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Will we soon be forced to eat jellyfish? Since the beginning of the 2000s, these gelatinous creatures have invaded many of the world's seas, like the Japan Sea, the Black Sea, the Mediterranean Sea, etc. Is it a cyclic phenomenon, caused by changes in marine currents or even global warming? Until now, the causes remained unknown. A new study conducted by IRD researchers and its partners, published in Bulletin of marine science, exposes overfishing as the main factor.
The glaciers in the tropical Andes shrunk between 30 and 50% in 30 years, which represents the highest rate observed over the last three centuries. IRD researchers and their partners( 1) recently published a summary which chronicles the history of these glaciers since their maximum extension, reached between 1650 and 1730 of our era, in the middle of the Little Ice Age*. The faster melting is due to the rapid climate change which has occurred in the tropics since the 1950s, and in particular since the end of the 1970s, leading to an average temperature rise of 0.7°C in this part of the Andes. At the current pace of their retreat, small glaciers could disappear within the next 10 to 15 years, affecting water supply for the populations.
In February 2010, a violent earthquake struck Chile, causing a tsunami 10 m in height. Affecting millions of people, the earthquake and giant wave also transformed the appearance of the coastline: the dunes and sandbars were flattened, and the coast subsided in places by up to 1 m. But although the inhabitants are still affected for the long term, the shore system quickly rebuilt itself. A team from IRD and its Chilean partners( 1) showed that in less than a year, the sedimentary structures had reformed. The Chilean coast therefore represented a unique “natural laboratory” for studying coastal formation processes. The subsidence of the coast also revealed the effects of rising sea levels on shores.
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.
The second greatest economic resource of French Polynesia after tourism, black pearl culture has been facing a major crisis since the first decade of this century. Overproduction, falling prices, reduced activity that had boosted many remote atolls... In response, IRD researchers and their partners( 1) are helping to maintain and sustain the sector.
In particular, scientists have been studying the Ahe atoll lagoon (north of Tahiti) since 2008. Specifically, they coordinated studies on the plankton resources available to feed oysters and on water flow in the lagoon.
These projects contribute to decision-making tools intended for oyster farmers, for the sustainable exploitation of the "Tahitian treasure".