Download Million Species

About Island Press Saving a Million Species EXTINCTION RISK FROM CLIMATE CHANGE
Since 1984, the nonprofit Island Press has been stimulating, shap­
ing, and comm unicating the ideas that are essential for solving envi­
Edited by Lee Hannah
ronmental problems worldwide. With more than 800 titles in print
and some 40 new releases each year, we are the nation's leading
publisher on environmental issues. We identify innovative thinkers
and emerging trends in the environmental field . We work with world­
renowned experts and authors to develop cross-disciplinary
solutions to environmental challenges .
Island Press designs and implements coordinated book
publication campaigns in order to communicate our critical
messages in print, in person, and online using the latest tech­
nologies, programs, and the media. Our goal: to reach targeted
audiences-scientists, policymakers, environmental advocates,
the media, and concerned citizens-who can and will take action
to protect the plants and animals that enrich our wo rld, the
ecosystems we need to survive, the water we drink, and the air
we breathe.
Island Press gratefully acknowledges the support of its work
by the Agua Fund, Inc., The Margaret A. Cargill Foundation, Betsy
and Jess e Fink Foundation, The William and Flora Hewlett
Foundation, The Kresge Foundation, The Forrest and Frances
Lattner Foundation, The Andrew W. Mellon Foundation, The Curtis
and Edith Munson Foundation, The Overbrook Foundation, The
David and Lucile Packard Foundation , The Summit Foundation ,
Trust fo r Architectural Easements, The Winslow Foundation, and
oth er gen erous donors.
Th e opinions exp ressed in this book are those of the
,lllllI or(s) and do not neces sarily reflect the views of our donors.
2012
o
ISLAND PRESS
Wlr ~/lil(I//{J1I 1( :11111 '/11 1/ ,lIlItiml
Chapter 11
Quaternary Extinctions and Their Link
to Climate Change
BARRY
W.
BROOK AND ANTHONY
D.
BARNOSKY
Millennia before the modern biodiversity crisis-a wo rldwide event
I'i"ing driven by the multiple impacts of anthropogenic global
\ 11:lnge-a mass extinction oflarge-bodied fauna occurred. After a mil­
111'11 years ofsevere climatic fluctuations , during which the earth w(L'(ed
,!lId waned benveen frigid ice ages and warm interglacials, with appar­
1 'ild y few extinctions, hundreds of species of mammals, flightless
l lil'd s, and reptiles suddenly went extinct over the course of the last
" O,()()O years (Barnosky, 2009) . Due both to our intrinsic fascination
\\'i iii huge prehistoric beasts and to the possible insights these wide­
"III '\':h.l species losses might lend to the modern extinction problem,
rill' Ill ),stery of the "megafaunal" (large animal) extinctions have led to
1IIlI vil ri1wrizing, modeling, and digging (for their fossils or environ­
111,'111:11 proxies) over the last 150 years (Martin, 2005). The topic
" 'll linllt:s to invoke strong scientific interest (Koch and Barnosky,
' (l()(, ; Cr,lyson, 2007; Gillespie, 2008; Barnosky and Lindsey, 2010;
~ J I 'I 'I II\; ,~ - lklVO et ,)1., 2010; Price et al., 2011).
III Ihis dl:lpt<:r, we t(>ClI S on recent work that explicitly considers
il l!' I'~' LII ive ruk of !'larur:)1 climate change compared to nonclimate
111 111 1.111 c:ll.Isc.'d l'i1n::II'c.·nillg processes (stich as habitat loss and hunt­
1111\ ) ill Iki vill!'; 1'1ll' IIH')l,:ll:lIll1 :11 nrilll'liuns, Wl' heg in with a short
I' \ I' IV c ,i' I hI' )',Iuh,d p.IIII'I'1i I)t' (~II :II'l'rl1 , 1 ry l'X I'i n~' 1 iOlls and Sill 1111) :1­
I I I '1'11111 ' 1',\'III'I ';d 11'.I'it 'II', wllv 1.11'1'." ,lIlilll.l1.<: IlIi),:,hl ill' 1' , lIli ~' ld : ll'i )'
I ~" V
1--­
IHO
EVIDENCE FROM THE PAST
vldn t:rable to direct human impacts and climate change. We then ex
IIII II'L' how the pattern of megafaunal extinction corresponds to borh
II\I' chronology of human expansion and climate change and their pro
/('\ Inl impacts. Taken together, this body of information leads us (0
t 't IIld IId t: that climate change alone did not drive the mass extinctioll
'II 1.1Il" Quaternary megafauna, but overlain on direct and indirect htl
111.111 ,IClioIlS, it exacerbated overall extinction risk tremendously. Thl'
1.1 1l( ' IIIIIIIC message is that the synergy of fast climate change wil'h
III' 'I I' dirclT human impacts can have particularly fatal consequencl'~
',ll III.III,VIionhuman species-and this is particularly true today, wh~'1l
111 1111.111 ildhl L'IlCeS, including climate disruption, are so dramaticallv
,',II ,11"1 111.111 I'hcy have ever been in the past.
Quaternary Extinctions and Their Link to Climate Change
-40kyr ~
1>'/ \
4'
2'
~~--:-i"~~~]
1
17· 11.5
2
1
13.5 kyr ~
3P/ \
181
15
ISO. 13 f lcyr I~i= 11 .C~1 Holocene
11\ 5. 3
~<~:rJ
'3'
' .
\
~Jj~locene I , .0i!~.
6
-r
~'
I ~O~72.44k
kyr II 51'~O
-- II
__
yr I
I'~x t incri on and Vulnerability ofMegafalma
t/
/
> 16
1?
4q .28
I.....
------'
1'111' "lid () II.III.: nLlry (late Pleistocene and Holocene) die-offs COI11
I" 1,', ('..1 ,I :,i}'.lIi1i ~' : 1I11" g lobal mass extinction event, which led to the eli III
11 1,11 11111 ,II h.dt' lit' :111 mammal species heavier than 44 kilograms (100
I" 1111,,1:,) ,llleI 1I1 'II~T brg<.:-bodied fauna across most continents (Au.,
I, ,lii,l , I ':"":I.,i :l, Norl"ll alJd South America) and large islands (West I II
cI 11',', , M,ld,I).!,:ISI\lr, alld N<.:w Zealand), between 50,000 and 600 ye:ll"
1"" 11 ,1 ' 1"\"'("111 (Koch and Barnosky, 2006). The losses included large
111.1111111:11., (L·.g., mammoth, genus Mammuthus), reptiles (e.g., gialll
l' I" lIeI:, ~; lIdl :1., MCJla /t,lnia), and huge flightless birds (e.g., New / ,(',1
1.11111 111'1 :1:lIId Ausrralian Genyomis). In Australia, around fifty spccic.\ ,
lilt Ilid i1I,l!, rli inoceros-size wombats, Short-faced kangaroos, and pr<.:d,1
I, 'I I' I" I.'ISI II IlS disapp<.:ared (MacPhee, 1999). In North America, 1'111
el l"llll Inll was SOI11<.: sixty species of large mammals plus the laq.!,('hl
l, il'e1:: ,lIld !"orroiscs, and South America saw the disappearance o( .11
1('.1',1 ,~ix l y·six Iarg<': -Jl)<1111maJ species. Eurasia and Mrica were less 1I.1le!
Ii ii, 1'"1 II I,'Vl'l'I'hc!t.:ss saw major losses in their large-mammal faulI:! , Id
" "'11 ,lIld 8<.:vcmet;n specics, respectively. Region by region, these n
1i,It lin ll I,'VCllrS f()lIowni within a few centuries to a few millenlli:1 IIIi
11" 111 di8pL'rS :11 or 1-l00'YUlsapiens to new lands, and wne parricularl y :W
1'1 '1(' IV hl'lI Iht;y We re also <.:l1twined with changes in rhc n.:g ioll :" ')I
1,.II ,b:II l'Iill1:lI~' SY.'I~l'lJ l (fig. II - I ).
SCI IV".II W. IS Ih l ' 1..':11 IS:" IIlCCh:lIIisll1 hdlind dll's(" eX Iilll'l inns \ I,
111"1, ,, 1111111:111.'" Ill' hlll 'h? The drivers 11f'I,il"il ('xlililliIIIlS, P:I:;I ,lilt!
l ' I" ~t' lll . ,Ill' 'lfi "11 '~ lIq1J'i.':i ll!,,Iy din illill I" I,ill '.I"IVII (Nit I\i llll\ 1'.
fi nu608 of extinction
Moslly Human
Moslly Climale
InsuHicient data Relative size of extinct­
Correlations in time
Numbers indicate how
taxon icon corresponds
many genera have robust
to relative magnitude of
L oJ Humans arrive
dating control evidence
extinction. Number of
except as indicated:
•
Climatic change
extinct genera is listed Provisional evidence
on each icon.
? Needs more work
-,
I I ' Ie 11(/, JT-I. Late Quaternary megafaunal extinctions, human hWlting, and di­
lilol lt' ( /lange on the continents. The dashed box indicates the credible bounds of
IIi, I IrsI' arrival of modern people, Homo sapiens sapiens, with the best estimate ad­
i'" , ' III In the human figure (the latest estimate for Australia is about 48,000 years
III" I ky r BP]). Substantial climate change events, predominantly the last glacial
Iii 1\ il I IlIlI1 ,lnd Holocene warming, are indicated by gray shading inside boxes.
" !III' (' : K.och and Barnosky, 2006.
1'1 1),/ ), hut plausibly include: (i) being outcompeted by newly evolved
II I Illv;tsive spccies; (ii) failing to adapt to long-term environmental
, I101 II }',l' (e .g. , climatic shifts); and (iii) reduction in abundance caused
11\ 1,IIIdpm disturbance events (e.g., epidemics, severe storms) with a
IIi "wl/lIl"m bilur<.: to recover to a viable population (Blois and Hadly,
'( 1)')), !\ C()llJlllOllly cited g<': llcralization is that larger-bodied verte­
1".1 11" , (w il'll I'he L'xtrctne rccwr t()rm being the Quaternary mega­
11111101 ) .11'1' 11101'1.' eXt'illCrio/1 -prone I'h;lIl smaller bodied ones (Bodmer
I I ,iI , 1')')7: McKi'lIH'Y
, II)()?). I\n ':IlISl' hody sizc is inversely corI I,'oj I'd Willi 1'"1,"1.11 i,,, I ",iI,\" 1.11'/',1' h, It lit'd .lIlirn:lls rL' nd ro h<: kss
11\ 1
Quaternary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
.11 IIIlld :1I1r and so more intrinsically vulnerable to rapid change and de­
Illographic disruption. Indeed, when armed with some knowledge of
('llIpiridly well established biological scaling rules (allometry; Da­
111111 h, 1981), such a hypothesis makes a lot ofsense. Large-bodied an­
III 1.1 Is such as elephants or whales produce only a few, precocious off­
1'1 'I'illg, but invest substantial resources into their care. This life-history
:;II.IIl'!'\Y kads to the death of juveniles being a major demographic set­
I•. Ide ()II a population-wide basis, even an apparently small additional
1.-,,1'1
chronic mortality can result in rapid declines in abundance
.llld , within a few centuries, a collapse to extinction (Brook and John­
:.(111 , 2()()6; Nogues-Bravo et al., 2008). The extinction proneness of
I.II,}"C bodied animals is further enhanced because of other correlated
11 .lil s such as their requirement oflarge foraging area, greater food in­
1.1"(" high habitat specificity, and lower reproductive rates (West and
I ~i'( 'WII, 2(05).
Why thcn (in evolutionary terms) be big? Three reasons are that
I.II'~\(' ~\llil11al s arc long-lived (so have multiple attempts at reproduc­
Iic '11), have relatively better heat regulation and water retention than
';111.111 .lI1inJais, cmd have lower predation rates, especially when herd ­
III)',. Their size protects them from all but the biggest predators, thcy
11 .11It' :1 great capacity to ride out hard times by drawing on their fat re­
·.C·I \Irs, rhc)' can migrate long distances to find water or forage, and
t1lC' y L'all ()pt not to reproduce in times when environmental condi
II. 'IIS .IIT unt:1vorablc, such as during a drought (Brook et al., 2007).
I'IIIIS ill I'he majority of circumstances, being big is good, because il
.IC I~ .IS .1 demog raphic buffer. Indeed, such ecological specializatioll
I. '11i Is Ic. evo lvc repeatedly because, in relatively stable environments,
'~ I '1 ' 1 I.llisl species tend to be better than generalists at particular narrow
1.1.·.k::. Ilmvevt:r, when an envirorunent is altered abruptly at a rail'
.11 II . " " lie )l'In:11 b:Kkgrollnd change, speciallst species with narrow cco
I. 'I',Ic .11 j\l'l'It:n.: nl:cs bear the brunt of progressively wlfavorable contli
II, "I S Sll l' h as habitat loss, degradation, and invasive competitors (ll
I'II" 1.11 III'S ( B:lllllf'(lrd, 1996; Harcourt et al., 2002). An extremc CVC: III ,
'III, It : I.~ :1 holid e strike tt'OI1l space (Haynes, 2008) or an inrclligC: III,
"" "'1" l1l , w Ic:lding bipedal ape (Martin, 200:;), tbar also widely allrl"
1.I IIoI",,·:IPI:S by pracrices such ,IS burning and farming, can be rbc; k vc'l
111.11 IIIIIJillgl.·S Illl' upl"ill1ality ofrhis r(:gu larly evo lved srrat(:gy o/'l :lI l',c
hunted by invading prehistoric people in Pleistocene Australia, arbo­
real (tree-dwelling) species occupying closed forests suffered far fewer
extinctions than saVaru1a (grassland) species, and of the latter group,
tbose with high per capita population replacement rates (e.g., grey
kangaroos; Macropusgiganteus) or the ability to escape to refuges such
as burrows (e.g., wombats; Vombatus ursinus) were best able to persist
(Johnson, 2005).
0"
I"" Iy . , i'I.I·.
III
' I'IH' ,·ll viI'Clnllll·1I1.l1 (,()III~'XI : lI11II Y P~·I)t'II\1'( · .11 .1I ,~ c) IIdps di ('t.II l' ,III
I\"~ I)IIII I;(' Ic. dl.lll1\(· CII IIl) VI· 1 I.II·C··.·,,'I ·. l:clI illl·:I.IIIlI" WIIl'II
1'..11 Ii.';) 11 \
183
The Role of Human Arrivals
During the last 100,000 years, modern humans have spread across the
world from their center of origin in Africa, reaching the Middle East
by 90,000 years ago, Australia by 48,000 years ago (based on tlle most
s(:cure evidence presently known, Gillespie et al., 2006), Europe by
40,000-50,000 years ago, SoutllAmerica by 14,600 years ago, NOrtll
America by 13,000 years ago, most of the Pacific Islands by 2,000
lears ago, and New Zealand by 800 years ago. (For dates estimated by
radiocarbon dating, the radiocarbon age is calibrated to calendar
I(:<lrs.) This wave of human dispersal was likely to have been medlated
hy climate change: a wet penultimate interglacial probably encouraged
111(: spread of early Homo sapiens out of Africa, and in the Northern
Ilcmisphere, end-Pleistocene immigration into tlle Americas was fa­
,ilirated by glacial ice sequestering water and lowering sea levels,
which in turn exposed a land bridge between Eurasia and North
\ l1l erica and opened coastal migration routes. At the very end of tlle
I'ki stocene, it was global warming that melted ice and opened an ice­
II'n : CI)rridor through central Canada for a wave of Clovis hlUlters.
A striking feature ofthe megafaW1al extinctions is tllat, in every ma­
l' '1 ' Illstance where adequate data exist, the extinction follows the first
Ill'i v:d of people on a "virgin" continent or large island within a few
111111l11'(:d to a few thousand years (fig. 11 -1). This point is further un­
1I" I':K'(lred in figure 11-2, which shows the short overlap period for well
1,I 1(',llllc!4aflllnal remains and archeological artifacts, in New Zealand,
r~ I '1111 America, and Australia, based on the latest dating and sample se­
I, , Ii, III protocols (Gi llespie, 2008). (Note the different time scales on
11.11 1o ·IN1\ , B, and ( :- rh(:se three (:vents wcre not synchronous in time.)
I 111 111 idene\.· :donl' is nor sulri(iC:1l1 evidence for causation, but this conI'" 1'111 Y.11 IhI' vny k.I .~ 1 1)1'( )vil k s sl)'( 1I1g L'irCIln1Sr:111rial support for the
,I 111.11 .1 1111111.111 pn':"'111 (. \V.I .'; .1 lit ·, ' ·S.~ .II'V pl'rc 'l )nd iI ion 1;)1' :H.'(I.; lc:rar~·d
It "
IH4
Quaternary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
A,_
~
Rattus exulans
=
& rat-gnawed seeds
-====
Moaeggshell
1­
~ooo
New Zealand
1500
1000
500
0
-500
-1000
-1500
-2000
-2500
Calendar Age (years caiAO/BC)
B
~
Clovis-age ~ Archaeology ~
i
~
. Mammuthus Smilodon fatalis
& Canis dirus
-­
North America
~
10
15
20
25
30
35
Calendar Age (ka calBP)
c
~
-
Archaeology
1·e charcoal
indirect OSL
185
fauna, We are a species that broke a fundamental ecological rule: large
predators and omnivores are typically rare (Tudge, 1989), A recent
analysis by one of us (Barnosky, 2008) has shown that in achieving eco­
logical dominance, a rising biomass of people ultimately and perma­
nently displaced tl1e once-ablmdant biomass of megafauna, The point,
well illustrated in figure 11-3, is that when the species richness ofmega­
fauna crashed to today's low levels, their equivalent total biomass was
replaced by one species (Homo sapiens), Indeed, we surpassed the nor­
mal prehistoric levels of megafaunal biomass when tl1e Industrial Rev­
olution commenced, and now, when combined with our livestock,
vastly outweigh the biomass ofmammal faunas of the deep past- an ex­
plosion of living tissue supported primarily by the use of fossil energy
(which, for example, makes it possible to produce and distribute inor­
ganic fertilizers), The energetic trade-off between a large human bio­
mass (lots of people) and a large nonhuman biomass (lots ofother spe­
cies) demonstrated by tl1is Pleistocene history has a dear conservation
implication: to avoid losing many more species as the human popula­
I'ion grows in tl1e very near future, it will be necessary to formulate poli­
cies that recognize and guard against an inevitable energetic trade-off at
the global scale, The pressing need is to consciously channel some mea­
sure of natural resources toward supporting otl1er species, ratl1er than
Extinct megafauna
direct CSUS-ESR &
"c gelalin
• Megafauna Loss vs, Global Human Population Growth •
C/)
Q)
'1:;
Q)
Q.
Australia
400
(/)
:'(1
30
35
40
45
50
55
60
65
70
75
80
85
90
-
Americas
.... ,
:;:J
300
~I ~I f"'"
1ii
Ol
Q)
Dating data on human-megafauna overlap in New Zealand (A) ,
N III 'I h AnH.:ri ca (B), and Australia (C), The dates are stacked from youngest (t'ol' )
I,. ,.1. il-SI (htIITom) for the archeology (dark shading) and oldest (top) to young<""
(I" 'lit lIll ) li)/' Ihe animal remains or proxies (light gray shading), Bars rcprt'S"11i
,jdtilll\ IIIh:crr:lillfies, SOl1l'ce: Gillespie, 2008 (includes detailed legend),
...
.--..
350' -
III
1I11 I I1I U , 11 - 2 ,
Eurasia
Beringia
Australia
III
c::
Calendar Age (ka)
1
q'
250
::2
200
'0
150
..0
ill
100
E
::l
50
Z
oB
It)
100,000
~ t " ~
It)
~
10,000
14
12
0
X
c::
10
0
8,0
:-§
6,0
4,0
2,0
0,0
:;:J
Q.
0
(L
•
1,000
Years before Present
the evidence that mo~ t o( 11 II
slirvi v<.:d through pn:vioLls, <.:qll:lll y pronounced Cli vi 1'1 III
111('1\,11 :1111):11 l: Xrin <.:tioI1, l:spc<.:iaJly given
" XI illl' l I.IX :I
1/1\' 111.11 Ill'l'llIrh : II' ioll,~ bd(lI'(':
/\ f'llIlIwi' IiiII'
1i1(' I',I"I>,1I
oj'
hum:uls :uTi vnl.
illdin:cl
l'vidl'Il\\ ' \ 'III1I\ ' ~ 1
11'1)111
,l.~,~rssill!-!-
Il ,t 11 11(1,
1/-3, Dcclinc in gloh:l1111l'gaEllma hiodiversity (number of species; light
1\1,1\' ) l'l't.: r rh t.: i:l~r g I:Ki :ll - ill,.,: rgl :l c i ~ 1 cyrle, plottl'd against tbe increase in world
i'''11111.11 i(lll
jOlllllv
l 'i N( ' ill 1111111.111 :lhlllld,lIh '\' ,\lld 1111 ' 1'"' \ 11'IIIIII ,' :III,'il' "I"III1 T ,,1
, 11, '.1
,~i 'l.t' (11'1/011-10 .l'11/,ir'll,I ,
I 'y .I :II 'k
)',1':1)' ,II'I'IIW::'
II'"II" lIkl', ./,OOH ,
",I
1\1\.11111' l'Xlill\:I'ioll ev e l1t~ by (;t)ntincllt arc indi­
1'111 "10'1.111.111 oi' Y" :II'S hdc Irc p/'l';,~l'I'lI') ,so\lrce:
I H(l
Quaternary Extinctions and Their Link to Climate Change
E V IDE NeE FRO M THE PAS T
,~ e
lldy toward humans, for example, in the form of enhanced sustain­
:Ihk farming practices and stepped-up efforts to protect and expand ex­
iSI ing nature reserves. Also critical will be developing alternatives to
l,~sil fuels for the energy that currently sustains the global ecosystem,
" ~ IIL' c iall y humans, so far above its pre-anthropogenic level of mega­
1.11111:1 hiomass.
Iluman impacts on late Quaternary enviromnents were many and
\'.Iried (Barnosky et aI., 2004; Lyons et aI., 2004a). The role of prehis­
I'll'i( pcople as hunters of big and small game has been reviewed ex­
Il'Ilsi vdy (Martin , 2005; Surovell et al., 2005; Grayson, 2007); meat
IV.IS (learly a component of the hunter-gatllerer lifestyle (Bulte et al.,
'()()(l), blll killing may have also occurred for reasons beyond subsis­
11 '111 I ' (eg., hunter prestige). Beyond direct predation, however, hu­
111,,"': ~lT llI ro have stressed megafauna by burning vegetation on a
1.11 II I ~I ,Ipl' Sl':lk (and in doing so, perhaps radically altering local di­
III ,I!! ': Milln ct :Ji., 2005) and by introducing commensal species such
pi" 01 11 )', ," (I:inkl, 2005), rats (Duncan et al., 2002), and disease (Lyons
C', ,II , , W()/I,h). Ovcrkill, the hunting of a species at a level sufficient to
,It iV(' il 1'1 nl ill(\ ion, with or without an additional pressure from fac­
Ie 1\", ,'''H' I! ,IS hahirar modification and clin1ate change, has been shown
\1,111'.1 vi,lhle killing mcchanism for megafawlal species (fig. 11-4) if'
II H ' 1111111 CI'S :t1so could LIse other species when they deplete the original
1.11 ,)',1'1 speci<.:s Ixlow viable ablmdances (Bodmer et al., 1997; Alroy,
I()O I, Bruok and Johnso n, 2006).
1000
N idlc' Illodding indicates strong correlation between specific climale
V;II 'i.lhk·s and spccies distributions (Hijmans and Grallam, 200() :
NeI) ',III'S Bra.vo ct ai. , 2008 ), and it now seems clear that climate i ,~ ,I
k('y d rlC rtllill ~lIlr of whether or not a species can exist in a given 10Clk ,
111.':1 likl.: hUll1an imp:1cts, climatic impacts on species are direct and ill
tlil ~'I. I , Direcr impacrs incilide exccedin~ physiologically imposed rnll
1'1.'1',1111 1'<.' :t llli prn:ipirarioll limits on a species, such as criticalrc.:mpcl,1
1111 '(' I I! r',,'sII 0 Ids li)r J1lllsk oxen o r pikas, whieh have limited heal'-lo!,,'1
,Ihilil i('s, Il1Ilil'l': l'l' irnpa (t~ incilidc misrnarch o f lil'(; hist'Ory SF!':lll')',\,
",ill I I illlill)" l,r .~(, : ISllIlS or nl'hl'1' dim:!1 ie p:lr:IIIK'rCI'S (phcllology), 11_1
,'\,11111,1,' , VlIll,'l'g illg ('1'11111 lIihnn:llillll I(Hll 'a d y ill I Ill' ,~ pl'illl!. , IlI'l i lll
A
750
I,
Role of Climate Change
187
500
250
1c
1000
1000~
l!l
'iii
750
750
500
c:
0
<U
S
Co
n.
500
I
..........
250
250
0
0
100
200
300
Year
400
500
FiGURE Ii-4-, Overkill by the selective harvest of juveniles (less than 6 years old) of
,) simulated population of the extinct giant marsupial Diprotodol~ Ifptatum. Solid
line is the total regional population (can)/i ng capacity = 1,000) and the (barely
visible toward the bottom ofeach graph) dotted line is the annual number ofjuve­
niles killed by hunting (human population size = 150). (A) Constant hunting off­
lake. (B) Type II functional response (asslU11cS prey are na'ivc). (C) Type III func­
rional response (assumes adaptive prey and higher hunting pressnre), Source:
I ~ rook and Johnson, 2006.
snowmelt has exposed critical food resources (Parmesan, 2006; Bar­
11osky, 2009).
Although numerous examples of climatic change stimulating
Changes in local abundance or geographic range changes exist, there are
I ~' w examples ofclimate change causing worldwide extinction in tlle ab­
,.I.'IKe of any other biotic stressor. Examples such as the golden toad
/l/~li) perigle11.es) and harlequin frogs (genus AtelOp~H) may qualify
( 1',lrl11esan, 2006 ) for recent times, and in deeper time, the demise of
Il'ish dl<.. (Megaloceras) in Ireland, and horses (Equus) and short-faced
11~' , lrs (Arct()du~' ) in Beringia seems artributable mainly to late Pleis­
I ilL CIllo' climate changes (lhrnosky, 1986; Gutllrie, 2003; Barnosky et
tI ., 2()04 ; Koch ~lIld Bamosky, 20(6). Although available models fail to
,I,f"qll:lld y simllble Il)cg:1 t:JlIll:11I.'xt"incrions based on climate change
,tI, 1\ Il' ( Hre )()k :lIld Hll\ov111:111 , ,2.00·1,; I.Y()IlS 1..'1' :11. , 2004:1), model ing <thd
IHH
Quatern ary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
"Il)pirical evidence has shown climate change alone to cause extinctions
t(species ranges are restricted by barriers that prevent them from mov­
ill g' to track their needed climate space (Barnosky, 1986,2009; Thomas
: 1 ;\1., 2004). It is precisely this latter situation in which the world's
1:11111;\ (and flora ) today find themselves.
'I'he late Quaternary was a period of major natural climate change
(Iig. Il-5). The most prominent events were the glacial-interglacial cy­
< ks, which have repeated thirty-nine times over the last 1.8 million
y,·.lrs; the last nine cycles show about a 100,000-year periodicity. Dur­
iIlg Iltese shifts in climate, the globally averaged temperature changed
hy 4 6 degrees Celsius-comparable in magnitude to but at a much
·,1, IIV~T rate than that predicted for the coming century due to anthro­
II( ') 'SII ic g-Iobal warming under the fossil fuel-intensive , business-as­
11 ' .11.11 .~rl'l w·io (AIFI; http: //www.ipcc.ch:IPCC.2007).Triggered by
<l1 'l> il.l1 Ie )rcing and reinforced by albedo changes (ice-sheet retreat or
) ',1 i 'wilt ) ,IS well as the feedback of terrestrial and oceanic greenhouse
9
7
1/i ,/cII MIU)
4 ~
11
l
:j
NIl.';;'
o
~
'i
: . Tv
Tv,
'. TVII
" \~ ""
,
.
~, ; ! - - - ":;",.'. - .~.:.
-
,.; ;
lJ
100
200
300
400
Age (kyr BP)
,1',/,
.v~,
"
!,
­
~
!d.',I
'1J'1'
~:' \<~/
~ '1.Ii'1
··· ·u
:- - ,
.
11111
T~X
TvII ,
- 1?
t,
'-
I
500
600
700
000
ill( i IIltl l, II 5. /\lltarctic icc corc record of polar temperature (top; dClitcriulll d,il ,I)
,11,,1 ( ,1I'h, III Ii il ,xide.: rOllcclltr;lI'ion (bortoll1 ) for the.: pas!' 800,000 ye.:a rs. I I, wi'I' Ii,
I,d lillnl show m t;;11l I'C1l1pel'ature.: and c~rholl dioxide.: v;llll e.~ ove.:r dif'l\;I\:llt ilill I
",110" M,ll'in<.' isot'opc SI : I~CS arc in il':lli<.:.'> :111(1 !\b ~'i: III ~'l'Il lill : l t i () Il ~; by'l'x (c' I'" , 'I,)
' 1'1,,' I'\' ll i" III>I.I<·k lillrs show till' lilllillg .,1' III\,!\,II:'IIIII.II (·,llilll.'li'"IS ill New '/ ,1,1
1." .. 1, NI II ill /\1I1l'I'i, .1 , ,11111 /\IISII',lIi .1 (k 'i 11'1 ;" ,111 ), S' 1111 '. ,': M. Idil i~·.1 1'1'11111 1,111111 , I
.d" 'DOH ,
189
gas release, the longer-term glacial cycles also were punctuated by nu­
merous short-lived (and likely regional-scale) abrupt climatic changes,
such as the Younger Dryas, Dansgaard-Oeschger, and Heinrich climate
events (Overpeck et al., 2003). These short-term, high-magnitude cli­
matic changes probably exacerbated any stresses that the larger-scale
glacial-interglacial shifts were placing on species, although all of these
kinds of cyclical cbanges seem within bounds of what species have
evolved to withstand in the absence of impermeable geographic barri­
ers (Barnosky, 2001 ; Barnosky et al., 2003; Benton, 2009).
Mechanistically, climate change over the last 100,000 years
changed vegetation substantially in many parts of the world, although
rhe naUlre and magnitude of the changes were different in different
places (Barnosky et al., 2004). In central North America, for example,
rhe end-Pleistocene witnessed a relatively rapid transition of vegeta­
1io nal struculre and composition from a heterogeneous mosaic to a
1I10re mnal pattern that was relatively less suitable to large herbivores
(G raham and Lundelius, 1984; Guthrie, 1984). Abrupt events such as
'he Younger Dryas probably superimposed even more rapid vegeta­
I ion shifts (Sulart et al., 2004). In Australia, the climate became more
.trid as the depth of an ice age was approached, and the surface water
.Ivailable to large animals would have become scarcer and more patch~
il y distributed (Wroe and Field, 2006), Yet, most megafauna species
,IJlpear to have persisted across multiple glacial-interglacial transitions,
' lill y to become extinct within a few thousand years of, and in some
' , I.~es, coincident with, the most recent one (fig. 11-5; extinctions
1II.Irked with black vertical bars).
'I 'he resilience of species can be inferred from the fossil record and
1111 )k;cular markers (Lovejoy and Hannah, 2005). In the Northern
I k misphere, populations shifted ranges southward as the Fennoscan­
.1 1. 111 :u Ki Laurentide ice sheets advanced (or persisted in locally equa­
Ioli ' n.Jugia ; Hewitt, 1999), and then reinvaded northern realms dur­
!1I1', illterglacials. Some species may have also persisted in locally
1,II'ilr:lhle rdllgia that were otherwise isolated within the ntndra and
il ,' /I Irewn landscapes (Hewitt, 1999). In Australia, large-bodied
i', 1.111 I111:1 Is were able to persist throughout the Quaternary (Prideaux et
II I -t o() 7 h), even in remarkably arid landscapes such as the Nullarbor
l'l.dll ( I'ridc:wx ~t :11., 2007:\ ).
' 1'lll'I'C w<:n; nun y lilll l.o's durillg I'IH: h~r 100,000 years when the
I 11.111,111 ' ''''P:II'<'lIll y ,~ 11 iii ,." rrl 'Ill ,', II II 1i,'YIi' w;\rm · w~r conditions, and
li d' I~ ,1)'" lill (Ii !" , I I ,(I , 1>\ 1.~ l'd 1111 III" C"("' lIl.lIld il'l' l'orC d :l l':l), :1 point
~.
1')0
Quaternary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
Calcium concentration (ppb)
Range of dated extinctions
0
400
8?0
ing (in comparison to previous glacial-interglacial transitions) at that
time negatively affect such a wide range of species and habitats (Bur­
ney and Flannery, 2005; Johnson, 2005) to the extent that once­
abundant, ecologically dominant animals simply disappeared? The an­
swer to this question probably lies in threat synergies.
12?0
o
Madagascar, N.Z and Hawaii
West Indies and Mediterranean
North America
191
I
I
I
20
Eurasia
Australia
Threat Synergies, Past and Present
I
40
80
100
Thousands of years before present
1: 11 illIW II Ct .
till ' I.WI
d\'1Io'il'1'
G rc;c.: nland ice core calcium concentrations (parts per billion)
O Wl '
100,000 yc.:a rs. Low values indicate wet-warm conditions with relativc.:l y
vL' ~l,; rarivL:
(ovc.:r, and high values point to a cool-dry climate with spars\'!
1,.1, ,h,d w!,l:l'arion. Also marked are the last glacial maximum, YOlmger Dry:\"
,iI '11'I il , 'III lling c.:vc.:nt, and the Holocene warm period. The timing of extincriuw,
• 'II i',l.l1ld ,~
II' t1I N
:\1ld (OlltinUlts is indicated; also shown are the earliest and latest cxtilll
III Ik rillg ia with Eurasia. Source: Burney and Flannery, 2005.
i'( 'illl<>n.:cd by Ilew stable isotope data from Australia, as described ill
1\1'1)Ilk \.:1' :,1. (2007) ;)nd summaries presented in recent reviews (lbl
III I ,~ky l' l :d., 2004; Koch <lnd Barnosky, 2006). Although such challg...,
1I11111111hrl.'dl y ltd to the disappear~l11ce of various species in local ;11\'.1 ',
,111.1 ,1 lrrrn l r1H.'ir abllllllalH.:e whcre th ey rcmained 0 11 the hnd~c1 1l(' ,
II \,V(' I'lllv1 n,s riley persisted regionall y or gloh~lI y lJnrii I'hc,; die-Ilil o
I 1IIIIIn\ ·d ill r1h' 1:1SI li:w rens of" J)lilll'lllli:l 01' 1'1ll' Plcisl()(t; nc :1I1d illill
1111' I hllll\('IIl·. II' dilll,ll(' d l:1I1!\(' WI'I',' .1 dl'i vl'I' III' Ihost' t"Xlim'lillllll ,
1\' 11.11 '11,1": ,'l1 lllill;'I'I'11I .1 .': 111111.11<1' rill' , 1 1'1'"I1I1/',I\, 11'l1l1l.d !',lllh.1I \\1.11111
The Pleistocene megafauna I die-offs provide a salutary lesson about
the future of biodiversity under projected global warming scenarios,
Over most of the last 2 miilion years, there was a lack ofwidespread ex­
tinctions, particularly of plants (Willis et ai., 2004), despite regular
bouts of extreme climatic fluctuations (fig. 11-5). So what made the
last glacial cycle different? We believe it was the synergy of mutually re­
inforcing events brought by the double blow of anthropogenic threats
and natural climate change. Together, these produced a demographic­
ecological pressure of sufficient force and persistence to eliminate a
~izeable proportion of the world's megafauna species (Barnoslcy et al.,
2004; Brook, 2008; Barnosky, 2009; Blois and Hadly, 2009)-a
group whose evolved life-histo.ry strategy left them particularly vulner­
able to chronic mortality stress from a novel predator and modifier of
habitats (Brook and Bowman, 2005). Without humans on the scene,
dimate change would not have been enough.
A good example of this interaction, using a method of coupling
hioclimate envelopes and demographic modeling in woolly mammoth
Nogues-Bravo et al., 2008), shows how the human-climate synergy
pmbably operated in the High Arctic. The model indicates that mam­
Illoths survived multiple Pleistocene climatic shifts by condensing
II H.:ir geographic range to suitable climate space during climatically un­
1:lvorable times. Finally, however, the new presence of modern hu11I.IIlS during the late-Pleistocene and Holocene, at the same time as a
liJll:1tically triggered retraction of steppe-tundra reduced maximally
I\d l;l blc habitat by some 90 percent (fig. 11-7), resulted in extinction.
'1'11<: important message is that mammoth populations' resilience was
\\,\·:1k.em:d by habitat loss and fragmentation, as it may weil have been
II I pl'\.:violis inrcrgl;1Cia is, bur during that last range reduction the
1Il,lIl1ll1ol'hs wen: 1111;lhk III CI>PI' hl'CllISc,; ol"rhe addition of predatory
1111 ..... .111\ . (and po,~si hl y IIlhl'I' 1.1I111.~\': I!l(' Illodifications) by human
11!11!11·1'11 .
t,
i
11)2
EVIDENCE FROM THE PAST
Quaternary Extinctions and Their Link to Climate Change
193
ing a similar collision of human impacts and climatic changes that
caused so many large animal extinctions toward the end of the Pleis­
tocene. But today, given the greater magnitude of both climate change
and other human pressures, the show promises to be a wide-screen,
technicolor version of the (by comparison) black-and-white letterbox
drama that played out the first time arotmd.
Conclusions
I:11 111111 II '7, (:1im:lI'(; l:I1velope model of habitat suitability in Eurasia for woolly
111 ,11111111 'I'll (M I11NNU/,tfJUS primigenius) at five times over the last interglacial-glacial­
1I11 1'I'!', I... i.t! Ly.:k:. (hrk.(;\' shading indicates higher suitability. Full glacial condi­
I ill ll l, 111\ I I1'J'l'l I :11' 2 1,000 years before present (kyr BP), warm conditions (as warm
"I ' W,l l'lm'\' 1'11 :111 I'()day) at 126 and 6 kyr BP. The white lines indicate hlcely north­
1'1'11 lin Iii .. I' J1(;l)pk:. Line is dotted where there is uncertainty about the limit 01'
11111.1('1'11 IHIIH;l1lS, Source: Nogues-Bravo et al., 2008.
III prin cip le, the same sort of fatal synergy is now attacking many
,-:pl'l'ics, bu t in a much magnified way. Modern climate change is oc­
I IIITiII!!. ~I t a ml1ch faster rate than past events (Barnoslcy et al., 2003)
,II id hCP.~111 in ;) world that was already relatively hot because warming.
,'; l.Irl'nl ill :111 interglacial ratller than in a glacial. By 2050, the planet is
l'I'"jrl'I'l:d ro be hotter than it has been at any time since hum ans
I'l' l li ved ~lS a spec ies. And the backdrop of human pressures on whi<.:h
tid,,, r Xll'e11l..: dimate change is taking place is more pronounced thall
I'WI' hdhr..:; in rhe twenty-first century the human enterprise reacil<.: s
illll) :-tli W 1'1le rs or rile planet (Brook et aI., 2008). Not only arc \oW
":111 1> 111).:, d1c d im;l !'e irsdfro change (Miller ct aI., 2(05), but thanks I'()
IHII' :tll'<":lll y hi /}. h popul:1rioll tknsi ry ;1I1d ongoin g popu lati on g rowl'll
(III',. II .~) , l'Xlv11sivv :lppropri :ll'i()11 nrn:HIII':tI ('; lpir:11 , :H1d recl1llolugi
l.tI I' XI'.IIISil \l1 (,"i ld1 l'll ('1 :tI., 2()()7), WI ' :II'('l illli li11)" m()l'L' I'h :1I1 L'VCI' 1)('
lllil ' 1)llIn' : : pl'~' il" ';' :ll1ilil )' iii Ir.I \'k 1111 '11 111 'I'1"'tI lI,d)II.II :' :IS dim,lll '
I'III", 1''1,illl V :i ll III .11 II ,,.:n II II' ('0 11 111" 1'11 11 f 01'
III :11 II 'I I , w( ' ,11'\' \V i 111\ ,,'i:,
I
,
The important message from the late Quaternary megafalmal extinc­
tions is not so much that humans caused extinctions in many (maybe
most) places and climate caused them in others. Rather, the key point
is that where direct human impacts and rapid climate change coincide,
fatalities are higher and faster than where either factor operates alone.
It is the synergy that presents the biggest problem, and that synergy is
exactly what we find ourselves in the middle of today. Indeed, syner­
gies between seemingly different causal mechanisms seem to charac­
terize mass extinctions in general (Barnoslcy et al., 2011).
Today, that intelligent predatory ape, tlle human species, is driving
a planetwide loss and fragmentation of habitats, overexploitation of
populations, deliberate and accidental introduction of alien species be­
yond their native ranges, release of chemical pollution, and tlle global
disruption of the climate system. Most damaging of all is tlle interac­
tions among tllese different threats, which mutually reinforce each in­
dividual impact. Are the modern extinctions resulting from these pro­
cesses a much magnified version of what already happened once to
canse the late Quaternary megafauna extinctions, and can this perspec­
I·ivc illuminate how to chart the future to avoid an even more severe
hiotic collapse? The emerging consensus quite clearly says yes, and
Ihat conclusion, in turn, implies that only a systems-based approach to
til reat abatement will be effective in staving off future extinctions.
Conversely, coming at the problem from trying to figure out what
v:llIscd Quaternary extinctions, the question "Was it humans or natu­
1,11 ,'I i111 ate change that t(xever ended the evolutionary journey ofhtm­
drcds of mcgabllnal species?" is the wrong one to ask. That question
i1 111 ic ip ~ltcs ;) uni cau ,d IllCch:lIJisrn, which might be appealing on parsi­
illOllioliS gT() 1I11d,~ , hIli ,':111Iltll h<.: ,~lIpported by fossil, archeological,
l i lll : ll()l()g i~·: tI , :l1ltlllltllldill)" ('vi dclI l·(' . IllSI' ~lS I()r our modern global
Il;'Hliv('rsil y ' I'i ,,:i,", 1,111' i.lill'l (1" 1'" , ()VI'1'IlIJllring) mil)' dotl1i ­
11 ,111 ' III 1'111' II!.\( I' , ,111.1 ,I /11 '11111.11.111111 :,111111 '\\11,,'1 '1' d,-:\, (1',1'" , .1 ,~ p(·, ' i\' ,'·:
I
1')4
Quaternary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
disappearing off a mountaintop that heats up too much). But at the
global scale, synergy among the distinct proximate causes adds up to
IIlOI"C than the sum of each individual cause. If one insists on a mini­
malistic answer for what caused the late Quaternary extinctions, it
seems to be this: the actions of colonizing and expanding prehistoric
hllmans (primarily hunting and habitat modification) seems omni­
pn.:scnt in the past global extinction (Brook et aI., 2007; Gillespie,
OOH), but in many cases, species were left much more vulnerable be­
(:lllSC of climate-induced range contractions and changes in habitat
(JI':llity (Guthrie, 2006; Nogues-Bravo et al., 2008).
The degree to which climate change was the "straw that broke the
~ .lInd's back" probably differed to some extent for each species of ex­
r iIll:t Quaternary megafauna, and will only be really understood after
(ktailed study of each extinct species (Koch and Barnosky, 2006). But
Ille bet that even "natural" climate change synergistically exacerbated
t.:Xtinctions when human pressures first increased is worrisome in the
i11( )dcrn context. The climate change is now far outside the bounds of
whar is normal for ecosystems (Barnosky, 2009), and the other kinds
()j" 11lIman pressures on species are so much greater than Earth has ever
seen. In the end, it will not only be the extent to which we can mini­
Illize each individual cause of extinction-increasing human popula­
ri( >11 and attendant resource use, habitat fragmentation, invasive spc­
('il:s, and now, global warming-but also the degree to which we call
Illinimizc the synergy between each separate cause that will determine
jllSt how many species we lose.
Aclmowledgments
\lVt.: thank Marc Carrasco, Kaitlin Maguire, Lee Hannal1, and
t'I'V( I
lymolls reviewers for constructive comments. BWB's research
(Ill ('his topic was supported by Australian Research Council gr:lIli
I )I'OXX 1764, :)lld ADB's by grant DEB-OS43641 from the US N:l
i ;( III :d S<.:icllcc foundation.
. 1I1<)!
REFEREN C I';S
I\I, '''Y, J. l OIlI . "1\ 1IIIIIIi" I)('(' i('" () vrrk ill :.1111111.111. 111 "I li1l" "Iltl 1·It:I S I(l~·~·ll l· 1IIl','.>'
1.11111,11 1I1.1·i:. '·~ IIII'III)II." Sli"'/I ·,. I 'I.I : Ili'I ,1 I)r.
11 ..11111"'.) ,1\ , l'IIlro , " I ': ~II"'II"" 1.1,. '11: ,,11.1, li ll l~ l iI I, ".111 '111I': ' 1'11\' :: II\lIill' .1111 1 .1/
195
past selection pressures for conservation biology." Trends in Ecology and Evolu­
tion 11: 193-96.
Barnosky, A. D. 1986. "'Big game' extinction caused by Late Pleistocene climatic
change: Irish elk (Megalocel'osgiganteus) in Ireland." Quaternary Reseanh 25 :
128-35.
Barnosicy, A. D. 2001. "Distinguishing the effects of the Red Queen and Court
Jester on Miocene mammal evolution in the northern Rocky Mountains :'
Journal ofVertebl'ate Paleontology 21: 172-185.
Barnosky, A. D. 2008. "Megafauna biomass tradeoff as a driver of Quaternary and
future extinctions." Proceedings of the National Academy ofSciences, USA 105 :
11543-48.
Barnosky, A. D. 2009. Heatst1'Oke: Nature in an Age ofGlobal Warmil'!5 . Washing­
ton, D.C. : Island Press.
Barnosky, A. D., and E. L. Lindsey. 2010. "Timing of Quaternary mega faunal ex­
tinction in South America in relation to human arrival and climate change:'
Qptatel'11a17 Jnternational 217: 10- 29.
Barnosk)', A. D ., E . A. Hadly, and C. J. Bell. 2003. "Mammalian response to
global warming on varied temporal scales." Journal oflvlammalogy 84: 354­
68 .
Barnosky, A. D., P. L. Koch, R . S. Feranec, S. L. Wing, and A. B. Shabel. 2004 .
''Assessing the causes of Late Pleistocene extinctions on the continents:' Sci­
ence 306: 70-75.
Barnosicy, A. D ., N. Matzke, S. Tomiya, G. O. U. Wogan, B. Swattz, T B. Quental,
C. Marshall, et al . 2011. "Has the Earth's sixth mass extinction already ar­
rived>" Nature 471: 51-57.
Benton, M. J. 2009. ''The Red Queen and the Court Jester: Species cijversity and
the role of biotic and abiotic factors through time:' Science 323: 728-732 .
Blois, J. L., and E. A. Hadly. 2009. "Mammalian response to Cenozoic climate
change." Annual Review of Earth and Planeta17 Sciences 37. doi:10.1146
/ annurev.earth.031208.100055.
noclmer, R. E., J. F. Eisenberg, and K. H. Redford. 1997. "Hunting and the like­
lihood of extinction of Amazonian mammals:' Conse1'Vatiort Biology 11: 460­
66 .
Ilrook, B. W. 2008. "Synergies between climate change, extinctions and invasive
vcrtebrates." Wildlife Research 35. doi: 10.107 1/ wr07116.
1:l()ok, D. W, and D. M. J. S. Bowman. 2004. ''The uncertain blitzkrieg of Pie is­
!OCtllC megafauna:'Jou1"nal ofBiogeogl'aphy 31: 517-23.
III'nok, It W., and D . M. J. S. Rowman. 2005. "One equation fits overkill: "Vhy al­
lomerry underpins horh prehistoric and modern body size-biased extinc­
li(lII S." P(JPJtIt1.tili1',l !({)II~f(" 4 2 : 147- S1.
111'1\,,1<., II. W. , :md (:. N. ",Ii, l.~" '" 2()()(1. "Scic<:l'ivc hUl1tingofjuveniles as a cause
"i' !'ill' iIl1l1('I'('('1 11ihl. · "\'I 'I'kl li .. i' lilt' I\IISIr:lli :1I1 Pki:;roccilc ' megafauna:"
, 1I1 '11t ' 1 ';/~1111 S/,I" /IIIIIII/" I : ,il) III
'LI ,)I
IiI
1l)6
Quaternary Extinctions and Their Link to Climate Change
EVIDENCE FROM THE PAST
llrook, B. W., D. M. J. S. Bowman , D. A. Burney, T F. Flannery, M. 1(. Gagan,
R. Gillespie, C. N. Johnson, et al. 2007. "Would the Australian megafauna
have become extinct if humans had never colonised the continent?" QJtater­
nary Science Reviews 26: 560--64.
Ilrook, B. W., N. S. Sodhi, and C. J. A. Bradshaw. 2008. "Synergies among extinc­
tion drivers under global change:' Trends in Ecology and Epolution 23: 453-60.
IllIlte, E., R. D . Horan, and J. F. Shogren. 2006. "Megafauna extinction: A pale­
oeconomic theory of human overkill in the Pleistocene:' Journal ofEconomic
Behavior&Otganization 59: 297-323.
lIlimey, D. A., and T F. Flannery. 2005. "Fifty millennia of catastrophic extinc­
tions after human contact:' Ti'ends in Ecology & Evolution 20: 395-401. I ):lIllllth, J. 1981. "Population density and body size in mammals:' Nature 290: 699-700.
I )III1Cal1, R. P., T. M. Blackburn, and T. H. Worthy. 2002. "Prehistoric bird extinc­
tions and human hunting:' Proceedings ofthe Royal Society ofLomkm B - Biolog­
iL'f,ll Sciences 269: 517-21.
I:i,'( lei, S. ]. 2005. "Man's best friend - mammoth's wors t enemy? A speculative es­
sayan the role of dogs in Paleo indian colonization and megafaunal extinc­
tioll:' WorldArchaeology 37: 11-25.
( ; iIlespie, R. 2008. "Updating Martin's global extinction model:' Ouaternary Sci­
cnce ReJJiews 27: 2522-29.
(;illcspie, R., B. W. Brook, and A. Baynes. 2006. "Short overlap of humans and
megafauna in Pleistocene Australia:' Alcheringa Special Issue 1: 163-85.
(;r.l harn, R. W. , and E. L. Lundelius, Jr. 1984. "Coevolutionary disequilibriulll
~n d Pleistocene extinction:' In Quaternary Extinctions: A Prehistoric Revolu­
'ion, edited by Paul S. Martin and Richard G. Klein, 223-49. Tucson: Univer
silY ofArizona Press.
t ;1',1>'.~ (l1l, O. 1(. 2007. "Deciphering North American Pleistocene extinctions."
III/wnal ofAnthropological Research 63: 185-213.
(;lIlhric, R. D. 1984. "Alaskan megabucks, megabulls, and megarams : The issul'
(,I" I'lcisl"Occne gigantism :' Contributions in Qpaternary Vel1:ebrate Paleont(}It~1.'Y :
I Volmnc in Menwrial to John E. Cuilday. Carnegie Museum of Natural II i ~
IIH'y Spcci:ll Publication 8: 482-510.
( ;111 IlI'iI." , R. D. 2003. "Rapid body size decline in Alaskan Pleistocene horses Iw
Ii >rc cxrinctioll." Nat~tre 426: 169-71.
(:lIilll'k', R. D. 2006. "New carbon dates link climatic change with hllJ11:11l \'01"
lIi'/,:II iOIl :llld Pleistocene: extinctions:' Nature 441: 207-09.
I 1.1I \ lIlIrI, A. 11., -". A. Copperu, and S. A. Parks. 2002. "Rarity, speci:l liz:lrioll .111.1
0 1illLl"ion in primates." joumal ~fBi(}ge(~fTrrtp/~y 2lJ: 445- 56.
11.1 ), 11(",\ , ( ;. V. 200X. "Yollngcr Dryas 'hhH.:k Ill:lI S' :lnd 1ilc R:\Ilcholahren ll Il'I'illil'"
Ij'"1 ill N,>rtil I\rncri(:l." l 'rot"rrtlh(,J,I' I{,I'I" NII,iolllll I I,."tlOIIY I!/'S,.it'llt"l ,.(, l iS I
lOS; (IS20 2~ .
I I(\\, jll , l: , 'vI, I'I')!) , " 1'(>.\II',l.ui. rI 11 ' .111,,111 / .11111" 1111 .11'''1 ....111 l,j ll!.I ," l/ill/'I"i"tI
101lIlill/II('/i,' l,il//lI'II/I SO/ '1"' 1' 1.11 , II ' I I '
197
Hijmans, R. ]., and C. H. Graham. 2006. ''The ability ofclimate envelope models
to predict the effect of clinlate change on species distributions:' Global
Change Biology 12: 2272-81.
IPCC. 2007. I ntetgopent1nental Panel on Climate Change: Fourth Assessment Report
(AR4). Available at http: //v.rww.ipcc.ch.
Johnson, C. N. 2005. "What can the data on late survival of Australian megafauna
tell us about the cause of their extinction?" Q!tate'rnal'Y Science Reviews 24:
2167-72.
Koch, P. L. , and A. D. Barnosky. 2006. "Late Quaternary extinctions: State of the
debate:' Annual Review ofEcology, Evolution and Systematics 37: 215-50.
Lovejoy, T. E., and L. H,mnah, eds. 2005. Climate Change and Biodivmity. New
Haven : Yale University Press.
Luthi, D., M. Le Flodl , B. Bereiter, T. Blunier, ].-M. Barnola, U. Siegehnthaler,
D . Raynaud , et al. 2008 . "High-resolution carbon dioxide concentration
record 650,000-800,000 years before present." Natm'e 453: 379-82.
Lyons, S. K., F. A. Smith, and]. H. Brown. 2004a. "Of mice, mastodons and
men: Human-mediated extinctions on four continents." Evoltttiorla1'Y Ecology
Reseanh 6: 339-58.
Lyons, S. K., F. A. Smith, P. J. Wagner, E. P. White, and]. H . Brown. 2004b. "Was
a 'hyperdisease' responsible for the late Pleistocene megafaunal extinction?"
Ecology Letters 7: 859-68.
MacPhee, R. D. E. 1999. Extinctions in Near Ti'me: Causes, Contexts, and Conse­
quences. New York: Klllwer Academic/PlemUTI Publishers.
Martin, P. S. 2005. Tivilitfht ofthe Mammoths: Ice Age Extinctions and the Rell1ilding
ofAmerica. Berkeley: University of California Press.
McKinney, M. L. 1997. "Extinction vulnerability and selectivity: Combining eco­
logical and paleontological views:' Annual ReJJiI:lV of Ecology and Systematics
28: 495-516.
iller, G . H., M. L. Fogel, ]. W. Magee, M. 1(. Gagan, S. J. Clarke, and B.]. John­
son. 2005 . "Ecosystem coUapse in Pleistocene Australia and a human role in
megafaunal extinction:' Science 309: 287-90.
Nogues-Bravo, D., J. Rodigllez, J. Hortal, P. Batra, and M . B. Araujo. 2008. "Cli­
mate change, humans, and the extinction of the woolly mammoth:' PLoS Bi­
ology 6: 685- 92.
NOf!, ucs-Bravo, D., Ohlemuller, R., Batra P., and Araujo, M. B. 2010. "Climate
predictors oflate Quaternary extinctions." Evolution 64: 2442-49.
( )vl: lp;ck, J. T., C. Whitl()ck, and B. HlU1tley. 2003. ''Terrestrial biosphere dynam­
it:s in the climate system: Pasr and future:' In Paleoclimate, Global Change and
'he FutHrc, cdited by R. S. Br:ldky, T. F. Pedersen, 1(. D. Alverson, and K. F.
Iklwnann , RI- I () ~ . Ikrli ll : Springcr-Vcrl:l g.
l"IIIlII'san, C. 2()()(). " I':,'() I, 'I',k ,d ,II Id ('v()llIl'ion:lry rcspollsc to recent climate I'II:IIII \r ." 1 1/1/11/(" 1II""i,.,>, o(iilo/ill/v ";"o/Illioll Ilud SV.,·'t'I·Nr.ttics 37: 637- 69. I',,, ". (; , L, (; , I:" Wi''''' , I, :\ , 1'," ,\1" " , X, 1:"11/ '" A, S. MIIIT,'Y. 1\. N. C()oke, S. A. 11,,, kllllll , .111111 , II '; "101,, '1111 " 111111111'. 1I1i'1'"II:lIlIl.rI ~' s l i lhlillll ""i1I1'
,"1
I'IX
EVTDENCE FROM THE PAST
Pleistocene Darling Downs, eastern Australia: The promise and pitfalls of
dating as a test ofextinction hypotheses:' Quaternary Science Reviews 30 : 899­
l) 14.
1',"Jt,all x, G. J., J. A. Long, L. K. Ayliffe, J. c. Hellstrom, B. Pillans, W. E. Boles,
M . N. Hutchinson, et al. 2007a. "An arid-adapted middle Pleistocene vene­
hrate fauna from south-central Australia:' Nature 445: 422-25 .
I', id(';IU X, G. J" R . G. Roberts, D . Megirian, K. E. Westaway, J. c. Hellstrom, and
J. I. Olley. 2007b. "Mammalian responses to Pleistocene climate change in
,~()lItheastern Australia :' Geology 35 : 33-36.
'ill'lli: lI, W, P. J. Crutzen, and J. R. McNeill. 2007. "The Anthropocene: Are hu­
I\\an~ now overwhelming the great forces of nature?" Ambio 36: 614-21.
0.; 111,11'1, A. J., P. A. Kosintsev, T. F. G. Higham, and A. M. Lister. 2004. "Pleis­
locene to Holocene extinction dynamics in giant deer and woolly mam­
,"oth:' Nature 431: 684-89.
Slirovell, T., N. Waguespack, and P. J. Brantingham. 2005 . "Global archaeological
I.: vidcnce for proboscidean overkill:' Proceedings ofthe National Academy ofSci­
t'n ce.\~ USA 102: 6231-36.
' I ·!tomas, C. D ., A. Cameron, R. E. Green, M. Bal<kenes, L. J. BeaLUTIont, Y. C.
(:ollingham, B. F. N . Erasmus, et al. 2004. "Extinction risk from climate
change:' Nature 427: 145--48.
'1lulgc, C. 1989. "The rise and fall of Homo sapiens sapiens.» Philosophical Transac­
films ~f'the Royal Society ofLondonB 325: 479-88.
Wt'Sl, ( •. g" and J. H. Brow n . 2005 . "The origin of allometric scaling laws in biol­
ogy I'i'om genomes to ecosystems: Towards a quantitative unifYing theory of'
hiol vgical structure and organization:' Journal of Experimental Biology 208 :
I S7S- 92 .
Willi ,~, K. )., K. D. Bennett, and D. Wall(er, 2004. ''The evolutionary legacy ofthr
I.'r Ages:' Philosophical Transactions ofthe Royal Society ofLondon B - Biologicfll
SI'i1'1'I /:CS ~59:
157-58.
W" 11' , S. , ;Ind J. Field. 2006. "A review of the evidence for a human role in the ex
I illt'l iOIl of Australian megafauna and an alternative interpretation ?' Quat/:I'
lilli '\, Science Reviews 25: 2692-703 .
Chapter 12 Quaternary Tropical Plant Extinction: A Paleoecological Perspective from the N eotropics MARK B. BUSH AND NICOLE
A. S.
MOSBLECH
'': 1 ,
We have found no examples of global plant extinctions from the trop­
ics within the Quaternary, Examples ofextinctions over longer periods
of time are readily documented within the fossil record, with the loss
of whole families evident between Eocene and modern times (Morley,
2000, 2007). Herein lies a clue to the problem of detecting extinction
of tropical plants-the ta.,'(onomic resolution of the fossil record.
Most of the paleobotanical records that we have from the tropics
are based on fossil pollen, plus a few on wood, and even less on seeds
,1l1d other macrofossils. With a few exceptions, fossil pollen identiflCa­
tions are at the genus or family level, and so an extinction sufficient to
remove an entire genus would be the minimum detectable level of
loss. Because many tropical genera contain congeners that occupy very
diHerent habitats, losing all of them requires a huge change in the eco­
sy~tem, or a lot of bad luck. Over long enough periods of time, evolu­
I iOIl, luck, and continental-scale modifications of climate are possi­
Ilk, and extinction does become evident. Because of this taxonomic
I)i ::l.~, we actually have a clearer vision of extinction that took place be­
I w\.:cn rhe Eoccn( ;lI1d rhe M ioccilc than we do across the much
,II Ie )In: !' rill1csc lic e)f 1'11(' (J II ; lr~TI 1:11')'. We can sec at that scale that major
i lilll:llic ( Will'S :1t1d SI't'\':ld "i' lin' inil i:l rcd cycles of species loss and
'IP"i ' i :llil)tl , II i s 111)1 1I111'1',I!a)ll.lhk '" S IIPpCl.~~' rhar the spread of fire
II)"