Algemeen

In Nordspanien tötet eine Gruppe nah verwandter Viren unzählige Amphibien. Die zu den Ranaviren gehörenden Erreger befallen unter anderem Frösche, Kröten und Salamander. Sie verursachen regelrechte Massensterben. Am schlimmsten betroffen seien die Geburtshelferkröte, die Erdkröte sowie der Bergmolch, berichten Wissenschaftler im Fachblatt „Current Biology“. Besorgniserregend sei, dass einzelne Virentypen aus der Gruppe mehrere unterschiedliche Arten von Amphibien befallen. Dies könne katastrophale Folgen für die Amphibien-Gemeinschaften und ihre Ökosysteme haben. Zur Gattung Ranavirus gehören mehrere Arten von Viren. Sie infizieren Fische und Reptilien, sind aber vor allem als tödliche Gefahr für Amphibien in Amerika, Europa, Asien und Australien bekannt. Die Forscher um Stephen Price von der Zoological Society of London hatten die Entwicklung der Amphibien-Populationen vor allem im Picos de Europa-Nationalpark in Nordspanien verfolgt. Nachdem sie im Jahr 2005 erstmals ein Massensterben aufgrund einer Ranavirus-Infektion festgestellt hatten, begannen sie den Bestand von sechs Arten von Amphibien einmal jährlich an unterschiedlichen Orten im Nationalpark zu überwachen.

The Mountain Chicken isn’t a fowl, as its name suggests, but a frog. Kimisha Thomas, hailing from the Caribbean island nation of Dominica, remembers a time when she could find these amphibians or ‘crapaud’ as locals call them “just in the backyard”. Known also as the Giant Ditch Frog, these creatures form a crucial part of Dominica’s national identity, with locals consuming them on special occasions like Independence Day. Today, hunting mountain chicken is banned, as the frogs are fighting for their survival. In fact, scientists estimate that their numbers have dwindled down to just 8,000 individuals. Locals first started noticing that the frogs were behaving abnormally about a decade ago, showing signs of lethargy as well as abrasions on their skin. “Then they began to die,” explained Thomas, an officer with Dominica’s environment ministry. “People also started to get scared, fearing that eating crapauds would make them ill,” she adds. In fact, this fear was not far from the truth; preliminary research has found that Chytridiomycosis, an infectious disease that affects amphibians, was the culprit for the wave of deaths. Besides the mountain chicken, there has been a sharp decline in the population of the sisserou parrot, which is found only in Dominica, primarily in the country’s mountainous rainforests. Thomas says large-scale destruction of the bird’s habitat is responsible for its gradual disappearance from the island. Dominica is not alone in grappling with such a rapid loss of species. According to the Red List of Threatened Species, one of the most comprehensive inventories on the conservation status of various creatures, some 2,599 of 71,576 species recently studied are thought to be endangered.

Calyptocephalella gayi, or the Chilean helmeted bull is the world’s largest frog and Chile’s largest amphibian. It measures around twenty centimeters in length and weighing over one kilo (roughly 2..2 lbs). It can only be found in this country and in 2008 it was listed on the Red List of Threatened Species compiled by the International Union for Conservation of Nature (IUCN). Experts now believe it could take as little as two decades for the species, which has been in existence since before the American continent was formed, to be wiped out completely.The frog was referred to under a different name until experts recently noted the strong similarity between a fossil genus of a Calyptocephalella gayi, which they believed to be extinct, and the twenty centimeter frog which can be found today in Chile. This observation brought the species out of extinction, with experts referring to the creature as a “living fossil,”yet is has swiftly become categorized as a “vulnerable” species, which is Chile’s penultimate category before extinction.

Since the 1980s, there has been a worldwide decline in the population of amphibians – frogs, toads and salamanders. For a while, biologists were skeptical that these declines were anything more than natural variations. However, study after study has revealed that the amphibian decline is a real and severe threat to biodiversity. Roughly half of amphibian species have decreasing populations, a third are globally threatened, and almost 500 species are critically endangered. The causes for this dramatic die-off appear to be varied. Some studies have concluded that farm pesticides are a major culprit. Other studies have identified a type of chytrid fungus that causes skin infections as a major contributor to the worldwide decline.

More than 200,000 wood frog tadpoles died within 21 hours last year at a pond in Nat Wheelwright’s backyard in Brunswick, in what may be the largest and fastest mass death of tadpoles ever reported. The Bowdoin College biology professor is trying to find out why. This year, the wood frogs came back to Nat Wheelwright's pond, but there were no 1-year-old frogs breeding and the number of tadpoles was lower than previous years. “It was something I had never seen before,” said Wheelwright, who has studied the frogs in his yard for 28 years. “It was like a nuclear bomb went off.” The tadpoles were covered with red hemorrhages and tested positive for ranavirus, which likely caused the die-off, said Wheelwright.

The world's soaring human population has slashed the numbers of creepy crawlies a study has found. However, researchers say the demise of slugs, spiders and worms is not good news for us humans and could spark an explosion in pests. The study, published in the journal Science, revealed that as the human population has doubled over the last 35 years to now stand at more than seven billion, invertebrate numbers have fallen by nearly half over the same period. Experts fear this could have an effect on ecosystems as insects, spiders, crustaceans slug and worms play an important role in pollinating crops, pest control, decomposition and ensuring soil remains packed with nutrients, as well as water filtration. In the UK these two factors caused a massive reduction in the number of beetles, butterflies, bees and wasps, a 30-60 percent fall over 40 years, according to the study.

Der US Government Fish and Wildlife Service hat soeben für alle Naturschutzgebiete im Zuständigkeitsbereich der Behörde ein Verbot von GV-Pflanzen und Neonicotinoide ausgesprochen. Es ist die erste derartige Entscheidung einer staatlichen Behörde der USA. Die im Jahr 1940 ins Leben gerufene Behörde ist für über 560 Naturschutzgebiete und Tausende anderer besonders geschützter Gebiete mit einer Gesamtfläche von rund 60 Millionen Hektar in den USA zuständig. Außerdem betreibt sie 70 Fischbrutbetriebe und unterhält 65 Büros für Fischereiressourcen. »Wir haben entschieden, dass der prophylaktische Einsatz, beispielsweise die Behandlung des Saatguts mit Neonicotinoiden, die sich systemisch in der Pflanze verteilen und ein breites Spektrum von Nicht-Zielarten beeinträchtigen können, mit der Politik des Service nicht vereinbar ist«, schrieb James Kurth, der Chef des National Wildlife Refuge System, am 17. Juli in einem Memorandum. Das landesweite Verbot der Neonicotinoide folgt auf Verbote der Behörde in den Bundesstaaten Washington, Oregon, Idaho, Hawaii und den Pazifikinseln.

Während der letzten 35 Jahre ging nicht nur die Zahl großer Wirbeltiere zurück, auch Insekten und andere Wirbellose mussten vielfach Bestandseinbrüche hinnehmen: Mehr als zwei Drittel der von Biologen beobachteten Bestände an Käfern, Bienen, Muscheln oder Spinnen schrumpften durchschnittlich um knapp die Hälfte. Deutlich mehr Insektenarten in so wichtigen Gruppen wie den Bestäubern zeigten Einbußen, nur wenige Populationen würden wachsen, warnen Biologen um Ben Collen vom University College in London. Allein in Großbritannien beispielsweise – wo ein ausführliches Monitoring auch mit Bürgerbeteiligung abläuft – verschwanden 30 bis 60 Prozent aller Käfer-, Bienen-, Wespen- und Schmetterlingsbestände; dagegen verzeichnen oft so genannte landwirtschaftliche Schädlingen Zuwächse.