Niedergang der Insekten

Abstract

The Decline of Insects – Why moths and other insects are becoming rarer

Fifty years of quantitative study of abundance of night-flying insects attracted to ultraviolet light revealed a decrease of more than 80 per cent in moths since the start of the study in 1969 and of 96 per cent in the other (small) insects for the margins of the arable land subjected to conventional farming, but no changes in insect abundance in several areas in the city of Munich. There, at present more insects fly despite light pollution than on the borders of agricultural land on the countryside. The trend of abundance in the quite insect rich riverine forests is inconclusive, and probably due to fluctuations caused by the uninhibited growth of the trees, which are no longer used for fire wood. Concerning agriculture the key factor is overfertilisation which creates conditions too cold and too wet due to vegetation which became much too dense. Additionally the extensive application of pesticides reduces insect population. Second to conventional agriculture, however, is the overzealous cleaning (in fact a shaving) of marginal land in towns, villages and along roads, called the duly public maintenance. This highly destructive practice could be cancelled quite simply.