Diversity, Threats, Decline and Conservation of European Stoneflies (Plecoptera, Insecta)

Commonly called stoneflies, Plecoptera is a small order of hemimetabolous insects with more than 3700 species described worldwide. Stoneflies are numerically and ecologically a significant component of the entomofauna of running waters. European Plecoptera shows a very high species richness and endemism, especially in the Mediterranean peninsular countries. Due to increasing pollution of running waters (mainly from sewage, agricultural and industrial waste), habitat fragmentation of streams, the alteration of water courses and their banks, and the narrow ecological requirements of stoneflies, many species are vulnerable or threatened with extinction. In fact, several species have already gone extinct and many others are reduced to small isolated populations. Regarding the conservation status, the order Plecoptera must be considered one of the most threatened animal groups. The risk of disappearance of whole stonefly faunas is here shown by a few examples of endangered Plecoptera from some European countries, especially those of lowland stretches, that are often heavily impacted by pollution. In this respect, also considering the risks reported regarding their conservation, it is astonishing to see how few Plecoptera species, compared with that of birds or mammals or vertebrates in general, are included in the lists of threatened species (cfr. IUCN red data lists, www.redlist.org) despite the widely held view that Plecoptera are highly sensitive to habitat alteration and pollution and that they are considered very good bioindicators of environmental quality. Also, almost no conservation programs have been developed for this insect order. So, provided that any conservation measure should be considered at a catchment scale, the first step to protect freshwater faunas and ecosystems is to fill the gap of knowledge regarding the biodiversity they contain. The priority in this sense is to draw up long-term, funded national plans to train new taxonomic and faunistic experts and to support the expertise where it already exists. The second compulsory step is to lower the anthropogenic pressure on freshwaters by adopting a different politics toward freshwater, that must be considered as a resource.