Scotland's Wildlife – an assessment of biodiversity in 20

Habitats and species that are strongly in decline or especially vulnerable have been
identified for targeted action and are referred to as biodiversity ‘priority’ habitats and
species. Appreciable progress is being made:
4. Of the 39 priority habitats in Scotland, six (15%) were increasing; 11 (28%) were
stable; and 13 (33%) were declining. For the remainder, the trend was unknown
for eight and unclear for one.
5. Of the 197 priority species in Scotland, nine (5%) were increasing / probably
increasing; 65 (33%) were stable / probably stable; and 43 (22%) were declining.
For the remainder, the trend for 14 was unclear and for 63 was unknown.
6. Components of woodland (natural and plantation) diversity sampled during 1995-
1999 were as follows: mean shrub layer cover was 17% in areas with an upper
canopy greater than 5m high; mean number of trees and shrub species (native
and non-native) was 2.2 / 0.25ha; mean volume of deadwood (fallen and
standing) was 4.4 m 3 per ha; total woodland in old-growth stage was 4.8% (oldgrowth
conifers pre-1901; broadleaves pre-1861).
Fluctuating
3. Marine fishing places pressure on marine diversity in a number of ways – by
reducing the abundance and average size of target stocks; in-turn affecting
species that depend on them for food; and physical impacts on seabed
communities. Conservation of commercial fish stocks in the sea is important both
to the economy and to the biodiversity of the seas around Scotland. Eleven key
commercial fish stocks are assessed annually, of which six were reported to be
at full reproductive capacity, i.e. not in danger of collapse, in 2007.
4. Moth abundance among 185 of the commoner species fluctuated between 1975
and 2004. Emerging evidence from the Rothamstead Insect Survey indicates
long-term declines among common moth species in Britain.
Divergent trends
3. Among marine plankton: cool water Calanus finmarchicus had declined to just
8% of its 1958 abundance by 2007; C. helgolandicus, a warmer water species,
increased to 281%; total Calanus abundance declined to 56%; decapod larvae
increased to 117%; phytoplankton abundance increased to 152%.
4. Butterfly trends were stable between 1979 and 2007. Prior to the mid-1980s,
butterfly species that are restricted to specific and often isolated habitats
decreased to 48% of their 1979 abundance, but have been stable since.
Decreased / negative trends
4. Scotland holds internationally important numbers of breeding seabirds. Against a
marked increase since 1970 in the UK, the numbers of breeding seabirds and the
numbers of chicks produced each year had been in decline since 1992, although
appeared to stabilise between 2007 and 2009.
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