Malthusian Myth Busting: Easter Island Edition

Guest “Why bust Malthusian Myths? Because it’s fun and easy!” by David Middleton

You know the story…

In just a few centuries, the people of Easter Island wiped out their forest, drove their plants and animals
to extinction, and saw their complex society spiral into chaos and cannibalism. Are we about to follow
their lead?

Jared Diamond, 2005

While it is true that the Easter Islanders deforested their island, forensic historians have now determined that by converting the forest to farmland and innovatively adapting to prolonged Little Ice Age droughts, they avoided collapse.

BingUNews

Resilience, not collapse: What the Easter Island myth gets wrong

By Jennifer Micale
JULY 08, 2021

You probably know this story, or a version of it: On Easter Island, the people cut down every tree, perhaps to make fields for agriculture or to erect giant statues to honor their clans. This foolish decision led to a catastrophic collapse, with only a few thousand remaining to witness the first European boats landing on their remote shores in 1722.

But did the demographic collapse at the core of the Easter Island myth really happen? The answer, according to new research by Binghamton University anthropologists Robert DiNapoli and Carl Lipo, is no.

Their research, “Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island),” was recently published in the journal Nature Communications. Co-authors include Enrico Crema of the University of Cambridge, Timothy Rieth of the International Archaeological Research Institute and Terry Hunt of the University of Arizona.

Easter Island, or Rapa Nui in the native language, has long been a focus of scholarship into questions related to environmental collapse. But to resolve those questions, researchers first need to reconstruct the island’s population levels to ascertain whether such a collapse occurred and, if so, the scale.

“For Rapa Nui, a big part of scholarly and popular discussion about the island has centered around this idea that there was a demographic collapse, and that it’s correlated in time with climate changes and environmental changes,” explained DiNapoli, a postdoctoral research associate in environmental studies and anthropology.

Sometime after it was settled between the 12th to 13th centuries AD, the once-forested island was denuded of trees; most often, scholars point to human-prompted clearing for agriculture and the introduction of invasive species such as rats. These environmental changes, the argument goes, reduced the island’s carrying capacity and led to a demographic decline.

Additionally, around the year 1500, there was a climactic shift in the Southern Oscillation index; that shift led to a dryer climate on Rapa Nui.

[…]

In short, there is no evidence that the islanders used the now-vanished palm trees for food, a key point of many collapse myths. Current research shows that deforestation was prolonged and didn’t result in catastrophic erosion; the trees were ultimately replaced by gardens mulched with stone that increased agricultural productivity. During times of drought, the people may have relied on freshwater coastal seeps.

Construction of the moai statues, considered by some to be a contributing factor of collapse, actually continued even after European arrival.

In short, the island never had more than a few thousand people prior to European contact, and their numbers were increasing rather than dwindling, their research shows.

“Those resilience strategies were very successful, despite the fact that the climate got drier,” Lipo said. “They are a really good case for resiliency and sustainability.”

Burying the myth

Why, then, does the popular narrative of Easter Island’s collapse persist? It likely has less to do with the ancient Rapa Nui people than ourselves, Lipo explained.

The concept that changes in the environment affect human populations began to take off in the 1960s, Lipo said. Over time, that focus became more intense, as researchers began to consider changes in the environment as a primary driver of cultural shifts and transformations.

But this correlation may derive more from modern concerns with industrialization-driven pollution and climate change, rather than archaeological evidence. Environmental changes, Lipo points out, occur on different time scales and in different magnitudes. How human communities respond to these changes varies.

[…]

Binghamton University

This bit is priceless…

Why, then, does the popular narrative of Easter Island’s collapse persist? It likely has less to do with the ancient Rapa Nui people than ourselves, Lipo explained.

The concept that changes in the environment affect human populations began to take off in the 1960s, Lipo said. Over time, that focus became more intense, as researchers began to consider changes in the environment as a primary driver of cultural shifts and transformations.

But this correlation may derive more from modern concerns with industrialization-driven pollution and climate change, rather than archaeological evidence.

Binghamton University

However future forensic historians (archaeologists & anthropologists) will be right when they determine that our society collapsed because we decimated our reliable and affordable energy infrastructure in order to build a lot of useless statues due to “modern concerns with industrialization-driven pollution and climate change.”

Myth Busting…

The full text of the paper is available… Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island).

Discussion

When we assess the uncertainties of the Rapa Nui data and those involved in the analytic steps, the current evidence indicates that the island experienced relatively steady population growth from initial human settlement ca. 800 cal BP until the period following European arrival. The “wiggles” in the observed SPD curve all fall within the simulation envelope and result from details of the calibration curve combined with sampling error, and importantly, not genuine paleodemographic signals. Given these facts, we are unable to confidently distinguish between the four hypotheses. All of the fitted models, however, are consistent with a logistic growth pattern only marginally influenced by changes in climate and forest cover. The wide HPDs of the environmental parameters suggest a range of possible positive or negative effects, yet no values appear strong enough to cause major population declines (Fig. 3). Given the comparatively small number of radiocarbon dates, we cannot determine whether our inability to discern between the competing models is the consequence of small sample size, the small ‘effect size’ in models 2–4 (i.e., the absolute deviation of β_{palm and} β_SOI from 0), or a combination of both factors. Nonetheless, none of the fitted models support the notion of pre-contact population collapse (Fig. 3). Therefore, our results suggest that if deforestation or increasing SOI had effects on the island, Rapa Nui populations were resilient to them. These findings are independently supported by recent research showing that monument construction steadily continued even after European arrival^57,77. In addition, research now demonstrates that deforestation was a prolonged process, did not result in catastrophic erosion, and that land cover was quickly replaced by lithic mulch gardens that increased agricultural productivity^{66,67,80,81,82,83,84,85}. Moreover, while some claim that deforestation resulted in the loss of food^29,68, there is no evidence that palms were a significant dietary resource for islanders^66,86. Thus, it is more likely that the loss of the palm forest represented an expansion of cultivation opportunities and positively contributed to the initial growth and overall resilience of the population. In summary, there is no empirical support for the notion that deforestation resulted in strong negative impacts on the human population of Rapa Nui.

Our results also have implications for the effects of climate change on the island. Rull^71,73 has recently claimed that climate-induced droughts caused a large-scale societal disruption resulting in the cessation of monument construction and intra-island migration from coastal settlements to the crater lake at Rano Kau. Similar to previous analyses of the tempo of monument construction around the island⁵⁷, the vast majority of our ¹⁴C data derive from coastal settlements and do not show declines in activity or support claims of major climate-induced disruptions from drought. While climate perturbations seem to have led to desiccation of the crater lake at Rano Raraku⁷², recent research suggests Rapa Nui populations adapted to these changes by relying primarily on coastal groundwater sources^87,88,89.

DiNapoli et al., 2021

It turns out that the Malthusian myth of Easter Island’s demographic and ecological collapse was just a bunch of Rapa Hooey!

Reference

DiNapoli, R.J., Crema, E.R., Lipo, C.P. et al. Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island). Nat Commun 12, 3939 (2021). https://doi.org/10.1038/s41467-021-24252-z