This is a much argued question.

I think the data supports a conclusion that many more Native Americans died of diseases than from either warfare or ‘atrocities’ . The impact of disease on Native American demographics, may have been compounded, however, by dislocation and other conflict related problems, making demographic recovery more difficult.

To explore the question, let’s look at Native American demographics in Canada, Mexico, and the USA. We will also look at some estimates of Native American casualties in some wars and ‘atrocities’. We will also look at demographic data on the population of Iceland (which similarly collapsed due to disease) to get some comparisons.

Let’s start with some data.
(Warning: All this demographic data on Native American populations is based on estimates of uncertain accuracy.)

The First Nations populations of Canada were severely reduced, to a low point around 1900. In 1900 the First Nation population of Canada was 127,000, or about 2% of a total population of 5,300,000 (of which 5.1m European, 23,000 Asian, 17,000 African, and 127,000 Indigenous).

http://www.chrc-ccdp.ca/en/getBriefed/1900/population.asp

Since 1900, the Aboriginal population of Canada has grown to 1.4 million, and now makes up 4.3% of the population of Canada.

The demographics of American Indian populations in the USA are similar.

http://www.ewi-ssl.pitt.edu/econ/files/courses/110103_misc_nativeamericanpopulationgraphs.pdf

By the time of the first US census (in 1800) the Native American population (in a smaller area than today’s USA, and of dubious accuracy) was enumerated as 600,000. The low point in American Indian population was 1890 at 228,000 (0.4% of the total population of 63m at the time) (Alaskan Natives were included in the “American Indian” category in the 1890 census).

The low point of the American Indian population in the USA was 1890. Although American Indian populations began to recover after 1890, the American Indian percentage of the population did not start to grow until after 1950, as the non-Indian population (largely through immigration) grew as fast, or faster, than the Indian population.

Since 1950, the American Indian share of the population has grown. By 2010, in the USA, the American Indian and Alaska Native population only identified as such, was 2.9m (0.9% of the population), while those identifying as American Indian or Alaska Native in combination with one or more other groups in the USA was 2.3 million (0.7% of the population). Those identifying as totally or partially American Indian or Alaska Native made up about 1.7% of the population. Between 2000 and 2010, the population of American Indians and Alaska Natives was growing twice as fast as the growth rate of the overall US population, so their percentage of the population is gradually increasing.

http://www.census.gov/prod/cen2010/briefs/c2010br-10.pdf

In Mexico, Indigenous populations also got hammered in a demographic catastrophe by diseases arriving in the Columbian exchange. Estimates vary a lot, but it seems that the bottom of the demographic decline was in the mid 1600s, when the indigenous population in Mexico reached a low point of between 1.2m and 3.4m (down from pre-contact estimates between 5 and 25 m).

http://www.hist.umn.edu/~rmccaa/mxpoprev/cambridg3.htm

As well as the demographic crash bottoming much earlier in Mexico (250 years earlier), the numbers of the non-indigenous population, at the time of the low point of the demographic catastrophe in the aboriginal population, were much smaller. In 1650, it is estimated that there were 10,000 Mexicans of European descent, and 35,000 Mexicans of African descent. In addition, there were circa 600,000 Mexicans who were classified as “mestizo” (meaning of mixed Indigenous, European and or African descent) as well as the 1.2m to 3.4m (est.) remaining indigenous population.

Mexico became characterized by high birth rates (over 8 children per woman) and low life expectancy (circa 16 years average) due to very high child mortality. Still, the demographic catastrophe reversed, and the Mexican population began to slowly grow, reaching perhaps 5m by 1800. (Don’t have a breakdown between Native Americans vs. other groups.)

In the 1790s the Spanish government instituted a policy to try to inoculate the entire population of its American and Philippine territories against smallpox. Perhaps due to this initiative, the population of Mexico began to grow faster after 1800. The population is estimated to have grown to 8m by 1855. (Don’t have a breakdown between Native Americans and other groups.)

Native Americans in Canada and the US have had similar demographics. A population crash, bottoming about 1900, followed by a population recovery since then.

Mexico had different demographics, with a much earlier demographic trough in the Native American population.

Let’s look at the demographics of Iceland.

The population history of Iceland has been intensively studied. The Norse seem to have started settling Iceland in the late 800s. By about 1100, the population had grown to an estimated 70,000 – 80,000 (entirely rural). The population of Iceland presumably peaked in the early 13th century at circa 80,000 or more.

http://www.icelandexport.is/english/about_iceland/population_in_iceland/ In 1241 Iceland was struck by its first epidemic of smallpox. This was a catastrophe which knocked the population down to below 40,000. Smallpox epidemics recurred many times in Icelandic history with deleterious effects on population levels. (Smallpox never became endemic in Iceland, remaining an epidemic disease – epidemic diseases are worse for population levels than endemic diseases)

http://www.alternatehistory.com/discussion/archive/index.php/t-211600.html

As well as recurring smallpox epidemics, Iceland was hit with the Black Death in 1402. This smashed the population back down below 40,000 again.

http://www.sagamuseum.is/overview/the-black-death

In 1783, the eruption of the volcano Grimsvotn killed about 25% of the population of Iceland, again knocking the population down well below 40,000.

http://en.wikipedia.org/wiki/List_of_volcanic_eruptions_by_death_toll The population of Iceland did not ever recover to the 80,000 it had been in circa 1200 until about 1900.

So, from the example of Iceland, we can see that the impact of epidemic diseases can have a catastrophic effect on demographics.

In Iceland, the population did not recover for 650 years, due to recurring epidemics (and a volcano). However, the population troughs in Iceland, left a population somewhat less than 50% of the pre-disease population, whereas, at the population troughs, Native American populations seem to have been only circa 1/5th of the previous high.

What explains the difference?

One possibility is that Native Americans were less genetically (or culturally) resistant to these imported epidemic diseases than Icelanders.

Another possibility is that European warfare and ‘atrocities’ (plus their after-effects, such as dislocation) added significantly to the demographic collapse.

(To be continued)