IN a field near Ubud, in the hill regions of Bali, an exotically named zitting cistacola bird flits in an anxious manner. There have been two rice crops in that region every year for centuries, and the bird's muddy nesting habits among the rice plants have adapted to fit.
But in the past decade a new genetically modified strain of rice means three annual harvests, and the zitting cistacola has no time to raise its chicks before the nest gets torn up by farmers' hands.
A thousand years ago, a thousand kilometres to the north, the same bird's multi-great grandmother might have been just as agitated. Because early in this millennium Asians were learning to cultivate two harvests of rice a year instead of one. And civilisation was never quite the same again.
In 1002 the great king Suryavarman I became the ruler of the Khmer kingdom in what is modern Cambodia. He might have gained the throne 'by his sword, which broke the circle of his enemies', according to one inscription. But, according to social historians, he kept the throne because of rice.
It has been a question that has worried scholars for years: how could an agricultural community have become rich enough between the 10th and 14th centuries to create the extraordinary quality and number of monuments that can be seen today, in ruins, around Angkor Wat? The answer is to be found in an extraordinary system of agricultural hydraulics.
The problem of the climate was too much monsoon rain too quickly. To cope with this the Khmers built a huge hydraulic network around their capital, based on huge storage tanks, or barays, which could hold 10 to 30 million cubic metres each. They also developed an ingenious apparatus for carrying off the water and distributing it around the kingdom.