Náttúrufræðingurinn - 2010, Blaðsíða 23

23
Tímarit Hins íslenska náttúrufræðifélags
um jörðina sem heild og stuðla að
varðveislu sem flestra tegunda og
stofna á heimsvísu. Það eru léleg
skipti að auka tegundafjölbreytni
svæðis með tegundum sem eru
algengar á heimsvísu á kostnað teg-
unda sem eru sjaldgæfar eða gætu
orðið sjaldgæfar í nánustu framtíð,
en slíkt getur leitt til hnattrænnar
einsleitni.1,68 Þá er fátt sem bendir
til þess að heildarfjöldi einstaklinga
aukist þótt tegundir bætist við á
ákveðnu svæði.118
Viðbúið er að ágengum tegund-
um fjölgi á heimsvísu, jafnvel þótt
strax yrði hætt að flytja til tegundir.
Margar framandi tegundir sem
þegar má finna í náttúrulegum
vistkerfum eiga sennilega eftir að
færast úr tregðufasa yfir í vaxtarfasa
og verða ágengar.t.d. 49 Auk þess
geta loftslagsbreytingar haft ófyr-
irséðar afleiðingar fyrir framandi
tegundir152 en viðbúið er að áhrif
þeirra gætu orðið meiri, sérstaklega
á norðurslóðum153 og háfjallasvæð-
um.154 Með sífellt auknum sam-
göngum er einnig hætta á að nýjar
tegundir flytjist milli svæða, þótt
reynt verði að hamla gegn því.24 Því
er mikilvægt að vísindasamfélagið,
stjórnvöld og almenningur geri sér
grein fyrir vandamálinu svo unnt sé
að grípa til aðgerða með skjótum og
öruggum hætti.
Hér hefur ekki verið fjallað sér-
staklega um stöðu framandi, ágengra
tegunda á Íslandi en það er umfjöll-
unarefni greinar sem birtist í næsta
hefti Náttúrufræðingsins.
Summary
Ecosystems in peril, part one: A
review on alien, invasive species
Biodiversity is fundamental to ecosys-
tem services, the lifeblood of evolution,
and provides valuable resources neces-
sary for human well-being. Due to the
direct and indirect consequences of hu-
man activities, the present rate of spe-
cies extinction is 100–10.000 times great-
er than what can be considered natural.
One of the main drivers of species ex-
tinction is the presence of alien invasive
species in natural ecosystems. Humans
have imported species into new areas to
a growing extent, and at least 100–550
thousand alien species are now found
worldwide. Some of them have a con-
siderable negative impact on ecosys-
tems and natural processes, in agricul-
ture as well as on the infrastructure of
human society. The economic damage
associated with invasive alien species
amounts to more than 5% of the world
GNP. It is difficult to predict which alien
species become invasive, but factors
that add to the likelihood involve prop-
agule pressure, climate matching and
level of species specialization. One of
the most important factors to observe
when trying to predict the possible in-
vasiveness of a new alien species is its
invasiveness in similar surroundings
elsewhere. To facilitate information flow
on this subject, vast international open
databanks on invasive species have
been developed. When an invasive spe-
cies has been detected, immediate reac-
tion, such as population control or erad-
ication, is very important. There are
many examples of successful eradica-
tion programs, but measures have to be
taken to fulfil all necessary requirements
in order for such programs to succeed.
The number of invasive species world-
wide is expected to grow. Governmental,
public and scientific awareness of the
problem is therefore imperative.
Þakkir
Ég hef átt skemmtilegar samræður um ágengar tegundir við Róbert A.
Stefánsson undanfarin ár og fyrir það fær hann innilegar þakkir. Sömu-
leiðis þakka ég honum, Páli Hersteinssyni, Sigurði H. Magnússyni og
ónefndum yfirlesara fyrir gagnlegar athugasemdir við handrit greinar-
innar. Sigurði H. Magnússyni og Stykkishólmsbæ er þakkað sérstaklega
fyrir hvatningu til að sinna málefnum framandi ágengra tegunda. Global
Invasive Species Database (GISD), U.S. Fish and Wildlife Service og Calif-
ornia Invasive Plant Council er þakkað fyrir afnot af ljósmyndum.
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