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Paddy fields
Rice fields. Photo (cc) mackaysavage.

I’m making a note of this because I missed it when I was on campus today. There’s a report in Nature on the discovery of the earliest damming in prehistoric China. From the Register-Guard:

Stone Age Chinese began cultivating rice more than 7,700 years ago by burning trees in coastal marshes and building dams to hold back seawater, converting the marshes to rice paddies that would support growth of the high-yield cereal grain, researchers reported Thursday.

New analysis of sediments from the site of Kuahuqiao at the mouth of the Yangtze River near present-day Hangzhou provides the earliest evidence in China of such large-scale environmental manipulation, experts said.

This is interesting because the transition to farming is an interesting subject, but Neolithic Chinese farming may us something about Global Warming according to palaeoclimatologist Bill Ruddiman.

Bill Ruddiman has a controversial hypothesis that anthropogenic global warming can be measured before the Industrial Revolution. He argues that the invention of paddy fields in China may have prevented the onset of another glaciation. The evidence he argues is from the cycles of chemical composition of the atmosphere. Repetitive cycles seen in previous Ice Ages break down at the end of the last glaciation. This, he states, is due to agriculture changing the environment. Not only is there deforestation, but also Neolithic agriculture was very inefficient which yielded large amounts of methane.

I’ll be honest, all I know about Chinese agriculture is how to eat it – but his book Plows, Plagues and Petroleum is well written and suggests the idea shouldn’t be immediately dismissed. The Plagues in the title is of interest because he argues that the plagues of the early 2nd Millennium AD killed so many people that reforestation of abandoned farmland drew large amounts of CO2 out of the atmosphere. This drop in Carbon Dioxide caused the Little Ice Age, if he’s correct.

I’d like to write more about Plows, Plagues and Petroleum in the future, but at the moment it’s stretching me a little and I’ll need to read round other reports further. In the meantime you can hear what Ruddiman and other palaeoclimatologists have to say about the idea on this archived edition of Frontiers. It also gets a mention in Home Planet. I haven’t listened to the latter programme yet. They’re both from Radio 4, and you’ll need RealPlayer installed and to click the ‘Listen Again’ button on the left.