Lowly Icelandic midges reveal ecosystem's tipp...(n short the study implies that humans ar...)

Lake Myvatn, which means "midge lake" in Icelandic, makes a perfect laboratory for studying such environmental change. The algae-munching midge Tanytarsus gracilentus alone makes up two-thirds of the herbivores in the lake's biomass and is an important food source for birds and fish. But the populations of the midge fluctuate dramatically: "They fluctuate in abundance by six orders of magnitude; in some years you hardly see any, while in others you have to fight not to inhale them," according to rni Einarsson who directs the Myvatn Research Station.

"The odd thing about the Myvatn midges," Ives adds, "is that the fluctuations are not random, but neither are they regular."

The model developed by Ives and his colleagues reveals an exotic mathematical property known as "alternative dynamical states." In short, the midges of Myvatn can appear in cycles of great and regular abundance, or at stable high abundances, and natural variables or "noise" such as temperature or wind can unpredictably push the dynamics between these alternative patterns.

"A practical, and serious, implication of these dynamics is that they make midges potentially susceptible to even minor disturbances," says Ives. "The magnitude of the fluctuations could be highly sensitive to disturbances that affect how low the populations crash during the cycling phase. In the last 40 years, the fluctuations in midge populations seem to have become more extreme. "

So extreme, Einarsson notes, that the Lake Myvatn fishery, a resource used by local farmers for 1,000 years has collapsed. "The fluctuations in midge populations became so extreme that the fish populations couldn't cope during midge crashes. Basically, the fish ran out of food."

The model developed by Ives' team implica
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