Overige insecten

Le texte ci-dessous est une traduction de : "The Significance of the Druckrey-Küpfmüller Equation for Risk Assessment - The Toxicity of Neonicotinoid Insecticides to Arthropods is Reinforced by Exposure Time" à paraître in "Toxicology". Le texte complet en français est joint en PDF.

Dans cet article théorique, puisant aux sources de la toxicologie et des mathématiques, Henk TENNEKES s'intéresse à un domaine, ô combien crucial en toxicologie, celui des relations "doses - effets".

Despite widespread concern about declines in pollination services, little is known about the patterns of change in most pollinator assemblages. By studying bee and hoverfly assemblages in Britain and the Netherlands, we found evidence of declines (pre-versus post-1980) in local bee diversity in both countries; however, divergent trends were observed in hoverflies. Depending on the assemblage and location, pollinator declines were most frequent in habitat and flower specialists, in univoltine species, and/or in nonmigrants. In conjunction with this evidence, outcrossing plant species that are reliant on the declining pollinators have themselves declined relative to other plant species. Taken together, these findings strongly suggest a causal connection between local extinctions of functionally linked plant and pollinator species.

The Dwingelderveld National Park, located in the province of Drenthe in the north-eastern part of the Netherlands, is a heath and woodland reserve of 3,700 hectares, with 1500 ha of wet heath land, which makes it the largest wet heath land in western Europe. Sjouke van Essen surveyed the ground beetles (Coleoptera : Carabidae ) on 38 locations in the Dwingelderveld reserve in 1991 and 2008, in exactly the same manner, and observed a massive decline in the number of caught ground beetles, from 45,000 (94 species) in 1991 to 15,000 (79 species) in 2008. Within the same period there was a dramatic decline of the insectivorous Whinchat Saxicola rubetra (from 35 pairs in 1989 to 6-14 pairs in 1998-2003) and Northern Wheatear Oenanthe oenanthe (from 33 pairs in 1993 to just 3 in 2003) in the Dwingelderveld reserve.

The Black-tailed Godwit Limosa limosa used to flourish in the peat soil habitats in the western part of the Netherlands. Invertebrates profited from enrichment of the soil with manure and fertilisers and earthworms (Lumbricidae), leatherjackets (Tipulidae), snails and other species were abundant. The combination of abundant food, at least for adult birds, and the soft peat soil (which is easily penetrated by the long bill of the Black-tailed Godwit) made the western part of the Netherlands a prime breeding habitat for the Black-tailed Godwit. Nearly 80% of the western Europe population of the Black-tailed Godwit, currently estimated at 80,000 pairs and by far the largest in Europe, breed in the Netherlands. However, the key Dutch breeding population underwent a large decline from 120,000-135,000 in 1969, 85,000-100,000 in 1989-1991 to 62,000 in 2004. Over the last 15-20 years, the important breeding populations in Germany, Poland and Belarus have been reduced by 50% as well. Evidence collected in the Wormer- and Jisperveld reserve in the western province of North-Holland (a 2200 ha soft peat wetland reserve with high water tables and restrictions in agricultural management) suggests that the decline of the Black-tailed Godwit may be caused by a lack of larger insects on which the chicks depend for their survival.

The evidence provided by the Dutch Water Boards on imidacloprid contamination of surface water (attached) indicates that, in any case in the western part of the Netherlands, high concentrations of imidacloprid are diffused through the environment, which may kill or debilitate insects and possibly other arthropods. Attached is a map of Holland showing the agricultural areas where the use of imidacloprid is permitted.