Bosvogels

A 72-page 2010 publication raises new and troubling questions about a widely used insecticide's potential for harm to bees, beneficial insects, and bird populations. Using imidacloprid as an example, Dutch toxicologist Dr. Henk Tennekes reports on the hazards of imidacloprid to insects and birds. Imidacloprid is a neonicotinoid chemical, and has systemic action in plants. Other European researchers have linked this insecticide to significant risks for honey bee populations, including possible links to Colony Collapse Disorder.

Dr. Tennekes' findings indicate that imidacloprid (and possibly other neonicotinoid-type insecticides) can bind irreversibly to critical receptors in an insect's nervous system. If these receptors are permanently blocked, the insecticide would not follow a typical dose-response curve. He provides evidence that long term low level to imidacloprid exposure can lead to neurological problems and eventual death of insects.

Studies have shown imidacloprid to be highly persistent in the environment (RCC Compendium of Pesticide Information). In his book, Tennekes presents data showing that imidacloprid has contaminated most of the waterways in the Netherlands.

Systemic activity in plants combined with long-term persistence in the environment and toxicity at low concentrations can be a dangerous combination. Many vulnerable species over large areas could be exposed to this insecticide on land, in surface water following runoff from treated areas and in groundwater due to its potential for leaching through certain soil types.

Several previous studies have shown that imidacloprid is highly toxic to various forms of wildlife, including honey bees, certain beneficial insects, upland game birds, and crustaceans

Tennekes further suggests that imidacloprid has led to a general decline in the insect populations in the Netherlands, and this lack of food in turn has been responsible for declines in bird populations.

Since 1994 the Breeding Bird Survey (BBS) has revealed a major decline in the numbers of some woodland birds but those with the most specialist habitat requirements (some of which are also long-distance migrants), have shown the most dramatic declines, notably willow tit Parus montanus (down 77 per cent), spotted flycatcher Muscicapa striata (down 59 per cent), wood warbler Phylloscopus sibilatrix (down 57 per cent) and pied flycatcher Ficedula hypoleuca (down 54 per cent). In France, there has been a steep decline since the 1990s of the Wood Nuthatch Sitta europaea (down 48%),Willow Warbler Phylloscopus trochilus (down 54%), Marsh Tit Parus palustris (down 53%), Grey-faced Woodpecker Picus canus (down 62%), Wryneck Jynx torquilla (down 44%) and Common Crossbill Loxia curvirostra (down 54%) as well. Similarly dramatic decline took place in the woodlands of Germany since the 1990s (with the exception of the Wood Nuthatch). The German Golden-Oriole Oriolus oriolus is in decline since the 1990s as well. The dramatic woodland bird decline in the UK, France and Germany appears to be associated with decline of the Eurasian Sparrowhawk Accipiter nisus, which nearly exclusively takes birds. The Northern Goshawk Accipiter gentilis is in steep decline in Germany as well.

Imidacloprid can be applied as a systemic insecticide to trees by direct stem injections or by soil injections and drenches, and be indirectly introduced to aquatic systems via leaf fall or leaching, which may pose a risk to natural decomposer organisms. When applied directly to aquatic microcosms to simulate leaching from soils, imidacloprid was shown to be highly toxic to aquatic insects. Imidacloprid at realistic field concentrations in maple leaves had adverse effects on aquatic insects and earthworms. Imidacloprid at realistic concentrations in leaves can inhibit leaf litter breakdown through adverse effects on decomposer invertebrates. When imidacloprid is applied as a systemic insecticide to the soil around trees it may cause adverse effects on earthworms.