THE SEVEN SORROWS OF YUNNAN - Tambora: The Eruption that Changed the World - page 57

Figure 5.2. An idealized European impression of Chinese rice agriculture. (Thomas Allom, China in a Ser-
ies of Views Displaying the Scenery, Architecture, and Social Habits of That Ancient Empire [London, 1843-47],
3:26).
But the cultivation of rice, which is after all a tropical plant, does have its Achilles' heel:
cold snaps in summer. 8 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. 9
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 gratify-
ingly 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 season-
al 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 peas-
ants. In Guanyin valley to the west, the villagers resorted to eating soil, an undigestible yel-
lowish loam nicknamed “Guanyin noodles.” Many died from painful swelling of the gut.