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ISLAND DIRECTORY
Islands of Ascension Island (United Kingdom)
Ascension - including Boatswain-bird Islet [1421]
Group: Ascension Island
Country: United Kingdom - Ascension Island Region: South Atlantic
Lat: 7.95º S Long : 14.37º W
Area: 97.0 sq. km Altitude: 859 m
Depth to nearest land: 4000 m
Nearest island: 1300 km group: 1700 km
Nearest continent: Africa Distance: 1700 km Isolation Index: 119
ISLAND TYPE: volcanic Natural Protection Indicator: 0
GEOLOGY/SOILS:
Volcanic peak with rough lava fields and steep cliffs to south and
southeast,
sloping plain to northwest with sandy beaches; Boatswain-bird Islet is a
steep-sided flat-topped rock of 3 ha, 100 m high, 250 m off the
north-east
coast of Ascension
CLIMATE: dry tropical mean 709 mm rainfall, 10-32øC
ECOSYSTEMS: Number of Ecosystems - Terrestrial: 3 Marine: 3
Forests apparently never presert; barren areas with some grass and
Euphorbia
origanoides; thick scrub of introduced species with Opuntia at higher
elevations; fragments of natural vegetation high on Green Mountain;
beaches;
coastal rock pools, rocky shores with crustose coralline algae and
sponges and
abundant fish
| SPECIES NUMBERS: |
Total |
Endemic |
Threatened (EVRI) |
| Plants |
25 |
10 |
10 |
| Butterflies |
0 |
0 |
0 |
| Land snails |
0 |
0 |
0 |
| Rept/Amphib |
0 |
0 |
0 |
| Land birds |
0 |
1 |
0 |
| Mammals |
0 |
0 |
0 |
SPECIES OF CONSERVATION INTEREST:
Plants:
25 native vascular plants, 6 ferns and 5 flowering plants endemic, 1
extinct, 5 Endangered, 4 Rare
Sporobolus durus (grass) endemic, not seen since 1886, Endangered,
possibly
extinct
Sporobolus caespitosus (grass) endemic, c. 70 tufts remaining high on
Green
Mountain at 730 m, Endangered
Oldenlandia adscensionis (rubiaceous shrub) endemic, not seen since
1889,
probably extinct
Euphorbia origanoides, endemic, in desert to north and west,
declining, Rare
Dryopteris ascensionis, endemic, single plant seen 1976, in moist
ravines,
Endangered
Asplenium ascensionis, endemic, local on Green Mountain, Rare
Xiphopteris ascensionense, endemic, Rare
Pteris adscensionis, endemic, two populations of 10 plants, Endangered
Anogramma ascensionis, endemic, not found 1976, Endangered
Marattia purpurascens (fern) endemic, several hundred on top of Green
Mountain (1976), Rare
endemic lichens and bryophytes
ca. 300 introduced plants
Other invertebrates:
3 spiders and 3 pseudoscorpions probably endemic
Reptiles/Amphibians:
no native terrestrial species
Birds:
landbirds all introduced
major seabird breeding area (most important in South Atlantic)
Fregata aquila (Ascension Frigatebird) endemic, now restricted to
Boatswain-
Bird Islet, exterminated by cats on main island, Rare
Mammals:
no native terrestrial mammals
Marine life:
Procaris ascensionis (shrimp) endemic family, in rock pools
Typhlatya rogersi (shrimp) in rock pools
Chelonia mydas (Green Turtle) Endangered, major rookery, 1650-3000
females
Eretomochelys imbricata (Hawksbill Turtle) Endangered, possibly
breeding
SPECIES RICHNESS:
Species Richness Indicator - Terrestrial: 0 Marine: 2
few
ENDEMISM: Terrestrial: Terrestrial Endemism Indicator - Island: 2 Group: 2
moderate
Marine endemic species: 2
Marine Endemism Indicator - Island: 1 Group: 1
some
SPECIAL FEATURES : Special Features Indicator - Terrestrial: 2 Marine: 2
major seabird rookery major turtle nesting area
coastal pools with endemic shrimp; Boatswain-bird Islet
INVASIVE SPECIES: Invasive Species Indicator: 4
goats, feral cats, many introductions
HUMAN OCCUPATION: Inhabited
Population: 1372 (1983) Density: 14.1 persons/sq. km
Growth Rate: 10.0%/yr Increasing rapidly
Major Human Activities: postage stamps, communications
HUMAN IMPACTS:
Permanently settled in 1815; heavy grazing by goats until exterminated
during
World War II, when occupied by 4,000 American troops. Now small
resident
population and several military/communications installations, population
increased from 1022 in 1980 to 1372 in 1983. One farm to meet local
needs.
Vegetation highly modified by introduced species.
Accessibility: airport
Conservation support: government support, legislation
DATA RELIABILITY: good Data Rel. Indicator: 3
HUMAN IMPACT INDEX HI: 8
CONSERVATION IMPORTANCE INDEX CI-Terrestrial: 13 Moderate
CI-Marine: 14 Moderate
REFERENCES:
Johnson, Timothy H. 1989. Unpublished ICBP profiles of Atlantic
islands.
Last updated: 09/09/90
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Page last updated: 09/05/10