Prehistoric rice farming and modern consequences

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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.

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