40 years ago the Aral sea was the biggest landlocked body of water in the world. Now it is one of the driest places in Kazakhstan and Central Asia. That is why European researchers like Christian Opp are here.
“The Aral sea used to be a cool oasis between two deserts, the Karakoum and the Kusulkoum. It was a huge water store, with a very rich natural habitat and varied biodiversity. Today the old sea is called ‘Aralkoum’, or Aral desert. You can see the signs everywhere; where once was water is now only sand, a desert like its neighbours.”Oleg Semedov is a Physicist at the Kazak Research Institute of Ecology and Climate. “The main trouble after the sea levels dropped was the disappearance of the valuable fish species. This led to the fishermen and other people living along the seashore losing their jobs. But there was a second problem. The former seabed is now a dangerous layer of dust, salt, aerosols and chemicals that are blown away by the winds. Their spread has degraded vegetation for 150 kms around. Desertification of the whole region has indeed started”. Since 1960 extensive and ineffective use of its main tributary rivers has shrunk the Aral and split it into 3 lakes. 50,000 square kilometers of water have gone, and the social impact has been huge. Unemployment and poverty are rampant along its former shores. Diseases like tuberculosis or hepatitis are twice as common here than in other nearby regions. And then, there is the wind. Frequent dust storms claw at the former seabed, blowing away sand, salt and chemical compounds from farming activities. It’s a poisoned cocktail that local residents breathe every day. This bleak scenario is now under scrutiny in a European research project called CALTER. Leah Orlovsky is Project Cooordinator. “Firstly, we want to understand what’s happening with duststorms here in Central Asia and particularly around the Aral Sea, because the last studies ceased after the USSR’s collapse. Dust ignores borders. Dust from here can be blown to Europe and other parts of the world.We want to know how much dust and salt is blown away, its composition and direction. Secondly, we want to propose solutions to lessen the consequences of these duststorms”. Dust traps are set up at meteorological stations hundreds of kilometres away. Particles trapped during duststorms are weighed, measured and analysed. Scientists estimate that storms can blow away up to 400 kilos of dust per hectare every month in places like this. Christian Opp brings his Physical Geography skills to the project. “We have measured the size and mineral makeup of dust particles using techniques like radiofluorescence. With this data we have been able to find where they come from, and we have an idea. If this dust comes in part from the former sea bed of the Aral, it should be rich in salt. And we’ve been able to confirm that this is the case. Salt from the Aral has been carried all this way.” The tracking of dust storms then moves 1300 kms to the southwest, in Almaty, Kazakhstan´s former capital. At the National Space Research Center, duststorms are closely observed with satellites. Duststorms are a key element in climate change. Spread out in the atmosphere, dust is thought to cool ocean surfaces and prevent hurricanes, for example. In addition in Central Asia satellite pictures show they are further drying semi-desert ecosystems. Lev Spivak is at the National Space Research and Technology Centre. “Since 2000, the quantity of dust blown from the Aral region has grown; the intensity and frequency of duststorms are also increasing. Before dust was mostly blown to the north-west. Now it’s mainly going south; this means that every year new land is polluted by salt from the Aral seabed”. Researchers also want to understand the internal dynamics of duststorms; their volume, speed and density, and how they form and die away. For that, Oleg Semedov reproduces small duststorms in a wind tunnel, equipped with a laser and filled with desert dust and sand. “These experiments have allowed us to understand how and how much sand is blown away by winds at different speeds. Now we know that sand particles advance like an avalanche; the smallest particles are lifted and they push bigger ones, that push bigger ones, and so on. We also know that the maximum concentration of sand is achieved at the height of fractions of a millimetre. Mathematical equations help us calculate the total mass of sand blown away at different heights and different wind speeds”. Back in the desert, scientists study different geological sites. They are convinced that around the Aral Sea a man-made desertification is increasing duststorms, that are then further drying up neighbouring regions. It’s an vicious circle with few, but still feasible solutions. “Now we know the real quantity of dust fallout per area, measured in tons per year per hectare. We know the chemical composition of this dust; we also know where it comes from. So we have more new data to propose some solutions. We think the best way to stop further degradation around the Aral Sea is to cultivate local plants. Not over the entire former seabed, but in small green islands; these plants would bind the surface together; there would be much less dust blown away,” concludes Leah Orlovsky. Scientists also hope their work will help establish an early warning system for ecological hazard assessments in Central Asia.
“For more information”: http://www.epif.bgu.ac.il/CALTER/