Rooftop Insect Collectors Find Climate Change Already Affecting Species

by Christine Lepisto

In 1992, Ole Karsholt and Jan Pedersen started collecting bugs in light traps on the roof of the Natural History Museum of Denmark in Copenhagen. A quarter-million bugs later, their data on 1543 species of moths and beetles provides astounding evidence that we don’t need to wait for 2°C (3.6°F) of warming before seeing significant effects of temperature change on the insect community.

As might be predicted, the insect species—bugs that eat only a single species of plant —experience temperature changes more dramatically than generalists. “Earlier studies have confirmed that specialist species also respond rapidly to destruction of their habitats, so we are dealing with a very sensitive group of animals” according to postdoc Philip Francis Thomsen from the Center for GeoGenetics, one of the authors of the study published in the Journal of Animal Ecology.

The nut weevil, Curculio nucum, a connoisseur of the hazel nut, visited the museum roof in the early years of the study but disappeared in later years. Its place was taken by the acorn weevil, Curculio glandium, suggesting that both species are moving northwards to find cooler domains. The data on other specialist species supported the hypothesis, showing increases in populations of hotdwelling species and decreases in those that prefer cooler climates.

Rooftop Insect Collectors

Insects that feed only during the non-mobile larval stage were seen to range quite widely from the habitats of their infancy, at least 10 km distant from the museum roof. The team succeeded to register seven moth species and two beetles which had not previously been on record as inhabiting Denmark, including the Asian lady beetle (Harmonia axyridis) (pictured) which has now spread throughout the country and is considered an invasive species.

The conversion of the data gained from the long-term voluntary monitoring project proves how invaluable such records can be. It seems like citizen scientists could lend a hand in the effort with a little political guidance, benefiting both the people involved and the state of scientific knowledge of our environment.

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