Just found this interesting account of the demise of Easter Island (partial quote):Easter Island Mystery revealed using mathematical model:
When Easter Island was "discovered" by Europeans in 1722, it was a barren landscape with no trees over ten feet in height. The small number of inhabitants, around 2000, lived in a state of civil disorder and were thin and emaciated. Virtually no animals besides rats inhabited the island and the natives lacked sea-worthy boats. Understandably, the Europeans were mystified by the presence of great stone statues, some as high as 33 feet and weighing 82 tons. Even more impressive were the abandoned statues-as tall as 65 feet and weighing as much as 270 tons. How could such a people create, and then move such enormous structures? The answer lies in Easter islands' ecological past, when the island was not a barren place.
The Easter Island of ancient times supported a sub-tropical forest complete with the tall Easter Island Palm, a tree suitable for building homes, canoes, and latticing necessary for the construction of such statues. With the vegetation of the island, natives had fuelwood and the resources to make rope. With their sea-worthy canoes, Easter Islanders lived off a steady diet of porpoise. A complex social structure developed complete with a centralized government and religious priests.
It was this Easter Island society that built the famous statues and hauled them around the island using wooden platforms and rope constructed from the forest. The construction of these statues peaked from 1200 to 1500 AD, probably when the civilization was at its greatest level. However, pollen analysis shows that at this time the tree population of the island was rapidly declining as deforestation took its toll.
Around 1400 the Easter Island palm became extinct due to overharvesting. Its capability to reproduce has become severely limited by the proliferation of rats, introduced by the islanders when they first arrived, which ate its seeds. In the years after the disappearance of the palm, ancient garbage piles reveal that porpoise bones declined sharply. The islanders, no longer with the palm wood needed for canoe building, could no longer make journeys out to sea. Consequently, the consumption of land birds, migratory birds, and mollusks increased. Soon land birds went extinct and migratory bird numbers were severely reduced, thus spelling an end for Easter Island's forests. Already under intense pressure by the human population for firewood and building material, the forests lost their animal pollinators and seed dispersers with the disappearance of the birds. Today, only one of the original 22 species of seabird still nests on Easter Island.
With the loss of their forest, the quality of life for Islanders plummeted. Streams and drinking water supplies dried up. Crop yields declined as wind, rain, and sunlight eroded topsoils. Fires became a luxury since no wood could be found on the island, and grasses had to be used for fuel. No longer could rope by manufactured to move the stone statues and they were abandoned. The Easter Islanders began to starve, lacking their access to porpoise meat and having depleted the island of birds. As life worsened, the orderly society disappeared and chaos and disarray prevailed. Survivors formed bands and bitter fighting erupted. By the arrival of Europeans in 1722, there was almost no sign of the great civilization that once ruled the island other than the legacy of the strange statues. However, soon these too fell victim to the bands who desecrated the statues of rivals.
Easter Island is a prime example of what widespread deforestation can do to a society. As the forests are depleted, the quality of life falls, and then order is lost. The example of Easter Island should be enough for us to reconsider our current practices.http://news.mongabay.com/2005/0901-easter_island.html