Decline in Fishing Due to Deforestation and the Lack of Trees to Build Canoes?
The following description of Rapa Nui is from Paul Bahn and John Flenley's Easter Island, Earth Island (London: Thames and Hudson, 1992. 170-171):
"There appears to be a change towards the end of the island's prehistory to a greater dependence on marine resources that could be gathered rather than fished, and even these were being overexploited: the increasing collection of the shellfish Nerita is thought to reflect overexploitation of the more highly prized Cypraea. By the historic period, fishing had become relatively unimportant, though its former prominence survived in the number of legends with fishermen as heroes. Excavations in some of the island's middens have revealed a slight decrease of fish remains relative to other resources from about AD 1400 to the present. Evidence of the use of rock shelters for activities connected with fishing (e.g. hook manufacture) also shows a marked decrease after AD 1500.
"The major reason for the decline in fishing--enforced, as we have seen, by seasonal tapu, restrictions on marine resources by the high-status Miru clan--must be the limitations on offshore fishing caused by the decreasing number and size of canoes. The Dutch in 1722 reported that the islander who came out to their ship had a boat made of small, narrow pieces of wood glued together with some organic material, and so light that one man could carry it easily. The other canoes were poor and frail, and so leaky that the islanders spent half their time bailing. Bouman added that most natives came swimming out to them on bunches of reeds. They saw very few canoes, and the largest was only 3 m (c. lO ft) long. In 1770 Gonzalez saw only two canoes. Four years later, Cook said the island had the worst canoes in the Pacific - small, patched and unseaworthy. He saw only three or four small canoes, 3 or 4 m (10 to 13 ft) in length, and built of sewn planks of wood only up to 1 m (3 ft) long, and stated that most natives simply swam out. Beechey in 1825 saw three canoes on the beach which did not put to sea, while the Russian Kotzebue in 1816 had likewise seen three, each carrying two men. This is all a far cry from Hotu Matua's vessel which legend claimed was 30 m (c. 100 ft) long and 2 m (6 ft) high, and carried hundreds of people. Canoes, including possible double-canoes and Polynesian sails, are clearly depicted in the islanders' rock art, proving that they were acquainted at some time with more impressive vessels, a fact also supported by the numerous canoe ramps found near platforms.
"What, then, was the ultimate cause of all these changes? The answer must lie in deforestation, and particularly the disappearance of the palm. The first European visitors all commented on the island's bare, barren, treeless appearance: Roggeveen in 1722 described the island as 'destitute of large trees', and Gonzalez in 1770 wrote, 'Not a single tree is to be found capable of furnishing a plank so much as six inches in width'; Forster in 1774 reported that 'there was not a tree upon the whole island which exceeded the height of 10 feet'. So clearly, timber was in very short supply. Dupetit-Thouars in 1838 said that five canoes came out to his ship from the island, each carrying two men; what they most wanted was wood. Even driftwood was looked on as a treasure of inestimable value, and a dying father frequently promised to send his children a tree from the kingdom of shades. It is highly significant that the Polynesian word rakau (tree, wood, timber) meant 'riches' or 'wealth' on Rapa Nui, a meaning recorded nowhere else."
What caused the deforestation? Bahn and Flenley suggest the following factors (208-210):
Population growth and human activity: cutting down of trees to clear land for agriculture or for building houses and canoes; or to move and erect the giant statues found on the island; also wood was used for cooking fires.
Erosion of the soil from clearing of land; decline in soil fertility as population and agricultural useof the the land increased.
Climactic Change: The small land mass of Rapa Nui may have made it more vulnerable to climactic variations; severe droughts might have severely impacted an already heavily-exploited environment.
Rats introduced by the Polynesians ate the seed of a palm which was one of the main trees in the forests, thus preventing regeneration of the forests.