Saproxylic hoverflies benefit by modern forest management (Diptera: Syrphidae).

Saproxylic organisms are regarded as threatened in many European countries. Nevertheless, there have been some signals indicating a recent increase of saproxylic hoverflies in the Netherlands. This paper examines the change in occurrence of saproxylic hoverflies compared to other ecological groups of the same family. The trend analysis is based on the database of an extensive recording programme carried out in the Netherlands. The results show an increase in occupied grid cells for a majority of saproxylic species in relation to other ecological groups. This positive trend occurs among all five ecological subcategories of saproxylic hoverflies recognized in this paper. It is suggested that this increase could be attributed to the changes in the Dutch forests during the past 50 years. Important aspects of these changes are: the increase in forest area (including an increase in area of forest with large and very large trees), the increase in age of forests and the changes in forest management in favour of a more natural approach towards dead and ill trees. In the discussion the possible influence of climate change and the method of trend calculation are discussed. [ABSTRACT FROM AUTHOR]