Agricultural insecticides were a key factor, according to a study focused on the Midwest, though researchers emphasized the importance of climate change and habitat loss.

The latest insight comes from a study on butterflies in the Midwest, published on Thursday in the journal PLOS ONE. Its results don’t discount the serious effects of climate change and habitat loss on butterflies and other insects, but they indicate that agricultural insecticides exerted the biggest impact on the size and diversity of butterfly populations in the Midwest during the study period, 1998 to 2014.