Tambora: The Eruption That Changed the World (16 page)

SOUTH OF THE CLOUD

By the time of Tambora’s eruption in April 1815, the Chinese empire had achieved the massive territorial dimensions it still commands today, some twelve million square kilometers. One of the last territories to be brought under the Chinese banner, the mountainous province of Yunnan in the southwest had long been integrated within the Indian Ocean trade zone and enjoyed close cultural ties to the lands of the Mekong delta to the south: modern-day Burma, Laos, and Vietnam. A key transit point along the ancient silk road, Yunnan has served as a crossroads of cultures for millennia.
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When the legendary Mongol emperor
Kubla Khan sent Marco Polo to the capital Kunming in the 1280s, the intrepid Italian marveled at its diversity of peoples and religions. He also noted its abundance of rice and wheat fields, scattered across some two thousand valleys nestled in the mountains. Despite its elevation and rugged topography—the arable land is only 6% of its surface area—Yunnan is highly favorable to agriculture thanks to these fertile, intramontane lowlands, called
bazi
, which range in size from less than a kilometer to hundreds of kilometers across.

Until the disastrous upheavals of the nineteenth century, Yunnan enjoyed a more peaceful history than might be expected given its geographical circumstance, perhaps on account of its equable climate, which is likewise defined by convergence of differences.
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The extremes of China’s monsoonal climate are felt least in Yunnan, which acts as a buffer zone between the spectacular Indian monsoon and the rival Asian monsoon that largely dictates China’s weather east of 105°E. The province’s famously pleasant climate depends first on topographical discouragement of the southwest monsoon out of the Bay of Bengal. These grandiose storms are drained of their humid rage by their mountainous overland journey and enter Yunnan as no more than a mild, encouraging breeze and scattered rain showers. In a normal summer, the Tibetan plateau to the northwest—the “roof of the world”—acts as an enormous thermal engine, driving heat upward and depressurizing the atmosphere. The scale of this Himalayan warming is sufficient to offset even the effect of Yunnan’s lofty elevation. In Kunming, T-shirts are de rigeur at 1,500 meters above sea level. The southeast trade wind, too, an antiphonal presence, never fully yields to the Indian monsoon, ensuring that Yunnan experiences the fewest summer gales of any region in China.

Yunnan is likewise spared the worst of winter’s nick. Its mountains, running north-south, act as a vertical shield against the prevailing cold-air masses spilling down from Mongolia. The upward draw of the steep hillsides maintains a stationary high-pressure system, insulating the region like a meteorological version of the “pleasure dome” Coleridge imagined in “Kubla Khan,” his opium-soaked fantasy of medieval China written in 1816. Even in January, the highland Yunnanese benefit from the thawing effects of southwesterly winds. Indeed, Kunming enjoys the least variation in diurnal temperature anywhere in China: rarely below 10°C in winter or above 22°C at the height of summer. Awed by this moderation, Chinese folklore has it that there is no summer or winter in Yunnan at all, only spring and autumn.

Yunnan’s distinctness from core China is thus reflected in both its history and its climate. The name “Yunnan” means “south of the cloud”: from the Chinese point of view this designated a remote and exotic region blessed by perennial warmth. Yunnan’s popular moniker, “Land of Eternal Spring,” encouraged generations of Han Chinese to venture
westward in the boom times of the eighteenth century. Despite its elevation, winters in Yunnan were as much as 4°C warmer than in the flat plain country to the east at the same latitude, owing to its complacent situation beneath a largely stationary southwest air mass. Literally south of the clouds, Yunnan basked in abundant winter sunshine and was thus evergreen, a propitious country for growing rice and other food crops, and with abundant land yet undeveloped.

Until the seventeenth century, the population and agricultural output of Yunnan remained relatively stable. Then in the eighteenth century, at the height of the Qing dynasty’s westward march, came a period of enormous growth. The settlement of the west was a remarkable achievement in imperial central planning. That said, the doubling and tripling of Yunnan’s population in so short a period—from three million in 1750 to twenty million in 1820—could not have been sustained without an unwritten contract between Qing ambition and a benign climate, without an efficient and easily expandable agricultural system consciously adapted to an environment of pliable soil and sunny weather.
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By the turn of the nineteenth century, everything pointed toward the further extension of Chinese control over Yunnan and, more largely, to the province’s compliant role in the ever-greater expansion of an integrated, federalized Chinese agro-economic system. The intensification of agriculture across China, wrought by advanced technologies of irrigated land management and fertilization, supported huge increases in population—and was an object of jealous wonder among Western observers, who looked at the comparatively low-yield farming practices in Europe and America with dismay. By 1800 in Yunnan, almost all arable land had been brought under the plow, while more than half-a-million laborers worked in the copper, silver, gold, and salt mines, probably the largest mining operation in the world at that time.
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As this thumbnail description suggests, Yunnan resembled many of the world’s frontier regions of the early nineteenth century, where long-term indigenous residents gradually gave way to invading settler societies bent on mineral extraction, plowing the land, and building ever-expanding cities as hubs of trade. But this imperial growth plan
for Yunnan did not reckon with a period of drastic climate decline at precisely the wrong historical moment. The Tambora-driven weather emergency and ensuing famine of 1815–18 fatally altered the course of Yunnan’s development and played its part—as we shall see—in bringing down an empire.

YEARS WITHOUT A SUMMER

Disdained by the filmy Tamboran sun, the Himalayan plateau never warmed during the summer of 1816, nor did the surrounding oceans. In Tibet, just north of Yunnan, it snowed for a remarkable three days in a row in July, where a British surveying party reported famine among the native population and required emergency rations for their own survival. In this altered volcanic summer, the Tibetan plateau reverted to its wintry role, channeling the cold northern air southward and eastward toward the Mekong peninsula. Meanwhile, a cool and subdued Indian Ocean, likewise bereft of its monsoonal power, failed to deliver the warm winds necessary to moderate the cruel Mongolian northerlies.

Yunnan had the misfortune to suffer a cyclical drought in 1814, which meant its grain reserves were already depleted even as its normally benign weather patterns fell under Tambora’s chilling spell. The first signs of volcanic weather arrived quickly, a month after the eruption in the spring of 1815. Given the relative coolness of its elevation, Yunnan relied upon unstinting summer sunshine to ripen its grain crops. But in the late spring of 1815, the expected southwest winds did not arrive to disperse the clouds, which instead labored over the mountains, depositing flooding rains that drowned the winter crops. Wheat and barley sprouted underwater, while row after row of broad beans disintegrated into the mud. The bitter rains continued through the disastrous summer and into autumn. The aqueous rice fields might yet have survived had it not been for a frosty August, which strangled the budding rice plants at the critical point of their maturation.

According to one school of agricultural historians, the seven-thousand-year history of domesticated rice production begins in Yunnan. At the time of the Tambora eruption in 1815, a fifty-year accelerated settlement program had seen Han Chinese pioneers from the east “reclaim” vast areas of the intramontane lowlands for rice paddies, while picturesque irrigated terraces climbed ever further up the sheer mountainsides. Rice is a famously hardy crop, hence its role as the staple diet for half the world’s people. Once a rice-growing system is in place, and refined to allow double or even triple cropping, it will support rapid and continuous population growth, as in the case of eighteenth-century Yunnan. No other plant has the population-carrying capacity of rice, whose system of air passages connecting its roots and stem is formidably efficient, enabling it to self-regulate in widely differing contexts from irrigated fields, to dry upland soils, to riverbeds.

But the cultivation of rice, which is after all a tropical plant, does have its Achilles’ heel: cold snaps in summer.
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A recent study nominated 14°C as the “critical threshold of damage for rice.” But sustained temperatures below 20°C, combined with a deficit of sunlight, are
enough to spawn the uncontrolled proliferation of reproductive organs within the plant, or otherwise fuse, feminize, or deform them. Instead of ripening into its hardy oval shape, the cold-afflicted rice grain will fail to seal itself and assume the hideous, sterilized form of a tiny spiky claw or twisted stump.
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Because of the sustained abnormal cold conditions that prevailed during the Tambora emergency, accounts of the Yunnan famine of 1815–18 are full of descriptions of dehydrated rice grains “withered” or “shriveled” by the much-feared “dark winds” of the north. In East Asia, an old saying has it that a north wind in autumn reduces the rice yield by half. From 1815–18 in Yunnan, the impact of Tambora’s cold north winds on rice production may have been more than two-thirds. The branch-like panicles, which in a normal year drooped gratifyingly from the weight of their fruit, never came to flower, their mutant husks empty of grain.

The rice paddies of Yunnan are compensated for the relative coolness of their summer temperatures by the stillness of the intramontane air, allowing the sun to warm the surface of the watery field. When the water temperature is higher than that of the air, the paddy field emits a layer of protective warmth above the plants, insulating them from the chill. In the Tambora period, however, the presence of a sustained north wind fatally cooled the paddy water, upsetting the delicate balance of conditions for rice production. August temperatures in Yunnan for the three seasons from 1815 to 1817 were as much as 3°C below the seasonal average. This might not sound like much. On any given day, the difference between 15°C and 18°C (the low benchmark for optimum rice growth) is barely felt on the human skin. But seasonal averages are crucial indicators for temperature-sensitive crops. Every 1°C decrease in average summer temperature will reduce the rice growing season by up to three weeks, or the equivalent of a five-hundred-foot rise in elevation. At 3°C below average, almost no grain remains to be harvested at summer’s end.

By the end of 1815, the meteorological impacts of the Tambora eruption were unfolding across Yunnan with dismal inexorability. After
flooding volcanic rains in the summer, which destroyed both the spring and autumn harvests, food shortages gripped the province. The price of rice skyrocketed to 1,800 copper coins a bag, well beyond the reach of ordinary peasants. In Guanyin valley to the west, the villagers resorted to eating soil, an undigestible yellowish loam nicknamed “Guanyin noodles.” Many died from painful swelling of the gut.

After a traumatic winter with high mortality, the people’s hopes rose again in the late spring with the coming of the rains, this time in normal, moderate quantities. But the summer, of which these rains would ordinarily have been the sweet harbinger, never prospered. Instead, the bewildered and heartbroken Yunnanese endured unprecedented snows in July. In place of sunshine, the critical months of late summer and early autumn brought incessant rain, together with a meteorological phenomenon never before witnessed: great rolling icy fogs that lasted days on end. Even as late as the end of July, hopes persisted for a late harvest. But August brought a fresh onslaught of frosts and wintry gales, and the rice crop failed again, this time completely. The price of rice jumped once more into the thousands.