. >> professor qujian's students evaluate soil samples. if the sand's water content falls below four percent, the dunes are vulnerable to wind erosion. they destabilize and start to wander. wind corridors are designed to prevent the desert from spreading. at first, scientists tried putting up windbreaks made of straw. but now, straw is hard to find along the edges of the oasis. the newer fences are made of plastic. once grass and brush grow between them, the erosion will slow down. legend has it that the city of yang-guan, just seventy kilometers away, was swallowed by a sandstorm. the chinese cabinet has earmarked 650 mmillion euros to fund a ten-year-plan and spare dunhuang a similar fate. >> the bazaruto archipelago off the coast of mozambique is the place to see giant manta-rays. but like many other species, their body parts are sought after for traditional chinese medicine, putting pressure on their populations.the "marine megafauna foundation" has been monitoring the mantas and other wildlife for years.but science alone won't turn th