Little is really known about the total numbers of insect species our planet holds and it is estimated that only between 10 and 20 per cent of insect and invertebrate species have been classified and named. We may well ask ourselves as to why the world’s insect population is declining with some species facing extinction?
Bayer verkoopt al zo'n drie decennia zogenaamde neonicotinoïden, een groep insecticiden die het bedrijf ooit heeft uitgevonden. Ze worden ervan verdacht een roemloze rol te spelen in het wereldwijde verlies van bijen en insecten. De EU heeft nu drie van de vijf goedgekeurde neonicotinoïden in Europa verboden en wetenschappers over de hele wereld waarschuwen voor een "ecologisch armageddon". In het coververhaal van tijdschrift NATUR 3/20 ("Toxic Seed") wordt de chemische reus van verschillende kanten beschuldigd kritische wetenschappers en imkers te hebben geïntimideerd.
Our mechanistic understanding of the toxicity of chemicals that target biochemical and/or physiological pathways, such as pesticides and medical drugs is that they do so by binding to specific molecules. The nature of the latter molecules (e.g., enzymes, receptors, DNA, proteins, etc.) and the strength of the binding to such chemicals elicit a toxic effect in organisms, which magnitude depends on the doses exposed in a given timeframe.
Since the mid-1990s, populations of the common Japanese dragonfly Sympetrum frequens in rice fields have declined severely. Application of systemic insecticides—especially fipronil—to nursery boxes of rice seedlings is suspected to be the main cause of the decline. However, until now there have been insufficient population data to test the causality. We conducted a dragonfly survey from 2009 to 2016 in four prefectures of Japan and compiled the data to enable the comparison of population growth rates along five main census routes over the years.
The May 2019 newsletter of the Saitama Ecosystem Conservation Society describes how, before the introduction of neonicotinoids in the 1990s, numberless brilliant red akiakane or autumn darter dragonflies could be seen around rice fields in the fall. Experiments by Japanese dragonfly expert Tetsuyuki Ueda of Ishikawa Prefectural University showed how the pesticides reduced the number of surviving dragonfly nymphs to a small fraction, and that the chemicals persist for years in the soil of rice paddy fields.
Several reports suggested that rice seedling nursery-box application of some systemic insecticides (neonicotinoids and fipronil) is the cause of the decline in dragonfly species noted since the 1990s in Japan. We conducted paddy mesocosm experiments to investigate the effect of the systemic insecticides clothianidin, fipronil and chlorantraniliprole on rice paddy field biological communities.
Damselfly populations are being harmed by insecticides as researchers find the wildlife scourge of neonicotinoids continues to grow. Some chemicals in this group have already been banned by the EU but thiacloprid is still in widespread use. Similar chemicals in the neonicotinoid family have already been tied to severe decline in bee populations and now it appears the damage is more widespread.
Experts from Suffolk Wildlife Trust, Buglife and the RSPB have all pointed to species in danger of disappearing from East Anglia. They include stone curlew - only 202 pairs nested in the East of England last year; the shrill carder bee - common in the region 25 years ago but now found only in the Thames Gateway area; and the crested cow-wheat - a plant limited to a small number of roadside verges because grassland has disappeared to farming or construction. Indeed, habitat destruction and human disturbance are cited as the two most common reasons these species are on the brink.
De insectensterfte in Duitse natuurgebieden was veel in het nieuws vorig najaar. In opdracht van Minister Schouten van LNV is er nu een rapport verschenen over de uitkomsten van dat onderzoek, de vergelijkbaarheid met de Nederlandse situatie, de kennis over de trends bij Nederlandse insecten en de mogelijke oorzaken. Vlinder- en libellenmeetnetten vormen een belangrijke bron voor dit rapport.
In de rapportage worden vier onderzoeksvoorstellen geformuleerd die nodig zijn voor een integrale aanpak van de problemen:
Afgelopen zomer bleek uit tellingen in de Krimpenerwaard een zeer sterke achteruitgang van de groene glazenmaker (Aeshna viridis): maar liefst 90 procent vergeleken met 2016. Deze zeldzame en beschermde libel is gebonden aan sloten met krabbenscheer. Om nog onbekende reden werd deze plant in 2017 vroeg bruin in de Krimpenerwaard.