After various decades of decline, butterfly populations are now showing signs of tentative recovery. The Netherlands started counting butterflies in the early 1990s. Since 2006, slightly more butterfly species have increased in number than decreased, but the overall butterfly population has remained stable as is shown in the most recent figures released by Statistics Netherlands (CBS) and the Butterfly Foundation and presented in the Compendium for the human environment.
Between 2006 and 2015 the populations of twenty different butterfly species have increased, i.e. nearly twice as many as the eleven species which declined in number. The other 21 species remained stable or the trend could not be established on the basis of the data provided by the National Butterfly Monitoring Network. Over the entire period from 1992 onwards, the populations of 23 species in fact dwindled and 16 species showed population growth.
Rare and endangered species show notable signs of recovery
Various rare and endangered species like the dark green fritillary, the tree grayling and the small pearl-bordered fritillary show signs of tentative recovery after having reached a low ten years ago. The populations of these species were reduced by 90 percent or more in 2006 relative to the early 1990s.
A rare species like the ilex hairstreak is still declining in number, but the wall brown, a very common butterfly two decades ago, has all but disappeared by now.
Nature conservation and climate change
In recent years a great deal of effort was put into restoration of the natural habitats of a number of endangered species. This approach created new opportunities for these endangered species. Climate change is also an important factor. Butterflies are cold-blooded creatures, which means that they thrive in warm summers. Because their life cycle is short, they can respond quickly when living conditions are changing.
Total butterfly population stable in recent years
The overall butterfly population in the Netherlands has been stable during the past decade. Prior to 2005 butterfly populations were dwindling continually. Rare butterfly species which are now growing marginally were dramatically reduced in number over the past decades. Apart from that, these species also had to cope with extensive loss of habitat across the country. This situation not only applies to the majority of butterfly species which were reduced in number, but also to more commonly found species. The decline was well underway when the Butterfly Foundation - in cooperation with CBS - set up the National Butterfly Monitoring Network in 1990. Today, the number of butterflies is just over 60 percent of the total population in 1990.