just as an fyi, every time you read about Easter island they talk about the collapse theory, its complete bollocks, the islands eco system did not collapse until westerners introduced sheep and stopped the practices the islanders where using to keep the island fertile so they could use the land as pasture for their sheep(although the islanders did give up on part of it after a big wave, thats another story though, the people of the island where not the ones to brake it, thats the main point) those moai (big stone heads) where carved out of volcanic rock made from compressed volcanic ash and volcanic ash is a fantastic fertilizer, the dust was then spread across the island, effectively adding more fertilizer to the soil and mimicking (unintentionally) the way nature fertilises the amazon, dust blows from the sahara and falls in to the amazon, plants provide sugars to microbes which in turn brake down the dust, the microbes get eaten by other microbes and the plant or tree get the nutrients they are after(they can tailor their exudates to target specific microbes which brakes down specific materials) as a by product this process produces humates which help with nutrient transfer and soil water retention just as another side note, the islanders said they walked the statues in to place, westerners thought that was bullshit because obviously rock cant walk, but the story was not entirely untrue and the technique has been used in other places including stone henge, take 3 ropes, 2 on the side and one to stabilize the stone, then rock the rock turning it as you rock it so the stone moves forward, the 3rd rope is just to stop the thing falling over