Phys. org reports that Polynesian rats (Rattus exulans) may have played a larger role in the deforestation of Rapa Nui than previously thought. Some 15 million Rapa Nui palm trees (Paschalococos disperta) are estimated to have covered Easter Island before the arrival of Polynesians around A. D. 1200. When Europeans arrived in 1722, they observed just a few isolated trees, grasses, and shrubs. Terry Hunt of the University of Arizona and Carl Lipo of the University of Birmingham developed an ecological model of the island and found that a single pair of rats, feasting on nutritious palm nuts, could grow into a.