Beleid en debat

Einen „dramatischen Rückgang der Wasservögel“ haben Ornithologen in einer über 40 Jahre dauernden, großflächigen Untersuchung von rund 310 Seen und Weihern in Oberschwaben festgestellt. In einer Anfang des Jahres publizierten Übersicht – „Ökologie der Vögel“, Band 32/2, 2010 – stellen die Autoren Rudolf Ortlieb, Brigitte Schaudt und Roland Prinzinger die Bestandsentwicklung von knapp 30 Wasservogelarten von 1967 bis 2008 vor. „In diesen 40 Jahren ist der Gesamtbestand aller untersuchten Arten um mehr als 70 Prozent zurückgegangen. Das ist ein dramatischer Einbruch“, sagt Prof. Dr. Roland Prinzinger. Auch beim NABU sorgen diese Ergebnisse für Aufsehen, zumal viele NABU-Aktive bei der Untersuchung mitgewirkt haben. „Wie die Untersuchung zeigt, sind einige Vogelarten in den vergangenen 40 Jahren so gut wie ausgestorben, etwa die Rohrdommel Botaurus stellaris, die Zwergdommel Ixobrychus minutus, der Drosselrohrsänger Acrocephalus arundinaceus und die Knäkente Anas querquedula“, berichtet Harald Jacoby, Vogelkundler beim NABU. „Die Ergebnisse sind für mich umso erschreckender, als ich weiß, mit wie viel Sorgfalt und Aufwand die Daten über Jahrzehnte gesammelt wurden. An den Zahlen gilt es nichts zu rütteln. Das ist die traurige Realität.“ Selbst früher häufige Arten sind in ihrem Bestand extrem zurückgegangen: das Teichhuhn Gallinula chloropus etwa von rund 200 auf 60 Paare, die Wasserralle Rallus aquaticus von rund 330 auf 30 Paare.

The British public has helped scientists uncover what looks like a substantial decline in one of the UK's most common bumblebees over the last 20 years. By gathering valuable information about the insects, citizen scientists from across Britain have shown that the common carder-bee made up less than 10 per cent of bumblebee colonies from 2007 to 2009. Just 20 years previously, they made up a whopping 21 per cent. This is the first time anyone has shown that one of the UK's big six common bumblebees may be in decline. 'There seems to be a clear shift in how common different species in the UK are,' says Dr Gillian Lye from the University of Stirling, lead author of the study, published in the Journal of Insect Conservation. Professor Dave Goulson from the University of Stirling and Lye came up with the idea of getting enthusiastic members of the public to help them get to grips with bumblebee nesting ecology when they realised they could get a lot more information than they could on their own. 'People tend to spend quite a lot of time in their gardens, so spotting bumblebees and following them to their nests is a real possibility,' says Goulson. In this latest study, Goulson, Lye and colleagues asked members of the public to send information about which species they saw and what type of nest the bees used to the Bumblebee Conservation Trust. They encouraged people to send photographs, so that Lye could confirm the species. In total, over a thousand people sent information about the nests in their gardens.

Turtle Doves (Streptopelia turtur) are now the UK’s most threatened farmland bird, according to official figures. Turtle Dove populations fell by 21% between 2009 and 2010. Numbers have been falling since the 1970s, and it is now estimated there are only seven Turtle Doves for every 100 there were in 1970; a decline even greater than other struggling farmland species such as Tree Sparrows Passer montanus and Corn Buntings Miliaria calandra. As well as Turtle Doves, other farmland species whose decline are causing concern for conservationists include Common Starlings Sturnus vulgaris, Yellow Wagtails Motacilla flava, Lapwings Vanellus vanellus and Greenfinches Carduelis chloris. Greenfinch numbers are falling due to the disease trichomoniasis.

Viele Ackerkulturen werden heute von der Aussaat bis zur Ernte mit Pestiziden behandelt. Pestizide beeinträchtigen ganz erheblich die biologische Vielfalt. Neben bestimmten – für den Anbau schädlichen – Pflanzen und Insekten eliminieren viele Pestizide auch alle übrigen Wildkräuter und Insekten – und fehlen höheren Tieren dann als Nahrung. Etliche Arten der Feldvögel haben daher in den letzten Jahren radikal abgenommen. So wird die Stoffgruppe der Neonikotinoide für das Bienen- und das Vogelsterben in der Agrarlandschaft verantwortlich gemacht.

House Sparrows (Passer domesticus) were introduced to North America after 1850, increased and spread up to 1920, and stabilized or decreased thereafter until 1960. In the Maritimes (and perhaps some other areas), a further decline set in after 1970, continuing to the present. Now the species is rare to absent in much of the Maritimes, except around farms with livestock. Decline here since 1970 probably approaches 90 per cent in most other areas of human settlement except south of 45°N.

Anthropogenic habitat loss is usually cited as the most important cause of recent species’ extinctions. We statistically compared areas in Canada where imperiled species currently occur, versus areas where they have been lost. Using multiple regressions, we relate the numbers of species that had suffered range reductions in an ecoregion to variables that represent present habitat loss, pesticide use and human population density. We find high losses of imperiled species in regions with high proportions of agricultural land cover. However, losses of imperiled species are significantly more strongly related to the proportion of the region treated with agricultural pesticides. The relationship between species losses and area treated with pesticides remains significant after controlling for area in agriculture. Our results are consistent with the hypothesis that agricultural pesticide use has contributed significantly to the decline of imperiled species in Canada. Habitat conversion per se may be a less important cause of species declines than how that converted habitat is used.