Trollsländor i Närke 

DRAGONFLIES IN NÄRKE

The results from the survey of dragonflies in the province of Närke 2016-2020 is presented in this book. The few older records of dragonflies
from the province are also included.
 

The province of Närke covers 4,126 km2 in total. 13% of the area is water. The biggest lakes are Lake Vättern and Lake Hjälmaren. Närke can be divided into four natural geographic regions: The plains, the southern woodland, the western woodlands and Kilsbergen. The plains constitute mainly of cultivated agricultural land. Some big lakes, rivers and channels are located on the plains, for example Lake Kvismaren with more than 40 species of dragonflies. The woodlands and Kilsbergen are dominated by coniferous forests with many lakes, tarn and bogs. At the northern part of Lake Vättern there is an archipelago with cliffs and stony shores.

Before the survey started in 2016, dragonflies were a neglected group of insects in the province. Up to the start of the survey 44 species of dragonflies were reported and 1,100 observations were made in Närke. During the project more than 14,000 observations were made and 53 species of dragonflies observed.

The local entomology club Närkes Insektsförening held the survey of dragonflies in Närke 2016-2020. The survey was performed by volunteers. The participants had various degrees of knowledge, but most had taken part in similar surveys of birds in the region. The project received financial support from the Swedish Environmental Protection Agency, the county administrative board Örerbo and several others.

The province was divided into 65 10x10 km squares according to the coordinate system RT90. Each square functioned as a unit for the survey. Areas within the squares not located within the province was excluded.

 

The survey method was based on previous similar projects in Sweden, that is in Östergötland and Skåne. The participants were requested to survey at least one locality of each of the following types (if they existed in the square):

1. dystrophic lakes and ponds

2. oligotrophic lakes

3. mesotrophic-eutrophic lakes and ponds

4. newly created ponds or disturbed waters

5.  mires dominated by Carex spp.

6. fast streaming waters surrounded by forest

7. slow streaming waters surrounded by agricultural land

 

All types were expected to be visited at least once during each of the following periods: spring-early summer (late May-June), midsummer (July) and late summer (August). During the visit as many species of dragonflies as possible should be counted. All observations were reported on the Swedish internet based observations system Artportalen. The project leader controlled and verified all observations from the region during the project and also older records. For new species or very difficult species documentation in the form of photo were required.

Of the 65 squares 47 were fully surveyed according to the method. A further 11 squares were fully surveyed for at least one of the three periods. The average number of species per square were 33,6. Fourteen squares had 40 or more species, two of them 47 species. These two squares are situated in a transition zone between the plains and the southern woodlands, giving them many different habitats.

At the most species rich locality Åslaholmen in Lake Kvismaren Nature Reserve 40 species have been found. It is a small peninsula in a eutrophic
lake with surrounding reeds, willow and grazed meadows. Several of the recorded species are rare
non-breeding visitors. In the whole reserve a total of 45 species has been recorded.

The most five most observed species are Four- Spotted Chaser Libellula quadrimaculata, Brown Hawker Aeshna grandis, Ruddy Darter Sympetrum sanguineum, Common Spreadwing Lestes sponsa and Downy Emerald Cordulia aenea. The number of observations is to some extent ruled by how easy a species is to identify. Therefor the frequency of the species, the percentage of squares in which the species have been observed, were used to classify how common the species are in Närke. The system is based on studies in Latvia and Östergötland but have been modified for Närke.
 

During the survey four species were observed in all of the squares, giving them a frequency of 100%. The species were Brown Hawker Aeshna grandis, Downy Emerald Cordulia aenea, Brilliant Emerald Somatochlora metallica and Four-spotted Chaser Libellula quadrimaculata. A further nineteen species were classified as very common species in Närke. Five species are classified as sparse in the provinces, including Dark Bluet Coenagrion armatum, Azure Hawker Aeshna caerulea and Green Hawker Aeshna viridis. Three species are classified as very rare,
including Sedling Nehalennia speciosa, Scarce Chaser Libellula fulva and Red-veined Darter Sympetrum fonscolombii.

Compared with the two previous regional surveys in Sweden, in Skåne and Östergötland, Närke has the highest frequency for 41 of the 53 species!
From a European perspective the frequency for Eurasian Baskettail (60%) is unique. Other species with a remarkable high frequency in Närke
include Common Winter Damsel Sympecma fusca, Crescent Bluet Coenagrion lunulatum, Bog Hawker Aeshna subarctica, Hairy Hawker Brachytron pratense, Common Goldenring Cordulegaster boltonii, Keeled Skimmer Orthetrum coerulescens and Yellow-winged Darter Sympetrum flaveolum.
 

The global warming has caused a change in the European dragonfly fauna as several southern species expand northwards. On the other hand,
several northern species are expected to retreat. In Närke three species of dragonflies have actually established themselves during the survey project. First the Small Spreadwing Lestes virens was observed in 2018 at several localities. It has since expanded the range in the province and now become a rather common species. In 2019 the Emperor Dragonfly Anax imperator made a spectacular entrance in Närke and have established itself mainly in the plain area of the province. The last addition to the dragonfly species in Närke was the establishment of the Small
Bluetail Ischnura pumilio in 2020. It was observed in eight squares and at 14 different localities, most newly created roadside ponds. Both the Emperor Dragonfly and the Small Bluetail have dramatically expanded their range northwards in Sweden during the last few years. In the future several other species can be expected to reach Närke, including Lesser Emperor Anax parthenope.

The knowledge about the dragonfly fauna in Närke can be useful in nature conservation and monitoring. Dragonflies have not been given much attention previously in nature monitoring in Sweden. But as dragonflies are excellent indicators of biodiversity and climate change the results of this survey could be very useful for further studies.

Before the survey only 15 localities were known for species included in the Habitats Directive Annex IV. During the survey a further 150 localitites for those species have been added. At five of these localities three out of four species have been reported.

 

The only dragonfly species in Närke which are classified as threatened in Sweden is Sedling Nehalennia speciosa. Measures should be taken to
protect the only locality of the species in the province. As a group the dragonflies will benefit from general nature conservation and environmental protection.

The result of the survey shows that the dragonfly fauna of the province are relatively healthy and at a good status. Even so several species could
be put forward as a species the province´s local governments should regard as having a special responsibility for. These include Dark Bluet
Coenagrion armatum, Sedling Nehalennia speciosa, Baltic Hawker Aeshna serrata, Green Hawker A. viridis, Yellow-spotted Whiteface Leucorrhinia pectoralis and Lilypad Whiteface L. caudalis.