The Mediterranean region has about 18.5 million hectares of wetlands (± 3.5 million), around 1.5% of the world’s wetlands (Perennou et al., 2012). It hosts around 400 coastal lagoons, covering a surface of over 641 000 ha. They differ in both their typology and their uses. Fisheries and various forms of aquaculture have been traditionally carried out in Mediterranean coastal lagoons since ancient times and are part of the cultural heritage of the region (FAO, 2015).
What is a lagoon?
The Mediterranean lagoons are shallow coastal water bodies separated from the sea by a sandy cordon: the lido. Lagoons communicate with the sea through one or more passages called inlet: permanent or temporary, they allow the entry of sea water due to tides and wind. Freshwater inputs come from the watershed via rivers and storm runoff. The lagoons also maintain relations with their peripheral marshes which are not in direct contact with the sea.
Coastal Lagoon of Vic (34), France. © SIEL
Coastal lagoons under danger
If properly managed, coastal lagoons can, through their regulation services, be more cost-effective solutions to environmental threats than physical infrastructures, and can be used as coastal risk management tools in the context of climate change to mitigate its effects. The protection of these coastal ecosystems can bring innovative solutions to the stakeholders in the territories.
- Protection from extreme weather events
By having the ability to mitigate storms’ power and wave strength and speed, some wetlands act as buffer zones. Protecting wetlands, such as lagoons, can be an adaptation measure, as it reduces the vulnerability of populations to their impacts (Campbell et al, 2008; MA, 2005a; Pergent et al, 2012; ProAct Network, 2008; Ramsar Convention, 2010; Wetlands International, 2008).
- Flood control service
Lagoons are able to store water in the soil or retain it on the surface. Thus, they can be used to control flood peaks, to spread the water table, to reduce the speed of the current and to extend the flood duration to a low water level (RMC Water Agency, 2006; MA, 2005a; MWO, 2012; Turpie et al, 2010; Wetlands International, 2008).
- Maintaining low water levels service
The wetlands that store water in wet periods can be water suppliers in dry periods. In this case, the water was not returned directly but slowly infiltrated into the soil, so as to gradually feed the ground water and the watercourses, thus helping to limit the effects of drought (RMC Water Agency, 2006; MWO, 2012).
Coastal lagoons are in danger
Physical changes in the Mediterranean climate have been widely observed and such trends are projected to continue in the future (Plan Bleu, 2016).
The main expected impacts of climate change on coasts and wetlands are related to: a) an exceptionally high temperature increase compared to the European and global average, in the range of 2 to 6.5 °C by the end of the century (Travers et al., 2010); b) an important decrease in precipitation patterns; c) an increase in the frequency of extreme events; and d) an expected rise of 7 to 12 cm in the overall level of the Mediterranean Sea compared to the past decades, projected by 2050 (Gualdi et al.,2013), which could compromise the ultimate existence of Mediterranean coastal lagoons, in particular the deltaic lagoons of Egypt, France and northern Italy.
These main factors may act in synergy with several anthropogenic pressures and may severely threaten coastal ecosystems. Sea level rise may directly cause the loss of lowlands and beaches in coastal ecosystems and thus may determine both coastal erosion and loss of habitat for several species, most of which are endemic or endangered.
Sea level rise would thus be critical for some Mediterranean coastal habitats such as wetlands, lagoons, deltas and estuaries, etc.
How to act?
Keeping and maintaining the services provided by coastal lagoons can be a measure of adaptation to climate change since it reduces the population’s vulnerability to the impacts of these hazards.
The conservation of these ecosystems must be fully integrated into national and international strategies for action on climate and natural hazards.
Finally, the actions to be undertaken relate in particular to:
a) creation and management of protected areas and ecological continuities;
b) improved ecosystem management and use practices;
c) restoration of degraded sites; and
d) development of a methodology for assessing current and future vulnerabilities and coastal disaster risks. In this framework, a multi-scale coastal risk index, developed by Plan Bleu, has several advantages that make such a methodology particularly suitable for helping to make decisions despite scarce resources, limited local data and uncertain information about the future. To see the regional coastal risk assessment map click here (Plan Bleu, November 2016).
- Technical Report of Plan Bleu and la Tour du Valat ”Services écologiques rendus par les zones humides en matière d’adaptation au changement climatique” (report here)
- Report 2010 of UNEP and RAC/SPA: ‘’The Mediterranean Sea Biodiversity: state of the ecosystems, pressures, impacts and future priorities’’ (report here)