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The mangroves of Guyana, in South America, are gradually disappearing. Contrary to the coastline of its near neighbour, French Guiana, which is still relatively protected, that of Guyana has been largely developed. In order to develop agriculture and aquaculture, earth dikes were built, destroying the greater part of the mangrove forest.
A study( 1) conducted by IRD researchers and the University of Aix-Marseille shows that the reduced protection provided by mangroves against the swell will lead to the large-scale erosion of 370 km of the country's coastline. Only one ecosystem restoration programme will help contain this phenomenon.
A unique environment existing between land and sea, the mangrove is a type of forest found in tropical tidal zones, populated by mangrove trees. In New Caledonia, IRD researchers and their partners ( 1) have observed that mangroves situated downstream from mining activity contain between 10 and 100 times as much nickel and chrome as those that are unaffected by metal extraction. They have compared concentrations of various metallic elements in mangroves situated both downstream from mine locations and in areas unaffected by mining activity, in order to study the mangrove's effect as a plant filter. Their work has shown how the mangrove trees transform elements, particularly organic elements, and trap metals with their remarkable root systems. These plants have developed extremely selective adaptive capacities according to their conditions, notable examples being roots that form stilts or vertical growths.
A veritable well for contaminants over the long term, the mangroves have numerous other ecosystemic properties: protection against coastal erosion, as a food source, conserving biodiversity... However their surface coverage is decreasing by 1 to 2% per year, as a result of urbanisation and the exploitation of natural resources such as nickel.
- Dengue and chikungunya combine
Dengue and chikungunya hit Gabon in simultaneous outbreaks from March to August 2007. That resulted in 20 000 or so victims. An IRD team traced the spread of the two viruses. The agent responsible? The mosquito Aedes albopictus. Since 2005, this species has been stealing the limelight from its cousin, Aedes aegypti, in the role of leading vector. As Eric Leroy, IRD director of research on guest assignment at the Centre International de Recherches Médicales de Franceville (CIRMF) deplores, “Aedes albopictus is much more aggressive than its predecessor”.
- « Overfishing : a global and sistematic issue »
Interview with Daniel Pauly, fisheries biologist, professor at the University of British Colombia at Vancouver in Canada. He was awarded the Cosmos Prize in 2005 for research in ecology. Resident guest of the IRD at the Centre de Recherche Halieutique Méditerranéenne et Tropicale in Sète for several months, he talks to Sciences au Sud about his findings on overfishing-related issues question.