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| Study: Global warming sparked by ancient farming methods | |||||
| 2009-08-19 | |||||
Ancient man may have started global warming through massive deforestation and burning that could have permanently
The study, published in the scientific journal Quaternary Science Reviews and reported on the University of Virginia's Web site, says over thousands of years, farmers burned down so many forests on such a large scale that huge amounts of carbon dioxide were pumped into the atmosphere. That possibly caused the Earth to warm up and forever changed the climate.
"It seems like a common-sense idea that there weren't enough people around 5, 6, 7,000 years ago to have any significant impact on climate. But if you allow for the fact that those people, person by person, had something like 10 times as much of an effect or cleared 10 times as much land as people do today on average, that bumps up the effect of those earlier farmers considerably, and it does make them a factor in contributing to the rise of greenhouse gasses," Ruddiman said. Ruddiman said that starting thousands of years ago, people would burn down a forest, poke a hole in the soil between the stumps, drop seeds in the holes and grow a crop on that land until the nutrients were tapped out of the soil. Then they would move on. "And they'd burn down another patch of forest and another and another. They might do that five times in a 20-year period," he said. That slashing and burning on such a large scale spewed enormous amounts of greenhouse gasses into the atmosphere and warmed the planet, the study says.
Ken Caldeira, a climate scientist at the Carnegie Institution's Department of Global Ecology in Stanford, California, is among those who disagree with Ruddiman. He said Ruddiman is "exaggerating the importance of early man." Caldeira told CNN that while ancient farmers may have played a tiny role in climate change, "it just wasn't a significant factor." He added, "There are actually studies showing if you cut down forests for farmland, you actually cool the planet, because of the glare from the cleared land." Heathen! Ruddiman and study co-author Erle Ellis, an ecologist with UMBC, acknowledge that some models of past land use show it's only been in the past 150 years -- with a huge population explosion, the onset of the Industrial Age and the rise of fossil-fuel burning -- that global warming has accelerated.
Ruddiman's research also argues that the Earth was on its way to another ice age 10,000 years ago and that ice sheets were already forming in northern latitudes when ancient man started his slashing and burning method of farming.
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| Posted by:gorb |
| #23 Poor farmers in the heart of Bolivia's Amazon are being encouraged to embrace the annual floods - by using a centuries-old irrigation system for their crops. They are experimenting with a sustainable way of growing food crops that their ancestors used. Except when the weather fails to deliver or delivers too much. That's why man decided to try to have some influence over the situation because when crops fail lots of people starve [and as we've read that in fact seems to be an objective of some of the greenies - not them of course]. |
| Posted by: Procopius2k 2009-08-19 19:35 |
| #22 However, several plants have been discovered that uptake huge amounts of salts. With just normal irrigation, they can be harvested for disposal, stripping the land of much of its salt contamination. Where do I find out more about this, Anonymoose? |
| Posted by: trailing wife 2009-08-19 15:05 |
| #21 Here's an article about a ancient farming method that might be revived: Poor farmers in the heart of Bolivia's Amazon are being encouraged to embrace the annual floods - by using a centuries-old irrigation system for their crops. They are experimenting with a sustainable way of growing food crops that their ancestors used. Of course the method takes a lot of work to start & then a coordinated ongoing effort to maintain. Some farmers there doubt it will pay off. The method is touted as a way to deal with 'global warming.' |
| Posted by: Anguper Hupomosing9418 2009-08-19 14:19 |
| #20 "Salting" the soil is a function of irrigation not rainfall. Rain water picks up solubles and moves it lower into a soil profile. Irrigation water either from a river or ground water will concentrate salts into the upper profile. |
| Posted by: whitecollar redneck 2009-08-19 13:14 |
| #19 I heard this theory floated quite a few years back, but it was about the Chinese rice terracing. Wanna have some fun with a GreenGo, argue for them to admit that the mass slaughter of the Bison was in fact beneficial since it cut down significantly the amount of grazing animal farts. Then suggest gore award the Plains Indians' tribes with an award acknowledging their sacrifice in the name his cause of preventing Goebbal Swarming. That Africa's game parks should be disbanded, and all Africa grazing animals be put down or placed inside of methane harvesting structures. That whales quite possibly stifle the growth of phytoplankton and should be hunted down in the name of gore's cause. Its great fun. |
| Posted by: swksvolFF 2009-08-19 12:42 |
| #18 OK, one last comment before I go back to work from my lunch break. Grunter, consider the biomass of new trees vs. hundred+ year old ones. Reforestation does not replace the O2 production of old growth quickly. In any case, what is at stake is the burning of those trees, not simply their removal. Like I said, read the book and then come have a discussion about his work. |
| Posted by: lotp 2009-08-19 12:25 |
| #17 And by the way, Ruddiman's been mentioned at Rantburg in the past several times since 2004. |
| Posted by: lotp 2009-08-19 12:21 |
| #16 The major false assumption is that if a tree is cut down, no other tree will ever grow on that spot. Every time those early slash-and-burn farmers moved on, they left a regenerating forest behind them. Anyone concerned about deforestation would do well to go on Google Earth and spend a while looking over the Amazon basin. |
| Posted by: Grunter 2009-08-19 12:16 |
| #15 and from another review: The second hypothesis is the most plausible explanation I've seen for some of the puzzling short-term temperature/CO2 gyrations of the last 2000 years. He proposes that major plague pandemics have caused sufficient die-offs, abandoment of farms, and reforestration to temporarily lower CO2 and temperature. This could explain the later-Roman/Dark Ages lower temperatures, followed by the relatively disease-free Medieval Warming Period, in which Greenland was settled, and UK vineyards spread again to current levels, if not quite as far as early Roman. He ascribes the Little Ice Age drop to Bubonic plagues in Europe, and especially, to the death of estimated 50 million native Americans from smallpox and other European diseases. He does enough math to make these claims at least worth further study. He (ed: also) carefully observes that "correlation is not causation" and (ed: therefore) goes on to calibrate the mechanisms by which pandemic can lead to lower CO2. Ruddiman refreshingly understands the differences between early hypotheses and well-tested theories. He often starts with an observed behavior, then carefully evaluates alternate explanations for it, rather than just offering an answer. This is an exemplary approach to science, and while the hypotheses certainly need testing, this seems like a very productive line of thought that should incite useful further research. Climate analysis always faces the serious problem of extracting trends, and their causes from a very noisy signal. Compared to many competing hypotheses, Ruddiman's seem to be able to explain some gyrations that have often caused people to say "temperatures go up and down randomly anyway." |
| Posted by: lotp 2009-08-19 12:16 |
| #14 from a review at Amazon: (Ruddiman) presents a very persuasive case that starting about 8000 years ago, an increased "unnatural" output of carbon dioxide from early human agricultural endeavors began to measurably effect the earth's climate (with the effect intensified a few thousand years later by increased methane emissions from rice farming). It is Ruddiman's conclusion, very clearly presented and well supported with evidence, that this "extra" carbon dioxide has offset the "normal" global cooling that otherwise would have ended the present comfortable "interglacial" period and plunged us once again into an era of heavy glaciation. In short, into yet another Ice Age. Ruddiman's work challenges us to jettison many comfortable myths, among them being that "Mother Earth" is naturally a stable benign guardian and that pre-industrial humans lived in some idyllic, low impact manner. |
| Posted by: lotp 2009-08-19 12:09 |
| #13 Maybe our government should give this guy a ton of money tp study your buffalo theory, too. |
| Posted by: gorb 2009-08-19 12:03 |
| #12 Y'all might want to read Ruddiman's 2007 book before dismissing it. He's what a scientist should be: careful, fact-based, open about his assumptions and models. The 2007 book was written for the general public specifically to counter the global warming political movement. And he has been highly respected in his field, so when he spoke out a lot of on-the-fence scientists began to pay attention. The result is a slowly growing acknowledgement that the claims were way overblown and ungrounded. |
| Posted by: lotp 2009-08-19 12:00 |
| #11 And I thought it was due to the vast herds of farting buffalo here in N. America.... |
| Posted by: CrazyFool 2009-08-19 11:34 |
| #10 Moose, there is no irrigation of any consequence in the Western Australian wheatbelt. Doubtless the trees maintained a salt free zone near the surface. |
| Posted by: phil_b 2009-08-19 11:25 |
| #9 It seems to me that most of these "environmental" academics don't have much background in modern agricultural practices/theories and or just basic scientific methods. And they are really prone to specious assumptions for their theories. |
| Posted by: tipover 2009-08-19 11:06 |
| #8 phil_b: There is a twist to that. Plants open leaf pores to uptake CO2, and in doing so, lose water. But if more CO2 is in the air, they don't open their pores so much, retain more water, which remains in the ground. Likewise, the old question was, "Are plants more 'soil' or more 'air'?", that is, do they get more of their bulk from soil nutrition or from photosynthesis?, comes down squarely on the side of 'air'. Once they have their minimal needs met from the 'soil', they don't need any more from the 'soil', which remains behind for other plants to use. This means that higher CO2 levels reverse desertification by raising soil moisture levels, increase plant density in the same area, raise humidity where plant life is dense, thus lowering evaporation. I'd like to add that most land salinization doesn't come from liquefied salts rising, but from shallow irrigation. This is a major problem in California, where much farmland is lost every year. Typically, to restore land, it has to be flooded for weeks, to carry the salt far below the root level. However, several plants have been discovered that uptake huge amounts of salts. With just normal irrigation, they can be harvested for disposal, stripping the land of much of its salt contamination. |
| Posted by: Anonymoose 2009-08-19 09:28 |
| #7 TW, they might have reforest the wheatbelt anyway. Without trees that capture the rainfall near the surface and transpire it back into the air, the water seeps down and brings salt up to the surface making the land useless for agriculture. On a global scale cutting down forests results in less water transpired back into the air and more runoff to the ocean. Hence a drier, less cloudy world. A single tree will transpire 10,000s of litres of water (as water vapour) a year into the atmosphere. Multiple that by a few billion trees and the effect is suprisingly large. |
| Posted by: phil_b 2009-08-19 09:11 |
| #6 Like so many others in the green movement they see a depopulated earth as nirvana. Except for themselves. Someone has to stick around and manage nirvana ... |
| Posted by: Steve White 2009-08-19 09:00 |
| #5 I think he's trying to say that it's the evil People that have caused the destruction of his eden. Like so many others in the green movement they see a depopulated earth as nirvana. |
| Posted by: DanNY 2009-08-19 08:44 |
| #4 We'll name them...."green belts." |
| Posted by: Besoeker 2009-08-19 08:24 |
| #3 Proposed experiment: plant tree rows or hedge rows between the fields of wheat to encourage cloud formation. What do you think, phil_b? |
| Posted by: trailing wife 2009-08-19 08:22 |
| #2 My hypothesis is that it's the rabbits that cause the rain. Can I get a couple mill to study this? |
| Posted by: BrerRabbit 2009-08-19 08:21 |
| #1 He's right about the farming, but wrong about the CO2. You clearly see the effect of farming versus natural forest here in Western Australia along what we call the vermin fence. On one side is wheat fields and clear skies. On the other side is natural forest and frequently cloudy skies and as a result higher rainfall. The fence runs in a straight line and so does the cloud vs clear sky boundary. CO2 levels are of course identical on both sides of the fence. Link |
| Posted by: phil_b 2009-08-19 03:39 |