The Academy of Sciences has recently published a special themed issue, devoted to the vulnerability of intertropical coastal zones. Directed by Isabelle Manighetti, a researcher at the IRD and joint director of the Géoazur research laboratory, this issue involves many IRD researchers and partners.
In 13 articles, the issue explores: the main natural and anthropic mechanisms that contribute to the evolutions of intertropical coastal zones; the possible and/or desirable balances between socio-economic exploitation of intertropical coastal zones and sustainable development; the tools that science provides for societies to measure the evolutions of coastal zones and avoid or remedy their degradation.
Over 40% of the global population lives in coastal zones less than 100 km from a coast, and this population density continues to grow. Almost three quarters of the world’s largest cities are in coastal zones. This number is set to grow in future years. The growth of populations on the perimeter of the oceans can be attributed to the specific benefits they provide. However, as population densities and economic activities increase, the coastal zones are changing and becoming degraded, especially since anthropic pressures are accompanied by natural hazards that are particularly active in the intertropical regions: cyclones and storms, marine submersion, erosion by waves, major earthquakes and tsunamis.
Therefore, the coastal zones are both developed and fragile, both rich and threatened, refuges but vulnerable. In intertropical zones, they are particularly exposed, because they have the largest urban populations, as well as some of the greatest natural and anthropic hazards, and the weakest means of remediation.
Main observations and recommendations
Throughout the 13 articles in the issue, the researchers make several observations:
- Several of the studies presented show that, whether of natural or anthropic origin, the physical evolution of coastal zones can only be understood through a rigorous scientific prism, where the physics of processes is addressed on various levels.
- The exploitation of the coastal zones, originally intended to fuel the development and well-being of populations (coastal or otherwise), paradoxically leads to the degradation of some properties of these zones.
- Certain aspects of the usages of coastal zones and the current policies to protect these zones paradoxically make a segment of coastal populations more precarious and vulnerable.
- Science provides tools that allow us to precisely measure the evolutions of coastal zones on different temporal and spatial scales. These measurements are essential to monitor the current evolutions, and to be ready to optimally adjust our behaviours to remedy them.
The authors also formulate recommendations in the societal, political and scientific domains, because anthropic pressures in the intertropical zones currently seem to be the main cause of the degradations of the coastal zone, despite often acting in interaction with natural pressures:
- The current methods of governance for the coastal zones are based on a mixture of general international directives and local rules. However, there is little interaction between actors at the local and international levels. It therefore seems necessary to create new methods of government, at intermediary levels, which take into account both local specificities and global imperatives. These new methods of governance should be based on ongoing structures of interaction, involving scientists.
- Beyond the anthropic aspects, it is important to continue the scientific studies on natural processes, and in particular on the land/sea interface represented by the coastal zones.
- The study of coastal zones, which are composite and complex systems, is by definition interdisciplinary, combining physics at micro-and macro-scales, chemistry, geology/geophysics, hydrology, biology, ecology, epidemiology, the social and political sciences, etc. Only interdisciplinary approaches, combined with the acquisition of precise, spatial, long-term observation data, will allow us to better understand the evolution of these zones. They will also allow us to plan the introduction of tools and behaviours adapted to sustainable development. This will give a reasoned framework of exploitation that is beneficial for all: humans, environments and ecosystems.
