Deforestation driving CO2 buildup


January 22, 2011

Genghis Khan and his Mongol hordes had an impact on the global carbon cycle as big as today's annual demand for gasoline. The Black Death, on the other hand, came and went too quickly for it to cause much of a blip in the global carbon budget. Dwarfing both of these events, however, has been the historical trend towards increasing deforestation, which over centuries has released vast amounts of carbon dioxide into the atmosphere, as crop and pasture lands expanded to feed growing human populations. Even Genghis Kahn couldn't stop it for long.

"It's a common misconception that the human impact on climate began with the large-scale burning of coal and oil in the industrial era," says Julia Pongratz of the Carnegie Institution's Department of Global Ecology, lead author of a new study on the impact of historical events on global climate published in the January 20, 2011, online issue of The Holocene. "Actually, humans started to influence the environment thousands of years ago by changing the vegetation cover of the Earth's landscapes when we cleared forests for agriculture."

Clearing forests releases carbon dioxide into the atmosphere when the trees and other vegetation are burned or when they decay. The rise in atmospheric carbon dioxide resulting from deforestation is recognizable in ice cores from Greenland and Antarctica before the fossil-fuel era.

But human history has had its ups and downs. During high-mortality events, such as wars and plagues, large areas of croplands and pastures have been abandoned and forests have re-grown, absorbing carbon dioxide from the atmosphere.

Pongratz decided to see how much effect these events could have had on the overall trend of rising carbon dioxide levels. Working with colleagues at the Max Planck Institute for Meteorology in Germany and with global ecologist Ken Caldeira at Carnegie, she compiled a detailed reconstruction of global land cover over the time period from 800 AD to present and used a global climate-carbon cycle model to track the impact of land use changes on global climate. Pongratz was particularly interested in four major events in which large regions were depopulated: the Mongol invasions in Asia (1200-1380), the Black Death in Europe (1347-1400), the conquest of the Americas (1519-1700), and the Fall of the Ming Dynasty in China (1600-1650).

"We found that during the short events such as the Black Death and the Ming Dynasty collapse, the forest re-growth wasn't enough to overcome the emissions from decaying material in the soil," says Pongratz. "But during the longer-lasting ones like the Mongol invasion and the conquest of the Americas there was enough time for the forests to re-grow and absorb significant amounts of carbon."

The global impact of forest re-growth in even the long-lasting events was diminished by the continued clearing of forests elsewhere in the world. But in the case of the Mongol invasions, which had the biggest impact of the four events studied, re-growth on depopulated lands stockpiled nearly 700 million tons of carbon absorbed from the atmosphere. This is equivalent to the world's total annual demand for gasoline today.

Pongratz points out the relevance of the study to current climate issues. "Today about a quarter of the net primary production on the Earth's land surface is used by humans in some way, mostly through agriculture," she says. "So there is a large potential for our land-use choices to alter the global carbon cycle. In the past we have had a substantial impact on global climate and the carbon cycle, but it was all unintentional. Based on the knowledge we have gained from the past, we are now in a position to make land-use decisions that will diminish our impact on climate and the carbon cycle. We cannot ignore the knowledge we have gained."


What method does you use to justify this study?


Beating 2005\'s dead horses is unworthy of gizmag, a technology blog that is supposed to bring us the future.

A headline like \'Deforestation driving CO2 buildup\' assumes a percentage of the readership hasn\'t already figured out the AGW nonsense for themselves. The subject is completely dead in the MSM, so it\'s surprising to see the corpse re-animated here of all places.

Deforested areas have grown back completely to their pre-1970\'s levels due to third world farmers returning to the cities. And unless you are in a \'Department of Global Ecology\' paid to keep the inflow of grants coming in, there\'s not too much anymore for a Greenie to do.

Todd Dunning

Todd, hard to imagine more ignorance crammed into a couple of paragraphs, but if you think deforestation has slowed, let alone reversed you need to get out more into your own world if not the third world.

Just as a small sample of what you will find, here is a simple graphic from Borneo (third world enough for you?);


Interesting enough but I would have appreciated either an explication of their methodology or a link to the study.

Ludwig Heinrich

The biggest problem facing mankind today is apathy.


Mongol expansion \"causing\" GW and even investigating that the Black Death did not \"cause\" global warming. It\'s so funny that I almost spewed my coffee over my keyboard.

Many historians consider that extension of the Mongols south into China was partly driven by pronounced climate cooling following the Medieval Warm Period.

This hit Europe rather suddenly when an unusually active period of volcanic activity erupted in Iceland beginning in the early 1300s. Such cooling and increase in precipitation forced severe crop failures such that there was a 10 percent die off. Cooling continued and some researchers consider that this weakened the health of the population which made Europe more susceptible to the Plague, when deaths amounted to one/third to one/half of the population.


mcsblues, since I am not a Lefty I will not insult you personally; simply educate you on the value of facts instead of emotions:

Der Spiegel, \"Tropiocal Comeback\":,1518,642199,00.html

\"...Is the rainforest truly recovering from overexploitation? And could it be that the consequences of deforestation are not as devastating as environmentalists have been preaching for years?

\"There are more secondary than primary rainforests in most tropical countries today,\" explains American biologist Joe Wright. \"On the whole, the amount of land covered by vegetation is stable.\" In tropical countries, in particular, rural flight and urbanization have led to more and more farmers abandoning their fields, allowing new vegetation to grow rampant on the fallow ground. \"The numbers speak for themselves,\" says Wright.\"

Todd Dunning

Those of you who do not believe in global warming are tratorous to themselves, their country and, of course the environment the we need to survive with.

Here\'s proof: CO2 is an infrared absorber, proven.

No more need be said, really, but here\'s more. The count has risen 40% in exact correlation with our fossil fuels use (About 100 CUBIC MILES FF\'s converted into CO2).

Ice caps are coincidentally melting.

What more do you want! Oh, \"it\'s not nice to mess with mother nature\" (that\'ll do it!)

Solution: Robotically mass produce solar PV. We already have the tech, just not the will to overcome (yell with a bit of sarcasm) OIL DEPLETION...

The Chinese are already doing it successfully (and do you think they are doing it just to be green?), We should be doing it for the THOUSANDS OF SQUARE MILES OF INSTALL JOBS TOO! Here\'s the link...

Get it?

Facebook User

Todd, did you actually read the article you referred me to?

\"\"The conditions in the small country of Panama cannot be generalized. In the Amazon, cattle ranchers and the agricultural industry are destroying the jungle on a large scale. The undergrowth that thrives in cleared areas is a caricature of a forest.\"

Even Wright concedes that Brazil is a \"key region\" for the future of the rainforest. Three-quarters of the Amazon jungle lie in Brazilian territory. Nowhere else is the forest being destroyed so recklessly.\"

\"\"Within no more than five years, most of the secondary forests will be burned down or cut down again,\" he says. Cattle ranchers use the fallow fields as pasture, while farmers plant soybeans or cereal crops.\"

There\'s more - try reading it again.

Oh, and its interesting you think I\'m a \"lefty\". What does politics have to do with being able to see the overwhelming evidence of, and sound science behind our influence on climate change? Are you saying because of your political views you just don\'t want it to be true?


mcsblues, global climate disruption; which one are we arguing? Let\'s just pick the middle one for now.

We deniers are in a comfortable spot, without our reputation on the line or the possibility of being publicly shown to be fools susceptible to the most juvenile hoax of the century so far. It\'s why I can show my real name here, and you don\'t want to.

After you graduate and get a few years of life experience you\'ll find that things that sound oh-so right and good not only mean nothing, but usually are the opposite. The apocalypse theme in particular has always worked for those who seeking to influence the naive and impressionable. In today\'s world, this means liberals.

That is why not only do I \"think\" you\'re a Lefty, it is proven by what you have written, and your emotional attachment to this \"scientific\" subject. Followed by ad hominems of \"ignorance crammed into a couple of paragraphs\" that show you can\'t really prove your point.

Like creationism, AGW was invented to serve an ignorant, easily swayed demographic searching for validation of their views. Your response is directly in line with the rest of your group, blissfully unaware that AGW has already dropped out of MSM news cycle for a year, and has been publicly declared \'under review\' by the IPCC itself.

Todd Dunning

Todd I graduated rather a long time ago (not that its relevant) but I see now your claim that \"Deforested areas have grown back completely to their pre-1970\'s levels\" has been exposed as nonsense (and thanks again for the link which says it is) you are now out of arguments and just want to attack the messenger.

It really doesn\'t matter to me, and as you don\'t like science or facts there is probably very little I can do for you.

However, on the off chance anyone else might be swayed by your bluster;

Warming is just one of the serious effects of climate change which is why the later term is used most often these days (but then I\'m sure you know this).

Of course deniers have their reputations, and of course a great deal more at stake. If the scientific community is wrong (and we end up belatedly taking their advice) the costs would be comparatively small and benefits such as less pollution and an easier and earlier adaptation to a coal and oil free energy market (which is coming anyway) could be made. If your tiny band of \"deniers\" is wrong, the result may well be devastating. Have a read up on the \'precautionary principle\' - don\'t panic, it also applies outside of science. Do you insure your house? Is that because you expect it to burn down?

The IPCC has the existence of climate change (or man\'s role in it?) under review? Well that is just a lie, but if it helps you sleep at night ... Speaking of sleeping, you also must have missed the thousands of news articles about climate change in the last year in ... yes the \"MSM\" not just science journals (ever hear of Cancun?)

Climate change and Creationism? Are you serious? One has overwhelming science and direct observational evidence in support. The other has neither. If you really must make baseless political judgements about this and you say that only liberals are \"naive and impressionable\" then I guess that must mean that the Tea Party are all 100%, dyed in the wool evolutionists?

Sure they are.


There is only one solution to the energy crisis. If there was more fuel and cheeper fuel - we would all use more. So more is not better. Society today is not self-sufficient. We are like a liter of piglets all sucking on the tits of big business. The entire economy is based on \"jobs\" which require most people to use energy every day to get from point A to point B. This is a vicious circle that never ends. In the last 200 years - man has done more harm to himself and to the planet than all his previous years of existence. Example: From day one each family could have build a home equipped with a garden for food, a self sustaining energy source, man powered transportation, sail planes and boats for travel, plenty of personal time to train and guide their own children and have a volunteer government. But no! We all are willing to pay for these things and suffer the consequences.


mcs you are evasive about your politics because we both know it is the basis for the AGW hoax. Warmists seek the largest new tax in human history, a 15% \'carbon tax\' on everything requiring energy to produce. With much of the proceeds doled out to third world dictators like Mugabe. And you on the Left brokering the deal.

But as we\'ve seen twice now in Copenhagen and Cancun, nobody\'s going for it. It\'s thanks to the Internet that you were found out, because we can each look at the raw data, check daily observations, and conclude for ourselves. Darn technology.

If only your side had allowed us to adopt nuclear power two generations ago. But you ignored the science and forced us into today\'s oil and coal dependency with terrible consequences.

We on the right are sitting back with popcorn as you twist in the wind, forced to accept nuclear power as you should have, daily hoping desperately for the tiniest uptick of warming to show us that the far left are correct about something for once.

Todd Dunning

I must confess Todd I haven\'t told you what breed my dog is ... which is just as, if not more relevant to the science on climate change as my politics. Sorry about that.

But there I go again. For obvious reasons you don\'t like science and facts and stuff ... I\'ll try not to bring them up. Sorry.

Honestly, I can\'t thank you enough for explaining all this stuff to me but let me see if I\'ve got it right now;

We don\'t need to worry about climate change because it is all a leftist plot/hoax that no one is buying or reporting in the MSM, but our dependence on fossil fuels is going to have some other, definitely not climate related, terrible consequences, but that\'s ok too because it is all my fault?

Does that sum it up?

Seems I need to apologise to all Gizmag readers, not just you.


Fido* says \"woof\" (I think that also means sorry).

*Obviously not his real name (clever of you to spot that Lenin poster in his kennel - Boy you are good!)


re \"Deforestation driving CO2 buildup\"

It doesn\'t seem likely that the co2 produced from burning down forests is \"more than\" co2 produced from other sources, yet the article title certainly indicated this to me.

Fred Meyers

Trees have also have a massive additional benefit. They make clouds.

How? They have hygroscopic (water attracting) bacteria on their leaves and when these little critters get into the air (which they do a lot when wind blows through forests) they coalesce low level clouds.

More airborne bacteria means more clouds and as little as a 2% low level cloud increase could halt global warming regardless of the carbon sequestration.

Bill Liao
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