© Hollandse Hoogte
Between 1890 and 2017, butterfly populations in the Netherlands declined by at least 84 percent; 15 species have disappeared completely. This is evident from an analysis of long-term data carried out by Statistics Netherlands (CBS) and Dutch Butterfly Conservation and published recently in the scientific journal Biological Conservation.

It is the first time that the historical trend in butterfly species distribution has been established. As of 1992, data from butterfly observations have been collected systematically as part of the Dutch Butterfly Monitoring Scheme, developed by Dutch Butterfly Conservation and CBS. Over the past few decades, the distribution of butterfly species has remained stable but there has been a steady decline in population, as indicated by the latest figures published in the Environmental Data Compendium.

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Butterfly population (1992=100)
 ObservationTrendOnzekerheid trend
1992120.20100.0092.11 - 109.18
199390.6293.2387.62 - 99.78
199463.5687.4983.34 - 92.11
199588.5682.779.28 - 86.74
199682.3678.8475.41 - 82.51
199776.6275.7272.46 - 79.28
199878.5073.0469.61 - 76.17
199956.9370.9267.56 - 73.92
200076.6269.4066.22 - 72.46
200155.2868.1364.91 - 71.02
200272.6066.8063.62 - 70.31
200382.6765.3962.36 - 68.24
200461.3064.1461.13 - 66.88
200568.2363.1860.52 - 66.22
200663.8062.4859.92 - 65.56
200747.3161.8859.32 - 64.26
200847.0261.3458.73 - 64.26
200977.7860.8058.15 - 63.62
201075.4860.4257.57 - 62.99
201165.6760.1557.57 - 62.99
201244.8559.7457.00 - 62.36
201367.9859.1957.00 - 61.74
201469.0558.6556.43 - 61.13
201553.6058.0055.87 - 60.52
201647.1757.2054.76 - 59.32
201765.0756.2953.68 - 58.73
201853.9555.3352.09 - 58.73
Source: CBS, Dutch Butterfly Conservation

Decline in distribution levels off, numbers continue to decline

Distribution trends of all butterfly species found across the Netherlands have been summarised in a Multi-Species Indicator (MSI). Between 1890 and 1990, the MSI dropped by 67 percent, after which distribution stabilised. Downward trends were detected for 42 species, 15 of which have disappeared completely from the Netherlands.

As of 1992, CBS and Dutch Butterfly Conservation monitor not only the distribution of species but also their abundance. The combined trends in distribution and abundance show an estimated overall decline in butterfly populations of no less than 84 percent between 1890 and 2017. Given the fact that a population decline always exceeds a decline in distribution (a population decline from 100 to 10 still indicates the presence of a particular species), one can assume that the population decline was even more substantial.

Three years ago, CBS and Dutch Butterfly Conservation still reported that slightly more butterfly populations had increased rather than decreased for the first time since population monitoring started in the early 1990s. Populations of some rare species such as the dark green fritillary, the tree grayling and the small pearl-bordered fritillary in particular showed a modest increase again following specific conservation efforts. However, the latest figures - published in the Environmental Data Compendium - show a continued downward trend, also among the rare species. Out of the 50 species monitored, 25 declined while 14 increased in number over the entire period, with 31 species declining and 9 species increasing over the past decade.

Trend stabilises in grassland and woodland, decline continues in heathland

Predominantly until 1980, butterfly abundance dropped sharply in all three major butterfly habitat types in the Netherlands: grassland, woodland and heathland. The trend has stabilised since then in grassland and woodland, but the decline has continued in heathland.