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ISLAND DIRECTORY
Islands of St Helena (United Kingdom)
St Helena [917]
Group:
Country: United Kingdom - St Helena Region: South Atlantic
Lat: 15.95º S Long : 5.72º W
Area: 125.5 sq. km Altitude: 819 m
Shoreline: 50.1 km (scale 1:1000000) Coastal Index: 0.3992
Depth to nearest land: 4000 m
Nearest island: 1200 km group: 1200 km
Nearest continent: Africa Distance: 1920 km Isolation Index: 113
ISLAND TYPE: volcanic Natural Protection Indicator: 0
GEOLOGY/SOILS:
Mountainous volcanic island 14-7 million years old, with high coastal
cliffs
ca. 300 m, cut by a few steep-sided valleys; heavy acidic clay soils,
mountain
streams
CLIMATE: dry subtropical 15-32øC, 152 mm, more in hills
CATASTROPHIC THREATS: drought (1984)
Threat Indicator: 1
ECOSYSTEMS: Number of Ecosystems - Terrestrial: 4 Marine: 1
Formerly scrubland and woodland, mostly destroyed by 1650 by heavy
grazing;
surviving Gumwood woodland at Peak Dale (2 ha), some semi-natural
vegetation
on central mountain ridge, pasture, abandoned flax plantations,
replanted
woodland, dry rocky lowland, mountain streams; coastal marine ecosystems
| SPECIES NUMBERS: |
Total |
Endemic |
Threatened (EVRI) |
| Plants |
60 |
50 |
47 |
| Butterflies |
0 |
0 |
0 |
| Land snails |
6 |
0 |
6 |
| Rept/Amphib |
0 |
0 |
0 |
| Land birds |
0 |
1 |
1 |
| Mammals |
0 |
0 |
0 |
SPECIES OF CONSERVATION INTEREST:
Plants:
60 native and 260 introduced species of flowering plants and ferns
50 endemic species: 7 extinct, 23 Endangered, 17 Rare
Pelargonium cotyledonis (RDB)
Trochetiopsis (Trochetia) erythroxylon (St Helena Redwood) endemic,
less
than 10, Endangered
Trochetiopsis melanoxylon, endemic, 2 individuals discovered 1980,
Endangered
Wahlenbergia linifolia, endemic, 5 individuals, Endangered
Nesiota elliptica, endemic, i individual, Endangered
Psida rotundifolia, endemic, 1 individual, Endangered
Commudeudron spurium, endemic, 3 individuals, Endangered
Insects:
157 endemic beetles
Aplothorax burchelli (Ground Beetle) endemic, Endangered
Labidura herculeana (St Helena Earwig) endemic, rediscovered 1965-67,
only
dead remains found since, Endangered
Other invertebrates:
6 molluscs Extinct
Reptiles/Amphibians:
no terrestrial species
Birds:
7 extinct species
Charadrius sanctae-helenae (St Helena Wirebird or Plover) endemic,
upland
habitats at medium elevations, population 200-300 (1986), Rare (RDB)
Marine life:
81 shore fishes including 11 endemic
SPECIES RICHNESS:
Species Richness Indicator - Terrestrial: 0 Marine: 1
poor
ENDEMISM: Terrestrial: Terrestrial Endemism Indicator - Island: 3 Group: 4
high
Marine endemic species: 11
Marine Endemism Indicator - Island: 3 Group: 3
good
SPECIAL FEATURES : Special Features Indicator - Terrestrial: 1 Marine: 0
seabird rookery
INVASIVE SPECIES: Invasive Species Indicator: 4
many introduced species
HUMAN OCCUPATION: Inhabited, discovered 1502
Population: 5499 (1982) Density: 43.8 persons/sq. km
Growth Rate: 0.0%/yr Stable
Major Human Activities: government, agriculture, fishing
HUMAN IMPACTS:
Vegetation devastated by introduced animals and plants, starting with
goats in
16th century; soil badly eroded over 2/3 of island; recent attempts to
reintroduce endemic species; former flax and hemp production, now
abandoned;
livestock grazing
Accessibility: port, airport
Percent population in agr/mining/fishing: 20% Human Threat Indicator: 1
Conservation support: government support, legislation
PROTECTED AREAS: Protected Area Coverage Indicators - Terrestrial: 0 Marine: 0
Number: 4 Area: Terrestrial: 0.0 sq. km Marine: 0 sq. km
Diana's Peak conservation area (nominated for World Heritage)
Old Joan Point conservation area
High Peak conservation area (nominated for World Heritage)
Casons and Hardings National Forest
DATA RELIABILITY: Data Rel. Indicator: 2
HUMAN IMPACT INDEX HI: 6
CONSERVATION IMPORTANCE INDEX CI-Terrestrial: 28 Very high
CI-Marine: 22 High
REFERENCES:
Johnson, Timothy H. 1989. Unpublished ICBP profiles of Atlantic
islands.
Last updated: 15/09/90
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Page last updated: 09/05/10