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428 - The Sahara olive tree: a genetic heritage to be preserved
March 2013
The Saharan cousin of Mediterranean olive trees remains largely unknown. However, this subspecies (called the Laperinne's olive tree) is of great interest for several reasons. IRD researchers and their partners showed that its longevity is ensured by its original vegetative reproduction. Extremely drought-resistant, this "relict" tree could act as a genetic resource to improve its domestic counterparts, provided conservation actions are implemented to prevent its disappearance.
401 - A new method for tracing the Sahel water cycle
April 2012
Water vapour is the primary greenhouse gas, and it is still an unknown factor (along with its associated cloud processes) when creating climate projections for 2100. A new technique, developed by IRD researchers and their partners( 1), enables measurement of the isotopic composition( 2) of atmospheric water vapour. It will enable study of such diverse elements as the movement and the origin of masses of air, or the formation of clouds, in a more precise fashion than had previously been offered by standard meteorological variables.
Isotopic data collected over a full year at the IRI( 1) in Niger has enabled researchers to deconstruct the mechanisms behind the Sahel water cycle. It has revealed that humidity plays its part, even during the dry season, and that this regular influx of humid air comes from the Mediterranean. This humidity is present before the monsoon, and probably plays an important role in triggering rainfall( 3).
Now routinely used in Africa, this technique can be extended to other tropical regions such as the Andes, where the topography casts even more doubt over projected changes in precipitation.
392 - Lake Chad: Inhabitants adapt to lower water levels
December 2011
Lake Chad used to be one of the biggest lakes in the world, but its volume has been reduced to a tenth of what it was in the 1960s. The way this lake has dried up has become a symbol of climate change in action. It’s true that the lake’s water level has always changed, but this hasn’t diminished the major changes to the lifestyle of the inhabitants of the lake’s shoreline. Yet, as demonstrated by a French-Nigerian team including the IRD( 1), lake dwellers have made the best of these changes to their environment. Formerly fishermen or herdsmen, they have become farmers, often growing for export. The land that was part of the lake has made it possible for them to develop highly productive crops such as corn, rice and cowpea. In the valley of the Komadugu Yobe River in Niger, they have even commenced the intensive farming of peppers, which is highly lucrative although risky.
Rewatering the lake, as proposed by the Ubangi( 5) international project, would cause upheaval once again to the farming system, particularly if the yearly rise and fall in lake water levels were to cease.
389 - Cards reshuffled in Saharan geopolitics
November 2011
Since the early 2000s the Sahara has come back strongly into the international political and media arena. The whole region is going through a period of turbulence stemming from its growing economic and strategic importance and a highly confused geopolitical environment. This situation stems from the “Arab spring” events, the fall of Colonel Gaddafi and the installation of Al Qaeda Organization in the Islamic Maghreb (AQIM) in Mali.
A special issue of the journal Hérodote has published review articles on these upheavals by IRD geographers and economists and their and their research partners. Beyond the geopolitical and security aspects, they describe the economic changes, the development of the trans-Saharan migrations and the race for raw materials pursued by the world’s great powers. All these powers seek the underground wealth the region conceals (such as oil, uranium, iron). Simultaneously coveted and feared, the Sahara never ceases to arouse concern in the international community.
388 - Revised Earth history favours the search for African gold
November 2011
Potential treasures lie concealed under the West African savannah in some of the Earth’s poorest countries. Extensive gold fields occur, over hundreds of kilometres, from Senegal to Niger. The rapid rise in precious metal prices over the past five years has prompted hugely intensified mineral exploration. Yet new veins must be found if this African gold rush is to continue.
A new discovery, published in Nature Geoscience , is now shaking up our understanding of the Earth and the prospects for exploration. The research team ( 4), led by an IRD geologist, used innovatory modelling software to take a fresh look at the origins of plate tectonics in the light of the geothermal history of the gold deposits in the West African gold fields. These investigations will lead to better ways of locating the emplacement of veins and their depth. This result is a fundamental one for the science which furthermore offers promising applications for West African countries.
