The ecological transformation of Easter Island (Rapa Nui) has become one of the most revealing but controversial case studies in the field of environmental archaeology. Central to this discussion is the role Polynesian rat (The rat runs away) in deforestation on the island. This process led to the destruction of approximately 15-19.7 million. palm trees (Easter coconut disperta) approximately between 1200 and 1650 AD.
Easter Island, known to its original inhabitants as Rapa Nui, is one of the most remote inhabited islands in the world. It is located approximately 3,512 km off the western coast of Chile, and its closest inhabited neighbor, Pitcairn Island, is located approximately 2,075 km to the west. For reasons still unknown, the early inhabitants of Rapa Nui began carving giant statues from volcanic rock. These monumental statues, called moai, are some of the most incredible ancient relics ever discovered. Image credit: Björn Christian Thorrissen / CC BY-SA 3.0.
Before human settlement, Rapa Nui was dominated by large palms of a variety that is now extinct; however, they were associated with Chilean wine palm (Jubea chilean).
These massive trees can live up to 500 years; they are also slow-growing, taking about 70 years to reach maturity and begin bearing fruit.
By the time of European contact in 1722, little of the palm tree remained. By the time Europeans began to take an interest in the ecology of the island, they were already gone.
“Europeans mostly describe a treeless island, but they also describe palm trees and palm fronds,” said Binghamton University professor Carl Lipo.
“It's hard to know if they're using that term to describe some other tree.”
When going to a new island, the Polynesians took with them their set of food items: taro, sweet potatoes, bananas, yams, dogs, chickens and pigs. The Polynesian rat inevitably followed us.
Unlike Norway rats (Norway rat) Introduced to the island after European contact, this small arboreal species prefers to live in tree canopies. For researchers, rats are a treasure trove of information.
“Due to their genetics and the founder effect, they have unique haplotypes,” Professor Lipo said.
“We can track the colonization of humans, and to some extent the amount of colonization, by how variable the rats are as they move across the Pacific Ocean.”
Exactly how they ended up in Polynesian outrigger canoes is a matter of debate: were they stowaways or deliberately introduced as a backup food source? Ethnographic data indicate the latter.
“After the arrival of the Europeans, a naturalist collecting specimens for the British Museum saw a man walking along a path with rats; he told the collector that they were there for lunch,” Professor Lipo said.
Rat bones are also found in debris deposits—essentially ancient trash heaps—on Pacific islands.
When Polynesians arrived on Rapa Nui around 1200 AD, the rats found a virtual Eden, devoid of predators and full of their favorite foods.
The population, capable of producing several litters per year, grew to millions within a few years.
“Palm nuts are rat candy. The rats ate the bananas,” Professor Lipo said.
Rapa Nui palms co-evolved with birds and never developed the boom-bust productivity cycle that would have ensured that some nuts would survive exploitation by rodents.
The rats ate the palm nuts, preventing the next generation of trees from taking root.
Meanwhile, people are cutting down rows of trees to make way for sweet potato fields. The combination of these two factors led to the deforestation that marks the island today.
In addition to plants and animals, the Polynesian survival kit also included techniques such as slash-and-burn agriculture to improve soil fertility.
Old volcanic islands such as Rapa Nui can suffer from poor soils, with nutrients being washed away by rain.
Clearing and burning areas of forested land can temporarily replenish the soil with nutrients.
Once the nutrients are depleted, farmers move to another location, leaving the land to recover and the trees to regrow.
“We see this in New Guinea and other places in the Pacific,” Professor Lipo said.
“But on Rapa Nui the trees grow so slowly and don’t grow back because of rat attack on the palm nuts.”
Eventually, the islanders adopted a new style of farming, using rock mulch to enrich their crops.
While the loss of the palm forest was an undeniable environmental change, it was not a human catastrophe.
The islanders did not need palm trees to survive; instead, their food sources depended on cleared land.
Additionally, palms are not deciduous trees; they are associated with grasses and cannot provide wood for canoes, houses or firewood.
“It's a sad loss of the palm forest, but it's not a disaster for the people,” Professor Lipo said.
“It was not a necessary part of their survival.”
Although some palms may have survived European occupation, the advent of sheep farming in the 19th century may have been the final call for extinction; any remaining seedlings would be eaten by sheep.
Ironically, Polynesian rats suffered the same fate as palm trees; on most islands they have been driven to extinction, driven out by the Norway rat or eaten by introduced predators such as hawks.
Even though the specific species have changed, islanders still tell stories of rodent boom and bust cycles—years when populations explode, followed by mass extinctions.
The story of Rapa Nui is one of unforeseen consequences, as well as adaptation and survival on one of the most remote inhabited islands in the world, with its closest neighbors 1,931 km (1,200 miles) away.
“We need to understand environmental changes in more detail,” Professor Lipo said.
“We are part of the natural world; we often change its shape for our own benefit, but this does not necessarily mean that we create an unsustainable world for ourselves.”
conclusions appear in Journal of Archaeological Science.
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Terry L. Hunt and Carl P. Lipo. 2025. Reassessing the role of Polynesian rats (The rat runs away) on Rapa Nui (Easter Island) deforestation: faunal data and environmental modeling. Journal of Archaeological Science 184:106388; doi: 10.1016/j.jas.2025.106388
