Bijen

Eidechsen, Mauersegler, Schwalben, Fledermäuse und verschiedene Schmetterlingsarten sind nur ein Teil der Tiere, die im Landkreis Ebersberg immer seltener anzutreffen sind und irgendwann, wenn nichts dagegen unternommen wird, vielleicht gar nicht mehr. Inzwischen ist es etwas Besonderes, wenn Tagpfauenaugen und Distelfalter durch den Garten flattern. Der Sommerflieder, auf den sich in den letzten Jahren immer mehrere Exemplare niederließen, lockt nach heutigen Zählungen höchstens einen Schmetterling am Tag an. Auch Hummeln werden immer seltenere Gäste.

There has been a lot of discussion about the decline in bee populations and its dire consequences for agriculture. We have also talked about the efforts to save the monarch butterfly, whose numbers have been dropping dramatically over the years. But the rest of the insect world does not get much attention. For the most part, we think of insects as a nuisance or as potential pests. A number of studies in recent years in Germany, Great Britain, and in the United States have concluded that many insect populations worldwide are in severe decline, and this is not a good thing.

D'après une étude britannique publiée mardi 16 août, le taux de mortalité des abeilles sauvages aurait triplé à cause des pesticides. Les pesticides néonicotinoïdes auraient multiplié par trois la mortalité des abeilles sauvages. Voilà le constat d'une étude britannique parue mardi 16 août dans la revue Nature Communications. Les apiculteurs alertent depuis plusieurs années sur le lien entre l'usage de ces puissants pesticides et l'effondrement du nombre de colonies d'abeilles sauvages. La Commission européenne avait d'ailleurs interdit l'utilisation de trois insecticides dès avril 2013.

Traditional farming and gardening has long taken a straightforward approach: if an unwanted plant or animal interferes, it is to be killed. We even developed a special vocabulary to help justify our actions: the animals were “vermin” and the plants were “weeds”. And, in the case of one hen-house plunderer, we came up with the elaborate ritual that is fox hunting, complete with a special ‘language of avoidance’ that anthropologists have found in cultures around the world (the fox is a “dog”, its face is a “mask”, its tail is a “brush”, the dogs are “hounds”).

Pflanzenschutzmittel aus der Gruppe der Neonicotinoide können nicht nur Honigbienen, sondern auch Wildbienen und Schmetterlinge gefährden. Das zeigen einmal mehr aktuelle Forschungsergebnisse britischer, US-amerikanischer und deutscher Wissenschafter. Für ihre Untersuchung analysierten Forscher um den Entomologen Ben Woodcock, wie sich der großflächige Einsatz von Neonicotinoiden auf 62 Wildbienen-Arten in Großbritannien von 1994 bis 2011 auswirkte. 2002 waren die Pestizide dort erstmals zugelassen worden.

The link has been established before. When we reduce pests with most insecticides, they discriminate too little between friend and foe. We can’t always see butterflies as friends because of the function of their caterpillars. However, as birds, reptiles and mammals rely on these insects and their relatives for food, what happens is simply Silent Spring, all over again.

Wild bee declines have been ascribed in part to neonicotinoid insecticides. While short-term laboratory studies on commercially bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape.

Twenty-two honeybee (Apis mellifera) colonies were placed in four different cornfield areas in order to study the potential in situ effects of seed-coated systemic neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Two apiaries were located in two independent neonicotinoid-treated cornfield areas and two others in two independent untreated cornfield areas used as controls. These experimental hives were extensively monitored for their performance and health traits over a period of one year.

There is clear evidence for sublethal effects of neonicotinoid insecticides on non-target ecosystem service-providing insects. However, their possible impact on male insect reproduction is currently unknown, despite the key role of sex. Here, we show that two neonicotinoids (4.5 ppb thiamethoxam and 1.5 ppb clothianidin) significantly reduce the reproductive capacity of male honeybees (drones), Apis mellifera. Drones were obtained from colonies exposed to the neonicotinoid insecticides or controls, and subsequently maintained in laboratory cages until they reached sexual maturity.