(Opposite) Dayak children in West Kalimantan, Indonesia, holding the winged fruits of tengkawang (Shorea macrophylla).
Pontianak (S0°1´21´´; E109°19´49´´), West Kalimantan, Indonesia, and assorted locales in Sambas, Sanggau, and Kapuas Hulu Regencies, 1989–1994
The winged seeds produced by several species of trees in Borneo contain an edible oil whose physical and chemical properties are remarkably similar to cocoa butter. The seeds are known locally as illipe nuts, and large quantities are collected and sold to be used in the manufacture of chocolate, soap, candles, and cosmetics. The triglyceride fractions in illipe nut oil occur in similar proportions to those found in cocoa butter, and the oil can be blended with chocolate without altering the texture, gloss, or taste of the original confection. The higher melting point of illipe nut oil makes it especially useful as a chocolate hardener or to provide added body to face creams, so that the chocolate, as they say, “melts in your mouth, not in your hand,” or the cream stays on your face during a hot day at the beach.
Illipe nuts have five wings and come in a variety of sizes and shapes. Some of the smaller seeds are the size of a marble, and the long wings twirl the falling seed like a helicopter, helping to disperse it. The larger-seeded varieties are the size and weight of a golf ball, and the short wings on these seeds do little to prevent them from plummeting straight to the ground directly under the crown of the parent tree. Regardless of the size of the seed produced, however, all species of illipe nut trees flower and fruit synchronously at unpredictable intervals of from two to ten years. This reproductive behavior, which is known as mast fruiting, is thought to limit the abundance of frugivores and seed predators in the forest by concentrating their food supply into a single brief period every few years when they are confronted with more food than they can possibly eat. Some seeds will inevitably be left uneaten on the forest floor to germinate and recruit new seedlings into the population.
As can be appreciated, this unpredictable reproductive strategy creates serious supply problems in the illipe nut market. Neither the buyers nor the sellers know exactly when the next fruit crop will be produced, and neither the dried seeds nor the oil can be stored for significant periods of time.
I had been thinking a lot about the illipe nut market when I arrived at West Kalimantan—Borneo, the third largest island in the world, is divided into three countries: Malaysia (Sabah and Sarawak) and Brunei in the north, and Indonesia (West Kalimantan, East Kalimantan, Central Kalimantan, South Kalimantan, and North Kalimantan) to the south—in 1989 to continue my investigations on the ecology and management of tropical forest fruit trees. It seemed to me that finding an illipe nut tree that fruited every year would solve both the buyers’ and the sellers’ problems. On my first trip to the field, I went by cab from Pontianak to the Raya-Pasi Nature Reserve in the Sambas district, a roughly two-and-a-half-hour ride. We stopped in Bagak Sahwa, a small village near the reserve, to pick up the park warden. As we were walking up the mountain into the reserve, I casually asked the warden whether he knew of any annually fruiting tengkawang, or illipe nut, trees that grew in the reserve. He said that he did, and took me to see several dozen large illipe nut trees. The forest floor was carpeted with the seedlings and saplings of this species, Shorea atrinervosa,1 which I found surprising, because the previous year had not been a mast year and none of the other illipe nut species in West Kalimantan had produced any fruit.
I spent the next three years studying a marked population of these illipe nut trees in the Raya-Pasi Nature Reserve to determine whether the warden was right about the annual fruiting behavior of these trees.2 My study plot contained over 180 species of trees.3 Included among these were 25 species that produce edible fruits or nuts, 35 timber species, 5 species that produce a valuable oleo-resin,4 3 species whose leaves and bark are used medicinally, and a species whose fruits are used as a fish poison. There were 19 adult trees, several thousand pole-sized individuals, 7,000 saplings, and 50,000 seedlings of that illipe nut species in my one-hectare study plot—the population was experiencing a huge surge of growth. This made sense. If the illipe nut trees were producing fruit every year while the associated tree species were mast fruiting, the former were producing many more seeds and establishing orders of magnitude more seedlings each year. Additionally, I never saw hordes of wild pigs ravaging the fruits on the ground, so perhaps the selective advantage afforded by mast fruiting—to satiate seed predators—no longer operated on the site.
I obsessively followed the reproductive behavior of the adult illipe nut trees in the population for two years. All together, they produced over 160,000 illipe nuts—equivalent to a total production of about one metric ton of fresh fruit—per hectare. And they did this both years. The warden was right.
In addition to working with the warden, I did much of my fieldwork at Raya-Pasi with an older Dayak (a collective term for the indigenous people of Borneo) man who knew all the local trees. He would show up for work in shorts, a T-shirt, and flip-flops, with a dingy white towel wrapped around his head. He carried a razor-sharp parang (bush knife) in his hand and always had a crumpled plastic bag in his pocket with a box of matches and a pack of clove cigarettes (kreteks).5
He was extremely hard working and never stopped telling stories, such as the time when he was a boy and the Japanese army marched into Bagak Sahwa; everyone except the village leaders ran into the forest. He told me about the first time he saw a car. He described how the local people would cut off the buttresses of certain trees to make pans for mining gold, and why everyone in the village had left the new water hydrants put in by the development project running all the time until the pump burned out—because water is supposed to flow. And he related wonderfully detailed, ethnobotanical anecdotes about every one of the tree species we measured and tagged.
The best times came when the wind would pick up and the rain would start pouring down. We would squat at the base of the nearest buttressed tree, and I would dig out the rain poncho from my daypack and try to cover us with it. After a few minutes, once it had become really hot and stuffy under the poncho, he would pull out his plastic bag and light up a kretek. And we would soon be sitting in a dense cloud of clove smoke. Although I could no longer see his face, I could still hear him telling me his stories.
The city of Pontianak has eight different produce markets, and all of them sell native fruits. The fruit offerings vary throughout the year, but if you visit the markets every couple of weeks for several years, you will encounter almost a hundred different species. There are breadfruits (Artocarpus heterophyllus), jackfruits (A. altilis), and cempadak (A. integer), closely related fruits in the Moraceae family; numerous varieties of mangos (Mangifera spp.); several different types of rambutan (Nephelium spp.); stinky beans (Parkia speciosa) that make your urine smell funny; durians (Durio zibethinus), mangosteens (Garcinia mangostana), and crunchy fruits from spiny palms (Salacca zalacca); and always a large assortment of fruits (Baccaurea spp.) that when peeled reveal a neatly packed cluster of seeds, each surrounded by a layer of delicious, fleshy pulp.6 Pop the whole fruit in your mouth, suck on the pulp, and spit the seeds out one by one.
Unlike in the central market in Iquitos, where a similar diversity of native fruits, mainly wild harvested, was observed, all the fruits offered for sale in Pontianak were cultivated to some extent. Even the commercial fruit trees in the forest were planted. Or at least, someone spit out the seed there.
Durian is unquestionably the premier market fruit of Southeast Asia. The fruit is the size of a large football and has a thick, woody husk covered with sharp thorns. It has several sections, each containing a row of seeds covered with thick, creamy pulp. The pulp, the edible part, emits a distinctive odor that people find either extremely agreeable or completely disgusting. I personally love the fruit, but it is definitely an acquired taste. My favorite description of the flavor was a colleague’s “it tastes like French custard that has been dragged through a toilet.”7
Durian can be counted on to be a conversation starter in Pontianak. In the weeks leading up to the fruiting season, everyone speculates about the harvest. Will the fruits be large, meaty, and aromatic? Will the price be as good as last year? Which villages will bring the best fruits to market? Once the durians start showing up in town, the conversation turns to where to find the tastiest and best-priced varieties. The answer can change from week to week during the fruiting season, so people talk about it all the time. Once the season has ended, people reflect on the quality and quantity of the fruit from the past season, sharing anecdotes such as the way a seller was tricked into accepting a lower price by a long-time resident, or how a local durian connoisseur went through the entire season and never selected a bad fruit. And this conversation continues until the next fruiting season.
During durian season, the sellers start piling their fruits onto plastic tarps along the streets in the late afternoon to keep them from the hot sun, which would cause them to dry out or even to split open. Some areas of town are more desirable for market stalls than others, busy streets with lots of traffic, for example, and the more senior and successful durian sellers always claim these spots.
The preferred evening activity in Pontianak during durian season is to shop for fruits. After dinner, the entire family gets in the car or piles on the motorcycle or flags down a becak (three-wheeled cycle rickshaw) and heads downtown.8 They slowly cruise around looking at the different stalls until they see a pile of fruits they like. The mother and father will talk to the vendors, whom they may know from previous seasons, and pick through the pile, hefting and smelling favored fruits. Animated discussions will ensue over each fruit; a lot of head nodding goes on. Once they have selected their fruits, they negotiate a price with the vendor, pile the fruits and the family into the car, the motorcycle, or the becak, drive home—and eat them all. At the end of the evening all that remains is a pile of thorny husks and seeds and the lingering odor of durian. The same scenario will be repeated the following night. And the night after that and the night after that until the durian season ends.
In an effort to determine how many durian fruits were being sold in Pontianak, in 1991 we toured the city every evening by motorcycle, stopping occasionally to talk to vendors and count fruits. The durian season lasted forty-five days that year, and the availability of fruits followed an expected pattern. Early and late in the season, several thousands fruits were for sale throughout the city. During the peak season, we counted over sixty thousand, and mountains of durians dotted the town. The selling price of the fruit, however, stayed relatively constant. The first and last fruits of the season cost only about twenty cents more than those available during peak fruit production. (Data show that similar patterns of inelastic demand are characteristic of the markets for illegal drugs and gasoline.) Pontianak produces an abundance of native fruits, but durian remains the number one choice of the locals.
Durians produce large, creamy-white flowers with abundant nectar and a distinctive, buttery smell. The flowers open at night and are pollinated exclusively by a single species of frugivorous cave bat (Eonycteris spelaea).9 There are two fruiting seasons for durian in West Kalimantan, the main reproductive event and a smaller episode in which only a few trees bear fruit; each of these lasts approximately a month and a half. When the durian trees are flowering, they offer the bats an ample supply of nectar and pollen. But what do the bats live on for the rest of the year?
Apparently, during most of the year, the bats forage on a local mangrove species, Sonneratia alba,10 that grows along the coast. These trees produce a small quantity of fragrant, night-blooming flowers more or less continually throughout the year. The bats fly to the coast each night, covering distances of up to forty kilometers, to feed on the mangrove flowers. On their way, they’ll also check out any durian trees they pass for flowers, almost as a dietary afterthought. To put this in perspective, the exclusive pollinator of the king of market fruits in Southeast Asia, the source of a multimillion-dollar fruit trade, provides this service as a part-time job, a temporary, and somewhat unpredictable, supplement to its usual foraging behavior.
Things are changing fast for the cave bats, however, because the mangroves in West Kalimantan are being cleared to make room for coastal development. As the distribution and abundance of their main food source decreases, the number of bats flying though the forests of Borneo each night will also decrease. Fewer bats will lead to less pollination, and less pollination will lead to fewer fruits. Development activities far from where the fruits are growing can have a drastic impact on the productivity of durian. The farmers have no control over this—and might not even see it coming.
Madurese farmers from the village of Punggur, southwest of Pontianak, grow a delicious market fruit known as langsat (Lansium domesticum)11 in the extensive peat swamps that surround their village. The small yellow fruit is produced in grapelike clusters; the edible portion is the translucent, whitish pulp that surrounds each seed.12 The pulp tastes like a cross between a grape and a grapefruit. Savvy buyers in Pontianak specifically ask for langsat grown in Punggur, and the village makes a lot of money from the sale of this species.
The problem for the farmers in Punggur is that peat soils are too acidic for fruit trees. Peat is partially decomposed organic material that builds up in places where the rate of litter deposition exceeds the rate at which the material is broken down. This is the case in peat swamps because they have a low pH and reduced oxygen levels, both of which inhibit microbial activity and the rate of decomposition. In order to plant fruit trees, farmers need to go through a laborious process of hand digging a network of drainage channels through the peat.13 Water from the spongy peat drains into the canals, and the peat slowly subsides. The farmers repeatedly burn off the top layer of dry peat, and clean out and deepen the canals, as little by little the peat continues to dry out and flatten. The objective of this backbreaking work is to eventually get rid of the peat and expose the fertile alluvial soil underneath. After ten years of this digging and burning, the peat has usually subsided enough for the farmers to plant rice and coconuts.14 The peat continues to go down through successive rice harvests, and after five more years, the farmers can plant langsat trees. Durians, rambutans, bananas, several species of citrus, and a variety of other native fruits are also introduced into what has now become a species-rich, market-oriented, agroforestry system. Fifteen years later—a total of thirty years after clearing the forest and digging the canals—the farmers can start harvesting their fruit.
I don’t know exactly how long it takes for peat to accumulate—peat accretion is reported to be on the order of one to two millimeters a year—but suffice it to say that it takes a long time to make a meter of peat. One of the farmers at Punggur recalled having to work through ten meters of peat before he could plant his langsat trees. Burning and digging, burning and digging, he finally reached the point where he could plant rice, and before much longer he caught a glimpse of mineral soil. Much to his surprise, after the last layer of peat was cleared away, he found fragments of tools and earthenware. Another group of farmers had been living in the same place, thousands of years ago, and had probably planted their own fruit trees—without having to deal with the peat.
Today’s farmers’ ingenious solution to their fruit-growing problems brings both advantages and disadvantages. Draining and burning several meters of organic peat soil releases an enormous amount of carbon into the atmosphere. From a global-warming perspective, this is not an advisable form of land use. But at the same time, the farmers in Punggur have created a completely new plant community in an extremely restrictive environment that contains multiple tree species and generates a continual source of revenue. These habitats will undoubtedly stay forested and productive—and thus growing and fixing carbon—for many generations. As long as the native fruits of Borneo continue to command a good price in local and international markets, the farmers in Punggur are likely to care for and harvest their langsat trees sustainably.