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.