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Environment alert in US and Europe: pollution and intensifying agriculture kill

In EU the populations of grassland butterflies decline almost 50% over two decades. Pesticides commonly used in California's Central Valley have been found in frog species who live in State National Parks

Intensifying agriculture and abandoned land are the two main trends affecting the populations of grassland butterflies. Agriculture has intensified where the land is relatively flat and easy to cultivate, and, on the other hand,large areas of grasslands have been abandoned in mountainous and wet regions, mainly in eastern and southern Europe. Both intensification and abandonment result in the loss and degradation of habitat for grassland butterflies.

Agricultural intensification leads to uniform grasslands which are almost sterile for biodiversity. In addition, butterflies are also vulnerable to pesticides, often used in intensively managed farming systems.

Farmland is often abandoned for socio-economic reasons. When farming on low-productivity land brings only a small amount of income, and there is little or no support from the Common Agricultural Policy (CAP), farmers give up their enterprises and the land is left unmanaged. The grassland becomes overgrown and is soon replaced by scrub and woodland.

In some regions of north-western Europe, grassland butterflies are now almost restricted to road verges, railway sidings, rocky or wet places, urban areas and nature reserves. Areas using traditional low-input farming systems, known as High Nature Value Farmland, are also important habitats.

Seventeen butterfly species are examined in 'The European Grassland Butterfly Indicator: 1990-2011', comprising seven widespread and 10 specialist species. Of the 17 species, eight have declined in Europe, two have remained stable and one increased. For six species the trend is uncertain.

Butterflies examined in the report include the Common Blue (Polyommatus icarus), which has declined significantly, the Orangetip (Anthocharis cardamines), which seems to be stable since 1990, and the Lulworth Skipper (Thymelicus acteon), which shows an uncertain trend over the last two decades.

Hans Bruyninckx, EEA Executive Director, said: "This 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 recognise the importance of butterflies and other insects -- the pollination they carry out is essential for both natural ecosystems and agriculture."

California's Central Valley is one of the most intensely farmed regions in North America, producing 8% of U.S agricultural output by value. While the use of pesticides such as triazines, endosulfan and organophosphates is common across the U.S., California uses more pesticides than any other state.

"Our results show that current-use pesticides, particularly fungicides, are accumulating in the bodies of Pacific chorus frogs in the Sierra Nevada," said Kelly Smalling a research hydrologist from the U.S. Geological Survey. "This is the first time we've detected many of these compounds, including fungicides, in these remote locations."

The Pacific chorus frog Pseudacris Regilla can be found in abundance across the state's Sierra Nevada mountain range. As with other amphibians, agrochemicals potentially pose a threat to chorus frogs, as exposure to pesticides can decrease their immune system, thereby increasing the risk of disease.

The team collected frogs, as well as water and sediment samples, from seven ponds ranging from Lassen Volcanic National Park at the northern most point of Central Valley, to the Giant Sequoia National Monument in the valley's southern extent. All sites were downwind of agricultural areas.

"The samples were tested for 98 types of pesticides, traces of which were found in frog tissues from all sites," said Smalling. "We found that even frogs living in the most remote mountain locations were contaminated by agricultural pesticides, transported long distances in dust and by rain."

Two fungicides, commonly used in agriculture, pyraclostrobin and tebuconazole, and one herbicide, simazine, were the most frequently detected compounds, and this is the first time these compounds have ever been reported in wild frog tissue. Another commonly detected pesticide was DDE (Dichlorodiphenyldichloroethylene) a breakdown product of DDT which was banned in the United States in 1972. The continued presence of a DDT byproduct reveals how long this banned chemical can impact biodiversity.

by R. T.
05 august 2013, Technical Area > Science News

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