European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Vulnerable (VU)

Leucorrhinia rubicunda was previously common and abundant in the north as well as in large parts of Central Europe without signs to indicate that a strong decline was taking place, except for some southern populations. The species has however been declining at least locally for decades. The species is Regionally Extinct in Luxembourg and it is probably gone from eastern France and Switzerland. It is assessed as threatened in Austria, Belgium, the Czech Republic, Germany, and Slovakia. It shows negative distribution trends in countries such as Czechia, Denmark, Flanders, Lithuania, the Netherlands and has vanished from large parts of Germany. L. rubicunda faces threats due to a combination of factors that are amplified by ongoing climate change. These factors involve eutrophication through nitrogen deposition, recurrent droughts, increased rate of afforestation and scrub encroachment, lower oxygen availability through higher water temperatures, increased predation from thermophilic species and alien invasive fish, lack of or poor management plans and removal of tree cover essential for the species to escape hot summer temperatures. Based on occupancy modelling and distribution trends the species have been inferred to have declined by 15-35% during the past 10 years and the threats are not likely to cease during the next 10 years. L. rubicunda is hence considered to be Vulnerable (A2c+3c) in Europe as well as in the EU27.

The range of L. rubicunda is mainly found north of the 49th parallel, in Europe from north-eastern France to the Ural Mountains and further east to the Altai Mountains in Asia. It is quite common and widespread in Finland, Sweden, the Baltic states and probably the European part of Russia. South of this core range the species is gradually becoming rarer with an increasingly fragmented range in Central Europe, and especially the southernmost populations have been declining for a long time. Most of the latter populations are small, isolated, and confined to mountains (Kalkman 2010, Kalkman and Lohr 2015).

L. rubicunda is rather common in suitable nutrient-poor habitats in the boreal zone of Finland, Norway, Sweden, and probably also in Russia and the Baltic states. It appears to be stable in Finland and Sweden but has a more scattered distribution in Denmark, where it has disappeared from many sites. The latter mirrors the rest of its European distribution where it has a more fragmented distribution and is declining, especially along the fringes of its range. The species is Regionally Extinct in Luxembourg and probably gone from eastern France and Switzerland, and has disappeared from large parts of Germany (Bowler et al. 2021). It is threatened in Austria, Belgium, the Czech Republic, Germany, and Slovakia. It shows severely negative distribution trends in the Czech Republic, Belgium, Denmark, Germany, Lithuania, and the Netherlands.

L. rubicunda occurs mainly in acidic and very to moderately nutrient-poor, stagnant water in semi-closed forest environments. The habitats are often fish-free, at least 50 cm deep, lined with Sphagnum and the pH value is usually between 3.5 and 5.5. Moderately acidic conditions are favourable because most predatory fish do not thrive in these conditions. Its habitat overlaps with L. dubia and they therefore often occur side by side. However, L. rubicunda is also found more often in environments without Sphagnum, such as in shallow lakes with reed belts and along slow-flowing rivers and in calm and vegetated bays in large lakes. These populations tend to be smaller and more short-lived and are mainly found near areas of strong populations (Billqvist et al. 2019, Termaat and Groenendijk 2006).

L. rubicunda is one of the earliest dragonflies to emerge during spring. The male has lookout posts in and along the waters’ edge. Adjacent to the breeding sites L. rubicunda is found very low, usually on the ground where it sunbathes in exposed places. Foraging occurs along forest roads, in sunny clearings and similar open, warm areas. The females lay their eggs during flight. The larvae are found mainly in floating vegetation and in and between dense aquatic vegetation. They are vulnerable to fish predation but tolerate the presence of moderate fish populations better than the closely related L. dubia. The larval life cycle normally lasts two years. The exuviae are usually found directly adjacent to the water on straws a few decimetres up from the ground or the water’s edge (Billqvist et al. 2019).

The species has been in decline for decades, but as it is widespread and still common in large parts of northern Europe, the decline has not been perceived as serious on a European scale. In the past, the destruction of its habitats (such as peat extraction) and the large-scale introduction of drainage systems have been the biggest threats. Since these threats mostly have ceased, they have been perceived as reversible (Kalkman 2010), but nitrogen deposition in combination with climate change has meant that the habitats have crossed a threshold, where cascade effects have dramatically affected the sites negatively. This has been going on for a long time but slowly and when it really took hold, it had serious consequences for the species that are linked to nutrient-poor environments. This has resulted in significant declines for L. rubicunda in recent years.

The habitat has become less and less nutrient-poor, which has meant that the larvae suffer from an increased intra-guild predation from thermophilic species that previously were rare or did not occur in these environments, such as Crocothemis erythraea. Higher water temperatures lead to a lower oxygen availability for the larvae which leads to higher mortality, change in larval development and flight period. In the past, the species has been able to re-immigrate to places that have dried out during certain years, but as droughts return more and more often and more severely, there are fewer suitable sites to disperse to and from. The drought also fundamentally affects the wetland's plant communities since, for example, the crucial Sphagnum is disappearing. When a bog is trenched and dewatered, the peat is oxygenated, the levels of pH changes and as a consequence various substances such as metals and nutrients that have previously been bound in the peat, is released into the water (Billqvist et al. 2019, Rova and Paulsson 2015).

With more nutrients and lower water levels there is also an accelerated and ongoing afforestation which is occurring on a large scale, at least in Scandinavia. Trenching of bogs to acquire more land for forestry as well as old trenches that drain the bogs long after peat extraction has been abandoned is turning the former open mires into forest. When water levels are lowered it paves the way for the establishment of trees and shrubs, which in turn is increased by nitrogen deposition and climate change. The trees and shrubs that establish themselves also absorb water, which dries out the soil further and accelerates the afforestation (Rova and Paulsson 2015). In the southern part of the species' distribution, the opposite can be a problem, when tree cover essential for the species to escape hot summer temperatures is removed. This is often due to a lack of management plans or plans that are either poor or not designed for cold-adapted species (De Knijf et al. 2021). The Species Temperature Index (STI) shows that a decline or expansion can be explained by a change in a species preferred temperature (Termaat et al. 2019). For L. rubicunda this implies that higher mean temperatures alone can explain a rapid decline.

The decline is further accelerated by the presence of non-native invasive fish species such as Pumpkinseed Sunfish (Lepomis gibbosus) in an aquatic environment that is naturally fishless. Those invasive species do not only predate on the larvae but their presence leads to changes in behaviour (e.g. less active foraging) and finally to a longer larval development increasing the mortality rate. In some regions, such as the Netherlands, the Pumpkinseed Sunfish is particularly abundant in moorland pools i.e., habitats for oligotrophic dragonfly species. Studies show that the average macroinvertebrate abundance in ponds with Pumpkinseed Sunfish was 83% lower than in ponds without the fish, making Pumpkinseed Sunfish predation a plausible explanation for the apparent decline of these taxa in the presence of the alien fish (van Kleef et al. 2008).

Populations in lowlands and especially those along the fringes of the distribution range are most severely threatened and climate change is likely making those sites unsuitable for the species, now or in the near future. Most worrying however is that based on distribution trends the decline of the species is also clearly visible in countries situated in the core of its range, such as Denmark, Germany, and Lithuania. The species is Regionally Extinct in Luxembourg and probably gone from eastern France and Switzerland, and from large parts of Germany. It is assessed as threatened in Austria, Belgium, the Czech Republic, Germany, and Slovakia. It shows severely negative distribution trends in Denmark, Germany, Lithuania, and the Netherlands. In Flanders it has long been in decline, and this has become more severe with more than 27% during the period 2010-2020 (De Knijf et al. 2021).

There is no trade or use of this species.

L. rubicunda 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 fringe populations and isolated occurrences throughout Europe require immediate attention. To ensure that L. rubicunda and other cold-adapted species survive in the long run, restoration projects might have to be undertaken even in areas where they presently have strong populations. 

There is a great need to raise the awareness of the dragonfly species associated with nutrient-poor habitats. Fieldwork and studies are needed on cold-adapted species 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 are 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, at least 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 water level that is too high drowns the Sphagnum. A stable water table also makes it difficult for encroaching trees and shrubs to survive.

The alien invasive species Pumpkinseed Sunfish (Lepomis gibbosus) originates from eastern North America and has been observed in 24 countries in Europe and is established in all but one of these. It is estimated to be able to establish populations in all European countries and also in colder areas, as demonstrated by its wide range in Ukraine. It has also been found in the Nordic region, where many oligotrophic dragonfly species have their strongholds. It does not yet pose a threat to them there, but further climate change might change that. Humans have been shown to be the main vector in the spread of Pumpkinseed Sunfish and the probability of introduction is related to pond availability. For nature conservation planning, it is wise to choose basins that are least susceptible to introductions. Therefore, it is important to assess the availability of ponds and thus the vulnerability to introductions. Isolated waters with Pumpkinseed Sunfish are more often located near human settlement and infrastructure than would be expected based on randomly selected sites. This suggests that planning conservation practices are best done at distances greater than 250 m from human settlement and 100 m from roads and trails to minimise the chances of introductions (van Kleef et al. 2008, Lettevall 2022).