Did the massive scale of death in the Americas following colonial contact in the 1500s affect atmospheric CO2 levels? That’s a question scientists have debated over the last 30 years, ever since they noticed a sharp drop in CO2 around the year 1610 in air preserved in Antarctic ice.

That drop in atmospheric CO2 levels is the only significant decline in recent millennia, and scientists suggested that it was caused by reforestation in the Americas, which resulted from their depopulation via pandemics unleashed by early European contact. It is so distinct that it was proposed as a candidate for the marker of the beginning of a new geological epoch—the “Anthropocene.”

But the record from that ice core, taken at Law Dome in East Antarctica, shows that CO2 starts declining a bit late to match European contact, and it plummets over just 90 years, which is too drastic for feasible rates of vegetation regrowth. A different ice core, drilled in the West Antarctic, showed a more gradual decline starting earlier, but lacked the fine detail of the Law Dome ice.

Which one was right? Beyond the historical interest, it matters because it is a real-world, continent-scale test of reforestation’s effectiveness at removing CO2 from the atmosphere.

In a recent study, Amy King of the British Antarctic Survey and colleagues set out to test if the Law Dome data is a true reflection of atmospheric CO2 decline, using a new ice core drilled on the “Skytrain Ice Rise” in West Antarctica. //

Scientists estimate that about 60 million people inhabited the Americas before European contact. There’s archaeological evidence for numerous cities and settlements, such as miles of now-overgrown urban sprawl that was recently mapped in Amazonian Ecuador, or the city of Cahokia in Illinois, which is estimated to have been larger than London was at that time, or Llanos de Mojos in Bolivia. The Spanish conquistador Francisco de Orellana also described seeing cities in the Amazon in 1542.

Even today in overgrown parts of the Amazon, vegetation carries the imprint of past occupation in an overabundance of cultivated species such as Brazil Nut trees.

A century after the first European contact, some 56 million people had died according to one widely cited estimate. “What we're looking at here is first contact, and [then] 100 years when 90 percent of the population, basically, dies,” said Professor Mark Maslin of University College London, who was not involved in King’s study. They succumbed to wave after wave of pandemics, as smallpox, measles, influenza, bubonic plague, malaria, diphtheria, typhus, and cholera spread through populations with no natural immunity. People who survived one disease outbreak died in the next. With too few people to work them, cities and farms were abandoned and overgrown. //

Wheels Of Confusion Ars Legatus Legionis
15y
65,758
Subscriptor

Magog14 said:
A strong argument for limiting the human population to under one billion.

We're talking a drop of ~10ppm CO2.

If it happened today it would get us roughly back to where we were in the year 2010.

swiftdraw said:
I have a modest proposal in regards to the population…
Then we must act Swiftly! //

Ushio Ars Tribunus Angusticlavius
13y
6,642
Felix K said:
I can’t believe how much death and destruction my ancestors unleashed on the natives of the Americas. It must be the greatest genocide in history.

Not really sure what to do with the feelings it brings up except that none of this land is ours. It is all stolen.
Was it a genocide when it was accidental? The first people from Europe to land in the America's didn't set out to genocide anyone. Yes conquering and killing but when it was done in Asia and Africa there wasn't genocide.

Genocide's seem to be more a 19th century onwards thing with Native Americans and Aboriginals getting the worst of it long after the USA, Australia and New Zealand had been fully formed. //

A_Very_Tired_Geek Ars Scholae Palatinae
5y
1,290

freitzkreisler said:
Egad <Racist Rant Lacking evidence or merit and doesn't bear repeating>

Could you be any more trollish or racist?

Native Americans were humans, and none of them were these 'heathen savages' that Eurocentric arrogance saw them as. They engaged in warfare just like the rest of the world. But what you're going off on is demonstrably untrue while the rest is bigoted unsupportable opinion. Spiritually inferior? Seriously this is BS I'd hear spouted in some throwback fundamentalist Christian church (and why I became an atheist because I unfortunately grew up in such).

The fact of the matter is that Native Americans taught the European immigrants how to grow native crops in this land because many of their European techniques, plants, and livestock wouldn't work or grow here without changes. It's to the world's detriment that Europeans weren't more receptive to what they had to teach because slash and burn along with hunting species to extinction is mainly a European thing. Most of the modern agricultural advances used today are NOT from the colonial era. They are innovations that came out of America's Dust Bowl during the Great Depression (arguably caused by colonial era practices) while some are revivals of tenants of Native American or Aboriginal practices - don't screw with the natural order. (Who knew predators improves the general ecology of an area? Native Americans. Who knew beavers improved the soil and water quality on farm lands? Native Americans. And on and on...) //

A_Very_Tired_Geek Ars Scholae Palatinae
5y
1,290

Mad Klingon said:
Besides reforestation, having 10s of millions of people die and stop using firewood and coal for cooking and heating probably had something to do with the CO2 drop.

Also, several of the groups practiced planned burns as part of their crop and living space management. When they died off, no more planed burns.

The planned burns were more to keep nature from doing it for them when the underbrush collected to the point where it could begin with any random dry lightning strike. Native peoples weren't stupid. People died from uncontrolled wildfires then as now. Planned burns minimizes the loss of life in the short and long term. That way they could plan to move their village if needed. Wildfires could come up unannounced. That could cause panic and panicky people die in fires.

Edit to add: I don't think the planned burns were a major factor in CO2. They would have occurred naturally regardless and in greater range and intensity. Rather it's probably somewhat (although how much I wouldn't guess) CO2 from cooking, midden, and perhaps to a lesser extent religious rites fires.

That said, what bothers me is that the researchers seem to be assuming the CO2 content in the atmosphere is uniform, and it's not. It would have varied even in Antarctica in different areas simply due to atmospheric movements and what those areas are downwind from even if it's 10,000 mi downwind. (Example Dust from the Sahara regularly blows all the way to North America. Or the Deccan traps would have spewed megatons of sulfur into the air millions of years ago, but particularly any areas directly downwind on the jet streams would have had high sulfur oxides, carbon oxides, etc in any sediment layers.) It shouldn't be a surprise to anyone that CO2 levels varies in ice cores. What matters is having enough point data to form valid statistical analysis rather than relying on the data from a handful of point sources as if they are broad indicators. //