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Hubert the beetle
October 2012
Insects are the best example of biodiversity.
They represent the third of the living species and scientists discover new specie every day.
One group in particular has survived through many geological events : the insects.
While climate was changing regularly, they were able to adjust and develop.
Today, it is the human’s impact that is presenting a threat to insects.
With Philippe Le Gall, entomologist from IRD, we try to understand how, in this area of Cameroun mountains, the living is always in motion...
The coleoptera group accounts for about 350,000 species which is about a fourth of the total known species of one million.
Using the insects and their major biodiversity, availability and size, scientists have now a fundamental model that they can use for their research.
416 - Who deforested Central Africa: Man or climate?
November 2012
It is a much debated question: why did Central African forests become partially fragmented between 2,500 and 2,000 years ago, leaving room for more open forest landscapes and savannah? Recently, a publication attempted to explain that it was the farming Bantu peoples who were responsible for this, through the large-scale clearing that they undertook. But several IRD experts and their partners( 1) contest this argument in Science magazine. The fragmentation of the Central African forest was the result of drastic climate change. In fact, during this period a phase of general desiccation spread from the equatorial region right to the edges of the Sahel. Numerous data show that it was only 500 years later, in other words some 2,000 years ago, that Bantu colonisation became widespread. The first Bantu populations therefore merely took advantage of the opening up of the forest to enter these areas and start growing their crops.
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.
374 - Snakebites a public health problem in Africa
May 2011
One and a half million people per year are poisoned by snake venom in Sub-Saharan Africa. An IRD researcher recently analysed around 100 surveys and medical reports published over the past 40 years. No large-scale study of the situation had hitherto been conducted and public health authorities had underestimated the size of the problem. This means that currently only 10% of victims are treated, owing to a shortage of antivenoms * and lack of awareness among health care practitioners. Yet the clinical complications can be very serious, even fatal. A bite from a cobra or mamba can bring on death by asphyxia –due to respiratory paralysis– within 6h after the incident. Venom injected by the ocellated carpet viper, common in the African savannah, can cause haemorrhages leading to the victim’s death in a few days.
This new study provides authorities with more detailed and reliable figures which should enable them to readjust their health-care services in better tune with needs.
373 - Increasing rice production using genes from the African species
May 2011
Rice is the world’s most commonly used cereal food, feeding half of humanity. However, rice production will have to double within 20 years from now to meet the needs of a growing population.
Two species are used for cultivation, one Asian and the other African. The Asian species gives much stronger agronomic performances, but the African one is more rustic, more resistant to pathogens, more tolerant to drought and soil salinity.
With the aim of transferring these properties to Asian rice, IRD scientists and their research partners( 1) are seeking to overcome the sterility between the two species( 2). They used genome sequencing to compare the structure of a portion of chromosome, identified as the factor behind the reproductive barrier. These investigations, the first results of which were published recently in the journal PLoS One , have led to the definition of genetic markers allowing more rapid development of fertile lineages of improved Asian rice.
