African Heritage Sites threatened by coastal flooding and erosion as sea-level rise accelerates

The experts, in a project driven by the University of Cape Town’s African Climate and Development Initiative, have provided the first comprehensive assessment on the exposure of African cultural and natural heritage sites to extreme sea levels and erosion associated with accelerating sea level rise.

Over the course of a year, the international team, comprising scientists from South Africa, Italy, Netherlands, Norway, France and the United Kingdom, identified and mapped the physical boundaries of 284 African coastal heritage sites. They then modelled how each site would be affected at future global warming scenarios.

At present, 56 sites (20%) - including the iconic ruins of Tipasa in Algeria and the North Sinai archaeological Sites Zone in Egypt - are at immediate risk of being affected by what is considered a once-in-a-century coastal extreme event, the study shows. With global warming, by 2050 and in a high emission scenario, the number of sites at such risk  will almost quadruple. Extreme events – that is, storm surges, high waves, and coastal erosion – are expected to become more frequent and more severe with climate change, resulting in more sites risking damage.

But limiting emissions would reduce the exposure of the heritage sites, said IHE Delft Professor Roshanka Ranasinghe, co-author of the Nature Climate Change paper.

“Our results show that climate change mitigation can save some of the important heritage sites,” he said. “If climate change mitigation successfully reduces greenhouse gas emissions from a high-emissions pathway to a moderate emissions pathway, the number of very highly exposed sites by the end of the century can be reduced by a quarter. This would be a significant saving in terms of damage to heritage sites from climate change.”

Co-author Dr Trang Duong, IHE Delft Lecturer in Coastal Numerical Modelling, added:

“Through our research, we have seen both the beauty and value of heritage sites along African coast lines, as well as the potential threats they are exposed to from climate change,” she said. “We hope that this study will help spark action, both to reduce emissions and to protect vulnerable sites.”

Regardless of the warming scenario, at least 151 natural and 40 cultural sites will be exposed to a 100-year event from 2050 onwards, including all sites in Cameroon, Republic of the Congo, Djibouti, Western Sahara, Libya, Mozambique, Mauritania, and Namibia. Under the worst-case scenario, all sites in Cote d'Ivoire, Cabo Verde, Sudan and Tanzania could also be affected.

The authors hope that their findings could help prioritise sites that need urgent protective action through, for example, improving governance and management approaches; site-specific vulnerability assessments; exposure monitoring, and protection strategies including ecosystem-based adaptation.

The paper’s lead author is Michalis Vousdoukas from the European Commission’s Joint Research Centre. Other authors are: Joanne Clarke, University of East Anglia; Lena Reimann, Vrije Universiteit Amsterdam; Nadia Khalaf, University of Exeter; Birgitt Ouweneel, University of Cape Town;  Salma Sabour, University of Southampton; Carley Iles, Center for International Climate Research, Oslo; Christopher Trisos, University of Cape Town, Luc Feyen, the European Commission’s Joint Research Centre; Lorenzo Mentaschi, University of Bologna, and Nicholas P. Simpson, University of Cape Town.