State of Nature report - RSPB

EXTINCTIONS AND COLONISATIONS
You will probably be aware of some of the flora and
fauna that have become extinct in the UK over time,
from striking mammals such as wolves, which were
wiped out by around 1680, to delicate flowers like summer
lady’s tresses, which had disappeared by 1959. However,
keeping a close track on losses in recent years is surprisingly
difficult. Fewer than 50 species have been declared extinct in
the UK since 1970, but this underestimates the true number,
because we know so little about much of our native wildlife.
It is usually easier to detect the arrival of a new species than
the final disappearance of a threatened species.
In better studied groups, we know that 1–2% of species have
been lost from the UK – far too many. Thankfully, very few
UK species have become globally extinct: most can still be
found elsewhere in their range. However, this is not always
the case. One of the most high-profile global extinctions of
a UK species involved the great auk, a large flightless seabird
that once nested in large colonies on our northern coasts.
The species was driven to extinction by the mid-1850s as a
result of centuries of intense human exploitation – it now
provides a powerful lesson in just how much damage
people can cause.
Other lost species include the interrupted brome, a plant
which was last recorded in the wild in Cambridgeshire in
1972 (but later reintroduced to three sites). We can only
hope that other UK wildlife thought to be globally extinct
may yet be found in other places, like the Ivell’s sea anemone,
which was only ever known in one lagoon in Sussex.
Since 1970, hundreds of species previously unknown in the
UK have been found here. Some of these are long-established
members of our native wildlife that had simply eluded
detection before, such as the Alcathoe bat, which was not
found until 2010 1 . Such additions reflect advancements
in our understanding and technology, but they do not tell
us much about what is happening to our flora and fauna.
However, there are a large number of species that are new
arrivals to the UK, some of which have colonised naturally
– for example, over 27 species of moth have colonised
the UK since as recently as 2000, many feeding on
non-native plants 2 .
Not all colonisers have arrived naturally though.
Many new plants, fungi and animals have been imported
– either accidentally or deliberately – from all over the
world. This process started a long time ago with Neolithic
farming; a surprisingly high proportion of the UK’s wild
flowers, including many of our most familiar species such
as the common poppy and snowdrop, are “archaeophytes”
(introduced pre-1500) or “neophytes” (introduced after
1500). Arable land and brownfield sites are often dominated
by these plants. Whilst many of these introductions are
harmless, some non-native species have a devastating
effect on our native wildlife. The number of non-native
species arriving as a result of human actions is increasing,
and their impact on other wildlife is intensifying.
Case study
Non-native crayfish invasion
Signal crayfish
The American signal crayfish was introduced to the UK in
1976. As elsewhere in Europe, its appearance resulted in
a devastating decline in native crayfish, because it carries
a water mould that kills them 3 . It also affected fish stocks
and damaged habitat.
Another five non-native crayfish species are now found in
the wild in the UK, putting further pressure on our native
white-clawed crayfish, which has disappeared from much
of its former range and continues to retreat ahead of the
northward spread of alien species.
Some new species have colonised the UK
naturally, but many species have been
accidentally or deliberately introduced.
Case study
Starry Breck lichen
The rare starry Breck lichen was known in just a few places in
the Breckland of East Anglia. It was last seen around 2001,
and now seems to have disappeared completely 4 . Despite being
fully protected by law, this species probably declined because
of changes in its habitat. Unsuitable grazing and enrichment
from nitrogen pollution are thought to have contributed to its
demise. These factors still threaten other species in Breckland
and throughout the UK – if we do not act, some may go the
same way as the starry Breck lichen.
MalcolmSchuyl (FLPA)
STATE OF NATURE 2013 71