because rainfall disappears into their porous limestone karsts and thin soils. Mangaia and Henderson, both islands with histories of socioenvironmental stress, are examples.10
Within environmental limits, most Polynesian societies thrived—and evolved. The ability of Polynesian societies to adapt their main crop, taro (Colocasia spp.), to highly varying circumstances is the most significant “event” in Polynesian prehistory, second only to success at voyaging. All of these adaptations involved the control of water. On atolls, which are typically dry zones because of high soil porosity and low rainfall, taro was grown by pit cultivation: digging down through the sand or coral to the thin freshwater lens overlying the seawater. On high islands and makatea islands with swampy coastal valleys, it was by raised-bed cultivation: digging drainage canals through the swampy flats and heaping the spoils up into mounds where taro, yams, sugarcane, and other crops were planted. On high islands with well-developed stream valleys, irrigated pondfields were constructed, with streams diverted through barrages and ditches to a series of linked, walled paddies, in which flooding and drainage were controlled by means of headgates.
Several writers have pointed to a seeming paradox of Polynesians’ existence: though accomplished at seafaring and fishing, the majority of them derived their subsistence from the land. The dominance of the land over the sea would have profound effects on the history of Hawai‘i, as we will see later; here I will list just a few examples. E. S. and Elizabeth Handy, with Mary Kawena Pukui, in their classic study Native Planters in Old Hawaii, cite much evidence that most common Hawaiians were farmers, not fishers.11 Suggestively, the word for an island or a division of land, moku, is also that for a ship or a boat. The sea as highway is a frequent metaphor in legend and oral tradition, and it is even reported that some Polynesian navigators talked about the moving sea passing by the stationary canoe.12 In an agricultural society with a severely limited land base that practiced a form of primogeniture, younger sons would be pushed to sea in search of tillable land: as it was for many of the Scandinavian Vikings who sailed off in search of new lands, oceanic expansion was a farmer’s imperative.13
NATURAL HISTORY OF THE PACIFIC ISLANDS
The discoverers of Hawai‘i found the largest piece of unclaimed island real estate in the Pacific, excluding New Zealand: an area of 16,692 square kilometers (6,424 square miles) 30 percent larger than Connecticut.14 It was also the most remote: 2,557 miles from Los Angeles, 5,541 miles from Hong Kong, 3,847 miles from Japan, and 5,070 miles from Sydney.15 The insularity of the Hawaiian Islands, together with their geologic history, accounts for much of their physical—and in certain ways, their social—destiny. From its origin over a stationary, midplate hot spot now under the island of Hawai‘i, the Hawaiian chain extends 2,449 miles westward toward Kure Atoll, where the eroding volcanoes submerge, then carries on northward as the Emperor Seamounts, ending at Meiji Seamount, beyond which the Pacific Plate subducts into the Kuril Trench off Kamchatka. The oldest seamounts date to seventy-five million to eighty million years; the islands’ life span above water varies from eight million to fifteen million years.16 Active volcanism is limited to the zone directly over the hot spot: three volcanoes on the island of Hawai‘i—Mauna Loa, Hualalai, and Kilauea—and Haleakala volcano on Maui, have erupted historically (since 1778). Mauna Loa last erupted in 1984, while vents on Kilauea have erupted continuously since that year. The island-making process continues: Loihi, a new, actively building, submerged volcano southeast of the Big Island, is expected to surface in roughly one hundred thousand years.
On these islands, age is fundamental to form. The Big Island of Hawai‘i, so new that its surface rocks are no more than a million years old, has no significant stream valleys with developed soils, except on its northernmost and oldest coasts, Kohala and Hamakua. Offshore, its slopes drop precipitously into deep water, and consequently, the island has no fringing coral reefs. By the same token, as islands increase in age, erosion gradually changes their character: at the other end of the main group, five-million-year-old Kaua‘i is typified by deep canyons, broad and swampy coastal valleys, and more generous fringing reefs than on the other islands.
As age equals geomorphology in a general sense, topography is fundamental to climate at the local level, and variation is tremendous. Ten percent of the main island area is above 7,000 feet, with relatively cold temperatures; Mauna Kea volcano on Hawai‘i reaches 13,796 feet and boasts ancient glaciers and a seasonal snowcap. Precipitation varies abruptly and radically depending on local topography, with the main dynamic being orographic rain produced over windward mountains by the prevailing trade winds from the northeast and compensatory rain shadows in their lees: Mount Waialeale on Kaua‘i receives up to 486 inches of rain, more than forty feet, the highest total in the world; not far away, in its rain shadow, is a desert. The northeasterly trades are so predictable—blowing at or above twelve miles per hour 50 percent of the time in summer and 40 percent of the time in winter—that the windward/leeward (ko‘olau/kona) distinction orders climate, vegetation, and land use a priori in Hawai‘i.17 With the exception of areas too low to create orographic clouds (below about one thousand feet) and that are therefore largely arid—such as West Molokai and much or all of Lana‘i, Kaho‘olawe, and Ni‘ihau—windward areas are wet, and leeward ones are dry, irrespective of elevation. Windward coasts (with the previous exceptions) are well watered yet see some sunshine most days. With increasing elevation, windward ranges are wetter and more often cloud shrouded, clothed in deep forest dominated by ohi‘a lehua (Metrosideros collina), until the alpine zone, above eight to ten thousand feet. At higher elevations, the flanks and lees of mountains are covered in mixed mesic, or medium rainfall, forest dominated by koa (Acacia koa). Low leeward areas once grew a distinctive, variegated dry forest, though this has been very nearly wiped out since human colonization and replaced with grasslands. Precipitation gradients are commonly extreme, as much as 118 inches in a mile, though more typically 25 inches per mile.18 Nearly every main island has rain forests just around the corner, so to speak, from semiarid zones or near-deserts that see fewer than 20 inches per year. In between can be found a representative of every climate zone on Earth from subtropical to alpine, save true tropical humidity and polar cold. Mark Twain wrote in 1866 that if a person were to stand at the top of Mauna Loa, “he could see all the climes of the world at a single glance of the eye, and that glance would only pass over a distance of eight or ten miles as the bird flies.”19 Indeed, on the Big Island of Hawai‘i, one can deliberately select one’s preferred weather conditions by simply driving for five to twenty minutes.
Even so, fully half the islands’ area is below two thousand feet, with a stable year-round temperature ideal for cultivating the oceanic crop suite: temperatures average 77 degrees Fahrenheit at sea level and vary seasonally about 5 degrees Fahrenheit at Hilo and 6.5 degrees at Honolulu. Below five thousand feet elevation, the seasonal variation does not exceed 9 degrees, and this is almost exclusively where the precontact Hawaiians lived and worked.20
Insularity and isolation, more than any other factors, have shaped Hawai‘i’s natural history. Because of the “volcanic conveyor belt,” habitats have continuously evolved, fragmented, and disappeared as new islands have arisen, and old ones have eroded and disappeared.21 As specks of land in the mid-Pacific ocean, any animals or plants that reached Hawai‘i had to do so over vast expanses of water—limiting potential immigrants to those that could fly or ride exceptionally well. There were no reptiles, amphibians, or land mammals, save one species of bat, in Hawai‘i prior to human settlement. This lack of representation of groups common on more varied continental areas is called disharmony and extended even to types of insects and birds that presumably had better chances of colonization, so great was the difficulty of successfully establishing a population. Hawaiian flora and fauna is disproportionately made up of members of a handful of families. In fact, the prehuman Hawaiian flora of eleven hundred species can be accounted for by just 275 successful immigrants over 27.5 million years, a rate of one introduction every 100,000 years.22 A corollary of disharmony is impoverishment of diversity—that is, a biota made up of less than the full complement of species that made up the ecosystem in which the immigrant organism evolved:
