European regional assessment: Least Concern (LC)
EU 27 regional assessment: Least Concern (LC)

Somatochlora arctica is widespread and common in large parts of its northern range but has a fragmented occurrence throughout the lowlands and in some of the mountain ranges in South and Central Europe. It has for a long time decreased in Central Europe and has been assessed as threatened in Austria, Belgium, Bulgaria, the Czech Republic, Denmark, France, Germany, Ireland, the Netherlands, Poland, Slovakia, Slovenia, Switzerland, and the UK. The species is adversely affected by climate change, which may result in rapid decline and local extinction. This is particularly true of the populations in the Central European lowlands. It is expected that the species will become more restricted to higher altitudes and that its distribution gradually will shift in a northerly direction. Since the species is scarce we have very little significant distribution data. The one that exists seems to indicate that the largest decline was of 10% and occurred in the past, and that this decrease have since levelled off, so the species cannot be assessed as Near Threatened. In some regions, particularly Fennoscandia, Estonia, Lithuania and the European part of Russia, the species is believed to be more widespread than the available data shows today (Boudot and Karjalainen 2015). In some regions it has also been shown repeatedly that the species is easily found through more intense citizen science and targeted projects with visits to suitable habitats. The amount of sites has therefore recently increased and more locations would most probably be found through more monitoring. The species is thus assessed as Least Concern in Europe as well as in the EU 27 Member States. However, local occurrences in the lowlands and in the southern mountains will most probably be increasingly threatened and isolated and this development must be followed closely.

In Europe, the Northern Emerald (Somatochlora arctica) is found mainly from the southwestern Alps in a wide belt to the northeast covering parts of western, northern and eastern Central Europe, Fennoscandia, the Baltic states, Belarus, and the European part of Russia. Isolated occurrences are found at higher elevations in Bulgaria, the Massif Central (France), Ireland, the Pyrenees, Romania, and Scotland. In the northern part of its distribution as well as in the Alps, the Massif Central, and the Vosges Mountains, it is widespread and may be locally common. In other parts, and especially in the smaller and more isolated occurrences, it is usually rare and decreasing (Boudot and Karjalainen 2015).

S. arctica has a wide but disjunct Palaearctic distribution extending from southwest Ireland to the Bering Strait in eastern Russia..

The presence of S. arctica can be difficult to detect because the habitats are missed as they may look unsuitable for dragonflies. It also often occurs in low numbers even on sites with large larval populations, and the males in particular fly quite long distances back and forth between suitable habitats. It has a very fragmented distribution in Europe outside of Finland, Norway, Sweden, and Russia. The EOO seems to show that it is widespread, but it has a very fragmented AOO with large gaps where suitable habitats are missing. In some countries in the east, such as Estonia, Lithuania and the European part of Russia, the species is believed to be more widespread than the available data shows today (Boudot and Karjalainen 2015). In Belarus it is fairly common in the north in the Vitebsk region but also known from sites in the regions of Brest and Homel (Kitel 2022). In some regions, the species has recently been found at several new sites, such as in Sweden, Scotland, and Switzerland, through more intense citizen science and targeted projects with visits to suitable environments. This does not reflect an expansion but merely that S. arctica is easily found when you know where to look (Monnerat et al. 2021, Taylor et al. 2022).

The species occurs in lowlands as well as at higher altitudes, but in the northwestern part of the distribution (e.g. Belgium, the Netherlands, northern Germany) it is more common at lower altitudes, while the opposite prevails in the south, e.g. in the Alps. In Fennoscandia it occurs up to at least 700 meters above sea level, while in Switzerland populations have only been found at altitudes exceeding 680 m above sea level (Monnerat et al. 2021). Particularly recurring and prolonged droughts have adversely affected the species in lowlands throughout Europe, making it locally or regionally extinct, and it is therefore believed to become increasingly dependent on and limited to higher altitudes.

S. arctica is tied to very shallow, often nutrient-poor, aquatic environments, mainly with Sphagnum, such as peat bogs, fens, and marshes. There can be seemingly no open water, but the habitats have a high-water table or quagmires with Sphagnum just below the surface. The female lays eggs in natural, very small hollows as well as dips that are formed by fallen trees, animal trampling, peat excavation and hiking. These small hollows can be found in large open bogs with scattered stands of birch and pine along the edges or situated in small marshes or mires in semi-open forests (Billqvist et al. 2019). In the more isolated, southern range it is confined to higher altitudes, such as in Switzerland, where reproduction never has been confirmed below 680 metres above sea level (Boudot and Karjalainen 2015, Monnerat et al. 2021).

S. arctica can be found along sunlit edge zones on open bogs and where birch and pine grow sparsely adjacent to and on mires. They forage along forest roads at waist height and lower while flying back and forth along the roadside. They can also hunt prey among treetops and if this coincides with emergence they can be seen in the dozens. Mating and perching specimens are often found directly on the ground, unlike most other Somatochlora species. Sometimes single S. arctica are found far from seemingly suitable aquatic environments. The male patrols low and jerky over moss puddles and wet areas on bogs where it can be seen fighting short territory battles with other males. It can be quite a long distance between suitable small waters, and between these the males fly back and forth. The larvae live in wet Sphagnum, often not at depths greater than 15-30 centimetres. The larvae can withstand quite extreme conditions. The shallow water where they live can easily rise above 25° during the summer and in the winter the water freezes. The larvae can survive oxygen levels that can drop to zero, as well as having a very high tolerant degree of wide pH levels. The larval development normally lasts at least two years. The exuviae is left directly on or next to Sphagnum (Billqvist et al. 2019, Ketelaar et al. 2005).

In most of its more southern distribution S. arctica has historically declined through habitat destruction. Only a fraction of suitable environments remain and those that do are constantly under threat and are very fragmented. More recently it is threatened throughout the lowlands of Europe by the deterioration of habitats and diverse aspects of climate change, particularly prolonged and reoccurring droughts. The species occurs in raised bogs that are dependent on the supply and retention of groundwater and rainwater. Both ongoing and previous deforestation as well as drainage in favour of forestry or expansion of agricultural land, make the habitats sensitive to drought. Drainage in combination with nitrogen deposition deteriorates the habitats by changing the nutrient balance to more nutrient-rich conditions which accelerates scrub encroachment, afforestation with birch and pine, and the establishment of reed belts. This displaces the crucial Sphagnum and in just a few years the habitat is replaced by forest. The trees and bushes that become established also take up water, which further dries out the soil and accelerates afforestation (Billqvist et al. 2019, Ketelaar et al. 2005, Rova and Paulsson 2015). In recent decades, the management of habitats has further distorted the balance, often due to plans that are either poor or designed for other species. This can entail deforestation, particularly in the lowlands of Central Europe, which have a negative impact when all the trees adjacent to the habitat are removed. Some trees are necessary for the species to have somewhere to shelter during hot summer days (Ketelaar et al. 2005, De Knijf et al. 2021).

It is nationally threatened in Austria, Belgium, Bulgaria, the Czech Republic, Denmark, France, Germany, Ireland, the Netherlands, Poland, Slovakia, Slovenia, Switzerland, and the UK. It has disappeared locally from many sites and is declining at a local level. In Flanders, for example, it is now limited to about ten sites with a total population size of <250 adults (De Knijf et al. 2021). Even as far north as southern Sweden, the species is gradually declining due to recurring droughts and afforestation of its habitats (Billqvist et al. 2016). Since the species is scarce we have very little significant distribution data. The one that exists however indicates that the largest decline was in the past and that the decrease has levelled off. On the other hand, S. arctica is not in decline in the northernmost part of its range and probably not at higher altitudes in the mountain areas of southern and central Europe. In some of these regions, the species has recently been found at several new sites, such as in Sweden, Switzerland and Scotland. These are believed to be due to more intense citizen science as well as targeted projects with visits to suitable habitats (Monnerat et al. 2021, Taylor et al. 2022). This reflects that the species falls outside the usual scope as its habitats are not visited regularly but mostly by a few who know where the species should be looked for and how. It is therefore highly probable that the species, at least in several regions such as Finland, Norway, Estonia, Lithuania, the European part of Russia, Ukraine, and Sweden, is far more common than the available data shows today.

There is no trade or use of this species.

S. arctica still thrives in the northern parts of its distribution and locally also in its Central European range, but the impact of future climate change and nitrogen deposition is difficult to estimate. The diminishing isolated populations throughout Europe requires immediate local and/or regional attention. There is a great need to raise the awareness of the dragonfly species associated with nutrient-poor habitats. Fieldwork and studies are needed in general to conclude the exact threats and if they are reversible or not. They are often missed and lacking as indicators in peatland restoration projects. These projects often focus on birds and hence management plans and actions taken can be averse to the measures needed to restore habitats for dragonflies. Climate-adaptive management plans of mires is imperative. A review and analysis of experiences from different restoration projects from different countries is needed. Perhaps more knowledge on the exact threats can lead to more appropriate management plans. It should entail keeping scrubs and trees adjacent to sites in open habitats in areas where hot summer days is a threat to the species, but to keep afforestation and scrub encroachment to a minimum in smaller, more shaded sites on higher elevations and in the northern distribution range. It is conceivable that natural fires in Scandinavia played a role in the past in keeping the bogs from turning into forests. Perhaps controlled fires can be a tool in keeping habitats open. It is crucial that water levels are stable over time. If the level is too low for longer periods, vascular plants can establish themselves and out-compete the Sphagnum. Likewise, a too high water level drowns the Sphagnum. A stable water table also makes it difficult for encroaching trees and shrubs to survive.

While there are obvious threats to the species in parts of its European range, it is most likely more widespread than we know today. The species is often missed as it requires a good knowledge of its habitat and ecology to find it. In large parts of its distribution area, especially in the north and in the northeast, more intense citizen science as well as targeted projects with visits to suitable habitats would certainly find many more locations with the species.