Great Green Wall

CHINA is good at building defensive walls. But the record of its most celebrated one is mixed. In 1211 Mongol armies rode round the fortification in Zhangjiakou, the northern gateway to Beijing. Today the city lies on one of two routes that bring another relentless foe to the capital: sand. Blown from northern deserts and degraded drylands, it coats roads, clogs railways and desiccates pastures. According to Greenpeace, just 2% of China’s original forests are intact. Decades of rampant logging and overgrazing have speeded the degradation of its land and soil; over a quarter of its territory is now covered in sand.