Recovery and Further Protection of Rheophilic Odonata in the Netherlands and North Rhine- Westphalia
Total Page：16
File Type：pdf, Size：1020Kb
Recovery and further protection of rheophilic Odonata in the Netherlands and North Rhine- Westphalia Robert Ketelaar Introduction urban areas. The water quality of most running waters, However, since 1985, when this negative trend such as springs, brooks and rivers, reached came to a halt, most species have shown a an all time low in the period 1960-1980. Many remarkable recovery (table 1). Some species of the dragonflies and damselflies depending like Gomphus flavipes and G. vulgatissimus are on these habitats declined sharply and many possibly more common than they have ever been species either disappeared (Gomphus flavipes, in the Netherlands and North Rhine-Westphalia. Ophiogomphus cecilia), or almost disappeared This is mainly the effect of an improvement in (Calopteryx virgo, Cordulegaster boltonii). Since water quality, and re-naturalisation projects. then, environmental policies in Germany and the Although recent climatic changes have also Netherlands have resulted in an improvement probably helped. However, a few species have in water quality (see www.milieubalans.nl). In not benefitted from the recent improvement many cases, steps have also been taken to re- of lotic ecosystems, notably Coenagrion naturalise running waters that were canalised on mercuriale, C. boltonii and Ophiogomphus a large scale during agricultural land reforms. cecilia , all of which are still very scarce. This article describes which dragonfly species benefitted from these improvements, and the challenges still ahead for the further recovery of Table 1. Strictly and predominantly rheophilic the Odonata of fluviatile ecosystems. species of The Netherlands and North Rhine- Westphalia. Rheophilic Odonata A number of Odonata can be found in fluviatile Strictly rheophilic habitats. However, most of them are merely Calopteryx splendens species that occasionally reproduce in brooks Calopteryx virgo and rivers. Fifteen species of the odonates in the Netherlands and North Rhine-Westphalia can be Coenagrion mercuriale considered to be more or less rheophilic or lotic C. ornatum (table 1). Of these, eleven can be considered to Gomphus flavipes be restricted to fluviatile systems, while four of G. vulgatissimus them reproduce more or less regularly in a lentic Ophiogomphus cecilia environment. Cordulegaster bidentata Decline and recovery C. boltonii Most species declined rapidly during the 20th Oxygastra curtisii century (table 1). The distribution ranges of all O. coerulescens strictly rheophilic species shrunk (FOR A REVIEW Predominantly rheophilic OF THE DISTRIBUTION OF DRAGONFLIES, SEE NVL, 2002 Erythromma lindenii AND WWW.AK-LIBELLEN-NRW.DE). The main reasons Platycnemis pennipes for the decline of these species are deterioration Orthetrum brunneum of the water quality, canalisation, damming of brooks and river and intensive management Sympetrum pedemontanum aiming at optimal drainage of agricultural and 38 Brachytron 12: 38-49, 2010 39 Figure 1. Male (Photo: R. Ketelaar). Sympetrum pedemontanum Some predominantly rheophilic dragonflies in the Netherlands and only has a few, rather like Sympetrum pedemontanum (figure 1) and scattered populations in NRW (figure 2). The Cercion lindenii also increased in de past years recent records from near Aachen and Osnabrück (MENSING, 2002; VAN EIJK & KETELAAR, 2004). are interesting from a Dutch perspective. Also in Belgium, in the vicinity of Liège/Luik a small Current distribution in the Netherlands and population is present (DE KNIJF ET AL., 2006). North Rhine-Westphalia Although the chance of finding C. bidentata in In preparation for the German-Dutch the Netherlands is very small, these records symposium, data were combined in order show that (small) populations are present just 20 to prepare cross-border distribution maps, kilometres from the border. Vagrants may enter providing useful information on the status the Netherlands, and possibly there are potential of species on both sides of the border. The habitats for reproduction in the southern part of maps show the distribution from 1995-2003. Limburg, especially in very small streams in a The most recent data for the Netherlands is semi-forested environment. presented in BOUWMAN ET AL., 2008. Recent data for North Rhine-Westphalia (NRW) will appear Cordulegaster boltonii in the coming distribution atlas as well as on With tens of populations of Cordulegaster the website of Arbeitskreis Libellen NRW. The boltonii present, the situation in NRW is much current situation of six characteristic species will better than that in the Netherlands, where no now be described in detail. more than six populations are left (figure 3). Some recent (re)discoveries (E.G. KALKMAN & Cordulegaster bidentata KOESE, 2006 AND TERMAAT & GROENENDIJK, 2005) Cordulegaster bidentata is a characteristic do indicate that the species may be recovering species of very small springs. It does not occur very slowly. 38 Brachytron 12: 38-49, 2010 39 Figure 2. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004. Cordulegaster bidentata Figure 3. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004. Cordulegaster boltonii 40 Brachytron 12: 38-49, 2010 41 Figure 4. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004 (Photo: R. Ketelaar). Calopteryx splendens 40 Brachytron 12: 38-49, 2010 41 Figure 5. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004 (Photo: E. Schoppers). Calopteryx virgo 42 Brachytron 12: 38-49, 2010 43 Figure 6. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004 (Photo: E. Schoppers). Gomphus vulgatissimus 42 Brachytron 12: 38-49, 2010 43 Figure 7. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004 (Photo: E. Ruiter). Gomphus �lavipes 44 Brachytron 12: 38-49, 2010 45 Figure 8. The distribution of in The Netherlands and North Rhine-Westphalia in the period 1995-2004 (Photo: R. Manger). Ophiogomphus cecilia 44 Brachytron 12: 38-49, 2010 45 Figure 9. is one of the threatened dragon�lies that is insuf�iciently protected by the Habitat Directive (Photo: R. Manger). Orthetrum coerulescens The records from Naturpark Hohe Mark (not far Netherlands (but not in western regions!), and in from Winterswijk in the Netherlands) do indicate the mountain ranges of NRW (figure 5). that C. boltonii might also be present in the nearby Dutch regions of the Achterhoek and Gomphus vulgatissimus Twente. Gomphus vulgatissimus is a characteristic species of the lower reaches of broader brooks Calopteryx splendens and C. virgo and rivers. Genuine cross-border populations Although C. splendens (figure 4) has never are present along (north to south) the Dinkel, completely disappeared, its expansion in Berkel, Rhine and the Roer/Rur. The Dutch and the past two decades is one of the strongest NRW distribution areas connect very well; the recoveries among the European Odonata. It is range of G. vulgatissimus is still expanding on now a common damselfly of the lower reaches both sides of the border (figure 6). of brooks in both the Netherlands and NRW (figure 4). However, the species distribution is Gomphus flavipes interesting. It is almost absent from the western Most people have special memories about the part of the Netherlands and eastern NRW. In the first time they encountered Gomphus flavipes. Netherlands, this is because there are hardly Because of its ecology, the species almost any flowing waters, while in NRW, most brooks reaches mythical proportions among are cold, shadowy, fast-flowing waters in their odonatologists. Is it its preference for very large upper courses in mountain ranges (e.g. Eifel, rivers, is it the dramatic transition from larva to Westerwald). These are more suitable for C. adult dragonfly, sometimes accented by a walk virgo than for C. spendens. It is not surprising of tens of meters over sandy shores, or is it the that C. virgo shows an almost opposite dancing flight above rough vegetation along the distribution pattern, occurring almost exclusively river banks? Or maybe it has something to do along forested brooks in the southern part of the with its dramatic increase in the last few years. 46 Brachytron 12: 38-49, 2010 47 Its distribution areas in the Netherlands and in catchment areas, and consequently some NRW connect well. The largest populations can brooks suffer from desiccation in a dry summer be found in the Rhine system (with the rivers period. Nederrijn, IJssel and Waal in the Netherlands). The hydromorphology of flowing waters in the There are smaller populations along the Maas Netherland and NRW is anthropogenic, despite and Roer in the Netherlands, and along the many improvements in the past years. Many Weser and Rur in NRW (figure 7). rivers and brooks are canalised and dammed to improve drainage and facilitate shipping. Ophiogomphus cecilia The scarcity of Ophiogomphus cecilia is rather in Two international challenges for the future contrast to the commonness of other rheophilic There are many ways of further improving the dragonflies. This species has always been very ecological quality of flowing waters, as well as scarce in NRW; recent records are from the legal obligations to do so. However, working Rhine, Sieg and Weser, but nowhere are large within the scope of cross-border co-operation, populations present. In the Netherlands, O. societies for dragonfly conservation may be cecilia was locally common in the province of helped in achieving their common objectives Limburg in the first half of the 20th century (NVL, by two major European treaties, namely the 2002), but has since disappeared completely. Habitats Directive and the Water Framework However, populations were recently discovered Directive. Both directives are solid European along the Roer (IN 2000: VAN SCHAIK & GERAEDS, legislation. Especially with regard to lotic 2001) and Swalm (IN 2006: V. VAN SCHAIK, PERS. ecosystems, with their rheophilic flora and fauna, COMM.). The Dutch records indicated that it was the success of this legislation largely depends highly probable that O. cecilia occurred along on international co-operation.