The world’s largest population of giant tortoises thrives on a cluster of East African islands in the Indian Ocean. The tortoises on Aldabra Atoll in the Seychelles sit at the top of the food chain, an unusual feat for an herbivore.
A continent away, waters lap the banks of Kunta Kinteh Island in the Gambia River, a historical outpost for the West African slave trade that later housed a fort to stop slave ships. The island serves as a reminder of both the practice and abolishment of slavery.
Both Aldabra Atoll and Kunta Kinteh Island are UNESCO World Heritage sites, and both are at increasing risk of extreme coastal flooding from sea level rise. By 2100, 37% of Aldabra Atoll and 46% of Kunta Kinteh Island will be exposed to extreme flooding and erosion if no policy is enacted to stop emissions, according to new research.
These two sites aren’t alone. Twenty percent of World Heritage sites in Africa are vulnerable to rising seas today. And by 2050, that percentage will more than triple if emissions aren’t curtailed. The projection comes from an international team of scientists who mapped nearly 300 heritage sites along Africa’s coast. The scientists published their results in Nature Climate Change.
The latest finding is another example of countries that contribute little to climate change suffering disproportionately from its consequences. African countries were responsible for less than 4% of global carbon dioxide emissions in 2020. The average person in Nigeria or Mali is responsible for the same amount of carbon dioxide emissions each year as an Australian or American is in just over 2 days. Yet sea level rise will make flooding and coastal erosion worse at treasured cultural and natural sites along the continent’s 300,000-kilometer coastline.
“In Africa, our natural and cultural heritage defines us—it tells our story and can trace our history. Once it is lost, it can neither be replaced nor restored.”
“Outstanding Universal Value”
Heritage sites are recognized as having “outstanding universal value” and represent significant sites for culture, history, and science. Kunta Kinteh Island, for instance, is “an important but painful memory for many African countries,” said Nick Simpson, a climate scientist at the University of Cape Town in South Africa and a coauthor of the new research. There are more than a thousand World Heritage sites globally, and the latest analysis includes both official sites and those pending approval.
The study finds that rising sea level endangers both natural sites, like South Africa’s iSimangaliso wetlands (home to leopards, hippopotamuses, and elephants), and cultural sites, such as the ruins of the ancient trading post of Tipasa, Algeria, and Egypt’s grand sea fortress, the Citadel of Qaitbay.
The study focuses on extreme events that happen infrequently but are bolstered by higher sea levels. “What was a 1-in-100 year [flood] event in 2010, which is our baseline, will shift significantly with every decade moving forward,” said Simpson.
Eight African countries will be particularly affected: Cameroon, Republic of the Congo, Djibouti, Libya, Mauritania, Mozambique, Namibia, and Western Sahara.
“Every single one of their heritage sites will have some measure of exposure to extreme sea levels,” said Simpson. The study considered global warming scenarios that represent moderate emissions that peak at 2040 before declining, called RCP (Representative Concentration Pathway) 4.5, and high emissions that continue without policy intervention, called RCP 8.5. In both cases, all sites in the eight countries will be endangered.
Mozambique is the most exposed country by area, with 5,600 kilometers of coastline threatened by 2050 under a moderate-emissions scenario.
Natural heritage sites contain the most land, and by 2100 under moderate emissions, sea level will jeopardize a cumulative area of 15,000 square kilometers, roughly the size of Connecticut.
The study is “of particular interest to the African scientific and policy community for effective long-term planning solutions,” said Grégoire Abessolo Ondoa of the University of Douala in Cameroon. Ondoa served as a reviewer on the published paper.
Rethinking Climate Change and Heritage
Climate change compromises other World Heritage sites, including Australia’s Great Barrier Reef, Mexico’s Monarch Butterfly Biosphere Reserve, and Spain’s Garajonay National Park. Climate change is the biggest danger to sites in general, according to a 2020 World Heritage Report. In the Mediterranean, 37 of 49 low-lying coastal cultural sites are at risk from sea level rise, according to a Nature Communications paper from 2018.
Marcy Rockman, an archaeologist and member of the social welfare group Co-Equal, said that the new study shows how climate change adaptation and mitigation are connected with heritage, hazards, and our relationship to place.
Geophysics instrument scientist Errol Wiles at the South African Institute for Aquatic Biodiversity, who reviewed the paper, criticized the research.
“Considering the rise in sea level as purely anthropogenic is not appropriate,” he said. Comparing the effects of human-caused sea level rise with “natural” sea level rise would strengthen the work, Wiles explained.
“I agree that heritage sites are already at risk under current conditions, as shown in our baseline simulations of 2010,” said water and climate risk scientist Lena Reimann at Vrije Universiteit Amsterdam, who participated in the study. “Not considering sea level rise, we find 56 sites (20% of heritage sites) to be at risk from a 100-year coastal extreme event.”
—Jenessa Duncombe (@jrdscience), Staff Writer