Monitoring butterflies in Finnish agricultural landscapes

What is the status of butterflies in Finland?

Modern agricultural practices have drastically reduced the areas of meadows and semi-natural grasslands, which are most important habitats for butterflies. Many of the Finnish butterfly species have declined respectively.

Changes in the abundances of butterfly species need to be monitored in order to focus the conservation measures to the most relevant species. In 1999 Finnish Environment Institute started to construct a butterfly monitoring network in the southern half of Finland. In 2012 this network included 60 sites counted by volunteers and 9 sites by professionals.


European collaboration in butterfly monitoring is advancing

Currently there are active butterfly monitoring schemes in over 15 European nations, all using rather similar methodologies.  In the past few years collaboration between these national monitoring schemes has increased considerably. This co-operation has been coordinated by De Vlinderstichting in the Netherlands, and it has resulted with several European-level indicators on the current trends in butterfly diversity:

Monitoring method

Butterflies are monitored with the widely used transect walking method, which was originally developed in the Great Britain by E. Pollard. Today it is also used for butterfly monitoring in several other EU-countries, such as the Netherlands, Belgium, Germany and Catalonia in Spain.

Butterflies are recorded from a 5x5 meter area ahead of the observer. The butterfly count is conducted repeatedly during the summer along the same walking route, which is also kept constant from year to year. 

In Finland the suggested mininum number of annual counts has been seven, conducted once a fortnight from mid-May to late August. Weekly counts are recommended, and done on ca. half of the transects.  However, due to our northern location the butterfly season is typically no longer than ca. 16 weeks, and in the northernmost transects less than ten weeks.

Monitoring sites

During 1999-2012 butterflies have been recorded on a total of 95 voluntary transects. Their number has varied annually between 30 and 60. Locations of the transects in 2011 are shown below. Most of the sites are concentrated to the southernmost part of Finland. This means that the observed population trends may not be representative for the whole country.


Trends in butterfly abundances 1999-2011

Population changes have been estimated for 51 Finnish butterfly species with TRIM software (TRends and Indeces for Monitoring, CBS Netherlands). Monitoring results have been reported annually in the Baptria -magazine published by the Finnish Lepidopterological Society (in Finnish with English abstract). 

Population trends of individual grassland butterfly species are presented on web site (for 1999-2008; direct access here).

The two graphs below present some general trends derived  from the individual species indices. Annual variation in  butterfly abundances has been considerable, but so far there has been no general trend of either increase or decrease. Most butterfly species have increased considerably since 2009, and the summer of 2011 was the best for butterflies during the monitoring period. These last three summers have been long and warm, and the winters in between cold and snowy, both of which are very favourable conditions for butterflies. 

Observed butterfly and moth species

A total of  88 butterfly species and 721 459 individuals have been recorded during the monitoring period. Day-active moths have also been recorded along with butterflies on one third of the transects, with a total of 325 moth species and 129 486 individuals observed. All butterfly species and 50 most numerously observed moth species for 1999-2011 have been listed in the attachments below.

Basic facts about the Finnish BMS

First for the year 2012, then the averages and totals for the whole monitoring period 1999-2012.

2012 Average Total
No. transects 60 46 95
No. counts 680 533 7 452
- counts per transect 11,3 11,6 -
Length of transects, km 159 133 -
No. species 75 66 88
- per transect 29,6 30,0 -
No. individuals 62 394 51 533 721 459
- per transect 1 040 1 106 -
No. species 152 145 325
- per transect 23,1 24,2 -
No. individuals 11 905 9 249 129 486
- per transect 283 300 -

Further information

Janne Heliola, tel. +358 400 148654,

Published 2013-06-12 at 14:52, updated 2013-12-10 at 15:01