Although Easter Island currently has only 48 different kinds of plants as evidenced by botanical surveys of the island, it once possessed many more, shown through pollen analysis conducted on sediment layers from swamps or ponds. From these samples, 22 no longer present on the island were shown to have existed at some time there. These plants included a giant palm, the Rapa Nui Palm, that showed signs of being the largest palm species in the world, eclipsing the size of the Chilean Wine Palm if it were not extinct. There are also signs of Easter Island's once possessing a far more diverse collection of fauna. The skeletal remains of 25 different species of nesting bird have been located on the island, but have since been reduced to 16. This trend of extinction and extirpation is a common occurrence when humans populate a new area, because of tendencies to overhunt and overexploit resources.