Threats to UKOT's biodiversity

On many of the world’s islands, native plants and animals are increasingly under threat, largely as a result of human activities.

The UKOTs are no exception. Early settlers on the islands over-exploited natural resources such as trees which they felled for fuelwood and building timber. Agricultural land clearance devastated large areas of natural vegetation. Goats brought by the settlers relentlessly browsed on shrubs and other plants. Cats, rats and other animals that accompanied the settlers attacked indigenous birds and small native mammals and reptiles. Crop and ornamental plants escaped from fields and gardens and overwhelmed native species.

Under these onslaughts, much of the islands’ unique biodiversity was unable to survive within its original habitats and became extinct or critically endangered in the wild. Of the 49 endemic plant species that occur on St Helena (the most for any UKOT), six have become extinct since people colonized the island; most recently the St Helena olive (Nesiota elliptica) in 2003. Four other species on the island survive only in cultivation; and four have populations of less than 50 in the wild.

Many UKOTs are subject to natural disasters, such as Montserrat's volcanic eruptions or the effects of Hurricane Ivan in the Cayman Islands. Low-lying islands, including the British Indian Ocean Territories, are likely to be among the first places to suffer from sea level rises due to climate change.

Human activities continue to threaten the islands' native plants. Introduced exotic plants oust native species and accidentally imported pests kill plants outright. Land is still cleared for agriculture, but on many of the tropical UKOTs the major issues are the proliferation of tourist resorts, road-building and other developments taking over previously undisturbed areas.

Environmental degradation becomes a vicious circle; when plant cover is removed, soil erosion occurs reducing the likelihood of natural vegetation re-establishing itself. Populations of native plants are too small or are too far apart to sustain themselves without support from conservationists.

Extinction of a genus

The vulnerability of these unique island plants is highlighted by the recent extinction of the St Helena olive (Nesiota elliptica). The endemic genus Nesiota (family Rhamnaceae) was monotypic – that is, it was represented by this single species from St Helena. The last known tree on the island died in 2003, eventually succumbing to a systemic fungus infection following a very dry summer. Sadly, attempts to save the species from extinction, in collaboration with Kew’s Micropropagation Unit, were unsuccessful.

Kew’s DNA Bank holds samples of DNA collected from the island’s last St Helena olive as well as from some seedlings which predeceased it.

Find out more about threats to biodiversity in the UKOTs:

Joint Nature Conservation Committee - Biodiversity: the UK Overseas Territories
UK Overseas Territories Conservation Forum

Weed and pest problems in the UKOTs