Ghengis Khan pioneers reducing greenhouse gases via depopulation

Genghis-Khan.jpgAccording to this Slashdot article researchers from the Carnegie Institution credit Genghis Khan with eliminating 700 million tons of CO2 emissions from the atmosphere. He did this by slaughtering some 40 million people. The environmental researchers believe that by depopulating agrarian societies by massacring their inhabitants, he initiated a wave of reforestation. The resulting trees scrubbed the atmosphere of CO2 which they believe resulted in global cooling. The leader of the research project, Julia Pongratz, states here that:

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. […]. 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.

I had so many reactions to this, it’s difficult to know where to start. Even if the slaughter of millions of human beings would slow down global warming, presumably these researchers would have moral quibbles about doing so. But then it’s always hard to tell with environmentalists. Who can forget their recent public relations foray where they exploded those children who didn’t grasp the urgency of reducing CO2 emission.
In case you missed the video, you can see it here.

Lets give Prof. Pongratz the benefit of the doubt and assume that she believes it would be immoral to reduce the population in the same manner as Genghis Khan, but instead merely wants to see huge portions of agricultural land revert to forests. As far as I’m concerned, this is the “soft” version of killing people. Already we are seeing article after article claiming that the diversion of corn harvests toward ethanol production is contributing to global hunger. For instance in Our biofuel future: The bitter taste of land grabs and hunger, the authors state:

Consider that one SUV tank’s worth of corn ethanol can provide enough food to sustain a person living in a developing country for a year.

Other environmentalists at THE PLANET BLOG note:

The connection between grain-based biofuels and food prices is a scary and underestimated concern because using grain to feed cars and not people drives up the price of meat, dairy, and any food made of or fed grain, like livestock. Combined with climate change, the risk of starvation to communities around the world is too great, especially in a future where basic food ingredients are unaffordable or inaccessible to those who need it most.

In First Goes Tunisia, Next Goes…, the Business Insiders attributes the recent regime change in Tunisia to food price inflation. It also claims that food price inflation is contributing to civil unrest in Egypt, Algeria, India and China.

Ironically this article in NewEnergyNews states that environmentalists are at fault for the shift toward using ethanol for fuel and the ensuing increase in food prices and hunger. According to the author:

Original calculations suggested the total greenhouse gas (GhG) emissions from agrofuels, even after the emissions in their growing and refining, were 20% (corn ethanol) to 90% (other crops) below those from burning petroleum fuels.

But there was a miscalculation. Grunwald: “…no one checked whether the crops would ultimately replace vegetation and soils that sucked up even more carbon. It was as if the science world assumed biofuels would be grown in parking lots…It turns out that the carbon lost when wilderness is razed overwhelms the gains from cleaner-burning fuels…”

And yet environmentalists wonder why people are hesitant to get behind their latest attempts to shape public policy.   If repurposing agricultural products as fuel is creating a food crisis, imagine how we could compound this crisis by taking agricultural land out of production in order to have more forests.

The abstract describing Prof. Pongratz’s research on Ghengis Khan is located at Sage Journals. but the full article is only available to subscribers. However I do note this closing sentence in the abstract:

Only the Mongol invasion could have lowered global CO2, but by an amount too small to be resolved by ice cores.

This actually makes it sound like there is no hard evidence to support their proposition that Genghis Khan’s depopulation of agricultural land scrubbed vast quantities of CO2 from the atmosphere. So now I don’t know what to think because the popularizations of her research on the Internet seem to confidently state that Khan’s killing spree eliminated “700 million tons of CO2” from the atmosphere. I wonder how they came up with that number?

I also found myself wondering about a basic assumption that seems to underly Pongratz’s research. It would appear that she simply assumes that the depopulation of agrarian areas resulted in reforestation. I am a bit skeptical about her reforestation angle, and I’d like to know whether she believes reforestation necessarily follows depopulation, or whether she has hard evidence that this in fact ensued. I am tempted to think that it’s just an assumption because she lumped the Mongolian expansion in with other historical periods of population decline, such as the Black Death, the conquest of the Americas, and the collapse of the Ming Dynasty. However the Mongols were known to strategically destroy agricultural areas in preparation for their invasions in order to create the grasslands that their nomadic lifestyle required. For instance in his book, Genghis Khan and the Making of the Modern World, Jack Weatherford states:

Before the actual invasion, the Mongols sent in small squads to … locate appropriate pasturelands and water sources for the Mongol animals… Where the natural grassland seemed inadequate, the Mongols opened up farmland for pasture by sending in small detachments of soldiers to burn villages and farm settlements in their future path. Without farmers to plow and plant the land, it reverted to grassland before the main Mongol army arrived.

It seems to me that the Mongols would have found woodland to be even less useful for their purposes than farmland. I think there’s certainly the possibility that they while they dominated an area they may have kept the former farmland open by having their massive herds graze there, or possibly by re-burning an area that was becoming forested.

Interestingly there is evidence that pre-Columbian Native Americans, instead of living in harmony with their natural surroundings, also repeatedly burned their environment to beat back the forest and expand grasslands. There is a Wikipedia article on Native American use of fire which states that

When first encountered by Europeans, many ecosystems were the result of repeated fires every one to three years, resulting in the replacement of forests with grassland or savanna, or opening up the forest by removing undergrowth. More forest exists today in some parts of North America than when the Europeans first arrived.

I have also read that Native Americans were responsible for moving bison eastward to such places as Ohio by opening up grasslands through burning. Surely the Mongolians would have frowned on reforestation and would have done something similar. And you would think to such massive burns would release plenty of CO2 into the atmosphere.

I’m going to close with one last look at Pongratz’s statement quoted above:

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.

Apparently three-quarters of the Earth’s “primary production” is utilized by non-humans… weird.

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