July 24, 2013
Europe’s Grassland Butterfly Populations Drop By Half In Two Decades
April Flowers for redOrbit.com - Your Universe Online
A report from the European Environment Agency (EEA) reveals that between 1990 and 2011, grassland butterfly populations have declined dramatically, caused by intensifying agriculture and a failure to manage grassland ecosystems.
According to the report, the drop in grassland butterfly numbers is particularly worrisome. These butterfly species are considered representative indicators of trends observed for a host of other land insects. Together, these terrestrial insects make up about two-thirds of the world's species. Scientists use these butterfly species as indicators of biodiversity and the general health of ecosystems.
The European Grassland Butterfly Indicator: 1990-2011 examines a total of 17 butterfly species. Of these, seven are widespread while 10 are specialist species. Eight of the species have declined in Europe, while two have remained stable and one increased. Scientists have as yet been unable to establish a trend for the remaining six.
Among others, the scientists examined the Common Blue (Polyommatus icarus), which has declined significantly, and the Orangetip (Anthocharis cardamines) which shows an uncertain trend over the last two decades. Hans Bruyninckx, EEA Executive Director, said, â€œThis dramatic decline in grassland butterflies should ring alarm bells - in general Europe's grassland habitats are shrinking. If we fail to maintain these habitats we could lose many of these species forever. We must recognize the importance of butterflies and other insects - the pollination they carry out is essential for both natural ecosystems and agriculture."
The researchers identified the intensification of agriculture and abandoned lands as the two main factors affecting the grassland butterfly populations. Where the land is flat and relatively easy to cultivate, agriculture has intensified. On the other end of the spectrum, large tracts of grassland have been abandoned in mountainous and wet regions, mainly in eastern and southern Europe. Both situations result in the loss and degradation of grassland butterfly habitat.
Uniform grasslands, which are almost always sterile for biodiversity, are the direct result of agricultural intensification. These managed farming systems also use pesticides to which butterflies are particularly vulnerable.
The reasons farmland is abandoned are usually socioeconomic in nature. Farmers tend to give up their enterprises and leave the land unmanaged when farming on low-productivity land brings decreasing revenue and there is little or no support from the Common Agricultural Policy (CAP). Such unmanaged grasslands quickly become overgrown and are replaced by scrub and woodland.
Grassland butterflies are almost completely restricted to road verges, railway sidings, rocky or wet places, urban areas and nature reserves in some areas of north-western Europe. Other important habitats include areas using traditional low-input farming systems, known as High Nature Value Farmland.
The De Vlinderstichting (Dutch Butterfly Conservation), Butterfly Conservation Europe and Statistics Netherlands compiled the European Grassland Butterfly Indicator, which was used to create the report. Information from national butterfly monitoring schemes in 19 countries across Europe, most of them European Union Member States, was brought together in the indicator. To gather that information, thousands of trained professional and volunteer recorders count butterflies on approximately 3,500 transects scattered widely across Europe. Volunteer fieldwork such as this is vital for understanding the state and trends of Europe's butterflies.
The report is based on data collected from 1990 to 2011. The scientists note, however, that in many areas of Europe the current changes in land use began before 1990, suggesting that the recent halving of butterfly numbers may be the most recent development in a much bigger long-term decline. The poor conservation status of the grasslands is recognized by the EU Biodiversity Strategy. Proper management is needed, the report states, both within Natura 2000 protected areas and on HNV farmland. The team suggests that a new system of payments under the Common Agricultural Policy could help support better management.
They also suggest that the European Grassland Butterfly Indicator could be used as a measure of success of agriculture policies. Sustainable funding of future butterfly indicator reports would allow researchers to validate and reform a range of policies and help achieve the goal of halting the loss of biodiversity by 2020.