Butterflies

Senckenberg-Wissenschaftler konnten gemeinsam mit Kollegen der Technischen Universität München nachweisen, dass derzeit weit verbreiteten Insekten zukünftig ein hoher Artenverlust droht. Als Gründe für den Rückgang dieser „Generalisten“ nennt das Forscherteam eine Verinselung von Lebensräumen sowie die Intensivierung der Landwirtschaft. Auch die genetische Diversität der untersuchten Schmetterlingsarten wird laut der heute im Fachjournal „Biological Conservation“ veröffentlichten Studie zukünftig stark abnehmen – die Insekten reagieren in Folge sensibler auf Umweltveränderungen.

In einer Anfrage an den Gemeinderat will die CDU wissen, wie es um die Insekten bestellt ist und was gegen das Insektensterben in der Fächerstadt getan werden kann. Die Stadt Karlsruhe hat bereits auf die Anfrage der CDU-Fraktion geantwortet. Sie bestätigt einen Rückgang der Insekten als "überregionales Phänomen, zu dem es belastbare Studien gibt". Das Sterben der Insekten in Karlsruhe lässt sich anhand einer der größten Insektengruppen nachvollziehen: Der Schmetterlinge.

Mit rund 25'800 bedrohten Tier- und Pflanzenarten sei im zu Ende gehenden Jahr ein neuer dramatischer Höchststand erreicht worden. Ein Jahr zuvor waren es noch 24'000 bedrohte Arten. "Wir Menschen verursachen das grösste Artensterben seit Ende der Dinosaurier", resümierte Eberhard Brandes, Vorstand des WWF Deutschland. Auch in der Schweiz gingen die Bestände einiger Arten merklich zurück. Mehr als 40 Prozent der Insektenarten in der Schweiz gälten als bedroht, darunter Bienen und Schmetterlinge, sagte WWF-Sprecherin Perrette Rey in Lausanne auf Anfrage.

In England, the total abundance of widespread butterfly species declined by 58% on farmed land between 2000 and 2009 despite both a doubling in conservation spending in the UK, and predictions that climate change should benefit most species. Here we build models of the UK population indices from 1985 to 2012 for 17 widespread butterfly species that commonly occur at farmland sites. Of the factors we tested, three correlated significantly with butterfly populations. Summer temperature and the index for a species the previous year are both positively associated with butterfly indices.

A recent assessment of higher tier studies on the toxicity and risks of neonics in honeybees by Solomon and Stephenson reported a colony-level NOAEC of 25 μg/kg (ppb) for imidacloprid and clothianidin. The toxicity of these insecticides to honeybees is however known to be reinforced with chronic exposure, and extrapolation of time-to lethal-effect toxicity plots compiled from published studies indicate that an imidacloprid level of 0.25 ppb, i.e. one-hundredth of the reported colony NOAEC, would kill a large proportion of bees nearing the end of their life.

In September, the U.S. Fish and Wildlife Service denied a petition to put the Bicknell’s thrush (Catharus bicknelli) on the federal list of endangered species. The Bicknell’s is a medium-size (6-7.5 inches) thrush—brown on the back with a white, spotted underside—that dwells in dense balsam-fir forests in high elevations in the Adirondacks. Following is a primer on other wildlife in trouble in the Adirondack Park.

Much attention has been given to the plight of bees because of their importance as pollinators of major crops. But there is growing evidence that butterflies and moths – many of which have suffered dramatic declines in recent years – play an important role as specialist pollinators of some of our favourite wild flowers. A Swedish study recorded pollen on the bodies of three-quarters of butterfly species examined with some individuals carrying up to 350 grains.

Bees and butterflies are experiencing widespread population decline, creating public concern in recent years. Data collected in Germany suggest that it’s not just bees and butterflies at risk: insect populations overall have plummeted by more than 75 percent since 1989. Scientists have known about the population decline for several years. However, they didn’t know how many species were declining, and they didn’t expect it to be happening so fast.

1. Small tortoiseshell butterfly (Aglais urticae). Once a common sight in gardens, parks and hedgerows, the small tortoiseshell is in steep decline. Once one of our commonest butterfly species, in 2013 it was reported that numbers had dropped by 77% in the previous 10 years.

The UK will back a total ban on insect-harming pesticides in fields across Europe, the environment secretary, Michael Gove, has revealed. The decision reverses the government’s previous position and is justified by recent new evidence showing neonicotinoids have contaminated the whole landscape and cause damage to colonies of bees. It also follows the revelation that 75% of all flying insects have disappeared in Germany and probably much further afield, a discovery Gove said had shocked him.