Over 80 percent of habitats within the European Union are currently classified as vulnerable, leading to butterflies declining and other adverse effects on the functional capacity of wildlife habitats and the services they offer to humans. To address this issue, the European Commission has introduced a fresh set of regulations known as the “Nature Restoration Law.”
This law is a crucial component of the EU Biodiversity Strategy 2030, which is scheduled to be released in May 2023, and aims to establish binding objectives for the restoration of diverse ecosystems throughout the entire EU. Within two years of the law taking effect, member states are required to submit plans outlining their strategies for achieving these targets and provide evidence of the effectiveness of their implemented measures.
However, this will be far from easy, since there are only a few indicators that can reliably show the state of biodiversity. For most plant and animal species, there is a lack of comparable data across Europe that could be used to assess the status of populations. Fortunately, there are a few exceptions, such as bats, birds, and butterflies, for which a larger amount of data is currently available.
Butterflies in particular are ideal bioindicators since they live in a wide range of habitats and react sensitively to environmental changes. Moreover, they are attractive and popular, making it relatively easy to motivate volunteers to participate in scientifically oriented butterfly counts.
For instance, since the establishment of the citizen science project Butterfly Monitoring Germany in 2005, such programs have been developed all across Europe, leading to over 5,000 volunteers currently participating in butterfly monitoring efforts, with data collected and analyzed in the central European Butterfly Monitoring Scheme (eBMS). This data can then be used to track the population development of individual species and identify common trends for the inhabitants of certain habitats.
This is the idea behind the recent “Butterfly Grassland Indicator 1990-2020,” which is based on the population trends of 17 butterfly species inhabiting Europe’s meadows and pastures.
This indicator currently shows that, across the 27 EU members states, only the Orange Tip (Anthocharis cardamines) butterfly is displaying a moderate increase, while three species – the Large Skipper (Ochlodes sylvanus), the Common Copper (Lycaena phlaeas), and the Meadow Brown (Maniola jurtina) – are stable.
Meanwhile, butterflies are declining across five species, including the Common Blue (Polyommatus icarus) and the Wall Brown (Lasiommata megera).
“The biggest loser in recent years has been the large blue (Phengaris arion), which for example has disappeared completely in the Netherlands,” said Josef Settele, an agricultural ecologist at the Helmholtz Center for Environmental Research (UFZ). For the remaining species among the 17 grassland butterflies, there is either no clear trend or insufficient data. If the analysis is extended to Europe as a whole, the situation is even more dire, with no species on the rise and only three currently stable.
According to the experts, the issue of butterflies declining across populations is mainly due to changes in agriculture. In Northwestern Europe, the intensive use of meadows and pastures and the heavy employment of fertilizers have particularly unfavorable effects. On the rest of the continent, the main problem is the complete abandonment of cultivation.
In order to reverse these negative trends, scientists and policymakers should urgently promote the sustainable use of meadows and pastures, while creating new valuable habitats and better connecting the already existing ones. Moreover, effective climate change mitigation could also play a significant role in protecting butterfly populations.
“Despite all efforts, these insects are still declining in many parts of Europe. We hope that the upcoming Nature Restoration Law can stop this decline so that our children can also enjoy butterflies in flower-rich grasslands,” concluded Chris van Swaay, an expert in Conservation Biology at Butterfly Conservation Europe.
Butterfly populations have been experiencing significant declines worldwide for several decades. The causes are multifaceted, and factors contributing to butterfly decline include:
This is perhaps the most significant reason for the decline in butterfly populations. Natural habitats are being destroyed at an alarming rate due to human activities such as urbanization, intensive agriculture, and deforestation.
These activities not only reduce the amount of space available for butterflies but also result in fragmented habitats that make it difficult for butterflies to migrate and find the resources they need for survival.
Changes in weather patterns, increased temperatures, and higher frequency of extreme weather events can disrupt butterfly life cycles and affect their survival. Some butterfly species are particularly sensitive to temperature changes, and global warming could lead to mismatches in the timing of butterfly emergence and the availability of food resources.
The use of chemical pesticides in agriculture can directly kill butterflies or reduce their food sources. Similarly, air and water pollution can have detrimental effects on butterfly populations.
Non-native plants and animals can outcompete native species for resources, change habitats, or even prey on butterflies directly.
Disease and parasites can also contribute to butterfly decline, especially when combined with other stressors that weaken butterfly populations.
To combat this phenomenon of butterflies declining, conservation efforts are being made, such as creating butterfly-friendly habitats, reducing pesticide use, and conducting research to better understand the needs and threats to butterfly species. Many of these efforts involve public participation, like citizen science projects where people help monitor butterfly populations and report sightings.