Marine Cultural Heritage in Northern Mozambique – Underwater survey and long-term climate change
Marine Cultural Heritage in Northern Mozambique
Northern Mozambique formed part of the Indian Ocean trade network from the 7th century, which gave rise to a vibrant maritime culture of settlement, travel and exchange. The most well-known site is Mozambique Island, a major port of significance for East African maritime trade from the 14th century. It became the capital of Portuguese colonial government from 1507 and its architectural diversity was recognised by UNESCO World Heritage Site designation in 1991. Despite the wealth of archaeological sites located in the waters around the Island, Marine Cultural Heritage (MCH) has not received the attention and protection it deserves. Pressures on the resource have ranged from damage by salvage operations, insensitive development, to poor fishing practises and pollution.
In response the Centro de Arquelogia Investigção e Recursos da Ilha de Moçambique (CAIRIM) is vitally important in providing a focus for the study and conservation of marine cultural heritage on the island and for efforts to reach and engage with the local community. An initiative of Eduardo Mondlane university, CAIRIM has been a key partner of the Northern Mozambique project as it develops new ways of exploring, understanding and celebrating Marine Cultural Heritage.
One such effort to develop new dimensions for MCH is a major campaign of underwater survey touching on themes hitherto unexplored in the region. The Mozambique coast is little studied from a coastal geomorphology perspective and very little baseline information exists on fairweather processes, storm impacts, or sea-level change, all of which shape the landscape and influence livelihoods. The coast and continental shelf contain important indicators of past sea- levels, including former shorelines now submerged. The nature of the geomorphic record provides indications of coastal response to former sea-level change and, taken in conjunction with the contemporary coastal morphology and projected future sea- levels, provides an insight into likely future conditions and the challenges they pose to inhabitants, the local economy and the cultural and biological heritage.
Survey work underway on SV Bom Dia at Ilha de Mozambique
Toward the end of 2019 we deployed a range of geophysical equipment in the waters adjacent to the island. In total over 100km of seismic data and c.25ha of multibeam sonar imagery were collected. The seismic technique is capable of penetrating the seabed and thus detecting buried features that reveal the changes to the environment, for example former river channels which were submerged by sea-level rise and now infilled with sediment. The multibeam sonar measures depth with great accuracy enabling a high-resolution 3D model of the seabed to be produced which includes natural and cultural points of interest. Mozambique Island lies within a large, shallow embayment with deeper channels approaching its anchorage to the north. These exit into the Indian Ocean where the bathymetry deepens swiftly at a submerged shelf that runs parallel to the East African coast. Work concentrated on this area of the shelf which can reveal ‘terraces’, palaeo-channels and other relic geomorphological features suggesting the presence of earlier shorelines and former landscapes under lower sea-level conditions.
Survey tracks and colour-coded multibeam imagery of the seabed in the environs of Mozambique Island superimposed onto a recent Sentinel-2 satellite image. Warm colours indicate shallow water, shading to colder colours for deeper water
An offshore channel meanders toward the deep-water shelf at the edge of Mozambique Island’s embayment.
Seismic data line revealing the presence of a submerged palaeo-channel (right) within the bay. Such channels demonstrate the former morphology of the bay and the environmental regime that produced them.
Survey data is still under analysis and will form a key element of the training and materials the project will be delivering on its return to Mozambique Island. The survey team’s field visit coincided with a UNESCO training workshop hosted by CAIRIM on the Island. This allowed not only CAIRIM personnel and community volunteers to join the survey vessel but also maritime cultural heritage practitioners from the wider region. In addition, we joined the workshop back at base to deliver training insights on the geophysical techniques employed and their display and interpretation. Once all data is processed a further set of interpretative and training materials will be developed to conclude the surveys findings.
Onboard training to UNESCO delegates, CAIRIM personnel and community volunteers
As fascinating as the emerging survey results are, they are not undertaken in isolation of the broader aims of contextualising past climate change in order to meet the challenges of current sea-level threats and other pressures. The project’s return to the island was disrupted by the COVID-19 crisis, however this involves an ongoing programme of training, community engagement and ethnographic survey. In addition work in partnership with CAIRIM will involve returning to shipwrecks imaged during the survey in order to enhance our understanding of them and assess their vulnerability.
Running a photogrammetry workshop in preparation for the second phase of fieldwork