De Levende Natuur nummer 6 van 2019 (English summary)

Verdigris navel profits from nature restoration 

M. J. van Tweel, M. W. Boomsluiter 

Verdigris navel (Omphalina chlorocyanea) is worldwide a very rare fungus. Since 2000 the distribution of this species has increased exponentially in The Netherlands. It is now a common species in open heathland-vegetations mostly dominated with haircap (Polytrichum spec.). Verdigris navel has profited of nature restoration projects in heathlands in which the top soil has been removed. It appears on average after 2 years after removal of the top soil and disappears after on average 5 years. It is a typical pioneer-species. Recently the restoration of heathlands has changed. The restored places are smaller, are limed and seeded with hay from rich heath-vegetations. This change may prove to have negative effects on verdigris navel. 

The Lilypad whiteface has unexpectedly returned to the Netherlands 

R.H.A. van Grunsven 

Lilypad whiteface disappeared from the Netherlands in 1970. In 2006 two individuals were seen in Limburg but no population was established. In 2009 another individual was found in the Weerribben and the next year a teneral animal was seen here. From that moment, the population in the Weerribben and the adjacent Wieden increased rapidly. In 2018 it was one of the most abundant dragonflies in these areas. In that year it was also found in other areas in the Netherlands and managed to establish new populations. This rapid increase is likely a result of increased water quality and the resulting recovery of aquatic vegetation. 

Recolonization of habitat by beech and pine marten in the Netherlands since 1960 

S.A. Westra, D.L. Bekker and V. Dijkstra 

After hunting was prohibited in the Netherlands in 1948, pine marten (Martes martes) and beech marten (M. foina) increased their dispersion considerably, with a real expansion starting in the seventies and eighties. Pine marten, as a forest species, profited by increased forestation and the aging of existing forests. It also seems that the species has grown more tolerant to human presence. Beech marten, as a species of small-scaled landscapes, and always been present in the surroundings of humans, started its expansion in the east of the country. As a generalist and opportunistic feeder it has been able to use all kinds of possibilities within the human environment. By some beech marten is even considered to have become a new ecotype. Nowadays their increased presence is starting to become a nuisance for some. Using attics as latrines is a problem, but chewing car cabling has become such an issue that some people are opting for lifting the protected status of the species. 

The recent spread of Myriocoleopsis minutissima in the Netherlands 

A. van der Pluijm 

Until 1980 on the European continent the Mediterranean- Atlantic Myriocoleopsis minutissima was found as far north as Normandy in France. Since then it has spread northward along the coast of NW-France (1983), W-Belgium (1985), the southwest (1987) and northwest (1995) of the Netherlands, and Denmark (2016). In the Netherlands this liverwort is a pioneer epiphyte, mainly found on the lower branches of trees and shrubs with mostly nutrient rich bark, in moist, sheltered forests and thickets. Until 2005 M. minutissima was found in 11 grid squares of 5x5 km2, and was at each station only present on a single tree. Afterwards, also local populations on tens or even hundreds of trees were found. In the past decade the species has spread very rapidly, from 42 grid squares in 2009 to 268 in 2019, some 16% of the total number. Climate change is probably the major cause for the recent spread. The shift of its range northwards along the coast, and the strong expansion in the lowlands of the Netherlands and Belgium suggest that especially mild winters are favourable. The species may also have benefited from lower levels of air pollution by SO2 and an increase in the area of nutrient rich forests in the Netherlands. The accelerated expansion in the recent decade may be a result of population dynamics with diaspores no longer being a limiting factor. 

Normandina pulchella 

L.B. Sparrius 

The epiphytic lichen Normandina pulchella occurred as a rare species in the coastal region up to the 1950s. It usually grew on liverworts. Until 2000 the species declined much as a result of air pollution and Dutch Elm Disease. From 2004 onwards, the species started to return at an increasing pace. Nowadays, it is a common species found during most field trips. Compared to the 1950s, the species range now covers the entire country. It often grows on thin algal mats on eutrophicated bark instead of liverworts. The shift in range can be explained by a combination of changes in air pollution and climate change. 

Nudibranch biodiversity dynamics in The Netherlands related to climate change 

Peter H. van Bragt 

The analyzes of observations of Nudibranchs in Dutch coastal waters over more than the last three decades indicate that current climate changes have most likely a positive effect on the biodiversity of Nudibranchs in the Dutch coastal waters. This is especially applicable to the populations in the southwestern Delta region. Some previously irregularly occurring species have settled permanently, sometimes even in very large numbers. Although more new species have not yet settled here permanently, more and more potential climate shifters are being found as new species on the Dutch biodiversity list. There are not yet examples of climate shifters that, by pushing up north, have disappeared from our coastal waters. For the Dutch Delta region, there is only one species known that possibly and partly due to the long-term higher seawater temperatures is losing its specific food source and has therefore more or less locally disappeared. There are not yet Nudibranch species known from Dutch coastal waters that are migrating north together with their climate shifting specific food species. 

Fast plants choose the highway 

B. Ode 

Dutch road verges, especially those of motorways and especially the zone close to the asphalt and inside the central reservation prove to be places with a special native European flora. These data mainly stem from botanists, observing these plants from a driving car. Due to the saline conditions in relation to salt spraying in winter conditions, several Dutch native plants from coastal areas (e.g. Cochlearia danica) may occur in large quantities. Also, some species (e.g. Atriplex micrantha) from saline steppe conditions have found their way through Europe to German and Dutch motorways. Furthermore, some plant species (e.g. Dittrichia graveolens and Conium maculatum) seem to profit from both hot conditions near the asphalt combined with climate change. Some of the motorway populations exceed by far the original population size of the species in natural habitats. Especially the central reservation seems to be favourable for these partly unexpected species, due to the extreme conditions and less frequent mowing of this zone. From a Dutch perspective it seems probable that new species may arrive through German motorways, so we should monitor botanical developments there. 

Comeback of the otter in the Netherlands 

A.T. Kuiters, G.A. de Groot, Ing. D.R. Lammertsma, H.A.H. Jansman, J. Bovenschen, M. Laar.

 Between the 1960s and 1980s the otter population in the Netherlands showed a severe decline due to an increase of traffic collisions related to an increase in road density and traffic intensity. Additional causes of decline were an increase in drowning victims in fish traps and a severe deterioration in water quality. In 1988 the otter was formally declared extinct in our country. A recovery plan of the Ministry of Agriculture and Fisheries was launched in 1989 with the ambition to offer a perspective for the recovery and preservation of a viable otter population by improving former habitats. After thirteen years, during which a variety of measures was taken to reduce the risk of traffic collision, prevent drowning in fish traps and improve water quality, the first otters from wild populations elsewhere in Europe were released in 2002 in peat wetlands in the northern part of Overijssel and the southwest of Friesland. Now, 17 years later, with an estimated population size of over 350 individuals, the reintroduction of the otter can obviously be called a success story. Yearly mortality by traffic collision, however, is estimated over 25% of total population size. This is still too high and requires the constant attention of road authorities to take mitigation measures, as does the drowning of otters in illegal fish traps.  

Badgers hardly disturbed by major highway reconstruction 

L.E.S., Bas Bakker, J.L. Mulder, V.J.T. Loehr 

Before and during the reconstruction of highway A27 in the centre of The Netherlands, badgers along the highway were studied using wildlife cameras and GPS-collars. We could not detect effects of the reconstruction on badger territories and the use of setts, even when a new, tarred bike path was constructed at less than ten meters distance of a sett. Some individuals reduced foraging at less than 100 meters from the road during and shortly after nights with active reconstruction works, but others did not. Existing badger tunnels under the road were extended in length, and were used again by badgers within days or weeks. These long (up to 65 m) tunnels were not essential for the daily life of the badgers, but were only used for social reasons (i.e., “sniffing out” the neighbours). We conclude that diurnal highway reconstructions do not need mitigation measures for badger territories or setts at >20 m distance, other than avoiding direct damage (e.g., sett collapse, road mortality). Nocturnal highway reconstructions can be carried out at > 100 m from setts without affecting territories and setts. We recommend to assess with contemporary techniques how badgers use the landscape (including defragmentation measures), before undertaking road (re)constructions in regions with badgers.