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360 - Small islands in the Pacific: duel between freshwater and sea water
November 2010
It is said that the first refugees of climate change will come from the Pacific. In the midst of this ocean’s tropical regions are scattered 50 000 small islands, 8 000 of them inhabited. They are particularly vulnerable to the impacts of global warming. These effects include rising sea-water levels, drought and diminishing stocks of freshwater. Such water is essential for the life of the fauna and flora and for the human populations’ food supplies. On the coral reef islands, freshwater occurs as underground reservoirs, as lenses in balance with the underlying sea water.
IRD scientists and their research partners [1] have investigated the processes behind such lenses, the way they change and develops, their capacity and vulnerability. The team’s geological, hydrogeological and geophysical surveys showed that the lens structure and internal processes depend strongly on the island’s vegetation cover and topography. This work opens up ways towards assessing what will happen to this resource as a consequence of expected changes in the climate and sea level.
357 – The impact of mining in Bolivia
October 2010
For many centuries, men have been exploiting the mineral wealth of the Andean Cordillera. The Incas, then the Spanish, extracted the gold and silver which gave their empires their splendour. Still today, gold and silver, but also tin, zinc, antimony, arsenic, cadmium and other metals are worked intensively. However, it is one of the most highly polluting of all human activities. Mines can eject enormous quantities of heavy metals into the environment. They are well known for their toxicity, yet poverty and strong economic dependence on raw materials mining too often lead to neglect of the environmental and health impacts.
Impressive cities have built up around these mines. This is the case of Oruro, perched 3 700 m high on the Bolivian Altiplano. The city has become one of the largest mining centres in Bolivia. Since 2006, in the context of the ToxBol programme, a multidisciplinary team involving the IRD and its partners( 1) has been investigating the origins, spread and effects of mining pollution on the environment and the health of the communities who live there.
355 - Chile: the earth shook and the coast rose up
September 2010
On 27 February 2010, a huge earthquake, with magnitude 8.8, shook Chile. It left 500 dead and 13 million Chileans were affected, amounting to nearly 80 % of the country’s population. The event was one of the six most powerful earthquakes since the beginning of the 20th Century. Coast uplift has been proved by research scientists from Chile, France, and Germany( 1). This rise reached as high as 2.5 m and resulted in an advance of the shoreline of as much as 500 m towards the sea in places. Conversely, in the hinterland, the ground subsided by nearly 1 metre.
Since 1835, date of the previous strong earthquake in this zone, the equivalent to 12 m of deformation of the earth’s crust, resulting from tectonic block convergence, had been stored at the contact zone between the Nazca Plate and the South-American Plate. On 27 February 2010, rupture of the lithosphere( 3), along a 500 km long fault segment, released most of this mechanical energy in a single abrupt shock.
This study helps better understand the seismic cycle, with the long-term objective of finding ways of predicting and preventing the seismic risk.
353 - The Great Green Wall: how to check the advancing desert
June 2010
The desert has been nibbling away at the Sahel’s fertile land for several decades. To halt this advancing desertification, 11 African countries( 1) have come together to build a “Great Green Wall”. This immense project, initiated in 2005, aims to replant with trees a 15 km wide strip stretching 7000 km across the Africa, from Dakar to Djibouti.
A community of international specialists, including IRD researchers, has been mobilized to ensure that this wall of greenery will be as effective as possible. Their objectives are to choose the revegetation techniques and the best adapted species. These experts( 2) are focusing on a natural process which functions in most plant species: symbiosis between the plant and a fungus. Favouring this process would improve plant growth in degraded soils and increase their drought resistance. A tree with remarkable properties( 3) is one of the various recommended species that will be used: the filao tree, which can fix nitrogen from the air and hence colonize impoverished land.
It remains to be determined how the project can be integrated into an environment which is already used and how to enable the local communities to benefit from it.
350 - Patagonian glaciers in danger
May 2010
Remote lands at the far Southern reaches of the Latin American continent, Patagonia and Tierra del Fuego, the archipelago at the extreme Southern end*, support the world’s most majestic monuments of ice. The Patagonian glaciers, including the famous Pio XI, the largest in Latin America with its 1292 km² surface area, standing high above the valleys of Chile to the West and Argentina to the East. The Tierra del Fuego icefields, plunge sheer into the ocean, deep into the meandering fjords.
These glaciers are retreating. The extent of their regression has recently been quantified at regional scale. An extensive survey by IRD researchers and their partners( 1), focusing on 72 of them, shows that the vast majority of the glaciers of Patagonia and Tierra del Fuego have diminished considerably since 1945. Some scientists consider them to have lost up to 40% of their former size.
