Posted on: Monday, November 1, 2004

By Jan TenBruggencate
Advertiser Staff Writer

The native Polynesian inhabitants of Rapa Nui, also known as Easter Island, have been blamed for the deforestation of the island, which has resulted in food shortages and battles over resources.

But recent studies by University of Hawai'i anthropologist Barry Rolett and UCLA geographer Jared Diamond suggest the deforestation may have had more to do with the island and its location than with the people who inhabited it.

The two researchers looked into why some long-inhabited Polynesian island groups, such as the Marquesas, retained dense forest cover, while islands such as Rapa Nui and Nihoa, northwest of Kaua'i, lost all or nearly all of their trees.

Rolett said that isolation is one key factor. Rapa Nui was so far from other islands that many useful plants were never successfully introduced. In some ways, Hawai'i had a similar problem. Hawai'i is among the few Polynesian islands where the Tahitian chestnut was not established, and only one of the 30 to 40 different varieties of breadfruit made it here.

"Polynesians needed their introduced plants. Very few native species are edible in Hawai'i," Rolett said.

Once a forest was lost, even if canoes existed or could be built, it was exceedingly difficult to go to other islands to bring in seeds and cuttings to re-establish trees.

Still, high islands like most of those in Hawai'i and wet islands like the Marquesas were able to retain forest cover. Key factors may be rainfall and temperature, Rolett and Diamond believe.

Rapa Nui is farther from the equator and has low rainfall compared with the Marquesas. Similarly, Nihoa is farther from the equator than the main Hawaiian Islands, and is too low to capture clouds and create its own rainfall.

Another feature: Forests in flat, easily tilled areas tended to be destroyed to create agricultural fields. Islands with cliffs and rock kept some of their trees.

Rolett and Diamond studied 69 Pacific islands and reviewed the records of early voyagers who were among the first European visitors to those islands.

In addition to rainfall, temperature and isolation, another key factor appears to be whether islands are in areas subject to windblown volcanic dust, or if continental dust — like that from massive China dust storms — periodically enriched the soil. Many western South Pacific islands get volcanic dust inputs, while North Pacific islands get China desert dust.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766, e-mail jant@honoluluadvertiser.com or call (808) 245-3074.