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354 - Réunion Island coral reefs in poor health
September 2010
The once splendid colours are dulled, algae growing everywhere and the biodiversity is impoverished Who would believe that this forlorn picture depicts Réunion Island’s coral reef, known for its beauty and rich living communities? Since the 1980s, these corals have lost much of their splendour, victims of high visitor pressure, waste water outflow and runoff, coastline development and deforestation which provokes ground erosion. Ten years’ monitoring of the coral reef has led to a report for the Réunion Marine Nature Reserve authority, co-published by an IRD research scientist( 1). It gives a stark warning. Water quality in the lagoon is deteriorating and the corals are dying. The authors recommend restricted-access measures for the reef, with the aid for example of waymarked pathways, special wildlife refuge areas and intensified surveillance of fishing and leisure activities. Such an approach is vital if human activities and ecosystem conservation, all essential for the island’s economic development, are to be reconciled.
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.
345 - Sounding the ocean to help improve fisheries management
March 2010
There is not enough oxygen in the ocean. Over 50 years, climate change and human activities have been causing the expansion of oxygen minimum zones (OMZ). These now cover almost 10 % of the world’s ocean and exert a strong constraint on the vertical habitat for marine pelagic organisms. To monitor how these zones change, IRD and their partners 1 have developed an innovatory acoustic method. It is straightforward to put into operation and yields data on the upper limit of these anoxic zones 2 every second. Applying the technique off Peru, the team established maps about 100 000 times more detailed than those obtained with standard hydrological profiles. Scientists can thus produce very high-resolution estimates of the available surface habitat for fish. This research opens great prospects especially for fisheries management.
343 – When sea-level rises, corals remember
March 2010
It is essential to trace back and explain long-term climate variations in order to understand current global warming and predict its impact for the coming centuries. This is especially true for the countries of the South. Fossil corals are excellent indicators of rises in sea level, a direct consequence of ice-cap melting. IRD scientists and their partners 1 used core samples from reefs lying off Tahiti to realize highly accurate uranium/thorium dating of the penultimate deglaciation: 137 000 years ago, sea level had risen to about 85 m below its present level. At the same time, the solar energy received by the Earth in summer (summer insolation), a determinant parameter for climatic cycles, was at its maximum in the Southern Hemisphere and at a minimum in the Northern Hemisphere. This is exactly the opposite to what the scientists previously thought: the glacial and interglacial periods can thus be set off in the southern parts of the globe, and not only in the Boreal latitudes.
340 – Snow cover monitoring in the Moroccan High-Atlas for better water resources management
February 2010
In Morocco, wide arid plains are irrigated at the edge of the desert. The snows of the High Atlas mountains are a substantial reservoir of water for the region, whose economy is strongly based on an agriculture. Water consumption for this farming is particularly high. An increase in water consumption and the uncertainties linked to the high inter-annual variability in liquid and solid precipitations and climate change are a serious concern for the future of this precious resource. IRD researchers and their Moroccan partners 1 used satellite imagery to follow up the trends in snow cover along the whole mountain range. These methods enabled them to forecast the streamflow rate of the wadis downstream which water the valleys throughout the dry season. They offer a decision-making aid for local water-managers, in the interests of sustainable management of this resource.
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