Algemeen

Thea Venckus from Nicasio sent in this week’s Ask the Naturalist question: Hi, I have lived on a ranch in Nicasio, for 13 years now. We used to have a multitude of western toads (Anaxyrus boreas) but I no longer see them. We still have abundant Pacific tree frogs, and bullfrogs in our deep pond. I was wondering what happened to all the toads?

I understand that Canada’s Pest Management Regulatory Agency recently announced that it “has determined that current agricultural practices related to the use of neonicotinoid-treated corn and soybean seed are affecting the environment due to impacts on bees and other pollinators” (based on findings in Ontario and Quebec). They are applied as seed dressings on wheat and canola on the prairies, and that PMRA is providing an opportunity for public comment. I would like to urge PMRA to conduct a serious, more comprehensive review of the environmental impact of neonicotinoid insecticides. My reasoning is as follows. Insects are quietly but rapidly disappearing. The great American biologist, E O Wilson, said insects were world-rulers, because they play a central role in maintaining ecosystems and the whole web of life. The recent alarms in Europe and America about the fate of the honey bee – colonies have been crashing in increasing numbers – have started to open people's eyes to insects' importance in a more general way. But it is only the beginning of an understanding, and much more is needed if we are to take the action necessary to preserve our populations of insects and other invertebrates, the creatures without backbones which make up the majority of animal life, including snails, worms and spiders (spiders being arachnids, not insects).

In a paper provocatively entitled “Counting the books while the library burns”, the researchers produce evidence that many wildlife programs round the world are monitoring species to the point of extinction – often without taking the necessary action to save them. Professor David Lindenmayer and Dr Maxine Piggott of the ARC Centre of Excellence for Environmental Decisions (CEED) and the Australian National University, and Assoc. Professor Brendan Wintle of CEED and the University of Melbourne warn in the journal Frontiers of Ecology that some conservation programs are standing by and watching species die out. Their work, funded through Australia’s National Environmental Research program (NERP), highlights the growing challenge of saving almost 20,000 endangered animals, birds and reptiles from extinction – and proposes a new action plan. “Of the 63,837 species assessed worldwide using the International Union for Conservation of Nature (IUCN) Red List criteria, 865 are extinct or extinct in the wild and 19,817 are listed as critically endangered, endangered, or vulnerable to extinction,” the researchers say. “Since the start of the 21st century alone, at least 10 species of vertebrates are known to have gone extinct, although this is likely to be a substantial underestimate.”

Sie knattern, pfeifen, quaken: Das Balzritual von Kröten und Fröschen ist eigentlich kaum zu überhören. Doch Forscher registrieren es in Berlin immer seltener: Viele Amphibienarten seien in ihrer Existenz bedroht, warnt der Biologe Rolf Schneider. "Die Entwicklung der vergangenen zehn Jahre ist schrecklich", sagt der Wissenschaftler der HU Berlin. Wie zuletzt eine Arbeit an seinem Institut ergab, ist etwa die streng geschützte Kreuzkröte im Norden Berlins ausgestorben. Wenig anders wird es der Wechselkröte ergehen, befürchtet Schneider. In Deutschland leben nach Angaben des Bundes für Umwelt und Naturschutz (BUND) 21 der rund 6000 weltweit bekannten Amphibienarten - rund die Hälfte davon gilt als bedroht. "Problematisch ist es für Amphibien vor allem dort, wo Landwirte unser Essen anbauen", sagt Artenschutzexperte Julian Heiermann vom Naturschutzbund (Nabu). Pestizide machen Insekten den Garaus, die auf dem Speiseplan der Kröten stehen. "Zudem reagiert auch die Haut der Amphibien auf Chemikalien sehr empfindlich." Überdüngung wiederum zerstört den natürlichen Lebensraum der Kröten: Nitrat lässt Tümpel umkippen. Es gerate vor allem dort ins Wasser, wo intensive Landwirtschaft und Gewässer dicht beieinander liegen, wie in der Uckermark, sagt Heiermann.

Deadly amphibian disease chytridiomycosis has caused the extinction of Darwin's frogs, believe scientists from the Zoological Society of London (ZSL) and Universidad Andrés Bello (UNAB), Chile. Although habitat disturbance is recognised as the main threat to the two existing species of Darwin's frogs (the northern Rhinoderma rufum endemic to Chile, and the southern Rhinoderma darwinii from Chile and Argentina), this cannot account for the plummeting population and disappearance from most of their habitat. Conservation scientists found evidence of amphibian chytridiomycosis causing mortality in wild Darwin's frogs and linked this with both the population decline of the southern Darwin's frog, including from undisturbed ecosystems and the presumable extinction of the Northern Darwin's frog. The findings are published today (20th Nov) in the journal PLOS ONE. Professor Andrew Cunningham, from ZSL's Institute of Zoology says: "Only a few examples of the "extinction by infection" phenomenon exist. Although not entirely conclusive, the possibility of chytridiomycosis being associated with the extinction of the northern Darwin's frog gains further support with this study."

Birds that eat flying insects are in a shocking and mysterious decline, says the co-editor of the new Atlas of Breeding Birds in Ontario. “It is an alarm bell,” Gregor Beck, a wildlife biologist and the book’s co-editor, said. The atlas, created after five years of research and employing 1.2 million individual bird records from Pelee Island to Hudson Bay, found most of the birds that eat flying insects declined 30 to 50 per cent in the last 20 years. The birds include some swallows, the common nighthawk (Chordeiles minor), the whip-poor-will (Caprimulgus vociferus) and the chimney swift (Chaetura pelagica). The decline was the biggest shock that came from the research, Beck said. We need to be very concerned, he said. Other insectivores are in steep decline as well. Reptile populations have declined drastically in Ontario over the past century. The Ontario Endangered Species Act, 2007 considers 18 of the province’s 24 reptile species (75%!) to be at risk. Fewer amphibian species are considered to be at risk, although amphibian populations are declining in parts of the province. Three species – timber rattlesnake, spring salamander and tiger salamander – have been extirpated.