Greenland’s butterflies are shrinking in the heat

Text: Christina Troelsen and greenland today
Article from the former magazine, Greenland Today

The butterflies are getting smaller as climate changes cause the temperature in Greenland to rise. The rapid climate changes that are currently impacting the Arctic regions have already proved to have serious consequences for the area’s nature. Danish scientists from Aarhus University have found physical changes in the wildlife in the High Arctic regions. The butterflies in Greenland are having such a hard time in the heat that they have shrunk in size.

Scientists have measured the wingspan of two species of Arctic butterflies collected over two decades from 1996 to 2013 by the Zackenberg Research Station in Northwest Greenland.

The scientists measured the wingspan of almost 4,500 individuals and they found that the lengths have decreased considerably and at the same rate for both species in response to warmer summers.

– Our studies show that males and females follow the same pattern and that it is the same for both species. Evidence suggests that the climate is playing a crucial role for the body size of the butterflies in Northeast Greenland, says senior scientist Toke T. Høye from the Aarhus Institute of Advanced Studies at Aarhus University.

The larvae change metabolism

Change in body size in response to rising temperatures is an expected reaction to climate changes. But it can go both ways; for some creatures, a longer breeding season can mean an increased body size and for others, an altered metabolism at higher temperatures means a loss of energy which reduces body size.

The results of these new studies are consistent with results from experiments showing that butterflies and other insects which are reared under higher temperatures grow into smaller adults.

– We humans use most energy when it is cold because we have to maintain a constant body temperature. But the metabolism of butterfly larvae and other cold-blood-ed creatures, whose body temperature is dependent upon its surroundings, increases at higher temperatures because the bio-chemical processes work faster. Hence the larvae expend more energy than they can consume.

– Our results indicate that this change is so profound that the growth rate of the larvae falls. When the butterfly larvae are smaller, the adult butterflies are also smaller, explains Toke T. Høye.

Arctic species under pressure

The consequences for the Arctic butterfly could be significant. Smaller wingspans mean that the butterflies cannot fly as far. Since these are species that are already only found in the northern regions, their dispersal will probably be reduced as the Arctic warms.

– There is evidence that these High Arctic species are under pressure from several sides. They live so far north that they cannot relocate to cooler climates and they will probably disappear from their southernmost habitats due to the heat. In addition to this, their ability to disperse will be impaired and their smaller body size could mean lower fertility. So they are definitely facing serious challenges in connection with the ongoing climate changes, says Toke T. Høye.

Butterflies belong to the group of organisms that are particularly sensitive to changes in their environment. Long-term studies of butterflies and other insects are therefore especially well-suited to illustrate the ecological consequences of global climate change.

Facts about the studies

Behind the studies are scientists from the Arctic Research Centre, the Institute for Bioscience and the Aarhus Institute of Advanced Studies at Aarhus University, as well as the Natural History Museum in Aarhus and the University of California.

The results of the study have just been published in the scientific journal Biology Letters.

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