On temperate plains around the world summer is a time for growth and reproduction. Now the grass produces its flowers. New colours also come to the plains. The northern flowering is mirrored by the grasslands of the southern hemisphere. And nowhere is more impressive than on the belt of South Africa. Not all temperate plains are so rich and colourful in the summer. This is midsummer on the Tibetan Plateau the highest great plain in the world. Despite the conditions, grass survives, and in sufficient quantities to support the highest of all grazing herds those of the wild yak. Even in summer life is hard. Temperatures rarely rise above freezing, and the air is thin.