M.G. Pereira

Country-specific effects of neonicotinoid pesticides on honey bees and wild bees

Damage confirmed Early studies of the impacts of neonicotinoid insecticides on insect pollinators indicated considerable harm. However, lingering criticism was that the studies did not represent field-realistic levels of the chemicals or prevailing environmental conditions. Two studies, conducted on different crops and on two continents, now substantiate that neonicotinoids diminish bee health (see the Perspective by Kerr). Tsvetkov et al. find that bees near corn crops are exposed to neonicotinoids for 3 to 4 months via nontarget pollen, resulting in decreased survival and immune responses, especially when coexposed to a commonly used agrochemical fungicide. Woodcock et al., in a multicounty experiment on rapeseed in Europe, find that neonicotinoid exposure from several nontarget sources reduces overwintering success and colony reproduction in both honeybees and wild bees. These field results confirm that neonicotinoids negatively affect pollinator health under realistic agricultural conditions. Science, this issue p. 1395, p. 1393; see also p. 1331 Bee health is affected by neonicotinoids under field-realistic conditions across crops conditions. Neonicotinoid seed dressings have caused concern world-wide. We use large field experiments to assess the effects of neonicotinoid-treated crops on three bee species across three countries (Hungary, Germany, and the United Kingdom). Winter-sown oilseed rape was grown commercially with either seed coatings containing neonicotinoids (clothianidin or thiamethoxam) or no seed treatment (control). For honey bees, we found both negative (Hungary and United Kingdom) and positive (Germany) effects during crop flowering. In Hungary, negative effects on honey bees (associated with clothianidin) persisted over winter and resulted in smaller colonies in the following spring (24% declines). In wild bees (Bombus terrestris and Osmia bicornis), reproduction was negatively correlated with neonicotinoid residues. These findings point to neonicotinoids causing a reduced capacity of bee species to establish new populations in the year following exposure.

Spatial controls on dissolved organic carbon in upland waters inferred from a simple statistical model

Dissolved organic carbon (DOC) concentrations in upland surface waters in many northern hemisphere industrialised regions are at their highest in living memory, provoking debate over their “naturalness”. Because of the implications for drinking water treatment and supply there is increasing interest in the potential for mitigation through local land management, and for forecasting the likely impact of environmental change. However, the dominant controls on DOC production remain unresolved, hindering the establishment of appropriate reference levels for specific locations. Here we demonstrate that spatial variation in long-term average DOC levels draining upland UK catchments is highly predictable using a simple multiple logistic regression model comprising variables representing wetland soil cover, rainfall, altitude, catchment sensitivity to acidification and current acid deposition. A negative relationship was observed between DOC concentration and altitudexa0that, for catchments dominated by organo-mineral soils, is plausibly explained by the combined effects of changing net primary production and temperature-dependent decomposition. However, the magnitude of the altitude effect was considerably greater for catchments with a high proportion of wetland cover, suggesting that additional controls influence these sites such as impeded respiratory loss of carbon in wet soils and/or an increased susceptibility to water level drawdown at lower altitudes. The model suggests (1) that continuing reductions in sulphur deposition on acid sensitive organo-mineral soils, will drive further significant increases in DOC and, (2) given the differences in the magnitude of the observed altitude-DOC relationships, that DOC production from catchments with peat-dominated soils may be more sensitive to climate change than those dominated by mineral soils. However, given that mechanisms remain unclear, the latter warrants further investigation.