Road mortality potentially responsible for billions of pollinating insect deaths annually

Abstract

Pollinating insects are vital to the survival of many primary producers in terrestrial ecosystems, as up to 80–85 % of the world’s flowering plants require pollinators for reproduction. Over the last few decades however, numerous pollinating insect populations have declined substantially. The causes of these declines are multifaceted and synergistic, and include pesticides, herbicides, monoculture, urbanization, disease, parasites, and climate change. Here, we present evidence for a generally understudied yet potentially significant source of pollinator mortality, collisions with vehicles. Negative impacts from roads have been observed for the majority of vertebrate groups but studies of the effects on invertebrates have remained largely absent from the scientific literature. We documented road mortality of pollinating insects along a 2 km stretch of highway in Ontario, Canada and used our findings to extrapolate expected levels of road mortality across a number of landscape scales. Our extrapolations demonstrate the potential for loss of hundreds of thousands (on our studied highway) to hundreds of billions (generalised across North America) of Lepidopterans, Hymenopterans and pollinating Dipterans each summer. Our projections of such high levels of annual road mortality highlight the need for research to assess whether the mortality levels observed are contributing to the substantial declines of pollinating insects occurring on a global scale, thus putting the ecological functioning of natural areas and agricultural productivity in jeopardy.