Grassland butterflies in rapid decline in Europe

Two decades of plummeting population halves number of key species, adversely affecting bees, birds and biodiversity – study

Fiona Harvey, environment correspondent

Of the 17 species of butterlies found in Europe, eight have declined, including the common blue, above. Photograph: Getty

Europe‘s grassland butterfly population has plummeted in the past two decades, new research published on Tuesday shows, with a near halving in the numbers of key species since 1990.

The precipitous decline has been blamed on poor agricultural practices and pesticides, by the European Environment Agency, which carried out the research. Falling numbers of butterflies are bad news not just for nature-lovers and for biodiversity, but have a knock-on effect on farming, as – like bees – they act as pollinators, and their disappearance harms birds and other creatures that need them for food.

Butterfly populations are a leading indicator of the health of other insect species. The new study therefore suggests many other species of insect, which are also food sources for birds and small mammals, and which play a key role in the health of the countryside, are also under threat.

Scientists from the EEA, the European Unoin’s environment watchdog, looked at 17 key species of grassland butterflies, of which seven were common species and 10 more specialist, using data gathered from 1990 to 2011 in 19 European countries. Of the total 17 species, eight have declined, including the common blue, which has suffered a serious fall in numbers; two species remained stable, including the Orangetip; and only one increased. The trend for the remaining six species is still uncertain, including the much-appreciated Lulworth skipper, beloved of butterfly watchers.

Grassland butterflies make up the majority of butterflies in Europe, with over 250 species out of the more than 400 found in Europe. Others species prefer to colonise woods, wetlands, heaths and other habitats. Chris van Swaay, one of the authors of the report, from the Dutchconservation organisation De Vlinderstichting, said that the same pesticides that affect bees – leading to the EU to ban certain products, at least temporarily – also have an effect on butterflies. “The pesticide problem is especially a problem in the intensive agricultural areas of western Europe,” he said. “In eastern Europe, it is less of a problem.”

Grassland species are also particularly important because so much of EU land is given over to agriculture: if butterflies cannot thrive on farmland, they will suffer dramatic declines. The EEA warned that as a result of intensive practices, with the aggressive use of pesticides and other chemicals, the loss of hedgerows, field margins and other semi-wild areas, as well as the monocultures prevailing in many areas and the rapid turnover of land, many large areas of farmed land are becoming “sterile” in terms of biodiversity.

The EEA, which worked with conservation charities such as Butterfly Conservation Europe to put together the European grassland butterfly indicator, said that in some areas of affluent north-western Europe, agriculture had become so intensive that butterflies are now confined to marginal land such as road and rail verges and even urban gardens, as well as the small proportion of farmland that is managed with environmental aims in mind.

Hans Bruyninckx, executive director of the EEA, 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.”

Perhaps surprisingly, intensive agriculture is not the only threat to butterflies – the abandonment of previously cultivated agricultural land, in central and southern Europe, is also a problem when it results in the neglect of key grassland habitats. When farmland is abandoned, it rapidly turns to scrub, and Europe’s grassland butterfly species have evolved over millennia to live on grassland, including land under old forms of cultivation that were less intensive.

Paul de Zylva, nature campaigner at Friends of the Earth, said: “Bees, butterflies and pollinators in general are facing decline across Europe for the same reasons – loss of habitat, intensive farming and the use of pesticides. Unfortunately the recently reformed Common Agricultural Policy is worse for wildlife than its predecessor. European governments must stop using tax-payers’ money to prop up a farming system that isn’t doing enough to protect nature and biodiversity.”

Source: http://www.theguardian.com/environment/2013/jul/23/grassland-butterflies-europe-population

How the relationship between grasshoppers and spiders affect the carbon cycle

A new study shows that the predator-prey relationship can affect the flow of carbon through an ecosystem. This previously unmeasured influence on the environment may offer a new way of looking at biodiversity management and carbon storage for climate change mitigation.

The study, conducted by researchers at the Yale School of Forestry & Environmental Studies, comes out the week of June 17 in the Proceedings of the National Academy of Sciences. It looks at how the relationship between grasshoppers and spiders — herbivores and predators in the study’s food chain — affects the movement of carbon through a wild grassland. The study shows that predators can cause increased carbon retention in plants in the ecosystem.

“We’re discovering that predators are having important effects on shaping the make-up of ecosystems,” says Oswald Schmitz, professor of ecology and one of the co-authors of the study. “But we’ve not really spent a lot of time measuring how that translates into other functions like nutrient cycling and recycling.”

Carbon, the basic building block of all organic tissue, moves through the food chain at varying speeds depending on whether it’s being consumed or being stored in the bodies of plants. However, this pathway is seldom looked at in terms of specific animal responses like fear from predation.

The researchers manipulated the food chains of grassland ecosystem to see how the levels of carbon would change over time. Schmitz and his team created several controlled ecosystems: Some that contained only native grasses and herbs, others that had plants and an herbivore grasshopper, and some others that had plants and herbivores along with a carnivore spider species — all three tiers of the food chain. In addition, a form of traceable carbon dioxide was injected into sample cages covered with Plexiglas, which allowed the team to track the carbon levels by periodically taking leaf, root, and dead animal samples.

The study found that the presence of spiders drove up the rate of carbon uptake by the plants by about 1.4 times more than when just grasshoppers were present and by 1.2 more times than when no animals were present. It also found that the pattern of carbon storage in the plants changed when both herbivores and carnivores were present. When predators were around, the grasshoppers damaged grasses less because they were afraid of being eaten by the spiders, which caused them to be alert and eat less frequently and eat more herbs instead of grass as a preference. Herbivore consumption can cause plants to reduce their photosynthesis and increase respiration, which lets out carbon in the form of carbon dioxide. The predators reverse this physiological process by reducing herbivore damage to plants, leading to greater carbon uptake and storage.
Moreover, the grasses stored more carbon in their roots after the predators alleviated herbivore impacts on plants. These stress responses, then, caused both the plants and the herbivores to change their behaviors and change the composition of their local environment.

The findings have significance for biodiversity conservation and ecosystem management, according to Schmitz. Although the study was carried out on a small scale, the principles that were learned could inform practices done in much larger areas. Places such as the Alaskan wilderness, for example, are home to animals that have the same predator-and-prey dynamics that drive the carbon cycle, and so protecting lands and storing carbon could be linked at the same time. Appreciating the role of predators is also important now because top predators are declining at rates faster than that of many other species in global trends of biodiversity loss, as the study points out.

“It’s going to force some thinking about the vital roles of animals in regulating carbon,” said Schmitz, noting that the UN’s body of scientific experts who study climate change don’t consider these multiplier effects in their models. “People are arguing for a paradigm change.”

Source: http://environment.yale.edu/news/article/study-predators-affect-the-carbon-cycle/

CONTACT: Oswald Schmitz 203-432-5110 or oswald.schmitz@yale.edu

CITATION: Michael S. Strickland, Dror Hawlena, Aspen Reese, Mark A. Bradford, and Oswald. J. Schmitz. Trophic cascade alters ecosystem carbon exchange. PNAS (2013)

Paper available here: http://bradfordlab.files.wordpress.com/2013/07/strickland-et-al-pnas-2013.pdf