English
Grasslands form a major part of the European landscape and are the main habitat for many butterfly species. The decline of grassland specialist butterflies is much more severe than for other hibitats or generalist butterflies. Since 1990 butterfly populations have decreased by almost 60%. In Western Europe, the decline is associated with intensification of agriculture and heavy use of fertilisers and pesticides.
Indirect effects of pesticides, operating through the food chain, have been proposed as a possible causal factor in the decline of farmland birds. To demonstrate such a link, evidence is needed of (1) an effect of food abundance on breeding performance or survival; (2) an effect of breeding performance or survival on population change; and (3) pesticide effects on food resources, sufficient to reduce breeding performance or survival, and hence to affect the rate of population change.
Intensification of agriculture is believed to have caused declines in farmland bird populations. One of the key elements of recent agricultural intensification is the increased use of pesticides. Here, evidence is presented of indirect effects of pesticides on behaviour and nestling conditions of yellowhammers Emberiza citrinella. Insecticide use was associated with reduced abundance of invertebrate food at the field scale resulting, early in the season (when nestlings were fed exclusively on invertebrates, in a negative correlation with yellowhammer foraging intensity. There was also a negative relationship between insecticide use and nestling body condition. While cumulative effects of repeated spraying can have impacts, the occurrence of any insecticide spraying in the breeding season may be more detrimental than multiple sprays at other times.
A study was conducted over 3 years on an experimental home lawn to detect, measure and contrast the effects of white grub control products on the abundance of soil-active arthropods. Both short-term effects (those caused by a single application) and cumulative effects (those attributed to repeated yearly applications) were evaluated for five different control regimes: trichlorfon (an organophosphate contact insecticide), imidacloprid (a neonicotinoid systemic insecticide), halofenozide, entomopathogenic nematodes and elemental sulfur. A consistent short-term effect due to individual applications was not detected. But the cumulative results of three consecutive yearly applications to the same field plots showed that imidacloprid suppressed numbers of total hexapods, Collembola, Thysanoptera and Coleoptera adults by 54-62%. Trichlorfon, halofenozide, sulfur and nematodes had no discernible impact on the abundance of non-target arthropods as measured in this study. The fact that imidacloprid has a higher environmental impact than trichlorfon may be due to persistence in the field.
We estimate that, in the past 20 years, ten million breeding individuals of ten species of farmland birds have disappeared from the British countryside. For example, the corn bunting (Emberiza calandra) and tree sparrow have declined for periods of up to a decade at an average rate of more than 5% per year. The declines in bird numbers in part reflect those in the invertebrate and plant populations upon which they depend.
Britain's farmland birds have suffered alarming declines over the last twenty-five years. It would appear that their decrease in numbers coincides with a period of rapid intensification in farming in the mid-1970s, and they have continued to steadily drop in numbers ever since.
There is thought to be six main reasons for the decline in farmland bird numbers:
1) Loss of wild food-plants as a result of herbicide use
2) Change from spring-sown to autumn-sown cereals and the subsequent loss of winter stubble.
3) Insecticide use reducing invertebrate populations.
4) Conversion of pasture to arable land and the resultant decline in soil invertebrate numbers.
5) Land drainage making soil dwelling invertebrates less accessible.
6) Availability of nest sites due to removal of hedgerows
All of these factors are a result of agricultural intensification, and they have affected different species to varying degrees.
Sixty percent of Europe's bird species live on farmland. Insecticides are killing invertebrates (insects, beetles, spiders) - an important source of food for chicks. Herbicides remove arable weed seed - a food source of particular importance in the winter months. Herbicides also reduce invertebrate populations by removing host plants. Close temporal associations between onset of decline and pesticide use exist for Tree Sparrow Passer montanus, Turtle Dove Streptopelia turtur, Bullfinch Pyrrhula pyrrhula, Song Thrush Turdus philomelos, House Sparrow Passer domesticus, Lapwing Vanellus vanellus, Reed Bunting Emberiza schoeniclus, Skylark Alauda arvensis, Linnet Carduelis cannabina, Swallow Hirundinidae, Blackbird Turdus merula, and Starling Sturnus vulgaris.
A NATIONWIDE survey of dragonflies is being launched amid concerns that a third of British species are under threat. The winged insects have "survived the extinction of the dinosaurs and several ice ages", but are now threatened by habitat destruction and climate change, the British Dragonfly Society warned. The society has collected data showing that 36 per cent of the 39 dragonfly species in the UK are in decline.
There are concerns regarding the long-term environmental fate and environmental persistence of the widely used insecticide imidacloprid. The 2005 sales figures for insecticides in Germany show not only that imidacloprid is one of the most widely used active ingredients, but also that this compound is more toxic to honey bees, more persistent in soil with a higher leachability than most other insecticides used in that country. The neonicotinoid insecticides clothianidine and thiomethoxam have similarly unfavourable properties.
Western culture views insects and arachnids as pests and vermin that need to be controlled. They usually are not considered as something to be preserved. Accordingly, arthropods and other small organisms have not been taken seriously for conservation by policy makers and the conservation community at large. Arthropods, however, are major components of diverse ecosystems and are the major players in functioning of ecosystem processes. Arthropods are relentlessly vanishing before our eyes. They must be preserved because of their inherent values but also because we need them for human survival.