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Aesculus hippocastanum

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Taxonomy [top]

Kingdom Phylum Class Order Family
PLANTAE TRACHEOPHYTA MAGNOLIOPSIDA SAPINDALES HIPPOCASTANACEAE

Scientific Name: Aesculus hippocastanum
Species Authority: L.
Common Name/s:
English Horse Chestnut

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2013
Date Assessed: 2013-04-22
Assessor/s: Khela, S.
Reviewer/s: Leaman, D.J., Miller, R.M., Oldfield, S. & Vela, E.
Contributor/s: Aronsson, M., Barreto Caldas, F, Bazos, I. & Turonova, D.
Justification:
Global and European regional assessment: Near Threatened (NT)
EU 27 regional assessment: Near Threatened (NT)

The Horse Chestnut (Aesculus hippocastanum) is a major amenity tree native to Greece and the central Balkan peninsula and planted across Europe. It has been significantly damaged by the leaf miner moth Cameraria ohridella across its entire native and introduced range; the extent of decline caused by infestation is thought to be insignificant, however, compared to the multiple threats the Pindus Mountain mixed forest ecoregion is facing. The species is threatened or likely to be extinct across most of its native range: it is Endangered in Bulgaria (Petrova and Vladimirov 2009, Bulgarian Academy of Sciences and Ministry of Environment and Water 2011), where it remains in two locations, and in Greece, where the declining population is estimated at only 259-407+ trees; it is probably Extinct in Albania. The status of the population in Macedonia is unknown, but given the small range in the country, it is likely to be small. The species occurs in protected areas in Greece and Bulgaria, including national parks/reserves and Natura 2000 sites, although mining, deforestation, tourism development and other threats still impact some national parks.

Given the widespread and varied threats across its native range, the population is almost certainly suffering a continuing decline, though the overall decline has not been quantified. 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, all wild subpopulations are likely smaller than 1000 individuals. At the European level, Aesculus hippocastanum is therefore assessed as Vulnerable C2a(i). It also qualifies for Vulnerable C2a(i) in its EU 27 range (Bulgaria and Greece), where the majority of the native population is found. There is likely to be immigration of propagules into its native range as it has been introduced throughout Europe, so the original category is downlisted to Near Threatened in both Europe and the EU 27.

Recommended conservation measures include controlling the Cameraria ochridella leaf miner, enforcement of protection regimes in nature reserves, regulating human impacts on its habitats, and ex situ cultivation using genetic material from remaining natural populations. Research is needed on the genetic similarity between native and introduced subpopulations, to determine if introduced subpopulations likely to be the source of propagules may indeed help augment declining native populations.

Geographic Range [top]

Range Description: Horse Chestnut (Aesculus hippocastanum) is native to Greece and the central Balkan Peninsula and has been introduced throughout Europe and North America. It was introduced into the UK in the 17th century as an ornamental tree (Lack 2002, RBG Kew accessed 2013, Daws et al. 2004). Its native range includes Albania, Macedonia, Greece and a restricted area in eastern Bulgaria. In Greece, it is restricted to the Pindus mountain range in the regions of Epirus in the northwest, Thessaly in central Greece, Evrytania and Fthiotida in the south. It is found at altitudes up to 1,485 metres (Avtzis et al. 2007). The extent of occurrence (EOO) of its native extant range is estimated at 163,642 km².
Countries:
Native:
Bulgaria; Greece (Greece (mainland)); Macedonia, the former Yugoslav Republic of
Possibly extinct:
Albania
Introduced:
Denmark; Finland; France; Germany; Norway; Portugal; Spain; Sweden; Switzerland; United Kingdom
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In Bulgaria, only one population is known with a relatively high number of individuals and density (Bulgarian Academy of Sciences and Ministry of Environment and Water 2011). This species is rare in Greece (I. Bazos pers. comm. 2013). Between 2001-2004, 37 new scattered locations of natural trees were found in Greece, as isolated and scattered trees, in small or large clusters, and in mixed stands with beech (Fagus sylvatica), dominating an area of 750 ha. The trees were of various ages with diameters from several cm to over 100 cm; importantly, regeneration was observed in almost all locations. The total number of trees observed in the 37 locations was estimated to be between 259-407 or more (22 locations had <5 trees, 1 location had 6-10 trees, 7 locations had 11-20 trees, and 7 had >21 trees); approximately 45 were below a diameter of 25 cm (Avtzis et al. 2007). 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 is probably extinct (Xhuveli et al. 1996). The status of the population in Macedonia is unknown.

Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Horse Chestnut is a long lived monoecious broad-leaved deciduous tree found in deciduous and broad-leaved forests of the Pindus Mountain mixed forests. At present the only natural stands in southeast Europe are glacial relicts in canyon forests (Thalmann et al. 2003). The endemism rate of this region’s mountain ranges can exceed 35% (WWF 2013). This species shows remarkable habitat adaptability, as it occurs in a wide range of altitudes from 228 m to 1,485 m a.s.l. (Avtzis et al. 2007).
Systems: Terrestrial

Threats [top]

Major Threat(s): Horse Chestnut trees have suffered from severe defoliation by alien invasive species of leaf miner moth, Cameraria ohridella, which impairs the growth and survival of trees by reducing the weight of seeds; this may endanger the long term persistence of the species within its native range and throughout Europe. The leaf miner infestation was first observed in the late 1970s in Macedonia. Since 2002 it has been reported in the United Kingdom, Spain, Albania, Turkey, Ukraine, Moldova, Belarus and western Russia (Thalmann et al. 2003, Forestry Commission 2013).

In Bulgaria, Horse Chestnut has a restricted distribution and is threatened by local tourism and pollution, wood extraction and forest fires (Bulgarian Academy of Sciences & Ministry of Environment and Water 2011). 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 Pindus mountain ranges 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 logging has destroyed extensive forest areas, including certain National Parks in Albania. 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 for bauxite in 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).

Conservation Actions [top]

Conservation Actions: This species is listed as Endangered [EN B1ab(ii,iii)+2ab(ii,iii)] in Bulgaria, where it is located within a Natura 2000 site, part of the population is within the Dervisha Managed Nature Reserve, and it is a protected species under the Biodiversity Act (Petrova and Vladimirov 2009, Bulgarian Academy of Sciences & Ministry of Environment and Water 2011). The data derived from the survey in Greece by Avtzis et al. (2007) shows a natural population of 259-407+ trees, which is presumed to be suffering an ongoing declining given current threats. This species can therefore be classified as Endangered C2a(i) in Greece. 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 Pindus Mountains Mixed Forest ecoregion status is classified as Critical/Endangered (WWF 2013), and the population in Albania is probably Extinct (Xhuveli et al. 1996). It is classified as Least Concern in Norway (Artsdatabanken 2010) and Switzerland (Moser et al. 2002), though those populations are introduced.

Recommended conservation measures include controlling the Cameraria ochridella leaf miner, enforcement of protection regimes in nature reserves, regulating human impacts on its habitats, and ex situ cultivation using genetic material from remaining natural populations. Research is needed on the genetic similarity between native and introduced subpopulations, to determine if introduced subpopulations likely to be the source of propagules may indeed help augment declining native populations.

Citation: Khela, S. 2013. Aesculus hippocastanum. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 23 April 2014.
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