Changes in ranges of hoverflies in the Netherlands in the 20th century (Diptera: Syrphidae)

Changes in ranges of hoverflies in the Netherlands in the 20th century (Diptera: Syrphidae) In July 2001 the database of the Netherlands Syrphidae Recording Scheme contained approximately 200 000 records of Syrphidae. This database was used to examine changes in the hoverfly fauna of the Netherlands during the 20th century. The dataset was divided into two parts, before and since 1988, containing equal numbers of records. This revealed that there is a significant increase in the distribution of hoverfly species with saproxylic larvae. Probably this is a consequence of the changes in woodland management that have taken place in the past 20 years. Another result of the trend analysis is the conclusion that there is a high proportion of southern species among the increased species. A likely explanation for this is the change in climate in the past 20 years. Of a total number of 317 species, 29% increased, 40% remained stable and 31% has decreased. Eight species have increased strongly and 22 species show a strong decline. The causes of the strong trends are often unclear, but seem to be very different from species to species.