European regional assessment: Near Threatened (NT)
EU 27 regional assessment: Near Threatened (NT)

Leucorrhinia albifrons previously experienced a very strong decline in its western and southern European range. Based on distribution trends the species now also shows a declining trend in some of the countries that form its strongholds, mainly Finland and Lithuania. L. albifrons is Regionally Extinct in the Netherlands, Slovakia, and Denmark and threatened in Austria, the Czech Republic, France, Germany, Switzerland, and Ukraine. L. albifrons 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 intra-guild predation from thermophilic species, lack of or poor management plans and removal of tree cover essential for the species to escape hot summer temperatures. It has however returned to both Denmark and the Netherlands and shown positive responses to newly created wetlands and habitat restoration. The trends are thus ambiguous, but since the decline is more evident the species has been inferred to have declined by 20% during the past 10 years. The threats and trends are not likely to cease during the next 10 years. L. albifrons is therefore considered to be Near Threatened (A2c+3c+4c) in Europe as well as in the EU27. However, the species' situation could quickly change for the worse if the threats do not cease, so the development should be monitored, and if a change in a more negative direction occurs, a different assessment in the future may be relevant.

L. albifrons is listed in the EU Habitats Directive (Annex IV) and the Bern Convention (Annex II).

L. albifrons is a Palearctic species whose range extends from southwestern France to the Altai Mountains in Asia, but with large gaps in its European distribution. The species is scarce to fairly common and widespread in parts of north-eastern Europe, such as in eastern Germany, southern Sweden, Finland, and the Baltic states. It is probably also widespread in the European part of Russia since it is found in every region of Belarus (Kitel 2022). It had a severe decline in Northwestern Europe in the last century but recently reestablished here and now has several populations in western Germany and The Netherlands (unpublished data). South of the core distribution, apart from an insular area in south-west France, the species is generally rare, with small, fragmented, and isolated populations. The species occurs mainly in lowlands but is known from up to 1,150 meters above sea level in the Jura and 1,400 m in the French Alps (Sahlén and Kalkman 2015).

Throughout the 20th century L. albifrons declined dramatically in western and southern Europe. It disappeared completely from several regions (such as Baden-Württemberg in Germany) and entire countries such as Denmark and the Netherlands. It also decreased in Austria, the Czech Republic, France, Slovakia, Switzerland, and Ukraine. The species remains rare in these countries and most populations are small and isolated. It disappeared from Denmark in 1975 but was found on the Baltic Island of Bornholm in 2018 where a population was confirmed in 2020. Several new populations have been found in the Netherlands and it has re-colonised some sites in Switzerland. It is locally common in Belarus, the Baltic states, Poland, Sweden, Finland, and probably Russia. It has in recent years been found for the first time in some additional Swedish regions, but this is probably more due to an increased knowledge than an expansion of its distribution, but there it has benefitted from newly made ponds and disused gravel pits where very large populations thrive. These sites however might constitute sink populations if the sites are not managed. In Belarus it is found in all regions but is most common in the north. Overall, the species continues to show a declining trend, even in several of the countries that form its strongholds (Billqvist et al. 2019, Kalkman 2010, Kitel 2022, Monnerat et al. 2021, Sahlén and Kalkman 2015).

L. albifrons occurs in different types of clean, shallow, and stagnant water with rich floating vegetation which often consists of water lilies. It prefers nutrient-poor, largely unshaded ponds or bays in lakes in open to semi-open forest environments. The species has benefited from and can have huge populations in newly created wetlands and disused gravel pits where there are no fish. These sites might however in the long run become sink populations when the succession runs its course or if fish is introduced. It can coexist with predatory fish if there is a lot of aquatic vegetation for the larvae to take shelter in. It has a more fragmented distribution in more open settings, where it can be totally absent or found only locally. L. albifrons mainly occurs in the lowlands but up to 1,150 to 1,400 meters in the Jura Plateau and in the Alps (Billqvist et al. 2019, Sahlén and Kalkman 2015).

The male of L. albifrons is easily found as he monitors his territory from water lilies, protruding stones, or straws. From these the male flies erratically back and forth across the water. Females and younger males are found in sunlit, adjacent semi-open environments. They often perch directly on the ground but can just as well be found higher up among bushes and trees. The female lays eggs at the water surface without the company of the male. The larvae live in shallow, vegetation-rich aquatic environments and the larval development normally lasts three years. The emergence takes place almost synchronised, with entire populations leaving the larval stage at the same time. The exuviae are usually left directly adjacent to the water on vegetation a few decimetres up (Billqvist et al. 2019).

L. albifrons have for a long time shown a decline. Some of the previous threats have largely ceased, such as large-scale conversion of peat bog systems for agricultural purposes and pollution by pesticides. Nitrogen deposition in combination with climate change has however meant that primarily nutrient-poor habitats have crossed a threshold, where cascade effects have dramatically affected the sites negatively. These are becoming 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. Higher water temperatures lead to a lower oxygen availability for the larvae which leads to higher mortality, and a 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, Sphagnum is disappearing. When a bog is trenched and dewatered, the peat is oxygenated, the levels of pH changes and metals and nutrients that have previously been bound in the peat are 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 to acquire more land for forestry is turning wetlands 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 the species (De Knijf et al. 2021). It is plausible that 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).

L. albifrons is Red-Listed as Regionally Extinct in the Netherlands, Slovakia, and Denmark and threatened in Austria, the Czech Republic, France, Germany, Switzerland, and Ukraine, but has since been re-established in Denmark, the Netherlands and Switzerland. Based on distribution trends the decline of the species is visible in countries situated in the core of its range, such as Finland and Lithuania. The species is however also found in less nutrient-poor habitats which perhaps can explain why the trend is not as severe as other species connected to nutrient-poor habitats. It has benefited from newly created sites in Sweden and seems to respond well to restoration of peat bogs in Switzerland (Billqvist et al. 2019, Monnerat et al. 2021).

There is no trade or use of this species.

L. albifrons is protected in Norway and listed in the EU Habitats Directive (Annex IV) and the Bern Convention (Annex II). According to this, the distribution within the 27 member states must be mapped and measures should be taken to prevent a further decline. The distribution of this species in most member states is relatively well known. The impact of future climate change and nitrogen deposition is however difficult to estimate. Small fringe populations and isolated occurrences throughout Europe might require immediate attention. To ensure that L. albifrons and other species tied to nutrient-poor habitats survive in the long run, restoration projects might have to be undertaken even in areas where they presently have strong populations. Recent colonisation of some revived peat bogs in the canton of Neuchâtel in Switzerland is encouraging and illustrates the success of the efforts made (Monnerat et al. 2021). The recolonisation of the Netherlands might be a result of the reduction of nitrogen deposition over the last decades.

There is a great need to raise awareness of the dragonfly species associated with nutrient-poor habitats. Fieldwork and studies are needed in general to identify 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 are imperative. A review and analysis of experiences from different restoration projects from different countries is needed. Perhaps more knowledge of 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 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 played a role in the past in keeping the bogs from turning into forests, at least in Scandinavia. Perhaps controlled fires can be a tool in keeping habitats open. It is crucial that water levels are stable over time. A stable water table makes it difficult for encroaching trees and shrubs to survive.

The alien invasive species Pumpkinseed Sunfish (Lepomis gibbosus) originates from eastern North America and have been observed in 24 countries in the EU 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 settlements 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 settlements and 100 m from roads and trails to minimise the chances of introductions (van Kleef et al. 2008, Lettevall 2022).