Changing climate and outbreaks of forest pest insects in a cold northern country, Finland
Full text
49
© The Au ho (s) 2017
K. La ola, H. Sa ela (eds.), The In e connec ed A c ic — UA c ic Cong ess 2016,
Sp inge Pola Sciences, DOI10.1007/978-3-319-57532-2_5
Chap e 5
Changing Clima e andOu b eaks o Fo es
Pes Insec s inaCold No he n Coun y,
Finland
SeppoNeu onen andHeliVii i
Abs ac Pes insec popula ion dynamics a e species speci ic and complex due o
nonlinea i ies and in e ac ions among di e en ophic le els. Consequen ly, he
impac s o clima e change on pes s a e also species speci ic and hey a e o en di -
icul o p edic . Howe e , he e a e some clea examples o inc easing o es pes
isks due o a wa ming clima e. The damage caused by he Eu asian sp uce ba k
bee le has ecen ly inc eased in Finland as a consequence o mo e equen s o m
damage and longe g owing seasons. In a wa ming clima e, imely sal age and sani-
a ion cu ings will be needed o gua an ee he sus ainabili y o he o es y. Se e al
de olia ing pes s o e win e in he egg s age. Wa me win e s may no kill he eggs
and, he e o e, he incidence o ou b eaks is p edic ed o inc ease in he no he n
and con inen al a eas. The mos impo an socie al implica ions will be due o
Geome ids a acking suba c ic moun ain bi ch o es s. Toge he wi h hea y ein-
dee g azing, Geome ids educe he esilience o he ecosys em and hey a e h ea -
ening he sus ainabili y o local li elihoods.
5.1 In oduc ion
In he Bo eal zone, insec s ha e had an essen ial ole in he succession dynamics
and in s a ing he succession p ocess again in na u al o es s. Howe e , in no he n
Eu ope he o es s ha e been unde in ensi e o es y o a long ime. This has ag-
men ed he landscape s uc u e (Kouki e al. 2001), so ha la ge and ex ensi e insec
ou b eaks ha e occu ed only a ely. The e ec s o changing clima e on he popula-
ion dynamics o insec pes s a e complex and species speci ic, and only some spe-
cies a e p ojec ed o inc ease in a wa ming clima e (Bjö kman and Niemelä 2015).
Majo pes insec s a e a e mos o he ime bu hey cause damage e e y now and
hen. Fo example, he plo le el p obabili y o pine saw ly ou b eaks occu ing a
S. Neu onen (*) • H. Vii i
Na u al Resou ces Ins i u e, Joensuu, Finland
e-mail: seppo.neu [email p o ec ed]
50
leas once in 20 yea s a ied om abou 10% in he mos e ile si e ypes o 30–40%
in sub-xe ic o xe ic pine s ands (Ne alainen e al. 2015).
Insec ou b eaks can be classi ied in o di e en ypes based on he popula ion
dynamics in ol ed (Be yman e al. 1987):
(A) Regula ly cyclic ou b eaks: in no he n Eu ope he Geome id mo hs (Epi i a
au umna a, Ope oph e a b uma a) ha de olia e moun ain bi ches belong o
his ype (Haukioja e al. 1988).
(B) E up i e ou b eaks occu a i egula in e als. They may be igge ed by spe-
ci ic en i onmen al condi ions (e.g. d ough ) and indi idual ou b eaks a e
sho . Pine saw lies (Neodip ion se i e , Dip ion pini) exempli y his ype
(Hanski 1987; Juu inen 1967). Ano he pes ha has e up i e ou b eaks is he
Eu opean sp uce ba k bee le (Ips ypog aphus), which is mainly egula ed by
esou ce a ailabili y (Økland and Bjø ns ad 2006).
(C) Sus ained ou b eaks ha may las o se e al yea s also occu a i egula in e -
als and hey a e igge ed by en i onmen al condi ions. Al hough hese kinds
o ou b eaks a e a e in no he n Eu ope, a ecen example can be ound in he
damage caused by he la ge web-spinning saw ly (Acan holyda pos icalis) in
Finland and in Es onia (Pou u and Sil e 2016; Voolma e al. 2009).
A common ea u e o all ou b eak ypes is ha he e is a di e ence o se e al
o de s o magni ude in insec densi ies du ing he low densi y (endemic) phase e -
sus he ou b eak (epidemic) phase (Be yman e al. 1987; Hanski 1987). Thus, he
inc ease phase om endemic o epidemic densi ies equi es no mally a leas 2 o 4
yea s, du ing which he en i onmen al condi ions mus emain sui able o apid
popula ion g ow h.
The clima ic condi ions in he bo eal zone o no he n Eu ope show high yea o
yea a iabili y. This a iabili y can in e ac wi h o he ac o s a ec ing he popula-
ion dynamics o o es pes insec s (Neu onen and Vi anen 2015). Recen pa e ns
in he ou b eaks o he o es pes s in ela ion o ecen clima ic changes a e e iewed
and discussed in his chap e .
5.2 The Li e Cycles o Pes Insec s inRela ion oRecen
Clima e Change inFinland
Pes insec s ha e complex li e cycles and li e s ages. They li e in a a ie y o mic o-
habi a s ha expe iencing e y di e en clima ic condi ions. Consequen ly, conside -
ing he a iable esponses o di e en li e s ages o changing clima e is essen ial o
unde s and he impac s o clima e change on pes s (Kingsol e e al. 2011). Many o
he o es de olia o s in he Bo eal zone o e win e in he egg s age and eed on ea ly
season oliage (Hun e 1991). The clima ological win e s ( empe a u es <0 oC) las
se e al mon hs in no he n a eas, expe iencing occasionally ex eme empe a u es
ha a e much lowe han seasonal a e ages. These ac o s ha e impo an conse-
quences o insec pes s and o o he ecological p ocesses (Neu onen e al. 1999;
Williams e al. 2014).
S. Neu onen and H. Vii i
51
Ex emely cold empe a u es can kill eggs ha a e o e win e ing in he canopy
(Aus a å 1971; Nilssen and Tenow 1990). Consequen ly, highe win e minimum
empe a u es will inc ease he ou b eak isks o pes species o e win e ing as eggs
(Vi anen e al. 1996; Vi anen e al. 1998), bu may no a ec pes s o e win e ing
in he soil. The la e a e no mally p o ec ed by insula ing snow co e and a e no so
sensi i e o a ia ions in ai empe a u es (Vi anen and Neu onen 1999a).
The annual mean empe a u e in Finland has isen by a o al o 2.3 °C om he
mid-nine een h cen u y o he p esen (i.e. 0.14 °C pe decade) (Mikkonen e al.
2015). The la ges wa ming has been obse ed in win e empe a u es. The sp ing
(Ma ch–May) has also wa med mo e han he annual a e age, bu du ing he sum-
me mon hs (i.e. du ing he ime when mos o es pes s a e ac i ely eeding) he e
has been only e y li le o no wa ming (Mikkonen e al. 2015). The wa ming has
no been e en. Fo example, be ween he 1940s and he 1960s he clima e did no
wa m (Mikkonen e al. 2015), bu om he end o he 1960s onwa ds he mean daily
empe a u es ha e wa med on a e age by 0.3 °C pe decade (Aal o e al. 2016).
The a e age empe a u e sums ha e inc eased by abou 20% du ing he pas 20
yea s and he incidence o s o m damage has also inc eased du ing he las decade.
This has inc eased he isk o sp uce ba k bee le damage, especially in sou he n
Finland (Vii i and Neu onen 2016). Gi en ha he empe a u e du ing he summe
mon hs (June–Augus ) has no inc eased much (Mikkonen e al. 2015; Neu onen
and Vii i 2015), he inc ease in empe a u e sums is mainly due o inc eases in
sp ing and au umn empe a u es.
When e alua ing he po en ial impac s o clima e change on o es pes insec s,
he ollowing should be kep in mind:
(1) Fo es insec pes s do no gene ally expe ience he wea he and clima ic condi-
ions eco ded a wea he s a ions. The e ec s o mic oclima es should be con-
side ed when es ima ing he ecological impac s o clima e change (Daly e al.
2010; Po e e al. 2013). GIS echniques can be used when es ima ing he al-
ues o a ge a iables be ween o a ound he wea he s a ions (Vi anen e al.
1998).
(2) The in e -annual a iabili y o empe a u es in no he n a eas is e y la ge. Fo
example, in Finland he ange o a ia ion in mon hly mean empe a u es wi hin
a decade is 10–15 °C du ing win e and abou 5 °C du ing summe (Neu onen
and Vii i 2015). This a ia ion is abou an o de o magni ude la ge han he
obse ed o p ojec ed decadal ends in empe a u es.
5.3 Bi ch De olia o s
Cyclic ou b eaks (8–11 yea in e als) o de olia ing Geome ids (E. au umna a, O.
b uma a) a e ypical o he moun ain bi ch o es s o no h wes e n Eu ope (Babs
e al. 2010; Tenow 1972). In Finnish Lapland, he clima e is mo e con inen al han
in no he n Sweden and No way (Neu onen e al. 2005), and low win e empe a-
u es ha e his o ically educed he egula i y o ou b eaks (Neu onen e al. 1999).
5 Changing Clima e andOu b eaks o Fo es Pes Insec s inaCold No he n Coun y,…
52
The in ensi y o he peaks has a ied conside ably. The la ges ou b eaks ha e
killed hund eds o squa e kilome es o bi ch o es (Seppälä and Ras as 1980).
They can ha e de as a ing e ec s on ecosys em se ices and he condi ion o ein-
dee pas u es (Biuw e al. 2014; Jepsen e al. 2013) (Fig.5.1). Due o wa me win-
e s ha a e no capable o killing he o e win e ing eggs, he incidence o ou b eaks
is p edic ed o inc ease in u u e in he con inen al a eas o no he n Eu ope
(Ammuné e al. 2012; Vi anen e al. 1998). The numbe o de olia ion yea s has
inc eased because ou b eaks o hese wo species ha e ollowed each o he (Klemola
e al. 2008).
The la ges and mos de as a ing ou b eak was ha o he mid-1960s in U sjoki
( he no he nmos municipali y in Finland), which changed e y la ge a eas o
moun ain bi ch woodland o seconda y Tund a due o low eco e y unde hea y
eindee g azing p essu e (Chapin e al. 2004a; Kallio and Leh onen 1973). In he
mid-1990s, he mo e sou he n pa s o Finnish Lapland expe ienced bi ch de olia-
ion, whe e old bi ches we e a acked mainly a highe al i udes (Ruohomäki e al.
1997). In 2004–2005, moun ain bi ch o es s in Enon ekiö (NW Finnish Lapland)
expe ienced hea y de olia ion bu he bi ch o es s appa en ly eco e ed qui e well
du ing he subsequen yea s (Kopis o e al. 2008).
The i s eco ded ou b eak o Win e mo h (O. b uma a) in Finnish Lapland was
a he s a o his cen u y (Jepsen e al. 2008). I caused se ious de olia ion o bi ch
in a 400km2 a ea in Kaldoai i wilde ness a ea in U sjoki du ing 2006–2008 (Jepsen
Fig. 5.1 Au umnal mo h la ae ha e de olia ed moun ain bi ch o es in no he n Sweden, a ec -
ing ecosys em se ices, local li elihoods, and he ou is ic alue o he landscape (Pho og aph by
Seppo Neu onen)
S. Neu onen and H. Vii i
53
e al. 2009; San onen 2011). The e was no e olia ion a e his ou b eak and dwa
sh ubs we e also des oyed in he g ound laye . This caused ex ensi e changes in
ecosys em unc ions (Biuw e al. 2014) and socie al impac s since eindee pas u es
we e damaged in la ge a eas. This isked he sus ainabili y o local li elihoods
(Chapin e al. 2004b; Lempa e al. 2005).
5.4 Pine De olia o s
In no he n Eu ope, he mos common de olia ing insec s on Sco s pine a e N. se i-
e , D. pini and Bupalus pinia ius. Ou b eaks ypically occu in g aded sandy soils;
ha is, on d ie and less e ile o es si es (La sson and Tenow 1984; Ne alainen
e al. 2015). Regional N. se i e epidemics ha e occu ed e e y 10–20 yea s in
sou he n Finland and his has caused he de olia ion o la ge a eas (Juu inen 1967).
Al hough N. se i e damage may look se ious, o es s ypically eco e because
new shoo s emain undamaged. Ou b eaks occu a i egula in e als and no mally
hey only las 2–3 yea s (Hanski 1987; Soubey and e al. 2010). The ou b eaks end
due o a i us disease o he pes and/o inc eased pa asi ism (Juu inen 1982;
Olo sson 1987). Ea lie , i was common o use biological con ol (Nucleopolyhed osis
i us) agains N. se i e (Juu inen 1982), bu his i us is no longe allowed o be
ma ke ed in he EU.
Females o N. se i e lay eggs in o needles, whe e he eggs o e win e p edis-
posed o low win e empe a u es. The eggs can s and −36 °C in mid-win e (Aus a å
1971). Colde win e empe a u es han his ha e been common in no he n and
eas e n Finland, which has mean ha ou b eaks ha e been a e in hese a eas
(Vi anen e al. 1996). An excep ional case is he N. se i e damage a pine ee line
a eas in Saa iselkä (Finnish Lapland) (Niemelä e al. 1987) whe e he eggs su i e
a highe al i udes due o s ong empe a u e in e sions in win e .
No mally he common pine saw ly (D. pini) causes mo e local, mo e i egula
and mo e se ious damage because he la ae gnaw all needle classes a he end o
summe . I damage con inues se e al yea s in he same a ea, hen he mo ali y o
ees inc ease and o he pes s such as ba k bee les a ack he ees (Annila e al.
1999). In Finland, he ou b eaks o D. pini ha e been less common han hose o N.
se i e , bu du ing 1997–2000 he e was an excep ionally la ge ou b eak o D. pini
in he cen al pa s o he coun y (Ne alainen e al. 2010). A ough es ima e was
ha pine o es s expe ienced damage in an a ea o 500,000 ha, om which
200,000ha had mode a e o hea y damage (Va ama and Niemelä 2001). The causes
o his ou b eak emain unknown.
I has been p edic ed ha he ou b eak ange o N. se i e will expand in eas e n
and no he n Finland i win e minimum empe a u es inc ease (Vi anen e al.
1996). Howe e , his p edic ion does no apply o D. pini, which o e win e s as
cocoons in he soil, p o ec ed om cold empe a u es by he snow co e . Fu he mo e,
clea p edic ions abou he popula ion dynamics o pine saw lies in a changing cli-
ma e migh be impossible because he mo ali y a es a e s ongly a ec ed by p eda-
ion by small mammals (Hanski and Pa iainen 1985), and he popula ion dynamics
o small mammals a e complex and a he unp edic able.
5 Changing Clima e andOu b eaks o Fo es Pes Insec s inaCold No he n Coun y,…
54
5.5 Sp uce Pes s
Sp uce ba k bee le, Ips ypog aphus L, is he mos se e e pes on No way sp uce in
Eu asia. I has caused ema kable o es damage in many Eu opean coun ies
(Schelhaas e al. 2003). In Finland, sp uce ba k bee le damage has been a low le el
when compa ed o he o he No dic coun ies. Howe e , om he yea 2010
onwa ds, ou b eaks o I. ypog aphus and o he ba k bee les a acking sp uce ha e
inc eased in sou he n Finland. In summe 2010, hunde s o ms caused damage in
la ge a eas o cen al and eas e n Finland. Pa s o damaged ees emained in o es ,
which con ibu ed o he g ow h o he popula ion le el (Vii i e al. 2011). Summe
2010 was also ho and d y in la ge a eas o sou he n Finland, which lowe ed he
esis ance o sp uce ees and p edisposed hem o ba k bee le damage (Fig.5.2).
Sp uce ba k bee le success ully b eeds in esh logged No way sp uce imbe
and windblown ees (E iksson e al. 2008). I can a ack heal hy ees when he
popula ion le el is high (Økland and Bjø ns ad 2006). The isk o consequen ial ee
dea hs will inc ease conside ably when he amoun o windblown ees inc eases
(E iksson e al. 2007). Old g ow h o es s, wa m o es edges, esh clea -cu bo -
de s and d y si es a e especially ulne able o damage.
Fig. 5.2 Sp uce ba k
bee les ha e i s
ep oduced in s o m
damaged sp uce ees
( o eg ound), and du ing
he ollowing summe hey
ha e a acked and killed
s anding sp uces
(Pho og aph by Seppo
Neu onen)
S. Neu onen and H. Vii i
55
The second gene a ion o sp uce ba k bee le was no iced o he i s ime in
Finland in 2010 (Pou u and Annila 2010). The de elopmen o he second gene a-
ion emained mainly a la al and pupal s ages, which canno no mally su i e he
win e s in Finland (Annila 1969). E en hough he ba k bee le popula ion size did
no g ow wi h new o e win e ing adul s, mo e damage was caused by ex a a acks
on li ing ees. In addi ion, in sou he n Sweden he e we e obse a ions o he
de elopmen o wo gene a ions o sp uce ba k bee le a e he Gud un s o m in
2005 (Långs öm e al. 2009).
The wa ming clima e has made condi ions mo e a ou able o sp uce ba k bee le
in he no he n pa o Eu ope (Økland e al. 2015). Longe g ow h pe iods and
inc eased empe a u e sums ha e enabled he de elopmen o mo e sis e b oods
and e en he de elopmen o he second gene a ion in some summe s (Neu onen
e al. 2016; We melinge and Sei e 1999; Öh n e al. 2014). Sho e pe iods
o ozen g ound and hunde -s o ms in he summe ime ha e inc eased he amoun
o dead wood in he o es s, which a ou s b eeding ba k bee les (E iksson e al.
2007). Phe omone moni o ing s a ed in 2012 and i has shown ha popula ion le -
els ha e been a epidemic le el since 2013in many loca ions in sou he n Finland
(Neu onen e al. 2016).
5.6 Conclusions andFu u e P ospec s
The e a e se e al sou ces o unce ain y when he impac s o clima e change on pes
insec ou b eaks a e p edic ed. Fi s , he di e en global clima e models and al e -
na i e emission scena ios p oduce la ge a ia ion in p edic ed clima ic ou comes
(Jönsson and Bä ing 2011; Ruos eenoja e al. 2016). Downscaling o egional and
local le els and o mic oclima es b ings mo e unce ain y o wha will happen in he
speci ic mic ohabi a s whe e he pes insec s a e li ing (Neu onen and Vi anen
2015; Po e e al. 2013).
O he ypes o unce ain y a ise om he complexi y on pes insec popula ion
dynamics. These a e species speci ic, and include nonlinea i ies and ime-delays,
which may lead in o chao ic dynamics (May 1976). Fu he complexi ies a ise om
he in e ac ions among di e en ophic le els and he indi ec e ec s o clima e
change ia na u al enemies (Da is e al. 1998; Vi anen and Neu onen 1999b).
Gi en he di icul y in p edic ing clima e change and i s impac on insec ou -
b eaks, he ocus he e is only on wo sys ems whe e pes s ha e he mos impo an
socie al implica ions.
Geome ids A acking Suba c ic Moun ain Bi ch Fo es s When mul iple s esso s
like mo h ou b eaks and hea y eindee g azing (Biuw e al. 2014; Tenow e al.
2005) educe he esilience o he ecosys em, he changes can be d as ic and almos
i e e sible (Chapin e al. 2004b). Reduced eindee densi ies and changes in he
seasonal pa e ns o g azing (pas u e o a ion) will be necessa y o be e sus ain-
abili y o eindee he ding (Wielgolaski e al. 2005).
5 Changing Clima e andOu b eaks o Fo es Pes Insec s inaCold No he n Coun y,…
56
Ba k Bee les A acking No way Sp uce The isk o ba k bee le ou b eaks will p ob-
ably emain high in sou he n Finland in a wa ming clima e (Vii i and Neu onen
2016). The mos e icien way o con ol sp uce ba k bee le damage is o emo e
damaged and a acked ees om o es be o e new p ogenies eme ge (S adelmann
e al. 2013). In a wa ming clima e, he educ ion o sp uce ba k bee le isks wi h
managemen ac ions ( imely sal age and sani a ion cu ings) is u gen ly equi ed o
gua an ee he sus ainabili y o o es y, especially because o he high economic
impo ance o No way sp uce. Con inuous moni o ing o popula ion le els and phe-
nological su eys a e needed o accu a e isk es ima es and as a basis o imely
ad ice o o es owne s abou he bes managemen p ac ices (Vii i and Neu onen
2016). Logging o ees ha a e windblown a summe ime will be mo e u gen
because he swa ming ime o sp uce ba k bee les is longe han i used o be
(Neu onen and Vii i 2015; Öh n e al. 2014).
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5 Changing Clima e andOu b eaks o Fo es Pes Insec s inaCold No he n Coun y,…