Some Bugs Like It Hot

Wisecracks about baked Alaska notwithstanding, in the Interior we've had the mother of all summers. The other day I was braving the 90-degree heat to scrape aphid clusters off the daisies while ducking buzz-bombing yellow jackets, and I began wondering about the possible effects of global warming on northern insects. For example, the local entomologists have assured Fairbanksans that the hornet hordes come to us courtesy of the preceding mild winter; too many fertile queens hibernated safely through the cold season, so now we have their numerous offspring to battle. But what about other insects? What about the aphids?

Hallelujah--an excuse to get away from the bugs and do some reading!

I soon found a pertinent report. British entomologists have worked for the last three years on the buggy denizens of northern Spitsbergen, the main island of the Svalbard Archipelago in the European Arctic. At 79 degrees north latitude, the entomologists' study area is about as far north as human or bug can go and still stay on solid ground; the nearest town, Ny-Aalesund, claims to be the world's northernmost village.

(Svalbard is terrain well known to Geophysical Institute scientists, by the way, because it's an excellent place to study certain kinds of aurora. Among the institute scientists who pioneered work there is Chuck Deehr, and Deehr is one of the founding intellects behind this column--sort of a foreuncle, you might say, if founding author Neil Davis is the forefather. Ah yes--everything fits, somehow.)

Local weather records and the researchers' own experience suggest that Svalbard's summers are becoming warmer, although it's far from clear whether this is a short-term variation or a signal of bigger changes. However, their observations on aphids and other buggy beasts do not depend on the natural warmth. The British scientists have generated their own extreme greenhouse effect by setting up portable greenhouses. Some of them were small indeed, for the team used both transparent plastic pup tents and cloches, the bell-shaped objects northern gardeners use to protect or encourage temperature-sensitive young plants. Their aim was the same--to raise the temperature in the space enclosed by a tent or cloche. Appropriately, the highest warming some climate models predict for Spitsbergen by the middle of the 21st century is about 5 degrees Celsius, and that's about how much extra warmth the enclosures provided.

That increase, to 10 degrees Celsius (near 50 Fahrenheit), also about doubled the Celsius temperature outside the enclosures. Spitsbergen's summers reminded the researchers of London's winters, except for the unceasing sunshine of the High Arctic.

Some of the multi-legged animals the entomologists observed were apparently unimpressed by the higher temperatures. Soil-dwelling mites and springtails, who enjoyed only 2 degrees more heat because of the insulating plants above and the cooling permafrost below their realm, muddled along about the same as their excluded kindred did. By this summer, though, the springtail populations under the enclosures were actually lower than those outside. The springtails apparently didn't cope well with the drier soil that accompanied the greater warmth.

But the local aphids adored the increased heat. They seemed to take it as a kind of Hawaiian honeymoon and laid many more eggs than usual. They also matured more swiftly, so more generations could fit into one summer. The researchers found that the aphids were genetically geared to take advantage of warm weather. By season's end, the heated areas contained 11 times more aphid eggs than did the unheated surroundings.

Specimens of their preferred food plant, mountain avens, also thrived under cover, so the aphids had enough to eat--at least initially. The aphids' eggs easily survived the winter cold. In short, the extra heat permitted an aphid population explosion.

The next phase of the study will consider how the aphids' predators react to more warmth. I hope they love it--or someday visitors to a warmer Spitsbergen may be up to their armpits in aphids.