarcity of plant remains and organic sediments did not allow the recovery of a consistent chronological sequence for the SAL3, SAM5, SAM6, and SAM7 cores. Despite this, calibrated ages from all dated cores show a good chronological coherence, with an interval spanning from the Late Northgrippian (6206–6104 cal BP = 4256–4154 BCE, SAM9, Figure 8) to the Late Meghalayan (231–164 cal BP = 1719–1786 CE, SAL3, Figure 8). The age-depth model and sedimentation rate of the SAM9 core were built using the Bchron R package (v. 4.7.6), which fits a stochastic linear interpolation in the Compound Poisson–Gamma model. Such multi-proxy paleoenvironmental analyses allowed us to outline better the history of the evolution of this coastal ecosystem over seven millennia.

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Systematic collection, georeferencing, and GIS management of all available historical maps and data on known sites, infrastructural systems, field systems, and historical road networks, with particular reference to the wetland area of Salpia/Salapia/Salpi (the coastal area between the salt pans of Margherita di Savoia, and the courses of the Ofanto and Carapelle Rivers) (Figure 9);

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Aerial photo interpretation: analysis of vertical black-and-white IGM aerial photographs (years 1954–1955 and 1976), AGEA orthophotos from 1997 and 1999; Regione Puglia orthophotos from 2000, 2004, 2005, 2006, 2013, and 2015; oblique aerial photographs taken in the early 2000s, all as part of the systematic aerial reconnaissance campaigns of Northern Puglia conducted by the Department of Humanities of the University of Foggia. Examining this extensive and varied documentation within a GIS framework and considering its quality, resolution, and the years and seasons of capture allowed for the identification of approximately 1700 traces (weedmarks, cropmarks, soilmarks). These traces, primarily located in the hinterlands of Salpia vetus, Salapia, and Salpi, are attributable to settlements, infrastructure, agrarian divisions, and cultivation that no longer relate to the contemporary landscape [25] (Figure 10). With regard to linear features in particular, a series of basic spatial analyses (azimuth calculation, trace extrapolation by orientation classes) were also applied in a GIS environment to verify the possible existence of pre-modern land divisions;

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Systematic field survey: the archaeological field survey, conducted between 2017 and 2019, covered an area of approximately 29 km². This area, corresponding to the southeastern part of the ager Salapinus, is bordered to the north and east by the inner banks of the coastal lagoon (Saline di Margherita di Savoia), to the west by the Fosso della Pila (a tributary of the Carapelle River), and to the south by the route of the Regio Tratturello Cerignola-Casale della Trinità, which seems to run along the ‘boundary’ between the historical jurisdiction of Salpia-Salapia and the (much larger) one of Canusium (Figure 11);

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Extensive geophysical surveys recovered the urban core, including street grid, and city walls of the Roman city of Salapia and medieval Salpi [26,27,28], as well as suburban and artisanal quarters, the extra-urban road network, and landscape management infrastructure beyond the walls of these towns;

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Systematic, open-area archaeological excavations in 20 × 20 m grid squares, expanded as needed to expose complete architecturally defined spaces, to register contexts of daily life and associated artifacts over long time scales, and demonstrate settlement transformations [29,30];

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On-site archaeobotanical analyses of samples recovered from stratigraphically excavated sealed contexts dated by artifact analyses from Salapia and Salpi (predominantly midden deposits, cooking surfaces, floor surfaces, and burial fills); determined anthracological and carpological remains are compared with the diachronic environmental trends reconstructed through analysis of natural sedimentary sequences obtained from off-site coring [31,32,33].

4. Results

4.1. Salpia vetus

4.1.1. A Wrong Choice of Location?

During the Neolithic period (6500–3000 ca BCE), most of the coastal plain of Northern Apulia was occupied by a large lagoon, partially opened to the sea, extending for about 40 km from the Gargano to the mouth of the Ofanto River (Figure 12).

Over the centuries, this body of water experienced a progressive reduction in size due to the northward progradation of a system of coastal dunes. This development of sand barriers favored the incremental isolation of the lagoon from the sea, shifting from a marine-brackish environment into a more sheltered freshwater environment [13] (pp. 45–49).

During the Bronze Age (2000–1000 ca BCE) and throughout the Iron Age (1000–700 ca BCE) and the Daunian period (600–300 ca BCE), brackish marshland and freshwater swamps began to occupy most of the area of the southern part of the coastal plain [13] (pp. 49–50).

What do we know about the place where, already at the beginning of the 1st millennium, the settlement of Salpa vetus took shape?

The area in question is the one that the topographic maps of the Military Geographic Institute (IGM) identified as the wetland area of Marana di Lupara, with traces still visible in the mid-20th century: a depression subject to the stagnation of freshwater, following floods of the Carapelle River. In maps of the late 16th to 19th centuries, the area was drawn as a swamp or lake (the so-called Lago Giardino) (Figure 13).

Based on the shape of the place, Giulio Schmiedt [19] and Catherine Delano Smith [34] hypothesized that the settlement of Salpia vetus had developed on strips of land surrounded by the waters of a peripheral branch of the great coastal lagoon (Figure 14). How accurate is this reconstruction?

Evidence from recent cores drilled in the area surrounding this urban center offers data to reflect on the relationship between Salpia vetus and its environment.

The analyzed sediments of the SAL1 and SAL2 cores, located immediately west of the settlement (supra, Figure 8), do not provide any evidence of a lagoon environment. On the contrary, starting from the Final Neolithic period (3500–3000 ca BCE) and until quite recently, the area was configured as a floodplain, affected by the periodic overflowing of the waters of the Carapelle River, which, in ancient times, flowed immediately north of the settlement of Salpia.

The sediments analyzed from the SAM9 core (supra, Figure 8) also show how the brackish lagoon environment connected to the sea, documented in the immediate north-east area from the settlement during the Early Neolithic (6500–4500 ca BCE) and the initial phases of the Bronze Age (2000–1500 ca BCE). It was replaced, between the Middle Bronze Age and the mid-5th century BCE, by an alluvial plain characterized by the presence of marshes and swamps influenced, above all, by the freshwater inputs of the Carapelle.

Finally, starting from the beginning of the 4th century BCE and throughout the Roman period, but also afterward, the oppidum vetus of Salpia and its hinterland definitively lost any relationship with the coastal lagoon. Both to the east and to the west, the SAL2, SAM8, and SAM9 cores clearly attest to the presence of floodplains periodically affected by the formation of shallow freshwater or very shallow saline water pools (Figure 15).

An overall assessment of the data presented thus far, therefore, leads us to believe that, starting from the 10th century BCE, the Salapini community had begun within a territorial context whose environmental characteristics were unstable, but not necessarily unfavorable to the development of a complex socio-economic system [35,36] (Figure 16).

As Aristotle had already observed well before Vitruvius (Arist. Pol. 7, 11), a city could arise and develop optimally only if it was well connected to both the mainland and the sea, had an abundant water supply, was sheltered from the winds, and could be easily defended from enemy attacks.

All archaeological data and literary sources available allow us to understand that, over the long term, the oppidum vetus of Salpia benefited from all these favorable conditions, eventually becoming, especially between the 6th and 4th centuries BCE, with more than 300 hectares of land designated for human occupation, one of the main proto-cities of Daunia, along with Canusium and Arpi.

First, the proximity of the Carapelle River ensured the supply of fresh water for human and animal life and agriculture. It also allowed convenient access to the hinterland, the coastal lagoon, and the Adriatic Sea. It is worth mentioning again the testimony of the Greek geographer Strabo on the existence, between Salapia and the coastal settlement of Sipous/Sipontum (Cupola-Beccarini), of a navigable river and a large lagoon estuary, through which goods from Sipontum, especially grain, were transported.

Despite the progressive retreat of the lagoon from the Bronze Age onwards, the large coastal basin and its precious resources (in particular salt [37,38], fish [39]2, game and fowl3 [40]) remained easily accessible, enabling Salpia vetus to act, from the late Iron Age onwards, as an emporium both for the main settlements of inland Daunia (Strabo presents the settlement as the epineion of Arpi) and for Adriatic trade [41].

Furthermore, arboreal pollen from the SAM9 core reveals that, since the final stages of the Eneolithic period, an almost treeless landscape with scattered Mediterranean shrubs and trees stretched all around the settlement [13]. This open and, at times, wet countryside offered extensive pastures for sheep and goat farming and especially for horse breeding [42], while from the late 5th century BCE, bioarchaeological indicators point to the spread of cereal cultivation, horticulture, and olive growing (Figure 17). From the late 4th century BCE, see the increase of anthropogenic pollen indicators in SAM9 core, such as: Cichorieae, Asteroideae, Poaceae, Plantago (areas used for grazing); Apiaceae and Brassicaceae (horticultural crops); walnut, chestnut, olive. The cultivation of cereals is indirectly attested by pollen grains of weedy plants such as Centaurea (cereals are known to be very low-pollen producers) [13] (p. 44, Figure 5).

Finally, the presence of waterways, canals, and temporary swamps in the site’s immediate vicinity made the oppidum more defensible [43]. The analysis of the IGM historical aerial photographs clearly shows that only the southern side of the so-called Peninsula I of the settlement was protected by a massive fortification, consisting of a 2 km long ditch associated with an embankment toward the interior of the settlement [21] (p. 63) (Figure 18). This defensive structure, likely constructed between the 6th and 5th centuries BCE, roughly similar to that of the settlement of Arpi4 [44], faced an inland area farther from the course of the Carapelle River, where the lands were generally drier. Consequently, access to the site was easier. All the other sides of Peninsula I, just like all the other parts of the settlement (the so-called Peninsulas II and III), were closer to the wet area crossed by the river, and perhaps were not devoid of defenses but certainly were not protected by fortifications like that of the southern side. Wetlands and swamps themselves probably served as a deterrent to potential attackers.

4.1.2. Salubrity and Water Management at Salpia vetus: Challenging Roman Exceptionality

In Aristotle’s reflection on the optimal conditions for a city, the philosopher underscores the salubrity of air and water. Salubritas was an “foundational” value for the survival of human beings. Vitruvius reaffirms a similar attachment to salubritas as a central component to the juridical–institutional organization of urban settlements. The choice of the most suitable place for the establishment and construction of a city should be front of mind (electio loci saluberrimi: Vitr. 1, 4).

In Vitr. 1, 4, 11–12 [1], he explains the nature of salubritas through the true opposition between the “positive examples” of Aquileia, Altinum, and Ravenna and the “negative examples” of the Pontine Plain and Salpia vetus. It is therefore worth revisiting this opposition and delving into its meaning, with the aim of then returning to examine the archaeological data at our disposal from Salpia vetus for a more precise contextualization of the written sources.

Vitruvius’ discourse deserves evaluation on the empirical and technical level. There should be an adequate altimetric difference between the areas where lagoons and marshes are found; the internal waters should not be “dead”, but regenerated by river inputs, and strong tides should impel a flow seawater inland. Therefore, salubritas is primarily the result of geomorphological and environmental conditions “naturally” suitable for life. Therefore, it is nature that makes the difference between the healthy Gallicae paludes, where all these favorable circumstances occurred, and the wet plains of the Pontine region or the area surrounding Salpia vetus, significantly depressed below sea level and crossed by streams with torrential, seasonal, or sporadic character.

At the same time, in Vitruvius’ reflection, the simple empirical–technical observation takes on a much stronger significance: human hands can strengthen what nature already offers or they can realize what nature itself does not allow. Therefore, salubritas is achieved through the construction of canals and water drainage/management works, and is the result of culture, knowledge, and skill.

As is well known, Vitruvius wrote his treatise during the age of Augustus, pouring into this work his expertise as well as experiences, testimonies, and knowledge of places presumably gathered during his service following Caesar, proconsul of Cisalpine Gaul [45]. By that time, the Romans had conquered the Po Valley regions, accompanied by the construction of new road infrastructures, the establishment of extensive land allotment systems for viritim assignments, hydraulic regulation, and the founding of new colonies, often established in coastal or near-coastal contexts with problematic hydrogeological settings [46].

At Aquileia, 60 stadia from the open sea and connected to the north-Adriatic gulf by the Natiso cum Turro, which bordered the eastern side of the city, the foundation of the Latin colony (181 BCE) already had a massive environmental impact, not only for the creation of the new urban layout but also for the extensive reclamation works carried out: canals that flanked the northern and western sides of the city along with centuriation, initiated at the beginning of the 2nd century BCE and completed by the first half of the 1st century BCE. Moreover, to protect the western and southern suburbs of the city, both depressed areas prone to flooding, the contemporaneous excavation of the Canale Anfora was undertaken: this water collector started outside the western stretch of the urban walls toward the lagoon, with a straight path of 6 km, thus allowing the drainage of surface waters from the hinterland to the sea and the influx of brackish lagoon waters inland, brought by the push of the tides [47,48,49,50].

At Altinum, a city-island among the main endo-lagoon emporia of the Veneti, the establishment of the Roman urbs was marked at first, perhaps already by the time of Caesar, by the construction of the walls and, subsequently, by the excavation of the Canale Sioncello, which connected the Sile River with the pre-existing ring of watercourses that already enclosed the Altinate settlement by an internal navigable route. Therefore, a complete circuit of canals directly connected to the coastal lagoon was, promoting the ingress and outflow of tides near the settlement [51].

A city of governed waters, at least since the Augustan age, was also Ravenna. It directly overlooked a large internal lagoon, closed and crossed by a system of artificial canals and hydraulic works so sophisticated and complex that it was the center one of the most strategic military and commercial ports on the Adriatic coast [52].

It is the contrast with these territories and cities expertly shaped by Roman technical and engineering skill that Vitruvius made the case that the oppidum vetus of Salpia, founded not by Rome but (in his words) by the Greek hero Diomedes or by the oikist Elpias of Rhodes [1], was a paradigmatic negative example. The rationes that the Romans had at their disposal for some time, that is, that body of theoretical principles and skills matured precisely through the territorial planning carried out with the conquest of the peninsula, would never have led to an urban foundation in a depressed area, surrounded by stagnant marshes and devoid of waterways or canals connected to the sea.

The opposition is, therefore, ideological and cultural: it is no coincidence that, in the narrative construct, Marcus Hostilius’s intervention and the re-foundation (this time entirely Roman) of the second Salapia are presented as solutions to remedy the error of the mythical (Greek) founders.

Vitruvius’ narrative serves as an example of the “Roman exceptionality thesis” [53], persisting in scholarship until very recent times. However, archaeological evidence from pre-Roman settlements such as Salpia vetus provides the counterweight for such models. Elsewhere, recent, fruitful studies that have led to a revision of the paradigm that Roman conquest (and colonization in particular) introduced a structurally new territorial and socio-economic organization in conquered territories. The results of increasingly numerous and in-depth projects have now clearly demonstrated how many Italic communities of the peninsula, well before coming into contact with Rome, were capable of expressing forms of territorial organization and planning, creating scattered rural settlements, and innovating agricultural and natural resource exploitation. It is unsurprising then that Italic peoples already had a culture of managing local hydrogeology and, in particular, communities settled in transitional environments such as coastal wetlands.

At Salpia vetus, reference has already been made to the impressive moat with an embankment of the so-called I Peninsula, whose construction, beyond its defensive and symbolic value, was also functional for draining lands periodically flooded by the overflow of the nearby Carapelle River and the flow of floodwaters toward the lagoon. Along the eastern edge of the same peninsula, a dam or levee was built, extending about 10 m in length with a foundation of large stones (supra Figure 18). However, the most striking evidence of land management interventions comes from the immediate hinterland surrounding the Salpia settlement.

The integrated analysis of the extensive dossier of historical and recent aerial photographs considered in our study (see above) allowed us to recognize and map a complex and coherent system of linear traces immediately south of the settlement, within a maximum radius of about 7–8 km from the site (Figure 19 and Figure 20). (1) at least five main axes, with widths ranging between 13 and 20 m, that depart from the moat closing the southern part of the I Peninsula and fan out toward the hinterland; (2) a series of “secondary” axes arranged to connect the main axes or as further branches of them.

Unfortunately, reliable excavation data cannot yet confirm this interpretation. Giulio Schmiedt [19] and Giovanna Alvisi [54] had previously partially identified and mapped some of these traces, which they argued were evidence of the network of main and secondary roads connecting Salpia vetus to the surrounding territory.

This proposal is undoubtedly plausible, and it offers the most immediate and straightforward reading of the network of anomalies. However, two factors must be considered: (1) the traces are crop marks and damp marks have considerable widths and could well refer to tracks partially dug into the ground: thus ditches; (2) the traces closely interact with the intricate network of geomorphological incisions through which spring and runoff waters from the interior terraces of Daunia flowed toward the Carapelle River.

Therefore, we cannot exclude the possibility that this capillary system of dug or semi-dug paths, radiating from Salpia vetus, responded not only to the need to allow mobility in and out of the settlement but also to the need to organize the living space surrounding the oppidum, through water management and drainage strategies that ensured the area’s healthiness and facilitated agricultural practices.

As far as dating, the establishment of the road/ditch system might have been implemented concurrently or shortly after the construction of the large moat delimiting the I Peninsula. If so, the territorial infrastructure would have been the result of a socio-economic and cultural growth process that Salpia vetus experienced between the 6th and 5th centuries BCE, with the emergence of prominent élites capable of projecting their interests toward land control and managing alliances, reciprocity, and the exchange of goods. It is also worth noting that the sedimentary sequences of the SAM9 core, immediately northeast of the settlement, recorded a significant increase in the local sedimentation rate (c. 0.31 cm/yr) between 1250 and 450 BCE [13] (p. 48). Thus, the implementation of a general plan to protect the site from water and manage the territory’s hydrogeological arrangements fit well in a period of enhanced hydrological runoff.

4.1.3. The End of Resilience?

What has been outlined so far, based on the scarce archaeological evidence available from Salpia vetus and, above all, the most recent paleoenvironmental findings, encourages us to re-examine Vitruvius’ account and to consider with more robust critical tools the unsuitability of the place chosen by the Salapini for their original settlement.

Wetlands are ecosystems characterized by delicate, fragile balances, strongly conditioned in their expansion or contraction, by the impact of climatic conjunctures and by the outcomes of economic choices. Likewise, the same strategies deployed by humans in interacting with these ‘fragile’ ecosystems have fluctuated over time, moving from phases characterized by greater attention to water control, and more balanced relations between agriculture and the economic exploitation of fallow marshland, to phases increasingly marked by greater aggressiveness in the exploitation of local resources, with diminishing care for the land.

The relocation of the Salapini was a drastic response to a situation that had emerged after centuries of balanced coexistence and had gradually become unsustainable over time (quotannis aegrotando laborantes, the source reports) [1]; a situation that Vitruvius traces back to the presence of undrained internal marshes incapable of finding outlets to the sea (were these the freshwater marshes created by the Carapelle waters flowing into the alluvial plains surrounding Salpia vetus, as seen above?); and the consequent formation of miasmas harmful to the health of the city’s inhabitants.

Which events had an impact directly on the local ‘water culture’? What caused the failure of the territorialization efforts that had successfully transformed inevitably unstable spaces into permanently habitable places for centuries?

To answer these questions, we need to consider multiple factors, starting with the wetter climatic trends, that seem to have occurred at a peninsular level and, in particular, at a regional level between the 2nd and 1st centuries BCE [55] (pp. 19–22), [56]. This circumstance may have favored the recurrence of seasons with more intense rainfall, such as to increase the flow of the Carapelle River and its tributaries, and facilitate the release, in the plain, at the mouth, or within the lagoon, of sediment transported by river water, especially during floods and overflows.

This period of climatic instability coincided with a political, economic, and social crisis at Salpia vetus with the conclusion of the Roman–Carthaginian conflict. In fact, during the Hannibalic War, Salpia vetus was among the centers that betrayed its alliance with Rome and, at the end of the conflict, paid for its disloyalty with the punishment, if not the complete replacement, of its ruling class [57] (pp. 153–200). Diminishing grave goods from the necropolis of the II Peninsula, which ceased to be frequented precisely at the end of the 3rd century BCE, communicate social and economic impoverishment associated with the settlement.

At the same time, Salpia was deprived of vast portions of its territory. The Liber coloniarum lists sectors of the Sipontum and Salpia agri to Roman public lands, which then had policies of limitation imposed alongside allocation to settlers, probably in the wake of Gracchan land reform measures (Lib. Col. I, 210–211 L). Some faint linear aerial photographic anomalies oriented roughly 64–71° east, identified to the south of the settlement and immediately southwest of the site later occupied by the second Salapia, might at first glance suggest the presence of traces of the division intervention mentioned by the Liber coloniarum. Extreme caution is necessary, however, due to the following: (1) regular modules with recurring measurements (e.g., modules of 20 actus) do not seem to be recognizable; (2) the axial traces are numerically sparse.

To verify this hypothesis, we attempted to trace the persistence of orientations compatible seen in the aerial photographs by analyzing contemporary land organization patterns over an area much larger than the probable ancient territory of Salpia vetus. A surface of about 850 km² has been scanned, which also includes part of the current territories of Trinitapoli and Cerignola and extends to the valley of the Ofanto River. The outcome of the investigation has highlighted how, in several sectors of the examined area, there are numerous orientations compatible with the range between 60° and 75° east; therefore, the data is very problematic (Figure 21).

Written evidence of centuriation was exacted, as is also well attested in other areas of Daunia in the Republican period, to extend cultivable areas (also by virtue of the draining function performed by the centurial limites) by intensifying specialized vine and olive cultivation, alongside the more established cereal cultivation. From this point of view, all the indicators of anthropization gathered so far, for the periods after the 4th–3rd century BCE, point in the direction of an intensification of anthropic pressure on the area surrounding the city, with a persistent and intense activity of landscape clearing pursued by humans, also through the reiteration of fires, to the detriment of the woodland and to extend the spaces allocated to agriculture and grazing [13]. In fact, beyond agriculture, and not infrequently in conflict with it, the areas closest to the coastal brackish lagoon and salt-growing sites might also have been affected by the phenomenon of transhumant sheep-breeding, whose origins can be traced back to the post-Hannibalic period, with an increase in the 1st century BCE [58] (pp. 212–216).

Lastly, at the beginning of the 1st century BCE, the city took an active part in the Social War and was brought back to order by Cosconius, who nevertheless burnt it down in 89 BCE (App. BCE. 1, 52).

After the Roman pacification, therefore, the oppidum vetus of Salpia no longer found favorable conditions for a revival: the downsizing of the city induced by the prolonged conflict, the probable lack of coordination of the community in the management/maintenance of drainage systems and embankments, beds/swales and mouths of canals, streams, and the lagoon itself, in the face of the wetter climate mentioned above, contributed to the collapse of the entire local socio-ecological system. Aided by deforestation and the spread of agricultural areas and pastures unprotected from erosive processes, the formation of ‘dead water’ stagnation in the immediate surroundings of the settlement could be traced back to the difficulties encountered in containing or draining the masses of water poured into the depressed Salpia vetus plain by rainfall, the flooding of the nearby Carapelle or the overflowing of the coastal lagoon itself; finally, as is well known, humid summers and still, sun-soaked waters, whether fresh or brackish, are the ecological settings of choice for the reproduction of what has been, from antiquity to very recent times, the main vector of malaria in the Mediterranean area, the Anopheles mosquito [59] (pp. 43–114, 265–267).

The ironic tone with which, in 63 BCE, Cicero dismissed Servilius Rullus’s proposal to send new settlers to Salapinorum pestilentiae fines (Cic. leg. agr. 2, 71) is indicative of the difficult living conditions in which the city now found itself. The lengthy period of resilience of Salpia vetus was now over (the “release phase” of Holling’s adaptive cycle). This was the prelude to a necessary reorganization between the community and surrounding environment, in another place but still within the same precious coastal wetland.

4.2. Roman Salapia (1st c. BCE to Late 5th c. CE): Foundation, Growth, Floruit

4.2.1. Vitruvius on (Re)founding Salapia: Creating a Healthy Site in a Productive Wetland

The case study of Salpia vetus’ demise and Salapia’s refounding culminates in Chapter 4; through this account, he must summarize the chapter’s key themes. He provides many details of location, logistics, and infrastructure, whose confluence made the new site a superior one to the old [1]. Vitruvius places rhetorical emphasis through his repeated, but shifting, use of locus as a throughline for the reader: position becomes crucially important to the success or failure of any settlement. Salapia’s refoundation and transformation are also tracked by the evolving adjectives and indirect pronouns connected to locus. Section Twelve begins with a reference to the Pontine marshes, in his locis, where standing waters “putrefy” and emit unhealthy air because of the marshy water’s stasis. Salpia vetus was put in a place “of that kind” (in eiusmodi loco), i.e., pestilential. The Salapini’s request to Marcus Hostilius is for an appropriate place (idoneum locum); his intervention, by selecting a site adjacent to the sea, was made in a healthy place (loco salubri). The transformations did not stop there, as we see the former oppidum become a municipium, with the imposition of Roman walls, a street grid with insulae, and the sale of lots. However, this urban organization was not all that made the municipium. In fact, Vitruvius lingers over the idea of the lagoon’s remaking, which is thoroughly done (perfecit, with per- as intensifier), by creating a port for the again-emphasized municipium. In itaque, which concludes this chapter, we are reminded that the Salapini, only four miles distant from the old town (ab oppido veteri) finally lived in a healthy place (salubri loco). In other words, the discovery of a healthful site did not require a distant move, but it needed to be well-researched for selection within the broader wetland zone.

As Hostilius is said to have purchased the land, we might conjecture that its healthful position had already been uncovered by Roman centuriation in this zone. While pre-Roman peoples surely knew how to apply adept technological strategies to settlement problems, sometimes Roman exceptionality was born of being at the right place and time with the correct tools, resources, investment, and acquired knowledge. In fact, Altinum was a Roman refoundation, similarly not far removed from the pre-Roman site, while Aquileia and Ravenna were new urban foundations within long-exploited wetland contexts.

It is worth investigating each of these details in turn, as we have augmented them through the evidence recovered in our paleoenvironmental and archaeological investigations and through consideration of modern historical sources about the Salpi Lagoon. While Salapia was founded on a more healthful site, we might trace the interventions and infrastructure—indeed, the decisions made to modify and continually engage with this wetland environment—that solidified the settlement’s resilience and enabled it to thrive. We can contribute to understanding why Roman urbanism ensured long-term stability in such a context and brought this wetland in a new direction.

4.2.2. A Roman Urban Foundation: “Laying Out Lots”

Our geophysical prospection and field survey in 2013 [26,27,60], followed by six years of excavation (2014–2019) have confirmed the position of the Roman town [29,61]. We have resurrected its plan, along with details of its chronological development. The layout of city walls, with its urban grid, is clear from our magnetometry investigations, along with extra-urban structures, infrastructure, and the road network (Figure 22). The town’s orientation toward the north and east conforms to Vitruvius’s advice to eschew a western orientation, therefore avoiding the strongest of the sun’s rays (aspect). Turned north and east, the town would have also, in Vitruvius’s estimation, evaded the strongest of seaborne winds (I, 4, 1).

While Vitruvius advised against foundations in marshlands, he admitted that proper topographic conditions might be found. Such marshy deltas were difficult to avoid in a Mediterranean context, as they provided protected and profitable landings for ports (again Altinum, Aquileia, and Ravenna might serve as examples). Vitruvius emphasized that those marshes that are higher (by position) than the sea’s coast (eaeque paludes excelsiores fuerint quam litus marinum) should be preferred [1] (I, 4, 11), to facilitate drainage. The refounded Salapia, it should be made clear, had an elevation marginally elevated (by perhaps one meter), if not equal to the former Salpia vetus in what is an extremely low-lying coastal landscape. Salapia’s advantage, instead, was born of the confluence of its elevation, its position, and its geomorphological profile. The SAL3 and SAM4 cores, sunk to the northwest of Salapia, have revealed alluvial facies, stable since the Bronze Age, when compared to the marsh-like quality of the SAM8 core, proximate to Salpia vetus. These alluvial facies provided a land-based buffer for this town, protecting it from the vicissitudes and pooling of the inland marshlands afflicting Salpia vetus [13] (p. 49). Additionally, the new town was positioned on an outward facing lagoon, a large and extensive saltwater body.

Remote sensing, field survey, and excavation work provide an opportunity to reconstruct the material impacts of this new town on the surrounding landscape and to understand how water was managed. Its intramural area covered nearly 20 hectares, a typical size for towns in Apulia, while evidence of a suburban quarter to the south and artisanal activities to the north nearly double the surface area of this settlement [26,27]. As customary, its grid plan was organized around a north-south cardo and an east-west decumanus. We might conservatively say that the street grid was laid out around in the second half of the 1st c. BCE to the early 1st c. CE, based on the distribution of limited preliminary architectural features confirmed by residual ceramics and the long-lived position of streets we have uncovered. Our excavations have also revealed that the town’s bedrock foundation was undulating and uneven, of limited porosity, and likely slow draining. Evidence for water management in the town is patchy but might speak to broader patterns. An arched drain was found as part of a likely 1st c. BCE phase of construction, running west to east, with a downward slope toward a circular tank, was closed probably before the 2nd c. CE, with the imposition of the tannery [62] (p. 116) (Figure 23). However, it confirms the downward slope we registered in the floor and street surfaces oriented west–east. As Kolowski-Ostrow has noted for Pompeii [63] and observed in Herculaneum, streets and open drains had low-gradient slopes to ensure water—usually from heavy rainfall or ever-flowing street fountains—traveled down and out toward the sea. Most small towns lacked full and even partial coverage sewer systems. Salapia would not then have been out of place with such “low tech” intra-urban water management that brought water down and away toward the lagoon.

Small snatches of water-themed infrastructure are also evident in the late antique phases of the town. Sometime in the 4th c., a modest bath complex was built to the northeast of a well-appointed Roman domus. Water drainage for this structure, confirmed by a channel with piping, flowed from north to south toward a cesspool, in part dug deeply into the bedrock and in part constructed of masonry (Figure 24). We did not excavate to its base for reasons of safety, but its dimensions as documented would have held no fewer than 15,000 L, but likely more [64] (pp. 187–189). It is possible that elsewhere in this town, the drainage of wastewater was managed in this way, with an agglomerated urban “patch” of dampness in this wetland. The caldarium was constructed above ground level, on hypocausts (poorly preserved in our case due to their proximity to the surface of the modern plough soil), when more regularly, this radiant heating technology was constructed below floor level. Was this floor surface raised with the aim to protect the hot range from flooding, which would have been ruinous for this technology? Whether from the overflow of the adjacent cesspool, or intermittent flooding in the town, or both, this limited datapoint provides an inkling that mitigating flood risk was front of mind for this community [64], (pp. 189–194), [65], (p. 142, and Figure 8.22) and the architecture central to Roman life was built to adapt to its context.

These details can be contextualized among other indicators of water management from immediately beyond the town walls. Magnetometry investigations have brought forth long and narrow anomalies that might represent drainage canals running along the town’s northern edge and skirting its eastern side, traversing the proposed artisanal quarter and then moving between the city walls and the present-day lagoon edge [26] (Figure 25). This easternmost anomaly approximates the width of a street artery, which was perhaps 3–5 m wide. The SAM6–7 cores were either aligned with it, while the SAM5 core was immediately beyond the path of this canal. These cores have brought forth very limited evidence of sedimentation, with the SAM7 core’s sediment dated by ¹⁴C from the mid-3rd to early 4th c. CE, and the SAM5 core to the mid-4th to early 5th c. CE. SAM6 rather had sediment dated to the 15th c. [13] (Figure 8). Possible and interwoven interpretations present themselves. The first is that this drainage infrastructure processed increased sedimentation in a somewhat similar period (4th c.–5th CE) to when De Santis et al. charted increased sediment outputs in the Carapelle watershed to the north of Salapia, a result of infrequent but heavy flooding events [66]. Since Salapia was within the same watershed, such sediments might have also been transported downstream toward the town. Second, the town was subject to consistent, low accumulation sedimentation from its 1st c. BCE founding and beyond Late Antiquity, which might have been largely removed in earlier and later phases to manage the flow of water close to the site. The canals that were fundamental to the health of Altinum, Aquileia, and Ravenna have been discussed above, skirting around the outer edge of these towns, even defining them spatially, while negotiating the relationship between the marshes and sea. Each infrastructural system shared a similar chronology dated to the 2nd c. BCE–1st c. CE, in which span Salapia’s refounding occurred. The brackish sediments might be attributed to backflows from the lagoon toward the town, due to their proximity to the lagoon’s edge. The limited stratigraphy in the cores is intriguing because unlike Altinum and Aquileia, there appears no evidence so far of urban trash dumping into this canal, even though it might have separated the town from possible port infrastructure, as discussed below [47] (pp. 188–193), [67]. This attests to its likely continuous and crucial role in managing water around the site over centuries, especially the eastern flank, which would have encountered the town’s street-borne runoff.

The movement of these canals from the north, from the direction of Salpia vetus, might also speak to their role in draining the broader territory, instilling overall health in the hinterland. The eastern flank ran parallel to the lagoon edge as it moved south into a hinterland zone that our surveys have revealed to be somewhat unsettled over the imperial and late antique floruit of the town itself (Figure 9). We lack the evidence to say with certainty that this zone was dedicated to further drainage infrastructure. However, we must consider this datapoint, along with that of urban drainage, as part of an integrated system of waters, including lagoon to sea, as part of Vitruvius’ narrative.

4.2.3. “Making a Harbor of the Lake”

Although Vitruvius recounts that the town was situated adjacent to the sea (secundum mare), this was not the reality on the ground. A few phrases later, he reported that the lagoon was opened to the sea, making clear that the town was separated from the outer coastline that formed the lagoon’s eastern edge. This closed lagoon had only been formed a few centuries before Salapia’s founding, in the 4th c. BCE at the latest, but after Salpia vetus’s establishment and growth. The inner lagoon edge was already likely formed, but changeable, due to the sedimentation carried by the Carapelle River watershed at the north, and the Ofanto River watershed at the south. Vitruvius tells us of a cut made to provide this lagoon access to the sea, confirming the solidity and contiguity of the outer dunes to the east. With future coring, we hope to identify whether other naturally formed openings were also present.

Again, the SAM5, 6, and 7 cores uniformly reveal a brackish environment from about the 3rd c. CE to the 16th c. CE, confirming that the lagoon was salty, likely due to its connection to the Adriatic Sea. Although we lack specific data dated to Salapia’s refounding, the brackish environment, recorded for centuries later, might be evidence of a continued careful curation of this relationship, not only as a space for trade, but also for the general health of the lagoon, and therefore the sustainability of the town itself. Similar modifications have been registered at Cosa’s Lagoon and at the Acherusia palus in Campania dated to the Roman period [68] (p. 82).

Naturally protected approaches like the Salpi Lagoon were not uncommon in the antique Mediterranean. On the Tyrrhenian Sea, Pisa was such a port, as was Lixus in Morocco [69]. Contemporary examples include the Nador Lagoon, again in Morocco, and the Mar Menor, in southeastern Spain [70], among myriad others in North Africa [71,72]. From these examples, we can list the demands placed on such water features, which include the management of port traffic, population stress from their urban centers, and demands to accommodate river outflow, in addition to natural progradation that can influence the depth and spatial extent of a lagoon. Apparent in all cases is the delicate balance needed over time so that the lagoon’s ecosystem, its form, and interrelationship to land, seas, and rivers, might be maintained.

The Salpi Lagoon, while not subject to progradation in the Holocene period [73], was rather influenced by its position between the Carapelle and Ofanto Rivers and their watersheds. These patterns are sustained by the agglomeration of alluvial deposits, as evidenced by all cores studied by our research team, over a very long timespan up to and including the ancient period that is our focus. From the Roman period onward, the lagoon was likely impacted by agricultural activities not only in the immediate hinterland of the site, but also by those upstream of these two river systems, should we take recent survey work as indicative of intensive farming activities well into Late Antiquity [74,75]. Tending to the health of the lagoon would have therefore been tantamount for the successful evolution of the urban settlement, as well as to bolster its economic potential.

Early modern sources help provide a sense of the complexity attendant for this mediating body of water, between freshwater rivers and the Adriatic Sea. Saverio Russo details the conflicts created by divergent resource interests, which when coupled with natural processes, destabilized the lagoon environment [76,77]. On the one hand, there was the push to create industrial-scale salt production, requiring the necessary salty inflows from the Adriatic [78]5. These interests were at odds with those invested in large-scale fishing, which was dependent on freshwater inputs and an enclosed basin, so that the fish could breed and grow within this closed system of limited movement. Freshwater inputs, especially in large volumes, can destabilize salt production. Interchange with the Adriatic was therefore limited, while riverine outputs were halted. In very hot summers, this lagoon was prone to rapid evaporation and became quite shallow, leading to the formation of small pools which crystalized salt, enough to collect contraband salt produced and sold outside of the rigorously regulated monopoly. These pools also increased the potential for malarial breeding in the summers [79]6. Management of the lagoon’s relationship to the sea and to freshwater inputs was influenced by myriad human interests, prompted debates, and conflict, and could only be resolved by institutional decision-making and an enormous investment of capital in infrastructural changes related to both economic development and land reclamation for sanitary reasons, some of which were realized and others not.

Vitruvius’s small notation, therefore, underscores, at least in his telling, the unilateral decision of Hostilius, perhaps representative of the Roman interests in this region. A harbor would have actualized trade and connections with a broader Mediterranean network, in a Roman mode. The remains of structures at Torre Pietra, still visible on the shore in the form of rough masonry (Figure 26), stones bound with a mortar matrix in loosely horizontal courses, today imperfectly perpendicular to the coastline. The work of Cocchi et al., employing remote sensing technology, has also recovered the evidence of small blocks (50–60 cm in size) similarly oriented off the coast at a depth of about 10 m, which have been interpreted as piers related to this harbor infrastructure, perhaps part of a dragged-ship channel [80] (p. 99). Lopez also interprets a sizeable concrete mass, found a few kilometers from the shore, as a defensive post [81]. On a typical summer day, the wind can be quite strong standing on the remains of these walls, an indication that Salapia’s lagoon, while protected, did not have the easiest approach for sailors. The remains of shipwrecks immediately beyond these dunes might attest both to the level of harbor traffic and the necessity of finding an adequate entrance to the harbor itself [82]. However, this managed opening, in which there was clearly great infrastructural investment [83], both of money and labor, would have also served to open the lagoon more regularly, and likely continually, to the sea.

We are lacking the material evidence for the curation of the dune lands at the interior of the lagoon, beyond the harbor entrance at Torre Pietra. Modern reclamation works and the construction of both the Bourbon saltworks in the 18th c. and the contemporary salt installations have likely destroyed the material traces of ancient modifications to the interior lagoon and its shores, including compromising the remains of any interior harbor infrastructure. However, material evidence and the shape of the lagoon argue for certain orientations. The town of Salapia and this entrance appear to face each other across the lagoon, signaling a nearly straight approach to the opposite shore (Figure 27). We have hypothesized the lagoon basin as a single open pocket, oriented north-south, without any further inlets or dunes dividing it. Further to the south, two additional landings, one at the villa of San Vito and the other at the village of Mattoni, were likely positioned sequentially along the shore, conditioning the new harbor perhaps to have grown in the more immediate shores around Salapia and further north [82] (pp. 174–182) 7 [84]. In viewing the plan of Salapia as resurrected by magnetometry, the town itself is set somewhat inland from the current coastline. In the strip of land between these walls and the inner shore, our surveys have revealed a heavy concentration of ceramic finds, including numerous amphorae, that might point to spaces of temporary storage, or offloading, for this merchandise arriving into the harbor [85] (Figure 28). Ravenna’s relationship to Classe might provide a point of contrast, where a lagoon composed of various inlets saw its commercial and naval harbor separated by topography from the shores immediately adjacent to the town [86]. The Claudian infrastructure at Portus was a harbor complex designed to receive ships, offload, and store cargoes that assumed a form similar to the pocket harbor of Salapia, where offloading infrastructure was positioned opposite the entrance points along the shore [87] (pp. 71–103). The final piece is the position of the river systems, which would have discharged sediment most directly into the lagoon’s northern (Carapelle) and southern (Ofanto) ends. At Portus, too, considerations were taken to locate the harbor at the median space between these offloads, reducing the impacts of sedimentation [88]. Therefore, Salapia’s position might have been fortuitous in easing harbor management in this urbanized coastal space.

We might envision that docks were built for ships and wharves for unloading cargoes, cranes for unloading, and potentially spaces to perform ship repair and maintenance on this interior shore [89,90]. Underwater archaeology in the 1980s, as well as the ad hoc presence of sea-worn amphora sherds along the beaches of Margherita di Savoia, corroborate trading in this harbor, and potentially its scale [81,82]. Salapia itself was awash in amphorae, as noted by their reuse in urban buildings, such as in the foundations of walls (used mostly whole) and in fragments for earthen wall uprights. The ample presence of Italian, Aegean, and eastern Mediterranean amphorae, dated from the 1st c. BCE to the late 5th c. CE, demonstrates the activity of the port, with products consumed in the town itself [91].

With such activity and its supporting material culture, most harbors had to contend with the negative environmental impacts that prompted their own short- and long-term problems [92]8. Beyond this infrastructure, sailing activity would have affected aquatic animal and plant life, causing constant movement and introducing material pollution into the ecosystem. When added to the potential for wrecks of approaching ships and the role harbor infrastructure played—by virtue of its shape and position—in attracting waste deposited at the interior, the environmental effects cannot be understated [93] (pp. 199-202); [94]9. Therefore, these logistical challenges needed to be balanced alongside the economic growth such harbor traffic enabled, as well as the open contact it encouraged between the lagoon and the sea. Indeed, such continuous interchange would have ensured consistent water levels in the lagoon, crucial for maintaining the depths necessary to receive ships. Freshwater inputs, which could be variable, would not guarantee the same consistency.

As noted above, the SAM5 and 7 cores had limited evidence of sediment accumulation, and we might find support by proxy for the idea of a heavily curated lagoon environment to maintain the functionality of the harbor as well. The ancient epigraphic sources allude to dredgers responsible for removing sand from port basins to enable docking in other contexts [95], logistics that perhaps were also present in the Salapia context. The notable example of the Fossa Augusta, also referenced above, maintained clear channels and, therefore, lightened the effects of siltation in Ravenna’s lagoon, sustaining the myriad sites of docking that have been hypothesized at various scales [86]. Such harbor curation might have set the tone for a broader tending of the lagoon, not only its waters, but also the surrounding land.

Again, modern comparisons might be informative. In both the context of the Salpi Lagoon and the nearby Lesina Lake [77] (p. 78), coastal farmers insisted on the interchange between the water of these lakes and the sea, not only to prevent inundation from river waters, but also to encourage “movement” that would have unsettled problematic marsh plants and sediments hosting breeding insects, including mosquitos. While we have not conducted survey work along these dunes, the present-day small farms that inhabit them have a vested interest in maintaining their pest- and weed-free lands, including the removal of marsh plants to mitigate insect breeding; these plants could be for resource extraction (reeds and thrushes for building and fires), to liberate uncultivated land for other uses, or to keep the boundaries of one’s property clean [96,97,98]10. The transformation in land use, from pasture to garden and small farm cultivation, coincided progressively with the early 20th c. reclamation works, ensuring that the land was curated [99] (Figure 2). Flowing water with interchange surely hinders the egg-laying and gestation of anopheles mosquitos [90]. We might also conjecture a culling of unwanted plants to maintain and keep the harbor clean. The concomitant effects, then, of curating the lagoon space with a specific purpose would have aided water management and tended to adjacent areas. To this we might add again evidence from the cores (SAM9) and archaeobotanical data from our excavated contexts: the surrounding hinterland was a coordinated one as well, with a range of grain and vegetable crops typical of Roman farming regimes in Italy. These data have been supported by the archaeobotanical assemblage from the 5th c. CE town, where wheat, barley, and emmer were all cultivated, along with garden plants like cucumbers and melons [32]. Although the challenges posed by agricultural sedimentation were likely present, charcoal data from this same 5th c. CE context points to a mix of riparian, deciduous, and conifer forests nearby that would have helped to slow sedimentation and erosion and maintain a balance of moisture in the system [100,101]11.

Taken together, these data point to a vested interest by the town of Salapia in tending to its harbor and adjacent lands, which impacted water circulation and quality, at least into Late Antiquity.

4.2.4. Beyond Production: Salt-Making Infrastructure as Water Management Infrastructure

However, to understand fully Salapia’s relationship to the lagoon and its management of water, we must move beyond the account of Vitruvius and consider our only other textual sources linked to the Imperial and Late Antique town. Dating to the 3rd and 4th c. CE, when Salapia was still a vibrant town, the evidence of the Antonine Itinerary and the Peutinger Table directly reference Salapia’s role in salt production. Salapia does not appear in these itineraries, but the appellation salinis is in its place, literally “from the saltpans.” Although Meluta Marin, the renowned scholar of this territory, argued in 1989 that salinis referred specifically to the storage sheds for this salt [102], we know from other ancient contexts and “best practice” that cultivated sea salt should be stored outside, where the wind and sun help it to dry and solidify [103]12. Therefore, there were likely no dedicated structures for the storage of salt, but the infrastructure to produce it was surely visible [104]13. Building on the harbor’s position proposed at the center of the lagoon, we hypothesize that the ancient pans were found somewhere to the south of the town, along the inner shores of the lagoon, possibly as far distant as the village site of Mattoni. This would put the pans near where they appear now in the southern half of the lagoon (Figure 11). Although we cannot determine the scale of this production, the replacement of Salapia in these itineraries with salinis as a key landmark might underscore what was its relevance in the landscape to both local inhabitants and those traveling through the region [105]. While the mountains of salt, depending on size, might have been the first visual marker, as with the case of Utica in North Africa, we cannot discount the possibility that the infrastructure for salt-making itself stood out in this landscape.

While we have no material evidence for this production to date, it is likely, based on more recent archaeological studies and the weight the literary texts placed on evaporative technology in the Mediterranean that this was the infrastructure employed at Salapia [106,107,108]. In this case, in framing the site’s resilience vis-à-vis water, the pans themselves could be a highly efficient tool for water management. The technology of these pans would feed salt water through increasingly shallower and smaller pans as it increases in density via evaporation under the hot summer sun and with the help of the wind. The pans, built of compacted clayey earth, at times lined with stones or outlined by reused amphorae [106], regimented the marshes where they were placed, providing a certain regularity to the water and its flow through the system. While we do not know how large the pans at Salapia would have been, even a small installation would have required a certain level of attention and curation of the broader lagoon space. As attested by the modern sources, giving both space and time to fishing and salt production required plans for barrier walls to ensure that especially freshwater would not contaminate the system as well as sluices to control outflows of freshwater from rivers for this reason [76,77,78]. As we know from the examples of excavated remains, as well as from the modern example of pans of Barletta from the 18th and 19th c., these infrastructures required careful planning and knowledge of the lagoon environment, to be placed in an efficacious spot that would facilitate the entry of salt water into the system, and movement through the structure [109]. In the case of the Barletta pans, water screws and other mechanisms were employed to overcome the flatness of the zone and ensure the movement of increasingly salty water from one pan to the next.

What stands out in these early modern accounts is the cyclical nature of the production and operation of the pans in coordination with the seasons. As understood in greater detail from modern sources, the “spring cleaning” phase for these pans was an important one that required a significant number of workers to remove the marshy overgrowth and detritus that had accumulated over the winter months when the pans were not in operation [109]. This period of overgrowth fortuitously coincided with colder weather. Even if hibernating mosquitos and other pests passed their winters there, their homes would be dislodged each spring when the marshes were prepared for the new season [79]14. The “growing” of salt occurred over the summer months and into the early Fall, when the sun was strongest and the air hottest, to facilitate the evaporative technology. This would have helped confront the peak breeding season for mosquitos and other pests, reducing plant overgrowth through the concentration of activity and its product, as high salinity is not conducive to sustaining either plant or animal life in these pans.

One contends that the required attention to this wetland via salt production meant a consistent and regulated engagement with another swath of the lagoon. Balance was needed between the port and the pans; Portus and its own Stagno Maccarese saw that interrelated hydraulic works were part of a larger system of complete landscape organization [110] (p. 264). The example of Ficocle/Cervia and its own pans [111], likely situated to the north of the settlement, which was built on an island at the center of a natural lagoon, might also speak to the symbiosis of urban centers and salt production that extended beyond economic concerns and perhaps were part of a complementary strategy to manage the wetland. Such activity ensured attention and tending, while keeping threats from stagnant waters and insects at bay.

By prioritizing, as proposed here, the port and the salt infrastructure, the site of Salapia could maximize the advantages of its well-drained floodplain and its position in this marshy zone. Predictably, however, the maintenance of such logistically intensive infrastructures, which required both the investment of materials and labor owed to Roman administration and coordination over centuries, were probably not sustainable, at the same scale or intensity, as Salapia’s urban institutions waned with the dawn of the 6th c. CE. While beyond the scope of this argument, it is worth noting that settlement did persist at the site of Salapia for another three centuries. The community there, although declining in population with each passing century, continued a complex agricultural regime [31,33], saw the growth of olive cultivation beyond its scale detected even in the Roman period [13] (p. 49), and continued to produce salt, potentially still at scale into the 8th c. CE, as it was integrated into the new Lombard economic and social networks of exchange and obligation (CSS I, 11 cod. Vat. Lat 4939). The patrimony of the Roman city’s infrastructure and water management regime likely produced concomitant effects and influenced the long-term cultural engagement with the lagoon, in varying degrees, for many subsequent generations.

5. Discussion and Conclusions

In sketching the settlement history of Salpia vetus to its abandonment and then Salapia’s refounding and floruit, some key trends are worth emphasizing, as we have elaborated the complexity of human–environment interactions in this coastal ecosystem.

These reconstructed histories demonstrate how decisions taken and actualized around water and broader territorial management could be adaptive, dynamic, and responsive to environmental conditions on the ground, provided that actors had the resources and logistical capabilities at their disposal [112] (pp. 8–10).

Salpia vetus’s approach to environmental resilience grew with the expansion of the settlement, most visible in the 6th and 5th c. BCE. Strategies included reinforcing the natural topography of the peninsulas on which the settlement was built through excavating moats. This was likely coupled with a dendritic road network that would have doubled as a set of drainage channels to funnel water away from the settlement and toward its hinterland. However, as detailed here, over time, these strategies did not evolve as needed alongside both the changing environmental and geopolitical situation as contact and conflict with Rome increased. It is quite possible that the augmented agricultural exploitation detailed across the 4th and 3rd c. BCE was incompatible with the low-lying landscape, prone to pooling stagnant water, and putting the nearby urban ecosystem at risk.

With the waning resilience of Salpia vetus in the wake of greater external pressure, we are reminded that conversations between people and their environments are not just a singular, intimate dialogue but involve interruptions and, at times, new interlocutors. Salpia vetus was not only challenged by its deteriorating environmental situation but also exasperated by external political and military stressors. Viewed from the perspective of Holling and Gunderson’s panarchy model, adaptation was only feasible to a point before the system broke, represented by the abandonment of the town itself [4]. What might have become of Salpia vetus had it been able to regroup in a different political and cultural context not predicated on conflict with Rome?

In Vitruvius’ telling, the Salapini asked to be moved to a new site, but can we trust such an account when the Romans had so much to gain with their broad-scale settlement transformations and adaptive responses to environmental challenges? Their perspective was an imperialist one aimed at standardizing landscape infrastructure and organization, a plan being sold up and down the corridor of the Adriatic coastal wetlands. Given the Romans’ ability to mobilize resources, the outcome was that the Salapini, whether willfully or under duress, abandoned their town after the progressive collapse of their elite networks and their failing interchange with an increasingly waterlogged and destabilized landscape of inland ponds and lakes. We should not take such a break lightly, even if the new town of Salapia arose in the same coastal wetland. We are left to ask: Did resilience requiring such profound changes really work for this Daunian community? For only certain members, or perhaps no one at all? And at what social and cultural cost to their community identity?

If we are to fit these cases to a model of panarchy, should we consider the connection between Salpia vetus and Salapia as a continuity or a rupture of the system? If resilience is meant to entail a community that can absorb disruptive forces without altering function, processes, and identity [4,5,6,7,113], much depends on whether Salapia was a refounding of the old model, or a settlement made anew.

The founding of the Roman municipium at Salapia required the incorporation of new administrative structures and, at the material level, a new urbanism with formal differences to Salpia vetus, which included a port with seaward-facing infrastructure, city walls with a grid plan, and baths as leisure sites, for example. There was also the incorporation of new water management features and agricultural regimes, changes that surely insisted on new cultural modes and human connections. Coupled with a new context on a lagoon made to be outward-facing, with greater expectations for the scale of trade and salt production, a community now saltwater-based and not fresh-water-based, might lead us to see a new trajectory for this wetland rather than a remaking of the old.

As is apparent, in a way that panarchy does not wholly account for, local contexts and experiences matter in this case. Van der Noort’s model for climate change archaeology calls for particular attention to local conditions and customs to understand the human–environment relationship fully, and to counteract deterministic narratives [3,10,113]. Indeed, by any measure, the story of Salpia vetus and its long-lived and vibrant settlement is worthy of discussion for the particularly local and specific variables attendant in its life cycle (birth, growth, conservation, collapse). The same might be said for the birth, growth, and persistence of Salapia, if we accept the diversity of cultural, social, and material parameters involved, and put aside the flattening required of the panarchy model.

What links these settlements intimately, however, is born of their shared local context and the questions of how to manage a dynamic wetland. The Romans not only had the advantages of military might and resources, but they also had the knowledge born of observing Salpia vetus’ struggles directly. A sense of this prior history was worn in the material remains of the settlement, including its drainage works, its earthen barrier walls, and its former territorial organization. Rome therefore had the ability to cannibalize Salpia vetus’ past and miscues at adaptation. This co-option gets at the heart of Vitruvius’ message: search nearby to find a healthful place and try again, but do not make the same mistakes. Sharing a name, from Salpia to Salapia, might not have been a wholesale lifting of identity, but a nod toward this recognized, but troubled, past.

Salapia’s resilience was born of the selection of a more healthful site, in a well-drained floodplain on a lagoon they intentionally connected to the sea. There was careful attention to managing the outflows and interchange of fresh and saltwater in this system. Canal works drained to the lagoon, as did the intra-urban street grid. Salt-making infrastructure could have played double duty, in both producing a necessary resource and ensuring that parts of the lagoon not englobed by the port and its carefully tended infrastructure also received similar manicuring to tame changeable flora and fauna in the marsh over the year.

Our juxtaposition of Salpia vetus and Salapia furthers the charge for resilience models that bolster local histories and their particularities. Acknowledging breaks in the system rather than “remaking” are also crucial for the sake of accuracy. Failure matters as much as success, as does acknowledging the diversity of experience. Assuming continuity and ease of transformation due to a shared context or similar challenges risks flattening interpretations of the outcomes.

Jumping ahead, when we consider the end of Salapia, sometime between the late 8th and early 9th c. CE, we are confronted with a subsequent narrative of abandonment. There is no perceptible evidence of human life on the plain adjacent to the lagoon, and burials dated to the 9th c. CE, through ¹⁴C dating and stratigraphic interpretation, might signal that here too, resilience was not possible. Instead, a wholesale separation was required. Unlike the Salpia vetus–Salapia connection, the break was not caused by space, but by time. For nearly two centuries, there was no community to speak of. Were they regrouping? And where?

It was perhaps as early as the 10th or early 11th century CE that the settlement core of Salapia began to recompose itself in the western half of the ancient city of Roman foundation, further away from the waters of the lagoon and more elevated with respect to the surrounding landscape [28]. To maintain the strategic relationship with the wetland, therefore, the same floodplain was inhabited but made more suitable and protected by elevating itself in space, the chosen strategy to revitalize the settlement. Furthermore, the sedimentary sequences of the SAM5 and SAM6 cores indicate the marshes, already discernible in the 3rd century CE immediately east of Salapia, persisted into the 16th century. Links could be found in a shared sense of a saltwater lagoon and its potential.

It was the advent of Norman control, at the end of the 11th century, that marked the relaunch of the center of Salpi (this was to be the name of the Medieval city) in the geopolitical arena of northern Apulia; the settlement was redesigned on a large embankment surrounded by a deep moat, reworking a strategy that helped the interior Salpia vetus manage its own relationship to freshwater, now realized on the shores of the salty lagoon. While sharing space with its predecessor, the medieval town cannibalized much of its material legacy through its literal stones, reassembled on the elevated castrum and a loose reworking of the Roman urban plan. However, this was a new wetland community, with new concerns and institutions. In fact, the settlement thrived with such an organization regaining the dignity of civitas and bishopric; the settled community was reorganized with new roles and hierarchies; the ruling class was renewed. A new but different life cycle began, cognizant of the past lives lived on this lagoon.