WORLDWIDE PARTNERSHIP ON LOCATION NEWSWIRE Ecology. Research teams are studying mangroves across the globe to explore the crucial role these ecosystems play for the well-being of local populations and the planet. BY ARBY GHARIBIAN 38 CNRS INTERNATIONAL MAGAZINE Mangroves: An Asset to Treasure On December 9, 2014, a tanker carrying 350,000 liters of bunker oil collided with a cargo vessel in the Sundarbans region of Bangladesh, threatening part of the world’s largest tidal mangrove forest, a UNESCO World Heritage Site. Mangroves are forest ecosystems that cover nearly three quarters of the world’s tropical coastlines, where their ability to adapt helps them flourish in intertidal zones with large variations in water flow, sediment flux, and saline content. They offer invaluable ecosystem services by limiting coastal erosion, acting as a buffer zone against cyclones and tsunamis, and by trapping and storing carbon. They are rich in young shrimp and fish that eventually migrate to nearby coastal waters, thus providing an important source of food for local populations. Despite their importance, they have shrunk by 30% over the last two to three decades, and continue to decline at an alarming rate of one to two percent each year, primarily due to shrimp farming in many parts of the world. Surprisingly, there have been few detailed studies of mangrove forests, and growing international interest in recent years has not succeeded in slowing the retreat of these ecosystems. CNRS and IRD1 teams have acted to fill this informational gap by investigating mangroves from various scientific perspectives. They have also helped launch the CNRS/IRD’s 2015 Year of the Mangrove initiative, to raise public awareness of their importance, both in France and its tropical overseas territories, which boast some of the world’s best- preserved forests. Eco-engineering in Mayotte The French island of Mayotte, located in the Comoro Archipelago off the coast of Madagascar, is home to extensive mangrove forests, which are, however, subject to considerable strain from increased urbanization and population density. To help balance the island’s demographic expansion with the preservation of its natural habitat, researchers from the EcoLab2 worked with local authorities to set up a large-scale experiment aimed at testing the depolluting capacity of mangroves. “We established a network of homes to collect domestic wastewater,” explains EcoLab researcher and group leader François Fromard. “We then introduced this water into different plots of mangroves to track how they filtered out pollutants such as phosphorus and nitrogen, and the effect this has on the ecosystem in general.” Scientists observed that the mangrove plots exposed to wastewater © F. FROMARD/ECOLAB Malamani test site (Mayotte), where researchers study mangroves exposed to domestic wastewater. 1. Institut de recherche pour le développement. 2. Laboratoire Écologie fonctionnelle et environnement (CNRS / Université de Toulouse-III / INP Toulouse). 3. Laboratoire des sciences de l’environnement marin (CNRS / IFREMER / IRD / Université de Bretagne occidentale). 4. Agence nationale de la recherche. 5. Biodiversité et fonctionnement des écosystèmes dans les mangroves de Guyane française. 6. Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC) (IRD / CNRS / UPMC / MNHN).
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