Pesticide and resource stressors additively impair wild bee reproduction

Bees and other beneficial insects experience multiple stressors within
agricultural landscapes that act together to impact their health and
diminish their ability to deliver the ecosystem services on which human
food supplies depend. Disentangling the effects of coupled stressors is a
primary challenge for understanding how to promote their populations and
ensure robust pollination and other ecosystem services. We used a crossed
design to quantify the individual and combined effects of food resource
limitation and pesticide exposure on the survival, nesting, and
reproduction of the blue orchard bee Osmia lignaria. Nesting
females in large flight cages accessed wildflowers at high or low
densities, treated with or without the common insecticide, imidacloprid.
Pesticides and resource limitation acted additively to dramatically reduce
reproduction in free-flying bees. Our results emphasize the importance of
considering multiple drivers to inform population persistence, management,
and risk assessment for the long-term sustainability of food production
and natural ecosystems.