The Year Without a Summer

In the year 1816, an abnormally cold summer had a disastrous effect on human beings, particularly those in southeastern Canada, the northeastern United States and northern Europe. June began as usual in North America, with temperatures in the northeastern US and southeastern Canada rising into the 80s (Fahrenheit) during the day.

Then, on Wednesday, June 5, a cold blustery wind swept out of Hudson Bay and drove down across the St. Lawrence Valley and on into New England. Heavy rains whipped by strong winds lashed the land all afternoon and night. Each hour the temperature dropped. By the next morning, thermometers registered in the low 40s and were still going lower when the snow began. At Bennington, Vermont, snow fell that day from just after daylight until midafternoon. When finally, the storm stopped, the snow was 12 inches deep in Quebec city, and many parts of New England lay under a 6-inch blanket of snow. A farmer remarked in his journal that it was "the most gloomy and extraordinary weather ever seen". Day after day, the winter weather gave no signs of warming. Instead, it got worse. No thermometer climbed above 50 degrees, and most were in the low 30s. Tender crops that the hopeful farmers had put out earlier in the month were killed by the unseasonable frost, and the whole land looked as though it had been seared by a scorching fire. Through most of July and August, the days started with temperatures in the 40s. By late August, early morning temperatures were in the 30s. On the few successively warm days, people tried gardening again. Farmers planted corn and other crops, hoping that somehow they might still get a harvest before winter. Nevertheless, time after time their gardens and fields were devastated by frost and hidden by snow. The killing frost that came shortly after mid-September was the first of the new winter. It was slightly earlier than usual. The cold weather resulted in many deaths, including deaths from starvation. Although the winter of 1816–17 was an especially severe one, spring in 1817 came as usual. The summer of 1817 was normal.

What caused the year with no summer?

Most scientists believe that the bizarre weather of 1816 was caused by an unusually low level of solar activity combined with a great shield of dust from volcanic eruptions that blocked out the warmth from the Sun. Several large volcanic eruptions had occurred just before, culminating in the explosion of Mount Tambora, a huge volcano on the island of Sumbawa, just east of Java, in 1815.

RAINFORESTS

Ants and Plants

Some of the plants of the tropical rainforest have mutually beneficial, or symbiotic, relationships with ants. A symbiotic relationship occurs between Cecropia trees and Azteca ants in the Central and South American rainforests. The umbrella-shaped Cecropia trees often colonize abandoned farmlands, disturbed roadsides and old clearings. They are small, quick-growing trees that increase in height by at least 6 feet (1.8m) each year and live for 20 years at most. The trunkand branches are hollow and divided by partitions, with thin patches in the outer wall. Azteca ants bite their way into the trunk through these thin patches and establish colonies. These ants introduce small plant-sucking insects into the chambers. The ants care for these small insects themselves, feeding on the sugary solution which the insects excrete. The plant produces small outgrowths from the leaf bases, which are rich in food materials. The ants eat these outgrowths and feed them to their larvae. Azteca ants are fierce, but do not sting. They attack anyone who disturbs or tries to cut the Cecropia in which they live. They also bite through the tips of climbers, which could otherwise smother the Cecropia plant. In Africa, the plant Barteria fistulosa provides shelter for large colonies of ants which, in turn, appear to defendit. This small tree grows up to 50 feet (15m) tall and is most abundant in old clearings and disturbed places, but also occurs in undisturbed forest. Ants occupy its horizontal branches, which are hollow. The ants clear other plants from the area around the tree base by biting off their tips. They attack any animal that disturbs or breaks the tree. Their sting is painful, and its effects can last for a couple of days. In Southeast Asia two members of the family Rubiaceae, Myrmecodia and Hydnophytum; a member of the family Asclepiadaceae, Dischidia; and two ferns, Phymatodes and Lecanopteris, provide ants with shelter, while the ants supply the plants with food. All are epiphytes and, except for Dischidia, have swollen rhizomes, or stem bases, which contain hollows. The hollows form whether or not ants are present. However, these plants are almost always colonized by ants, which fill some of the cavities with debris, including insect remains. The plants probably absorb the nutrients from this debris as the debris decomposes.