Beleid en debat

De insecticiden die verantwoordelijk worden gehouden voor de bijensterfte blijken ook sterfte bij vogels te veroorzaken. De American Bird Conservancy (ABC) concludeerde in een dik rapport dat deze zeer effectieve insectendodende gifstoffen aantoonbare invloed hebben op vogels. Deze stoffen worden ook verantwoordelijk gehouden voor de bijensterfte die in alle delen van de wereld gaande is. In ons land wordt op grote schaal gebruik gemaakt van dit gif. Heel jammer dat een voorstel van de Europese Commissie voor een verbod recent verworpen is. De bioloog Arnold van Vliet op Youtube: http://www.youtube.com/arnoldvanvliet

At the request of the Dutch Nature and Environment Foundation, two scientists of the Dutch Centre for Agriculture and Environment (CLM) conducted an independent analysis of confidential studies on potential risks of the pesticide imidacloprid to bees through two visits to Bayer's 'reading room'. Their conclusions were as follows. The unpublished studies provide insufficient information on long-term (sub) lethal effects, combination toxicology or synergy between factors such as imidacloprid exposure and the impact of diseases and scarcity of alternative food sources. Sublethal effects mentioned in the studies were brushed aside by the Dutch regulators. The confidential studies worked with a limited number of crops and doses, and extrapolated data were used on other crops for which no residue measurements in pollen and nectar were available. The regulatory authority assessed the risks to bees on the basis of Good Agricultural Practice (GAP) and strict observance of the label text. This is, unfortunately, not in line with common practice, causing greater emissions, exposures and risks. The regulators applied little or no safety margins in the assessment of the data, rarely adopted worst-case scenarios and allowed the use of largely extrapolated data. Degradation models were frequently used instead of direct measurements. Since the basis for risk assessment was very thin, it was impossible to determine whether or not bees were at risk through the use of imidacloprid. There were so many uncertainties, that risks can not be ruled out. This is consistent with the conclusions of EFSA.

Bumblebee colonies die off in the autumn with only the queen surviving – to hibernate through the winter with eggs and sperm inside her – before starting a new colony the following year – so it’s the queens that we see first, big fat things twice the size of the workers, when they emerge. That happens in March or even as early as February. But in 2013, with April nearing the end of its first week, they’re still hunkered down.

It has been postulated that a general decline in insect abundance linked with intensification of agriculture may have contributed to farmland bird decline. We analysed insect catch data from a single suction trap run for 27 years in a rural location in Scotland, and showed that insect numbers have changed significantly over time. Measures of bird density were significantly related to insect abundance. These data from a broad suite of species provide support for linked temporal change between farmland birds, invertebrate numbers and agricultural practice in Scotland.

The Government must introduce a precautionary moratorium on three pesticides linked to the decline of pollinators - imidacloprid, clothianidin and TMX – that suspends their use on flowering crops attractive to pollinators, Parliament’s cross-party green watchdog has said. Environmental Audit Committee Chair, Joan Walley MP, commented: “Defra seems to be taking an extraordinarily complacent approach to protecting bees given the vital free service that pollinators provide to our economy. If farmers had to pollinate fruit and vegetables without the help of insects it would cost hundreds of millions of pounds and we would all be stung by rising food prices. Defra Ministers have refused to back EU efforts to protect pollinators and can’t even come up with a convincing plan to encourage bee-friendly farming in the UK.” Two-thirds of wild insect pollinator species - such as bumblebees, hoverflies, butterflies, carrion flies, beetles, midges and moths - have suffered population declines in the UK. Managed honeybees have also experienced unusually high mortality rates, decreased fertility, increased susceptibility to disease and the loss of hives. Similar trends have been observed in the US and other European countries.

Pesticides are important agricultural tools often used in combination to avoid resistance in target pest species, but there is growing concern that their widespread use contributes to the decline of pollinator populations. Pollinators perform sophisticated behaviours while foraging that require them to learn and remember floral traits associated with food, but we know relatively little about the way that combined exposure to multiple pesticides affects neural function and behaviour. The experiments reported here show that prolonged exposure to field-realistic concentrations of the neonicotinoid imidacloprid and the organophosphate acetylcholinesterase inhibitor coumaphos and their combination impairs olfactory learning and memory formation in the honeybee. Using a method for classical conditioning of proboscis extension, honeybees were trained in either a massed or spaced conditioning protocol to examine how these pesticides affected performance during learning and short- and long-term memory tasks. We found that bees exposed to imidacloprid, coumaphos, or a combination of these compounds, were less likely to express conditioned proboscis extension towards an odor associated with reward. Bees exposed to imidacloprid were less likely to form a long-term memory, whereas bees exposed to coumaphos were only less likely to respond during the short-term memory test after massed conditioning. Imidacloprid, coumaphos and a combination of the two compounds impaired the beesʼ ability to differentiate the conditioned odour from a novel odour during the memory test. Our results demonstrate that exposure to sublethal doses of combined cholinergic pesticides significantly impairs important behaviours involved in foraging, implying that pollinator population decline could be the result of a failure of neural function of bees exposed to pesticides in agricultural landscapes.

Surface runoff is an important process that affects the local water balance and causes soil erosion and rapid solute transport towards ditches, streams, and rivers. Surface runoff is the fastest route from field to stream and the main transport route for sediment and adsorbed contaminants, such as pesticides. It is the main contributor of pesticides to surface water bodies. The agricultural areas in The Netherlands most vulnerable to surface runoff are peat grasslands, where groundwater levels are kept close to the surface (less than 60 cm below soil surface), riverine heavy clay grasslands with low permeability and drainage by superficial trenches (less than 40 cm below soil surface), and sandy or clay soils with topsoil or subsoil compaction caused by treading, overstress due to large wheel loads of agricultural machinery, and tillage.