Insect species with specialized diets may weather climate change after all

In the race to fill environments changed by global warming, generalist species have long been considered winners due to their ability to utilize a wide spectrum of habitats and foods. Scientists have consequentially raised concerns that climate change may benefit a select group of generalists, driving specialist species to extinction as their limited resources shrink. However, research published in the Proceedings of the Royal Society B identified a suite of characteristics enabling butterfly and moth species to thrive with climate change, and dietary specifics is one of them.
 
Swedish butterflies and moths with diets rich in nitrogen plants as young larvae have expanded their northern range limits more rapidly than specialists who favor other diets. These nitrogen-favoring insects are benefiting from the combination of warming microclimates and intense eutrophication, which has occurred across 50% of habitats in the European Union due to humans introducing nitrogen-rich crop fertilizers.
 
Like previous research, the study also found that forest-dwelling generalist species active at warmer temperatures similarly expand northern range limits at faster rates than other insects. Because forests cover 75% of land area in Sweden, insects favoring forests over open habitats have more space available to them.
 
Collaborators from Sweden and Germany examined the northern range extensions of 282 Swedish butterfly and large moth species in national province catalog records from 1973 to 2010. Researchers compared a suite of traits to identify characteristics associated with faster and larger range expansions, including habitat type, dietary preferences, reproductive capacity and temperature during activity. Sixty percent of species expanded their ranges north by an average of 2.7 kilometers per year.
 
The study's finding that some specialists are broadening their ranges is encouraging because it indicates that greater biodiversity may prevail through climate changes than previously predicted. Furthermore, the research indicates that species able to take advantage of human environmental modifications, such as the addition of nutrients via fertilizers, may be able to thrive in otherwise unsuitable habitats. At the very least, decision-makers should prioritize nitrogen-rich habitats when managing environments and species with consideration to climate change.