Increasing neonicotinoid use and the declining butterfly fauna of lowland California

Abstract

The butterfly fauna of lowland Northern California has exhibited a marked decline in recent years that previous studies have attributed in part to altered climatic conditions and changes in land use. Here, we ask if a shift in insecticide use towards neonicotinoids is associated with butterfly declines at four sites in the region that have been monitored for four decades. A negative association between butterfly populations and increasing neonicotinoid application is detectable while controlling for land use and other factors, and appears to be more severe for smaller-bodied species. These results suggest that neonicotinoids could influence non-target insect populations occurring in proximity to application locations, and highlights the need for mechanistic work to complement long-term observational data.

Why are monarch butterflies declining in the West? Understanding the importance of multiple correlated drivers

“…Neonicotinoids include the five nitroguanidine neonicotinoid insecticides that are most persistent and prevalent in the West: acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam (Forister et al. , Mogren and Lundgren ). CDPR tracks agricultural and non‐agricultural use separately, and we kept these differences in our database.…”

“…Although land use change has not been evaluated as a driver of western monarch declines, neonicotinoid insecticide use is correlated with declines in butterfly diversity in California (Forister et al. ).…”

Impacts of a millennium drought on butterfly faunal dynamics

“…3), we cannot rule out the possibility that low elevation populations were buffered during the drought by irrigated crops or agricultural margins. If true, a reliance on agriculture would be interesting in the light of a recent hypothesis that long-term declines in low elevations butterfly populations are associated with intensification of pesticide applications [35]. It is possible that the rebound of the drought years could be followed by a more severe decline following concentrated agriculture dependency and toxin exposure.…”

Achteruitgang insectenpopulaties in Nederland: trends, oorzaken en kennislacunes

“…De effecten zijn vooral onderzocht bij honingbijen, solitaire bijen en hommels, maar recente studies suggereren dat ook voor andere insectengroepen negatieve effecten optreden. Bij vlinders is er zowel in Groot-Brittannië (Gilburn, Bunnefeld et al 2015) als in Californië (Forister, Cousens et al 2016) Hierin wordt geconcludeerd dat er duidelijk wetenschappelijk bewijs is dat wilde bijen (meer dan honingbijen), vlinders en zweefvliegen ook bij een minieme dosis neonicotinoïden negatief beïnvloed worden wanneer deze stoffen gedurende langere periodes in het milieu aanwezig zijn. Het gaat daarbij om negatieve invloeden op oriëntatievermogen, foerageergedrag en een verminderde werking van het immuunsysteem, waardoor insecten gevoeliger worden voor infecties door parasitaire en virussen (EASAC, 2015; Sanchez-Bayo, Goulson et al 2016).…”