Sunrise at Ahu Tongariki, Easter Island. (Photo by Focus Fusion via Shutterstock)
For decades, the story of Easter Island (Rapa Nui) has fascinated the world as a lesson in environmental collapse and societal downfall. The prevailing narrative paints a picture of a civilization that became too large, exhausted resources, and collapsed under its own weight. It has long been believed that the island’s inhabitants drastically remodeled the landscape with innovative “rock gardens” to boost food production and support a burgeoning population. But fascinating new research has turned this story on its head.
Where is Easter Island?
This remote island in the southeast Pacific Ocean, about 2,200 miles off Chile, is known for its mysterious giant stone statues called Moai. Made entirely of volcanic rock, the 63-square-mile island and the history of its incredible statues have long been shrouded in mystery.
Easter Island was first settled by Polynesian voyagers around AD 800-1200, who built a complex society that thrived for centuries. Known as Rapa Nui, the island’s inhabitants developed a unique culture characterized by monumental stone architecture, complex social structures and innovative agricultural practices. However, by the time European explorers first arrived in 1722, the island’s ecosystem had been significantly altered, its once lush palm forests had all but disappeared, and the population appeared to be in decline.
Central to this research are unique agricultural features known as “rock gardens” or “stone mulch gardens”. These innovative cultivation techniques were developed by ancient Rapa Nui to overcome the challenges of farming on an island with relatively poor soils and limited freshwater resources.
The main crop grown in these rock gardens was the sweet potato (Ipomoea batatas), a staple food of the Rapa Nui. Other crops that may have been grown in this way include yams, taro, and bananas.
Today, Easter Island is a major tourist destination, with approximately 100,000 visitors arriving each year to marvel at the Moai statues and experience the island’s unique culture. Approximately 8,000 people currently call the island home. Tourism has become an important part of the local economy, but it also poses challenges in terms of protecting the island’s fragile ecosystem and archaeological heritage.
Thanks to this new research, the story of Rapa Nui told by tour guides now appears to be in need of a major update: Using cutting-edge satellite technology and machine learning, researchers have discovered that the extent of Easter Island’s ancient agricultural infrastructure was significantly smaller than previously thought.
Today, Easter Island, commonly known as Rapa Nui, is home to around 8,000 people. (Photo by Sergey-73 from Shutterstock)
What did the study find?
The study, led by Dylan S. Davis of Columbia University, found that the rock gardens covered just 0.76 square kilometers of the island — roughly one-fifth of the most conservative previous estimates. The discovery has profound implications for our understanding of Easter Island’s past population size, agricultural practices, and the island’s purported “collapse.”
The research team took advantage of high-resolution shortwave infrared (SWIR) satellite imagery, a technique that can detect subtle differences in soil composition and moisture content. By training a machine learning algorithm on the locations of known rock gardens, they were able to identify these features across the island with unprecedented precision. Their results, published in Science Advances, paint a picture of a much more modest agricultural system than previous studies had suggested.
“This suggests that populations were not as large as previous estimates,” Davis, a postdoctoral researcher in archaeology at Columbia University’s School of Climatology, said in a statement. “The lesson is the opposite of collapse theory: faced with limited resources, people were able to be highly resilient by modifying their environment in conducive ways.”
The discovery calls into question long-held assumptions about Easter Island’s carrying capacity and pre-European contact population size. Previous estimates, based on less-than-precise assessments of agricultural extent, had suggested the island supported a population of up to 17,500 people. But the new data shows the population was probably much smaller, closer to early European estimates of around 3,000.
Ancient moai statues at Ahu Togariki on Easter Island, about 2,000 miles off the coast of Chile. (Photo by Kristopher Kettner for Shutterstock)
Methodology: Harnessing the power of SWIR
Key to the success of this study is the innovative use of SWIR satellite imagery. Unlike traditional visible or near-infrared imagery, SWIR can detect subtle changes in soil moisture and mineral composition, making it particularly well suited to identifying archaeological features invisible to the naked eye or other remote sensing techniques.
The researchers obtained high-resolution SWIR imagery of Easter Island from the WorldView-3 satellite, covering the entire island with minimal cloud cover, and then collected ground data by surveying known rock garden locations on the island between 2019 and 2023. This information was used to train three different machine learning algorithms: Maximum Entropy (MaxEnt), Random Forest (RF), and Maximum Likelihood Classification (MLC).
The research team compared the performance of these algorithms using both SWIR data and more traditional visible near-infrared (VNIR) imagery. In all cases, SWIR data outperformed VNIR at accurately identifying rock gardens. The MaxEnt model applied to SWIR imagery proved to be the most effective, reaching an overall accuracy of 82.44%, a significant improvement over previous attempts to map these features.
After running the best-performing model across the entire island, the researchers manually reviewed the results and removed any obvious errors, such as the misclassification of modern roads or natural lava flows. They also excluded identified areas smaller than 10 square meters, as these were likely artifacts of the analysis rather than actual garden features.
Robert DiNapoli, co-author of a new study on the so-called rock gardens that played a key role in feeding the inhabitants of Rapa Nui, better known today as Easter Island, tours one of them. (Photo: Carl Lipo)
Results: A dramatically different picture emerges
The findings are shocking: previous estimates had suggested that rock gardens covered between 4.9 and 21.1 square kilometers of Easter Island, but this new analysis finds that these agricultural lands cover only 0.76 square kilometers, representing an 80% reduction compared to the most conservative previous estimates.
The distribution of rock gardens also sheds light on ancient land-use patterns on the island. The majority of identified gardens were concentrated in coastal areas, with a smaller number found on inland highlands. This pattern is consistent with archaeological understanding of the island’s settlement patterns, where most habitation was concentrated along the coast.
To address the possibility that modern development may have destroyed the ancient rock gardens, the researchers also analyzed areas of the island that had been degraded by urbanization and modern agriculture. They found that about 25 square kilometers of the island have been affected by these activities. However, more than 5 square kilometers of this degraded area is an area where no rock gardens have been found through ground or remote sensing surveys.
Moai statues under a blue sky at Rano Raraku on Easter Island. (Photo by Aeonian Photography via Shutterstock)
Limitations: Acknowledging Uncertainty
While the study represents a major advance in understanding Easter Island’s agricultural past, the researchers acknowledge that their methodology has some limitations. One important consideration is that rock gardens may have been destroyed or hidden by modern development, especially in and around Hanga Roa, the island’s main settlement. The study attempted to account for this by analysing disturbed areas, but uncertainties remain.
Another limitation is the resolution of the SWIR images used (3.7 meters per pixel). Although this is the highest resolution commercially available SWIR data, it can still miss very small garden features. The researchers addressed this issue by excluding certain areas smaller than 10 square meters, but this may have resulted in some very small gardens being missed.
Finally, this study provides a snapshot of the area of rock gardens at a single point in time. The total area cultivated has changed throughout the island’s history, and it is likely that some gardens have been abandoned and new gardens created over time. Further archaeological research is needed to establish a more detailed chronology of the island’s agricultural development.
Discussion and Reflection: Rewriting the Easter Island Story
The impact of this study goes far beyond simply tweaking the numbers: by significantly reducing the estimated extent of intensive agriculture on Easter Island, many assumptions about the island’s past must be reevaluated.
First, the study challenges the idea that Easter Island’s population grew to an unsustainable level before European contact. Using the same methods as previous studies but with new, more precise data on agricultural extent, the researchers calculated that the maximum population the identified rock gardens could have supported was about 3,900 people. This is much closer to early European population estimates of the island than the higher figures of 15,000 or more proposed by some researchers.
Iconic Moai statues in the UNESCO World Heritage National Park on Easter Island, Chile. (Photo by Yoko Correia Nishimiya on Unsplash)
The find adds to a growing body of archaeological evidence suggesting that Easter Island did not undergo a dramatic “collapse” before European contact, but rather paints a picture of a society successfully adapted to the challenges of life on a remote, resource-poor island through innovative agricultural techniques and careful resource management.
“Life must have been incredibly tough for these people,” said co-author Carl Lipo, an archaeologist at Binghamton University. “Imagine sitting there all day smashing rocks.”
The study also highlights the potential of new remote sensing techniques, particularly SWIR imagery, in archaeological research. By providing a way to detect subtle topographical changes over vast areas, this approach could revolutionize our understanding of ancient land-use patterns in many parts of the world.
The story of Easter Island is widely known as an example of societal collapse due to resource overexploitation and has been used as an allegory for modern-day environmental issues. While there are certainly lessons to be learned from the island’s history, this research suggests that the reality is much more complex – and perhaps more hopeful – than previously thought.
Davis and his colleagues conclude: “Our findings add to a growing body of empirical evidence showing Rapa Nui to be a good example of an isolated population with limited natural resources that has developed a sustainable self-sufficient system, maintaining its population within the limits of its carrying capacity.”
This study rewrites the agricultural history of Easter Island, shedding new light on a fascinating chapter in human history and reminding us that with careful management and innovation, even the most resource-poor environments can support thriving human societies for centuries.
