European biodiversity under the microscope

A new European report on the diversity and abundance of butterflies on a European scale – in which Luxembourg participated, in particular through the Luxembourg Institute of Science and Technology (LIST) – has just been published by the European Environment Agency (EEA).

Entitled "The European Butterfly Indicator for Grassland species: 1990-2015", the report establishes the diversity and abundance of grassland butterflies on a European scale. It brings together the abundance reports of 22 participating countries for the period 1990-2015, including Luxembourg from 2010 onwards. This document is the sixth of its kind and provides a unique opportunity to obtain an indication of the population trend of butterflies on a European scale, insects representing one of the largest components of our fauna. The report was produced at the request of the EEA, which uses it as one of the biodiversity indicators for the European Union. On a European scale, the 9,200 sampling sites, also called transects, made it possible to demonstrate that there has been an overall decline of 30% in the abundance of butterflies since 1990, although the decline has been less marked in the last 5-10 years. The intensification of agriculture and the conversion of farmland areas into woodland areas have resulted in an increasingly unfavourable environment for grassland species. The report is based on a selection of 17 grassland species, divided into two categories. Seven species are considered common and widespread, to the extent that they can also be observed outside grassland areas. The ten other species are grassland specialists directly linked to the ways in which grassy areas are managed.

Common butterflies in decline in Luxembourg

In Luxembourg, the collection of these data was carried out by the Luxembourg Institute of Science and Technology (LIST), with the assistance of some enthusiastic volunteers, as part of national biodiversity monitoring, and with the co-financing of the Ministry of Sustainable Development and Infrastructure (MDDI). The sampling network is notable for the fact that it was realised in a random and stratified way, and is therefore especially representative of the common landscape in Luxembourg. 

With some 35 transects being monitored annually since 2010, two major characteristics are highlighted in the report. First of all, Luxembourg is one of the countries with the largest number of common species in decline (4 out of 7 common species). Although common species are not exclusively linked to grasslands, these do constitute the largest part of their habitat. Two particularly unfavourable phenomena for butterflies are routinely noted by observers: the destruction through ploughing of permanent grasslands in favour of intensive crops or pastures, and the silaging of grass to the detriment of hay or pastureland. Furthermore, grasslands are still regularly built on for residential, industrial or agricultural purposes. As regards specialist butterflies, only 1 in 10 species are represented in the common landscapes in Luxembourg. Moreover, it is in decline. As for the others, they are not found in Luxembourg except in protected areas or in brownfield sites. 

It must be noted that farming practices commonly applied in grasslands and changes in land use have largely confined these specialist species to the margins of our landscape in Luxembourg (mostly before 1990), and that species hitherto considered widespread are following the same path. 

From monitoring abundance to monitoring distribution

In order to understand the factors in this decline, it is essential to carry out further analyses. Therefore, an update of butterfly distribution in Luxembourg has been initiated, with the objective of producing an atlas and a new red list indicating the conservation status. LIST, the National Natural History Museum  (MNHN), natur&ëmwelt, the research unit ECOTOP, the biological stations and some highly-motivated volunteers have joined forces, with the financial support of the Ministry of Sustainable Development and Infrastructure, in order to fulfil this major task. A publication on this subject is scheduled for the second half of 2017.

>> Donwload the report « The European Butterfly Indicator for Grassland species: 1990-2015 » (PDF - 4Mo)

>> Below: two key figures based on the results of "The European Butterfly Indicator for Grassland species: 1990-2015" report

Figure 1: The grassland butterfly indicator for the European Union. The dotted line connects the annual index values of the indicator, and the solid line shows the trend. The blue area represents the confidence interval (95%). 

Figure 2: Detailed situation for Luxembourg species, as calculated by The European Butterfly Indicator for Grassland species (1990-2015). The value of 100 is attributed to the first year of monitoring. The table compares the trends at European Union and Luxembourg level.  / Click on the picture to enlarge /