The mathematics of midges

not myvatnMidges have become the subject of mathematical study, with Icelandic midges drawing scientist’s particular attention. According to reports in the New York Times, mating midges in Lake Myvatn in Iceland are subject to a mysterious ‘boom and bust’ cycle.

During the mating season some years, the midges around the lake turn out in such numbers the air is almost brown with them while in other years, they hardly appear at all. Anthony R. Ives, a professor of zoology at the University of Wisconsin, became interested in the wild fluctuation in numbers.

According to Dr. Ives’ research, which was recently published in the journal Nature, a simple mathematical equation can express the population dynamics of the midges. The equation captures the dynamics, not of the midges themselves, but of the algae they feed upon.

The research has been deemed important as it illustrates the fragile relationships which underpin complex ecological processes. Something as small as the number of algae known as diatoms can significantly increase the population of midges, as they form the basis of the midges’ diet; whereas something as large as a mining operation can decrease them significantly.

In 1967, a mining operation began near Lake Myvatn which took out rocks made of diatom shells and used them for filtering beer, among other purposes. Twenty years later, the lake saw a drastic drop in its fish population.

“There’s always been a suspicion the two were linked, but people couldn’t figure out what that link was,” Dr. Ives said.

The diatoms fed the midges who, in turn, fed the fish in the lake. Without the diatoms, the midge numbers dropped and eventually, the fish numbers fell too. While the new research does not absolutely prove the link, “at least it shows a mechanism that makes it seem possible,” Dr. Ives said.