Assessing the human footprint on the sea-floor of coastal systems: the case of the Venice Lagoon, Italy

Fantina Madricardo,Antonio Petrizzo,Aleksandra Kruss,Valentina Grande,Carlotta Toso,Elisabetta Campiani,Federica Foglini,Elena Catenacci,Fabio Trincardi

doi:10.1038/s41598-019-43027-7

Fantina Madricardo, Antonio Petrizzo + Show 7 more

Open Access

https://doi.org/10.1038/s41598-019-43027-7

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Abstract

Coastal systems are among the most studied, most vulnerable, and economically most important ecosystems on Earth; nevertheless, little attention has been paid, so far, to the consequences of human activities on the shallow sea-floor of these environments. Here, we present a quantitative assessment of the effects of human actions on the floor of the tidal channels from the Venice Lagoon using 2500 kilometres of full coverage multibeam bathymetric mapping. Such extended dataset provides unprecedented evidence of pervasive human impacts, which extend far beyond the well known shrinking of salt marshes and artificial modifications of inlet geometries. Direct and indirect human imprints include dredging marks and fast-growing scours around anthropogenic structures built to protect the historical city of Venice from flooding. In addition, we document multiple effects of ship traffic (propeller-wash erosion, keel ploughing) and diffuse littering on the sea-floor. Particularly relevant, in view of the ongoing interventions on the lagoon morphology, is the evidence of the rapid morphological changes affecting the sea-floor and threatening the stability of anthropogenic structures.

Highlights

Coastal systems are among the most studied, most vulnerable, and economically most important ecosystems on Earth; little attention has been paid, so far, to the consequences of human activities on the shallow sea-floor of these environments
We suggest that the maximum depth of erosion coincides with a major change in soil composition and geotechnical strength corresponding to the subcrop of the alluvial plain consolidated sediment (Caranto in venetian dialect) on which lay the foundation of the entire city of Venice[82]
The new bathymetric data presented in this study highlight the pervasive occurrence of direct and induced anthropogenic imprints and provide: a) unprecedented information locating the hotspots where sea-floor erosion is rapidly advancing in response to a variety of human pressures ranging from coastal engineering to ship traffic; and b) a direct assessment of the mean abundance of marine macro-litter in a large area of the Venice Lagoon and the characterization of marine litter hotspots

Summary

Introduction

Coastal systems are among the most studied, most vulnerable, and economically most important ecosystems on Earth; little attention has been paid, so far, to the consequences of human activities on the shallow sea-floor of these environments. The magnitude and increase rate of such human-induced changes has become dramatic since 1950, an abrupt shift often indicated as the ‘Great Acceleration’[6,7] This acceleration was observed by studying the trends from the 1750 to 2010 of the main socio-economic indicators, such as population, economic growth, use of non renewable resources, urbanization, globalization, transport and communication, and the indicators for the structure and functioning of the Earth System. Coastal wetlands are valuable ecosystems[25] extremely impacted by humans[26] Beside urbanization, these areas are threatened by sea-level rise[27,28], land subsidence[11,29] and the increase of flood and storm events[30,31]. None of the 152 reviewed studies published between 1991 and 2018 focused on the assessment of the human footprint on the sea-floor of coastal wetlands

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