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by Diamond, Jared

  Only gradually have European foresters come to appreciate the particular advantages of Casuarina oligodon, and the benefits that highlanders obtain from its groves. The species is fast-growing. Its wood is excellent for timber and fuel. Its root nodules that fix nitrogen, and its copious leaf-fall, add both nitrogen and carbon to the soil. Hence casuarinas grown interspersed in active gardens increase the soil’s fertility, while casuarinas grown in abandoned gardens shorten the length of time that the site must be left fallow to recover its fertility before a new crop can be planted. The roots hold soil on steep slopes and thereby reduce erosion. New Guinea farmers claim that the trees somehow reduce garden infestation with a taro beetle, and experience suggests that they are right about that claim as they are about many others, though agronomists still haven’t figured out the basis of the tree’s claimed anti-beetle potency. Highlanders also say that they appreciate their casuarina groves for esthetic reasons, because they like the sound of the wind blowing through the branches, and because the trees provide shade to the village. Thus, even in broad valleys from which the original forest has been completely cleared, casuarina silviculture permits a wood-dependent society to continue to thrive.

  How long have New Guinea highlanders been practicing silviculture? The clues used by paleobotanists to reconstruct the vegetational history of the highlands have been basically similar to those I already discussed for Easter Island, the Maya area, Iceland, and Greenland in Chapters 2-8: analysis of swamp and lake cores for pollen identified down to the level of the plant species producing the pollen; presence of charcoal or carbonized particles resulting from fires (either natural or else lit by humans to clear forests); sediment accumulation suggesting erosion following forest clearance; and radiocarbon dating.

  It turns out that New Guinea and Australia were first settled around 46,000 years ago by humans moving eastwards from Asia through Indonesia’s islands on rafts or canoes. At that time, New Guinea was still joined in a single landmass to Australia, where early human arrival is well attested at numerous sites. By 32,000 years ago, the appearance of charcoal from frequent fires, and an increase in pollen of non-forest tree species compared to forest tree species, at New Guinea highland sites hint that people were already visiting the sites, presumably to hunt and to gather forest pandanus nuts as they still do today. Signs of sustained forest clearance and the appearance of artificial drains within valley swamps by around 7,000 years ago suggest the origins of highland agriculture then. Forest pollen continues to decrease at the expense of non-forest pollen until around 1,200 years ago, when the first big surge in quantities of casuarina pollen appears almost simultaneously in two valleys 500 miles apart, the Baliem Valley in the west and the Wahgi Valley in the east. Today those are the broadest, most extensively deforested highland valleys, supporting the largest and densest human populations, and those same features were probably true of those two valleys 1,200 years ago.

  If we take that casuarina pollen surge as a sign of the beginning of casuarina silviculture, why should it have arisen then, apparently independently in two separate areas of the highlands? Two or three factors were working together at that time to produce a wood crisis. One was the advance of deforestation, as the highland’s farming population increased from 7,000 years ago onwards. A second factor is associated with a thick layer of volcanic ashfall, termed the Ogowila tephra, which at just that time blanketed eastern New Guinea (including the Wahgi Valley) but wasn’t blown as far west as the Baliem Valley. That Ogowila tephra originated from an enormous eruption on Long Island off the coast of eastern New Guinea. When I visited Long Island in 1972, the island consisted of a ring of mountains 16 miles in diameter surrounding a huge hole filled by a crater lake, one of the largest lakes on any Pacific island. As discussed in Chapter 2, the nutrients carried in such an ashfall would have stimulated crop growth and thereby stimulated human population growth, in turn creating increased need for wood for timber and fuel, and increased rewards for discovering the virtues of casuarina silviculture. Finally, if one can extrapolate to New Guinea from the time record of El Niño events demonstrated for Peru, droughts and frost might have stressed highland societies then as a third factor.

  To judge by an even bigger surge in casuarina pollen between 300 and 600 years ago, highlanders may then have expanded silviculture further under the stimulus of two other events: the Tibito tephra, an even bigger volcanic ashfall and boost to soil fertility and human population than the Ogowila tephra, also originating from Long Island and directly responsible for the hole filled by the modern lake that I saw; and possibly the arrival then of the Andean sweet potato in the New Guinea highlands, permitting crop yields several times those previously available with just New Guinean crops. After its initial appearance in the Wahgi and Baliem Valleys, casuarina silviculture (as attested by pollen cores) reached other highland areas at various later times, and was adopted in some outlying areas only within the 20th century. That spread of silviculture probably involved diffusion of knowledge of the technique from its first two sites of invention, plus perhaps some later independent inventions in other areas.

  I have presented New Guinea highland casuarina silviculture as an example of bottom-up problem-solving, even though there are no written records from the highlands to tell us exactly how the technique was adopted. But it could hardly have been by any other type of problem-solving, because New Guinea highland societies represent an ultra-democratic extreme of bottom-up decision-making. Until the arrival of Dutch and Australian colonial government in the 1930s, there had not been even any beginnings of political unification in any part of the highlands: merely individual villages alternating between fighting each other and joining in temporary alliances with each other against other nearby villages. Within each village, instead of hereditary leaders or chiefs, there were just individuals, called “big-men,” who by force of personality were more influential than other individuals but still lived in a hut like everybody else’s and tilled a garden like anybody else’s. Decisions were (and often still are today) reached by means of everybody in the village sitting down together and talking, and talking, and talking. The big-men couldn’t give orders, and they might or might not succeed in persuading others to adopt their proposals. To outsiders today (including not just me but often New Guinea government officials themselves), that bottom-up approach to decision-making can be frustrating, because you can’t go to some designated village leader and get a quick answer to your request; you have to have the patience to endure talk-talk-talk for hours or days with every villager who has some opinion to offer.

  That must have been the context in which casuarina silviculture and all those other useful agricultural practices were adopted in the New Guinea highlands. People in any village could see the deforestation going on around them, could recognize the lower growth rates of their crops as gardens lost fertility after being initially cleared, and experienced the consequences of timber and fuel scarcity. New Guineans are more curious and experimental than any other people that I have encountered. When in my early years in New Guinea I saw someone who had acquired a pencil, which was still an unfamiliar object then, the pencil would be tried out for myriad purposes other than writing: a hair decoration? a stabbing tool? something to chew on? a long earring? a plug through the pierced nasal septum? Whenever I take New Guineans to work with me in areas away from their own village, they are constantly picking up local plants, asking local people about the plants’ uses, and selecting some of the plants to bring back with them and try growing at home. In that way, someone 1,200 years ago would have noticed the casuarina seedlings growing beside a stream, brought them home as yet another plant to try out, noticed the beneficial effects in a garden—and then some other people would have observed those garden casuarinas and tried the seedlings for themselves.

  Besides thereby solving their problems of wood supply and soil fertility, New Guinea highlanders also faced a population problem as their numbers increased. That population increase
became checked by practices that continued into the childhoods of many of my New Guinea friends—especially by war, infanticide, use of forest plants for contraception and abortion, and sexual abstinence and natural lactational amenorrhea for several years while a baby was being nursed. New Guinea societies thereby avoided the fates that Easter Island, Mangareva, the Maya, the Anasazi, and many other societies suffered through deforestation and population growth. Highlanders managed to operate sustainably for tens of thousands of years before the origins of agriculture, and then for another 7,000 years after the origins of agriculture, despite climate changes and human environmental impacts constantly creating altered conditions.

  Today, New Guineans are facing a new population explosion because of the success of public health measures, introduction of new crops, and the end or decrease of intertribal warfare. Population control by infanticide is no longer socially acceptable as a solution. But New Guineans already adapted in the past to such big changes as the extinction of the Pleistocene megafauna, glacial melting and warming temperatures at the end of the Ice Ages, the development of agriculture, massive deforestation, volcanic tephra fallouts, El Niño events, the arrival of the sweet potato, and the arrival of Europeans. Will they now also be able to adapt to the changed conditions producing their current population explosion?

  Tikopia, a tiny, isolated, tropical island in the Southwest Pacific Ocean, is another success story of bottom-up management (map, p. 84). With a total area of just 1.8 square miles, it supports 1,200 people, which works out to a population density of 800 people per square mile of farmable land. That’s a dense population for a traditional society without modern agricultural techniques. Nevertheless, the island has been occupied continuously for almost 3,000 years.

  The nearest land of any sort to Tikopia is the even-tinier (one-seventh of a square mile) island of Anuta 85 miles distant, inhabited by only 170 people. The nearest larger islands, Vanua Lava and Vanikoro in the Vanuatu and Solomon Archipelagoes respectively, are 140 miles distant and still only 100 square miles each in area. In the words of the anthropologist Raymond Firth, who lived on Tikopia for a year in 1928-29 and returned for subsequent visits, “It’s hard for anyone who has not actually lived on the island to realize its isolation from the rest of the world. It is so small that one is rarely out of sight or sound of the sea. [The maximum distance from the center of the island to the coast is three-quarters of a mile.] The native concept of space bears a distinct relation to this. They find it almost impossible to conceive of any really large land mass . . . I was once asked seriously by a group of them, ‘Friend, is there any land where the sound of the sea is not heard?’ Their confinement has another less obvious result. For all kinds of spatial reference they use the expressions inland and to seawards. Thus an axe lying on the floor of a house is localized in this way, and I have even heard a man direct the attention of another in saying: ‘There is a spot of mud on your seaward cheek.’ Day by day, month after month, nothing breaks the level line of a clear horizon, and there is no faint haze to tell of the existence of any other land.”

  In Tikopia’s traditional small canoes, the open-ocean voyage over the cyclone-prone Southwest Pacific to any of those nearest-neighbor islands was dangerous, although Tikopians considered it a great adventure. The canoes’ small sizes and the infrequency of the voyages severely limited the quantity of goods that could be imported, so that in practice the only economically significant imports were stone for making tools, and unmarried young people from Anuta as marriage partners. Because Tikopia rock is of poor quality for making tools (just as we saw for Mangareva and Henderson Islands in Chapter 3), obsidian, volcanic glass, basalt, and chert were imported from Vanua Lava and Vanikoro, with some of that imported stone in turn originating from much more distant islands in the Bismarck, Solomon, and Samoan Archipelagoes. Other imports consisted of luxury goods: shells for ornaments, bows and arrows, and (formerly) pottery.

  There could be no question of importing staple foods in amounts sufficient to contribute meaningfully to Tikopian subsistence. In particular, Tikopians had to produce and store enough surplus food to be able to avoid starvation during the annual dry season of May and June, and after cyclones that at unpredictable intervals destroy gardens. (Tikopia lies in the Pacific’s main cyclone belt, with on the average 20 cyclones per decade.) Hence surviving on Tikopia required solving two problems for 3,000 years: How could a food supply sufficient for 1,200 people be produced reliably? And how could the population be prevented from increasing to a higher level that would be impossible to sustain?

  Our main source of information about the traditional Tikopian lifestyle comes from Firth’s observations, one of the classic studies of anthropology. While Tikopia had been “discovered” by Europeans already in 1606, its isolation ensured that European influence remained negligible until the 1800s, the first visit by missionaries did not take place until 1857, and the first conversions of islanders to Christianity did not begin until after 1900. Hence Firth in 1928-29 had a better opportunity than subsequent visiting anthropologists to observe a culture that still contained many of its traditional elements, although already then in the process of change.

  Sustainability of food production on Tikopia is promoted by some of the environmental factors discussed in Chapter 2 as tending to make societies on some Pacific islands more sustainable, and less susceptible to environmental degradation, than societies on other islands. Working in favor of sustainability on Tikopia are its high rainfall, moderate latitude, and location in the zone of high volcanic ash fallout (from volcanoes on other islands) and high fallout of Asian dust. Those factors constitute a geographical stroke of good luck for the Tikopians: favorable conditions for which they personally could claim no credit. The remainder of their good fortune must be credited to what they have done for themselves. Virtually the whole island is micromanaged for continuous and sustainable food production, instead of the slash-and-burn agriculture prevalent on many other Pacific islands. Almost every plant species on Tikopia is used by people in one way or another: even grass is used as a mulch in gardens, and wild trees are used as food sources in times of famine.

  As you approach Tikopia from the sea, the island appears to be covered with tall, multi-storied, original rainforest, like that mantling uninhabited Pacific islands. Only when you land and go among the trees do you realize that true rainforest is confined to a few patches on the steepest cliffs, and that the rest of the island is devoted to food production. Most of the island’s area is covered with an orchard whose tallest trees are native or introduced tree species producing edible nuts or fruit or other useful products, of which the most important are coconuts, breadfruit, and sago palms yielding a starchy pith. Less numerous but still valuable canopy trees are the native almond (Canarium harveyi), the nut-bearing Burckella ovovata, the Tahitian chestnut Inocarpus fagiferus, the cut-nut Barringtonia procera, and the tropical almond Terminalia catappa. Smaller useful trees in the middle story include the betelnut palm with narcotic-containing nuts, the vi-apple Spondias dulcis, and the medium-sized mami tree Antiaris toxicara, which fits well into this orchard and whose bark was used for cloth, instead of the paper mulberry used on other Polynesian islands. The understory below these tree layers is in effect a garden for growing yams, bananas, and the giant swamp taro Cyrtosperma chamissonis, most of whose varieties require swampy conditions but of which Tikopians grow a genetic clone specifically adapted to dry conditions in their well-drained hillside orchards. This whole multi-story orchard is unique in the Pacific in its structural mimicry of a rainforest, except that its plants are all edible whereas most rainforest trees are inedible.

  In addition to these extensive orchards, there are two other types of small areas that are open and treeless but also used for food production. One is a small freshwater swamp, devoted to growing the usual moisture-adapted form of giant swamp taro instead of the distinctive dry-adapted clone grown on hillsides. The other consists of fields devoted to short-fall
ow, labor-intensive, nearly continuous production of three root crops: taro, yams, and now the South American-introduced crop manioc, which has largely replaced native yams. These fields require almost constant labor input for weeding, plus mulching with grass and brushwood to prevent crop plants from drying out.

  The main food products of these orchards, swamps, and fields are starchy plant foods. For their protein, in the absence of domestic animals larger than chickens and dogs, traditional Tikopians relied to a minor extent on ducks and fish obtained from the island’s one brackish lake, and to a major extent on fish and shellfish from the sea. Sustainable exploitation of seafood resulted from taboos administered by chiefs, whose permission was required to catch or eat fish; the taboos therefore had the effect of preventing overfishing.

  Tikopians still had to fall back on two types of emergency food supply to get them over the annual dry season when crop production was low, and the occasional cyclone that could destroy gardens and orchard crops. One type consisted of fermenting surplus breadfruit in pits to produce a starchy paste that can be stored for two or three years. The other type consisted of exploiting the small remaining stands of original rainforest to harvest fruits, nuts, and other edible plant parts that were not preferred foods but could save people from otherwise starving. In 1976, while I was visiting another Polynesian island called Rennell, I asked Rennell Islanders about the edibility of fruit from each of the dozens of Rennell species of forest trees. There proved to be three answers: some trees were said to have “edible” fruit; some trees were said to have “inedible” fruit; and other trees had fruit “eaten only at the time of the hungi kenge.” Never having heard of a hungi kenge, I inquired about it. I was told that it was the biggest cyclone in living memory, which had destroyed Rennell’s gardens around 1910 and reduced people to the point of starvation, from which they saved themselves by eating forest fruits that they didn’t especially like and normally wouldn’t eat. On Tikopia, with its two cyclones in the average year, such fruits must be even more important than on Rennell.