Fróðskaparrit - 01.01.1987, Blaðsíða 54

58
WHEN, HOW, AND WHENCE?
Dispersal by wind is probably on a scale
not generally appreciated. Two modern
examples might illustrate the rapidity and
the large scale of such a process:
1) The volcanic island of Surtsey appear-
ed in 1963 off the southern coast of Ice-
land. In 1965 investigations started on the
island and already by 1968, 70 species of
arthropods, mainly Diptera (43 species)
had been caught there. By 1970 the num-
ber had risen to 158 (of which 105 were
Diptera) (Lindroth 1971, Lindroth et al.
1973). By 1981 the number was 197 (121
Diptera) (Ólafsson 1978, 1982).
2) It has been established that roughly 4.5
billions of insects per day are lost by wind
drift at the height of summer on the North
Sea coast of Germany from a coastal strip
30 km wide (Heydemann 1967). Several
similar examples could be given.
Thus, for a long time (on an ecological
scale) immigration to the North Atlantic is-
lands was by wind (and exceptionally by
other means mentioned above). The in-
creasing diversity and species richness of
the source areas in NW Europe probably
led to this process having increased its im-
portance for the immigration to the islands
over time.
Man’s influence
on the immigration process
A new dimension in the immigration pro-
cess was introduced with the advent of
Man, as discussed in detail for Scandinavia
by Brinck (1966a, b).
During the last 1100 years man has play-
ed an increasing role in changing the biota
of the North Atlantic islands by bringing
anthropochorous species to - in the first
place - the inhabited parts of the islands,
and by habitat perturbations. To identify
possible source areas for these species a
brief account will be given of the communi-
cation pattern between the Faroes and the
surrounding areas; this is because the
Faroes may be considered a representative
case in the North Atlantic.
The first inhabitants in the islands might
have been Irish monks (Dicuil 825). They
possibly cultivated cereals (Avena sativa;
Jóhansen 1979). It is thought that the
monks lived in Mykines (old fields have
been found there); a few other sites are
also probable. It is also not known whether
there was any communication between the
monks and Ireland. They were (probably)
ousted by Norsemen in the 9th century. It
is not known from where the immigrating
Norsemen arrived; recent opinion has it
that they came from Shetland (this at that
time occupied area forming a stepping-
stone during the expansion of the Norse to
the Faroes and Iceland; Nielung 1967-69).
From then until about AD 1050-1100 most
contacts (they were probably few) were
with Norway, although also Shetland, the
Hebrides, possibly Ireland, and on a small
scale Iceland were involved. Most commu-
nications, however, were with Bergen in
Norway (the Faroes were at that time
under Norwegian jurisdiction), where the
tribute to the Norwegian King, which con-
sisted of wool, was landed. This was a more
or less irregular communication, which be-
came regulated in the 12th century. There
is no record of what was brought back to
the Faroes but one can be reasonably sure
ballast was a minor part (scattered reports
indicate that beer, wine, cereals and some-
times perhaps cattle - with the necessary