|Scope: Global & Europe|
|Scientific Name:||Aesculus hippocastanum L.|
|Taxonomic Source(s):||The Plant List. 2017. The Plant List. Version 1.1. Available at: http://www.theplantlist.org/.|
|Red List Category & Criteria:||Vulnerable C2a(i) ver 3.1|
|Assessor(s):||Allen, D.J. & Khela, S.|
|Reviewer(s):||Matevski, V., Petrova, A. & Shuka, L.|
|Contributor(s):||Aronsson, M., Caldas, F.B., Bazos, I., Turonova, D., Shuka, L., Matevski, V., Dimopoulos, P. & Petrova, A.|
Global and European regional assessment: Vulnerable (VU)
EU 28 regional assessment: Vulnerable (VU)
The Horse Chestnut (Aesculus hippocastanum) is a major amenity tree in Europe that is native to the central, southern and eastern Balkan Peninsula, but has been very widely planted as an amenity tree across Europe. Populations have been significantly damaged by the leafminer moth Cameraria ohridella across both its native and introduced range; the extent of decline caused by infestation is not thought to be significant, however, compared to the multiple threats the Pindos Mountain mixed forest ecoregion is facing. The species has been assessed as threatened across most of its native range: it is Endangered in Bulgaria (Evstatieva 2011), where it is found in the eastern Balkan Range, and Critically Endangered in Albania. In Greece, the declining population is estimated at less than 1,500 adult trees, whilst in Albania, the population does not exceed c.500 individuals, whilst in FYR Macedonia the population size is not known but exceeds 100 individuals. The species is known to occur in protected areas in Albania, Greece and Bulgaria, including national parks/reserves and Natura 2000 sites, although deforestation, exploitation, mining, tourism development and other threats still impact some protected areas. Populations are considered to be severely fragmented.
Given the widespread and varied threats across its native range, the population is almost certainly suffering a continuing decline. Although the total population size across its native range has not been estimated, it is unlikely to consist of more than 10,000 mature individuals and may even be fewer than 2,500 mature individuals. Based on the subpopulation structure in Greece and the ongoing threats across its range, each wild subpopulations are likely to contain very much fewer than 1,000 individuals. At the global level, the species is therefore assessed as Vulnerable (C2a(i)). It also qualifies for Vulnerable (C2a(i)) in its EU 28 range (Bulgaria and Greece), where the majority of the native population is found.
Recommended conservation measures include research and control of the Cameraria ohridella leafminer, enforcement of protection regimes in nature reserves, regulating human impacts on its habitats, and ex situ cultivation using genetic material from remaining natural populations.
|Previously published Red List assessments:|
|Range Description:||This species is native to mainland Greece, the central and eastern Balkan Peninsula, and eastern Bulgaria. Its native range includes Albania, western FYR Macedonia (Galichica National Park: Galichica Mt.-Zli Dol; Mavrovo National Park - Bistra Mt., Suv Dol, Jama, Garska Reka, Mala Reka; the gorge of Crn Drim River-v. Globochica, v. Lukovo (Micevski and Matevski 2005), Greece, and a restricted area in eastern Bulgaria (the Preslavska Mountains, part of the East Balkan Range; Evstatieva 2011, Gussev and Vulchev 2015). In Greece, the species is found in two large but fragmented areas of distribution; the first is through the Pindos Mountain range from the northwestern part down to Sterea Ellas, and the second in East Central Greece (Olimbos, Ossa and Pelion mountains) (Dimopoulos et al. 2013, I. Bazos pers. comm. 2017). In Albania the species is observed in scattered subpopulations. The extent of occurrence (EOO) of its native extant range is estimated at 150,000-160,000 km2. The species has been very widely introduced, including throughout the European region and North America.|
Native:Albania; Bulgaria; Greece (Greece (mainland)); Macedonia, the former Yugoslav Republic of
Introduced:Denmark; Finland; France (France (mainland)); Germany; Norway; Portugal (Portugal (mainland)); Spain (Spain (mainland)); Sweden; Switzerland; United Kingdom (Great Britain, Northern Ireland)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is rare in Greece (I. Bazos pers. comm. 2013). Tsiroukis (2008) reported less than 1,500 mature individuals in Greece within 98 subpopulations surveyed, with subpopulations ranging in size from 1 to 135 mature individuals, however contrary to Avtzis et al. (2007), Tsiroukis reports satisfactory regeneration in only 6% of the population, with 62% showing no regeneration.|
Given the threats currently impacting the species in Greece, this population can be presumed to be declining, though evidence of regeneration is a positive sign. The population in Albania was considered probably extinct (Xhuveli et al. 1996), however, this is not the case, and populations are considered to be stable following declines during the period 1992-2010, however the population consists of not more than 500 individuals, with most subpopulations containing 10-15 individuals, with none containing more than 50 individuals (L. Shuka pers. comm. 2017). In FYR Macedonia the population size is not accurately determined but certainly exceeds 100 individuals (V. Matevski pers. comm. 2017). The largest population in FYR Macedonia is present in the Bistra National Park (Garska Reka and Suv Dol), however, the impoundment of the water of Garska River and the Mala Reka valley for a planned hydroelectric power plant Boshkov Most, would have a negative effect on the conservation of the population of Aesculus hippocastanum at this locality if the dam was constructed. In Bulgaria, only one population is known with a relatively high number of individuals and density (Evstatieva 2011).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The species is a long lived monoecious broad-leaved deciduous tree found in deciduous and broad-leaved forests, although it sometimes grows as a large shrub on rocky slopes (L. Shuka pers. comm. 2017). The only natural stands in southeast Europe are glacial relicts in canyon forests (Thalmann et al. 2003, Tsiroukis 2008). In Albania, the species is found on limestone rocky slopes of valleys and canyons, with the largest subpopulations found in Oriental Hornbeam forests (L. Shuka pers. comm. 2017). This species occurs from 228 m to 1,485 m a.s.l. (Avtzis et al. 2007) in Greece, and to c.1,600 m in Albania (L. Shuka pers. comm. 2017).|
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Use and Trade:||The tree is commonly planted for ornamental and landscape features in parks and urban areas. It is of economic importance for wood production and medicinally the major active substance Aescin (or escin) extracted from the seeds is used for upset stomachs (Avtzis et al. 2007). This tree is used in homeopathic medicine as a tincture (abc Homeopathy 2001-2009). The seeds (called 'conkers') are popular in children's games and the seeds are processed by the pharmaceutical industry to produce treatments for vascular problems such as varicose veins and haemorrhoids. The unprocessed seeds are poisonous and a decoction of the bark and leaves is used in Albanian folk medicine to treat circulatory problems. The species is also used in cosmetic skin-care products (Wilkinson and Brown 1999).|
Natural and cultivated Horse Chestnut trees have been impacted by severe defoliation by the alien invasive species of leafminer moth, Cameraria ohridella Deschka & Dimić, 1986, which impairs the growth and survival of trees by reducing seed weight, germination rates and seedling vigour, and this may endanger the long term persistence of the species within its introduced range (Percival et al. 2011). The leafminer infestation was first observed in the late 1970s in FYR Macedonia, from where the moth was described. Since 2002 the moth has been reported in Albania and Bulgaria (Gussev and Vulchev 2015) within its native range, and in introduced populations elsewhere, including in the United Kingdom, Spain, Turkey, Ukraine, Moldova, Belarus and western Russia (Thalmann et al. 2003, Forestry Commission 2013). Cameraria ohridella was described from Ohrid Lake in FYR Macedonia. The origin of the leafminer is uncertain (Kenis et al. 2005); Grabenweger et al. (2005) suggested that its biology and ecology, and the absence of effective control by natural predators within the region, indicate that it may be of exotic origin, however recent molecular study and review of herbarium collections suggest that the species originates from remote natural stands of Aesculus hippocastanum in the Balkan Mountains of Macedonia, Albania and Greece and that it moved to urban areas in these countries in the second half of the 20th century (CABI 2017). Grabenweger et al. (2005) visited known natural stands of Aesculus hippocastanum in Greece and Bulgaria and found the leafminer moth present 'in abundance' at all sites.
In Bulgaria, Horse Chestnut has a restricted distribution and was threatened by forest fires in the past; cutting of the forest of the adjacent areas that caused changes to the local microclimate; infestation of Cameraria ohridella, local tourism activities and pollution, wood extraction and forest fires (Evstatieva 2011, Gussev and Vulchev 2015). In recent years, Greece has been subject to increased deforestation and forest fires, which could occur within protected areas; rapid changes in the landscape through overgrazing, firewood collection and agriculture are accelerated with population growth, socio-economic and political instability, leading to deforestation and soil erosion. However, the Pindos Mountains still host significant old-growth forest stands, mainly related to inaccessible high mountain slopes and canyons. Human impact is high in this ecoregion, particularly in Albania where illegal felling (for fuelwood and construction timber) and fires impacted extensive forest areas in the past (L. Shuka pers. comm. 2017), including some National Parks. Mountain tourism, ski facilities and road construction are strongly degrading huge mountain forest ecosystems due to soil erosion and clear cutting operations, which have provoked significant landslides and the collapse of large mountain slopes. Mining, particularly of bauxite in the Iti National Park, is a direct and indirect threat. Related activities threaten certain protected areas and their endangered habitats and species. Overgrazing and over-collection of plants continue to threaten the region's ecosystems (WWF 2013).
Tsiroukis (2008) cites the collection of seed for pharmaceutical (and cosmetic) use as a threat in Greece, whilst in Bulgaria seed is primarily collcted form cultivated sources.
This species is listed as Endangered (B1ab(ii,iii)+2ab(ii,iii)) in Bulgaria, where part of the population occurs within a Natura 2000 site and within the Dervisha Managed Nature Reserve, and it is a protected species under the Biodiversity Act (Petrova and Vladimirov 2009, Evstatieva 2011). In addition, the habitat (29G1 Forests of Horse chestnut (Aesculus hippocastanum)) has been assessed as Critically Endangered (Gussev and Vulchev 2015). In Albania, the species was assessed as Critically Endangered (CR A1a) (MEA 2013). Data derived from the survey in Greece by Tsiroukis (2008) showed a natural population less than 1,500 mature trees, which is presumed to be undergoing a continuing decline given current threats. This species' mixed forest habitat is found within National Parks in Greece, where under half the natural population is included in reserves and 18 of 37 locations are within the boundaries of the Natura 2000 network of protected areas, managed by the Greek Forest Service and Ministry of the Environment. Protection and conservation of the southern populations should be a primary concern for conservation. The Pindos Mountains Mixed Forest ecoregion status is classified as Critical/Endangered (WWF 2013), and Tsiroukis (2008) proposed that the species would qualify as Critically Endangered for Greece (B2ab(iv,v)). The species occurs in three protected areas in FYR Macedonia; the National Park Mavrovo, National Park Galichica, and Bistra National Park
Recommended conservation measures include control of and further research into Cameraria ohridella, enforcement of protection regimes in nature reserves, regulating human impacts on its habitats, and ex situ cultivation using genetic material from remaining natural populations.
|Errata reason:||An errata assessment was created in order to correct a minor typographic error in the Rationale text.|
|Citation:||Allen, D.J. & Khela, S. 2017. Aesculus hippocastanum (errata version published in 2018). The IUCN Red List of Threatened Species 2017: e.T202914A122961065.Downloaded on 17 August 2018.|
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