The islands of the South-West Indian Ocean faced with rising sea levels

Jean-Marc Beynet, engineer in ports and waterfront infrastructure Article based on « La vie des îles autour du monde – Naissance, histoire, présent, futur probable » (“The Life of Islands Around the World - Birth, History, Present, and likely Future”) by Jean-Marc Beynet, to be published soon by Editions Nombre 7 (Nîmes, France). We tend to think of most islands as dream destinations, an invitation to travel, sail, and explore. Does time pass more slowly there than on the mainland? When and how did islands come into existence? When and how did they come to be inhabited? What legends and beliefs do islanders have? What is their philosophy on life? And what does the future hold for these islands and their inhabitants, with sea levels set to rise in the decades ahead? There are many lessons to be drawn from the islands of the South West Indian Ocean, which include the Mascarenes (Mauritius and Réunion), along with Madagascar, Comoros, Mayotte, and the Seychelles. These islands owe their existence to geology and volcanoes. This makes them excellent candidates on which to based a forward-looking analysis of the likely impacts of rising sea levels on islands and their populations, taking into account the latest report by the IPCC (September 2019), and more recent studies that will form the basis for the IPCC’s next report, due for publication in September 2021.This analysis can be based on Milankovic’s astronomical theory, which offers an explanation for major climatic variations in glacial cycles. With the world gradually heating up since the last glacial period, sea levels have risen 120 metres since the peak or “late glacial maximum”, which occurred around 20,000 years ago. However, since the advent of the Anthropocene period, industrial activity has altered the climate, pushed up temperatures, and accelerated the rise in the level of the seas and oceans. The average rise was 0.3 mm/year in the 18th century before the industrial era, 0.4 mm/year in the 19th century, then 1.7 mm/year in the 20th century, and finally 3.5 mm/year between 2004 and 2015. By the end of the 21st century, the sea could be rising at a rate of between 8 and 16 mm/year in the worst…