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- They changed global climate by killing people. (Issue #19)
They changed global climate by killing people. (Issue #19)
Welcome to the Anthropocene, circa 1492.
Chris Musei-Sequeira
July 08, 2025
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Warning: The following article discusses continent-scale violence against Indigenous peoples.
Did you know that European colonization of “the Americas” killed so many people that the global climate measurably changed?
That’s according to the paper “Earth system impacts of the European arrival and Great Dying in the Americas after 1492,” published in the journal Quaternary Science Reviews in March of 2019 by Alexander Koch et al. The article is freely available in full. Its abstract says the following:
Human impacts prior to the Industrial Revolution are not well constrained. We investigate whether the decline in global atmospheric CO2 concentration by 7–10 ppm in the late 1500s and early 1600s which globally lowered surface air temperatures by 0.15∘ C, were generated by natural forcing or were a result of the large-scale depopulation of the Americas after European arrival, subsequent land use change and secondary succession.
In other words: scientists know that the carbon dioxide (CO2) concentration in the atmosphere dropped about 7 to 10 parts per million (ppm) in the approximate 100-year period after 1492. This data comes from the measurement of ice core samples, as explained in the article. Scientists also know that the Earth’s global temperature dropped by 0.15∘ C around the same time, based on hundreds of paleoclimate records. How much of these changes were due to Indigenous “depopulation”… or as the title says, the “Great Dying”?
Now bear with me as I skip ahead to the section of the abstract that contains banger after banger:
We calculate a pre-1492 CE population of 60.5 million (interquartile range, IQR 44.8–78.2 million), utilizing 1.04 ha land per capita (IQR 0.98–1.11). European epidemics removed 90% (IQR 87–92%) of the indigenous population over the next century.
The article condenses numerous data sources to estimate a pre-1492 Indigenous population of roughly 60 million people, using about a hectare (ha) of land per capita for agriculture. One hectare is about the size of a rugby pitch (which is double the size of a USA football field; sorry Yanks).
Then Europeans and their diseases showed up, killing 90% of the Indigenous population.
This resulted in secondary succession of 55.8 Mha (IQR 39.0–78.4 Mha) of abandoned land, sequestering 7.4 Pg C (IQR 4.9–10.8 Pg C), equivalent to a decline in atmospheric CO2 of 3.5 ppm (IQR 2.3–5.1 ppm CO2).
One thing I wasn’t expecting was how the article summarized the many staple crops and innovative farming techniques used by Indigenous peoples of “the Americas,” including the use of fire. For example:
In the Caribbean: Sweet potato, cassava, and maize grown with techniques such as “stone-built terraces with drainage systems” and “raised fields”
In Mexico: Maize, cacao, “fruit orchards and house gardens,” plus “elaborate canal systems” and “complex systems of dams and weirs” along with Mayan slash-and-burn techniques that integrated fallow cycles
In Inca territory: Maize and quinoa grown on “extensive” terraced slopes, using “elaborate canal systems for irrigation and runoff control”
In the Amazon region: Rice, cassava, peanuts, and chili peppers grown in raised fields (earthen mounds)
North America: A variety of techniques based on location, including the growing of maize, squash, and beans (the Three Sisters), plus terraces with floodwater farming
When 54 million Indigenous people were killed over the period from 1492 to the early 1600s, roughly 56 million hectares (Mha) of “abandoned” Indigenous agricultural lands began growing shrubs, trees, and other plants. That’s secondary succession. 56 Mha, or 560,000 square kilometers, is greater than the land area of California… greater than the land area of France… greater than the land area of Morocco.
The plants that grew on former Indigenous agricultural lands absorbed comparatively more carbon dioxide than Indigenous crops. This removed 7.4 petagrams of carbon (Pg C), or 27 gigatonnes of CO2, from the atmosphere. 27 gigatonnes is almost double the CO2-equivalent emissions that China released in the year 2023.
Accounting for carbon cycle feedbacks plus LUC outside the Americas gives a total 5 ppm CO2 additional uptake into the land surface in the 1500s compared to the 1400s, 47–67% of the atmospheric CO2 decline.
The authors of the article estimate that secondary succession of “abandoned” Indigenous farmland caused about half of the decline in atmospheric CO2 in the century after the arrival of Europeans, due to complex aspects of the Earth’s climate system and associated land use change (LUC) outside of “the Americas.”
The result: global cooling, of around 0.15 degrees Celsius (as written at the top of the abstract). That sounds like a small number… but since the year 1975, the Earth has been heating up by roughly 0.15 to 0.20 degrees Celsius every ten years. That is to say: a fractional change in global temperature represents an enormous change in atmospheric carbon dioxide.
European arrival to “the Americas” in 1492 began a chilling phase of the Anthropocene… literally. It wasn’t a phase of global heating due to fossil fuel burning and CO2 release. Instead, it was a phase of global cooling due to genocide.
Where to find the perspectives you’ve been missing
FIRST: Subscribe to the Morning Tinto podcast, where my friend Heather Luna and I use the lenses of oppression and resistance to talk about events that happen right before recording.
SECOND: Subscribe to our professional offers-and-needs networking events announcement list. Heather and I regularly host FREE online events where professionals can offer help (free or paid) and ask other professionals to meet their needs.
THIRD: Follow these awesome folks on LinkedIn:
Heather Luna of keduzi: workshopping pro-connectedness and anti-oppression as a way of life
Lavinia Muth: deconstructing the (un)sustainable fashion industry
Dr. Vidhya Shankar, Ph.D: decentering whiteness in evaluation of non-governmental organization projects
FOURTH: Forward this issue to people you know who are doing decolonial and anti-oppression work.
Got something to say to me?
I’m Chris, the Principal of CJSC, LLC, and I’m (un)learning along with all of you — so hit the “reply” button and give me a piece of your mind!
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My position
My name is Chris Musei-Sequeira, and I use he/him pronouns. My mother was born in Trinidad and Tobago as a descendant of African slaves brought to the islands during the time of European colonization. She came to the United States of America (USA) at the age of 10. My father is Goan and was born in India, in Mumbai, and raised Catholic and English-speaking. He came to the USA for his graduate studies, where he met my mother.
My sister and I were born in the USA and lived a middle-class life in the suburbs of multiple American cities. I studied aeronautical engineering and technology policy in university, then worked at the Federal Aviation Administration and as an aviation consultant. I've lived in cities up and down the USA East Coast since the age of 18; I now reside in Queens, New York with my wife.
I thank Heather Luna and Lavinia Muth for showing me the importance of publicly expressing our positions. Because of our positions, all of us are very familiar with some aspects of the world while having no idea of other aspects. Positionality expresses how our individual positions affect our relationships with other people and with the world as a whole.
Introductory image: File:Columbus taking possession.jpg - Wikimedia Commons. (1893). https://commons.wikimedia.org/wiki/File:Columbus_Taking_Possession.jpg. This is a faithful photographic reproduction of a two-dimensional, public domain work of art. The work of art itself is in the public domain for the following reason: This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 100 years or fewer. This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1930.