Just after the start of the first COVID-19 lockdown (April 2020) I was isolating in a country house in a small coastal town in Greece. Aside from research on papers and modelling coastal hazards and impacts, plus satisfying the numerous demands of the IPCC WGI report, I was trying to maintain my mental health in the company of my cat and wood working for my campervan in a makeshift workshop. It was late afternoon when I had finished the day job and I was about to find my amateur carpenter alter ego when I remembered that I had a Zoom meeting. It was about a potential study on the impacts of rising seas on African Heritage Sites, a topic I knew very little about. It turned out to be the beginning of a very exciting journey into a new world of climate change-associated risks to cultural and natural heritage.

Africa has many thousands of heritage sites, 284 of which are recognised by UNESCO for their Outstanding and Universal Value, located along the continent’s 30,000 km long coastline. Many of these sites have survived the mists of time and have deep meaning and significance for Africa and the whole world. They are deeply interwoven with peoples’ identity and tradition, and they are essential for social wellbeing, safeguarding traditional knowledge and livelihoods. People have complex relationships with heritage. It took me a while to grasp how Africans have a different relationship with their heritage sites than Europeans like myself. For them such monuments can serve as a way to subvert memory and be an icon of reparation. For this reason the loss of the forts and castles along the coast of Ghana or Kunta Kinteh Island in the Gambia, both UNESCO World Heritage Sites, would have strong repercussions, not only for the people living in their vicinity, but also the international community.

We already had a feeling that African Heritage Sites might  be under threat from coastal flooding and erosion, but there were no detailed assessments; what we knew was mostly anecdotal. We also knew that climate change and sea level rise are very likely to add further pressure on these unique natural and cultural treasures, but again existing information was mainly limited to speculations and rough estimates or very localized assessments. Our mission in this study was to try to quantify the extent of the problem and provide continent-scale information to the people whose responsibilities, careers, and livelihoods relate to Africa and its natural and cultural heritage. The challenges were many; we were doing something for the first time and we had to help and learn from each other, integrating expertise from fields as diverse as coastal engineering, archeology, statistics, cartography, and climate risk modeling; while never actually meeting face-to-face. In fact, most of us had never worked together before and didn’t even know each other, being in different countries/continents (13 authors from 13 institutions across 8 countries). For some of the team working in the humanities, it was a crash course in scientific methods, while for those with a physical sciences background it was a daunting task to understand the way in which social scientists think! In the end, it all went much better than I could have imagined. Apart from presenting the results of our study and highlighting the challenges we faced, we believe that through this paper, we have highlighted the power of team science and transdisciplinary approaches to gain new insights on climate risk to heritage.

In our analysis, we found that African Heritage is already at substantial risk and things are going to get worse unless timely action is  taken. We found that 56 sites (20%) are presently at risk from a one-in-100 year extreme sea-level event, including the iconic ruins of Tipasa (Algeria) and the North Sinai archeological Sites Zone (Egypt). By 2050, the number of at-risk sites is projected to more than triple, reaching 191 sites (151 natural and 40 cultural sites) under moderate greenhouse gas emissions.

Alarmingly, there are several countries which are projected to have all their coastal heritage sites exposed to the 100-year coastal extreme event by the end of the century, regardless of the scenario. These are: Cameroon, Republic of the Congo, Djibouti, Western Sahara, Libya, Mozambique, Mauritania, and Namibia. Under the worst-case scenario, this is also true for Côte d'Ivoire, Cabo Verde, Sudan and Tanzania. Further, small island heritage sites are especially at risk. For example, Aldabra Atoll, the world's second-largest coral atoll, and Kunta Kinteh Island (The Gambia) could both see significant amounts of their extent exposed by 2100 under high emissions raising questions of their survivability under climate change.

Our results highlight the urgency for adaptation and the gains that can be made from mitigation responses to climate change, in terms of protecting African heritage sites. If global mitigation efforts very quickly reduce greenhouse gas emissions from a high-emissions pathway to a moderate emissions pathway, the number of at-risk sites by 2050 will decrease by 25%. However, informed adaptation responses to climate change that protect vulnerable heritage and their dependent communities will require in-depth research extending these findings to a broader range of heritage types, geographies and climate hazards.

Also, our analysis was not perfect, we tried to do our best with the data and models available, but we know that there is still a long way to go. In the end, so many heritage sites go unrecorded and are lost without us ever knowing they existed and what we have mapped and modeled is only a fraction of the sites already known about. If we had time and the resources, what would be amazing would be to model the entire African coast and then look for the archaeology and heritage in the regions that will be most impacted by coastal extreme events. The heritage that will be lost to coastal extremes in the future could be so much greater than the fraction that we might be able to save, but we are trying to make a difference, however small it might be.