NEW ECOLOGICALPERCEPTIONS
OF ARID RANGELANDS
A. ROTHAUGE
Neudamm
Agricultural
College,
PrivateBag13188,
Windhoek,
Namibia
ABSTRACT
T h e r a n g e s u c c e s s i o nm o d e l e x p l a i n sf l u c t u a t i o n isn
vegetationas an orderlychangebetweendifferentvegetation
s t a t e sd u e t o t h e i n t e r a c t i o n
of - and eventuae
l quilibrium
b e t w e e n - t h e i n h e r e n ts u c c e s s i o n atle n d e n c yo f p l a n t s
(improving
t h e r a n g et o w a r d sc l i m a xc o n d i t i o na) n d g r a z i n g
p r e s s u r e ( c a u s i n g r a n g e d e t e r i o r a t i o na n d a p i o n e e r
c o n d i t i o n ) .T h i s m o d e l d o e s n o t a c c u r a t e l yd e s c r i b ea n d
p r e d i c t c h a n g e s i n a r i d a n d s e m i - a r i dv e g e t a t i o n
communities
and is thereforeof limitedvalueto the rangeland
m a n a g e r . C o n s e q u e n t l ya, n e w m o d e lw a s d e v e l o p e di n
1 9 8 9 , b u t i s s t i l l u n t e s t e di n t h e N a m i b i a ne n v i r o n m e n t .
A c c o r d i n gt o t h e n e w s t a t e - a n d - t r a n s i t im
on
o d e l ,v e g e t a t i o n
can occurin a varietyof stateswithtransitions
betweenstates
occurringin an orderlyfashionor not. However,all states
a n d a l l t r a n s i t i o n cs a n b e d e s c r i b e da n d t h i s c a t a l o g u ew i l l
e x t e n d a s k n o w l e d g eo f t h e e c o l o g yo f a r i d r a n g e l a n d
i n c r e a s e sN
. a t u i a le v e n t s( p r i m a r i l rya i n f a l lb, u t a l s of i r e )o r
m a n - m a d ee v e n t s ( e . 9 . r a n g e l a n dm a n a g e m e n t d
) rive
t r a n s i t i o n sb e t w e e nd i f f e r e n st t a t e s . I n N a m i b i a ' sh i g h l y p u l s e de n v i r o n m e n t h
, e v e g e t a t i o ni s i n a c o n s t a n st t a t eo f
inequilibriub
me c a u s ee v e n t sf o l l o we a c ho t h e rr a p i d l y T
. his
h a s s e r i o u si m p l i c a t i o nfso r t h e t r a d i t i o n arl a n g e l a n d
manager,who prefersafairlyrigidmanagementprogramme
s e t b y a c a l e n d aa
r n d n o t t h e c o n d i t i o no f t h e v e g e t a t i o n l. f
t h e s t a t e - a n d - t r a n s i t i omno d e l p r o v e s t o b e a n a c c u r a t e
r e f l e c t i o no f t h e e c o l o g yo f N a m i b i a nr a n g e l a n d t, h e
r a n g e l a n dm a n a g e rm u s t b e c o m e m o r e f l e x i b l ea n d
o p p o r t u n i s t i c .S e v e r a l p r i n c i p l e so f o p p o r t u n i s t i cr a n g e
m a n a g e m e natr ed i s c u s s e dw, h i c hm i g h ts e r v ea s a g u i d e l i n e
t o w a r d sd e v e l o p i n ga n a p p r o p r i a t em a n a g e m e nst t y l ef o r
a r i dr a n g e l a n d .
INTRODUCTION
In theory,rangelandmanagersmanipulate
the productivity
and
conditionof naturalveldto achievethe highestpossibleanimal
productionoff the veld withoutcausingveld degradation.In
practice,veld degradationoften resultsbecausethe aim of
preventingveld degradationremainsa theoreticalobjective
only,or becauseof insufficient
knowledgeof the ecologyof
N a m i b i a nr a n g e l a n dA. c o r r e c tu n d e r s t a n d i nogf t h ev e l da n d
factorswhichcauseit to change,is of courseessentialin order
to managethe veld efficientlyand manipulateit to achieve
farmingobjectives.lt has long been understoodthat models
and theoriesare tools that aid this process(Fraser& Lugg,
1962). However,it is vitalthat the modelaccuratelyreflects
what is goingon in the plantcommunity,otherwiseit will lead
rangemanagementdown the wrongtrack.
T H E R A N G ES U C C E S S I O N
MODEL
The most widelyacceptedmodelwhich explainschangesin
the vegetationcommunityis the range successionmodel,
w h i c h w a s d e v e l o p e da t t h e b e g i n n i n go f t h i s c e n t u r yi n
northernAmericaand is basedon Clementsianconceptsof
plantecology.lt supposesthat the stateof a givenrangeland
v a r i e si n a c o n t i n u u ma n d i s d e t e r m i n e dp r i m a r i l yb y t w o
opposingforces,viz. the inherentsuccessional
tendencyof
plantsto developintomoreproductive
and stablecommunities
and grazingpressure,which forces plantcommunitiesback
into less developedstates. The most highlydevelopedand
stablestateis achievedin theabsenceof grazingand is termed
t h e c l i m a x( H o l e c h e cek t a l . , 1 9 9 5 ) .A s g r a z i n gp r e s s u r eo n
t h e v e g e t a t i o ni n c r e a s e s i,t s s t a t e i s c o n t i n u a l l yr e d u c e d
towardslesswell-developed
states,termedsub-climax
states,
u n t i l e v e n t u a l l yt h e r a n g e l a n di s h e a v i l yg r a z e d ,h i g h l y
degradedand poorlydeveloped.
Thisstateis termeda pioneer
state.The managercanachievea stablestatein hisrangeland
by manipulating
thegrazingpressureuntila balanceis reached
betweenthesetwo opposingforces,stabilising
the vegetation
at a statewhichsuitshis purpose(Figure1).This situationis
t e r m e da n e q u i l i b r i u m .
Otherfactorsthanplants'inherentsuccessional
tendencyand
grazingpressurealsohelpin shapingthe vegetation,
butwork
in similarwaysas thesetwo mainfactors.Droughtfor instance
a f f e c t sv e g e t a t i o ni n a s i m i l a rw a y t o g r a z i n g ,t h e r e f o r e
managementshouldrespondto droughtby reducinggrazing
p r e s s u r et o m a i n t a i ne q u i l i b r i u m .S i m i l a r l ys, u c c e s s i o n a l
tendencyis acceleratedin yearsof above-averagerainfall(Fig.
2) and can be balancedby increasedgrazing.
Successional
tendency
#
Poorcondition
earlysuccessional
heavily-grazed
Condition scale ----------------
Excellentcondition
climax ungrazed
Figure1. Generalschemeof the RangeSuccession
Model(Westobyet al., 1989)
AGRICOLA2OOO
49
Successional
tendencv
t
Poor condition
earlysuccessional
heavily-graze
conditionscale ____|>
(Westobyet al.,
rainfallvariability
Figure2. The RangeSuccessionModelincorporating
MODEL
C R I T I C I S MO F T H E R A N G ES U C C E S S I O N
The rangesuccessionmodelaccuratelyexplainsvegetation
c h a n g e si n h u m i da r e a s .H e r e , r a i n f a l il s h i g h a n d o c c u r s
tendencyof plants
regularlyso thatthe inherentsuccessional
occurs in a continuumfrom pioneerthroughsub-climaxto
climax states. However,in arid and semi-aridareas, plant
successionis not continuousnor is it consistent.Sometimes,
it is not even reversible(Westobyet al., 1989). The range
explaintheseunorderly
modeldoesnotadequately
succession
changesin statesbecausethey are not primarilythe resultof
grazingpressureor successional
tendencies.
In aridand semi-aridareas,rainfalldominatesall otherfactors
that affectvegetationstates.As everyNamibianfarmerknows,
there is no veld to be grazed during a prolongeddrought,
irrespectiveof the grazingpressureappliedto the range in
the precedingseasons. Similarly,Namibianveld types are
knownto be resilientand ableto recoverrapidlyin seasonsof
high rainfall,even if fairly heavilygrazed. These examples
demonstratethat changesoccur in the vegetationdue to the
rainfallit receivesand lessas a resultof grazingpressure.In
fact, the carryingcapacityof an arid rangecan be modeled
factorssuch as efficiencyof
directlyon rainfall,incorporating
rainfalluse,animaldry matterintakeand acceptableutilization
of the range plants(grasses)as constants(Sweet, 1997a;
19 9 7 b ) :
Carryingcapacity(ha/LSU)= 1/(mmmean annualrainfallx
0,00034)
I n a d d i t i o n ,r a i n f a l li n a r i d a r e a s i s h i g h l y e r r a t i c a n d
states.
of vegetation
causingfrequentdisruption
unpredictable,
climatic
event
The vegetationhas hardlyrecoveredfrom one
in
a
highly-pulsed
when the next one strikes.The vegetation
environmentlike Namibia'sis in constantflux, in a constant
and a balancebetweenopposingforces
stateof inequilibrium,
i s n o t a t t a i n e d( W e s t o b ye t a l . , 1 9 8 9 ) .
Africansavannasare mostlyin the arid and semi-aridzones
of sub-SaharanAfrica,wedged betweentropicalrainforests
and subtropicaldeserts.Theysupportthe biggestdiversityof
herbivorespeciesand the largestanimalbiomassof any land
1979;Skarpe,199'l).The
ecosystemin the world(Eltringham,
pressure
grazing
on the vegetation,
herbivoresexertenormous
yet it is in climaxcondition.The vegetationof Africansavannas
evolved togetherwith their herbivoryand the plants need
50
t
Excellentcondition
climax ungrazed
'1989).
defoliationjust as much as the herbivoresneed plant food
(McNaughton,
1979). Removethe grazingpressureand the
v e g e t a t i o nw i l l b e c o m el e s s p r o d u c t i v ea n d l e s s r e s i l i e n t .
T h e s e o b s e r v a t i o n sa r e i n d i r e c t c o n t r a s tw i t h t h e r a n g e
successionmodelas the climaxstatecan onlv be achievedin
the absenceof grazing.
Grazingpressureand stockingrateare essentialconceptsof
the rangesuccessionmodel,yet they are highlysubjective
t e r m s a n d d e p e n do n m a n a g e m e n ot b j e c t i v e s . D i f f e r e n t
interpretations
of stockingrate will influencethe equilibrium
state of the vegetationand lead to incorrectmanagement.
B e h n k e( 1 9 9 7 )a n d B e h n k ea n d A b e l ( 1 9 9 6 a ,1 9 9 6 b )h a v e
a r g u e d c o n c l u s i v e l tyh a t s t o c k i n gr a t e c h a n g e sw i t h a
manager'sobjectiveand that much of the overstockingand
part of the degradationdebate is based on misconceptions
betweenpeoplewho do not realizethat they have different
andthereforedifferentstockingrates,
management
objectives
all withinthe ecologicalcarryingcapacityof the range. Their
argumentsare brieflyrepeatedhereto illustratethe variability
"stockingrate"and its implications
for the range
of the concept
management.
model
and
rangeland
succession
On a curvethat depictsanimaloutput(in terms of individual
a n i m a lo u t p u ta s w e l l a s t o t a l a n i m a lo u t p u tp e r u n i t a r e a )
versusthe stockingrate,at leastthreedifferentstockingrates
can clearlybe identifiedas managementobjectives(Fig. 3).
They are MN, MY and K. At stockingrate MN, the numberof
animalson the rangeis smallenoughto preventcompetition
b e t w e e na n i m a l sf o r f e e d , a l l o w e a c h a n i m a l m a x i m u m
nutritionand thereforeenableseach animalto performto the
maximumof its geneticability. Totalanimaloutput per unit
l nimal
a r e a h a s n o t y e t b e e n m a x i m i s e d ,b u t i n d i v i d u a a
productionhas. This stockingrate intereststhe stud breeder
or any other farmer who sells animalsbased on their own
performanceor geneticmerit.
At a secondstockingrate MY the numberof animalsutilising
the range has been increasedto such an extent that they
competefor feed,consumelessthantheycouldand therefore
performat a lowerlevelthan geneticallypossible.However,
the numberof animalsis highenoughto compensatefor the
to such an extent
decreasein individualanimaloerformance
thattotalanimaloutputper unitareais at a maximum,beinga
f u n c t i o no f b o t h t h e n u m b e ro f a n i m a l sa n d t h e i r i n d i v i d u a l
"intensive"
output. This stockingrate is of interestto the
livestockfarmer,who aims for the highestpossibleanimal
productionoff his primaryresource,the veld.
AGRICOLA2OOO
pressure"needsto be carefullydefinedbeforebeing inserted
i n t o t h e r a n g e s u c c e s s i o nm o d e l , s i n c e o n e f a r m e r ' s
may be the nextfarmer'sunderstocking.
overstocking
lvlassgain (kg)
Thesethen in shortare some of the criticismsleveledat the
rangesuccessionmodel. Over time, it becameevidentthat
explainchangesin the semithis modeldid not satisfactorily
arid and arid rangelandand a new modelwas required.
MODEL
THE STATE.AND-TRANSITION
Stockingrate (livestockunits/ha)
rates(adapted
optimal
stocking
Figure
andeconomically
3.Biologically
fromBehnke,
1997).
At stockingrateK, the numberof animalson the rangeis very
high and competitionfor feed is intense.Animalsbarelystay
alive,theydie at the same ratethan youngonesare bornand
gain no weightbecausethey are at maintenancelevel. This
stockingrate is termedthe ecologicalcarryingcapacityas it
r e p r e s e n t st h e a b s o l u t em a x i m u mn u m b e ro f a n i m a l st h a t
couldbe sustainedon the range. lt mightbe of interestto the
game farmer or parks officerwho wants to maximisethe
n u m b e ra n d d i v e r s i t o
y f a n i m a l so n a r a n g e .
Anothertwo targetstockingratescan be identifiedon Fig. 3
on economicgrounds. The first is MP, the stockingrate at
which maximumprofitis obtained. This occursat a slightly
lowerstockingratethan MY sinceprofitis only madeas long
as the returnis largerthanthe cost or investment.This does
not happenat MY where return= cost, but at a unit below
M Y i . e .t h e l a s t u n i t t h a t s t i l ly i e l d sa r e t u r nh i g h e rt h a n i t s
"businessman"
cost. This stockingrate is of interestto the
farmerwho aims to maximiseprofitfrom his farm.
T h e s e c o n de c o n o m i c a l liym p o r t a nst t o c k i n gr a t e i s a t M O ,
s l i g h t l yb e l o wK . A t t h i sv e r y h i g hs t o c k i n gr a t e ,t h e a n i m a l s
are performingat a very low individuallevelsincecompetition
f o r f e e d i s i n t e n s e .H o w e v e rt,h e y s t i l lg e n e r a t ea n i n c o m e ,
h o w e v e rs l i g h t ,s i n c et h e y a r e s l i g h t l ya b o v e m a i n t e n a n c e
l e v e l . T h i s s t o c k i n gr a t e i s a m a n a g e m e n to b j e c t i v ei n
c o m m u n aal r e a s ,s i n c ee v e nc o m m u n asl u b s i s t e n cfea r m e r s
n e e d i n c i d e n t ailn c o m et o p a y f o r c e r t a i ne x p e n s e s ,e . g .
a c c e s s t o c o n t r o l l e db o r e h o l e s( C h r i s t i a n 1, 9 9 8 ) . l t
r e p r e s e n ttsh e m a x i m u mn u m b e ro f l i v e s t o c sk t i l lc a p a b l eo f
e a r n i n ga s m a l l i n c o m ef o r t h e i ro w n e ra n d s i n c e l i v e s t o c k
c u s t o m a r i l by e l o n g st o m a n yo w n e r s ,i t a l s oa c c o m m o d a t e s
a m a x i m u mn u m b e r o f o w n e r s .i . e . o o e n a c c e s s t o t h e
g r a z i n gl a n d s .
are basedon a misunderstanding
Accusations
of overstocking
of differentmanagementobjectives,sincedifferentaimsrequire
"Grazing
differentstockingrates (Behnke& Abel, 1996a).
AGRICOLA2OOO
The state-and{ransitionmodel was formally proposedby
Westoby and co-workersin 1989 to substitute the range
successionmodel in arid and semi-aridareas, althoughits
originscan be traceda longway back (Walter& Vlok, '1954;
Westoby,1980). lt statesthat vegetationcommunitiescan
existin severaldiscretestatesand can changefromone state
to the next by meansof a transitionthat was causedby an
event.Changesbetweenstatescan be orderlyand consistent
or not, dependingon the eventthat causedthe transition(s).
However,all statesand alltransitions
can be clearlydescribed
and this cataloguewill probablyexpandas knowledgeof arid
environments
increases.Eventscan be natural(e.9.climate,
f i r e ) o r m a n - m a d e( e . 9 . g r a z i n g m a n a g e m e n t ,v e l d
r e i n f o r c e m e n td,e s t r u c t i o no r i n t r o d u c t i o no f p l a n t s )o r a
combination
of these, but the dominanteventis rainfall.This
model abstractsand summarizesknowledgeabout range
dynamicswithoutdistortion,
as it is purelya descriptive
model.
Althoughno state-and-transition
modelhasyet beencompiled
for a Namibianveldtype,an examplefor tallgrassveldin South
Africais presentedin Figure4.
The veld manageris a tacticianwho has to identifythe various
transitions
whichmighttake placeat any one time and decide
whethertheypresentan opportunity
or ahazard. Opportunities
areto be exploitedandhazardsmustbe avoidedor,if theycannot
be avoided,thenat leasttheirdamagemustbe contained.By
understanding
which eventscausewhat kind of transition(s),
the veld managercan adjusthis managementin time. This
whichis unusualin a fieldshaped
enableshimto reactproactively,
by reactionto natureand crisismanagement.Traditional
farm
m a n a g e r st e n d t o f o l l o w a f a i r l y r i g i d , c a l e n d a r - b o u n d
managementprogrammethat does not suit the opportunistic
andflexiblemanagement
stylerequiredif aridrangeland
indeed
changeaccording
to the state-and{ransition
model.
H o w e v e r ,m a n a g e r sa l s o n e e d s u p p o r t i v es t r u c t u r e st h a t
management.lf,for example,a sudden
augmentopportunistic
droughtforcesa grazierto rapidlysell some of his livestock,
even if they are not yet in a marketablecondition,market
structuresthat are able to absorb these suddenfluxes are
needed(Scoones,
1994).lf rainfall
doesindeedplaya dominant
role in determining
the stateof the range,and meteorologists
are increasingly
ableto forecastunusualmeteorological
events
such as this year's El Nino successfully(Hutchinson,1993;
Olszewski,
1993),thenrangemanagerswillentera new phase
o f o p p o r t u n i s t im
c a n a g e m e nst u i t e dt o o u r h i g h l yv a r i a b l e
environmental
conditions.
whichwould have a positiveeffect
on the wholeNamibianeconomv.
51
Catarogue ot Siates
Slate/.
state //.
D o m i n a t e d b y l a r g e , c o a r s e p e r e ngnriaasl s e s , e gC. y m b o p o g o n e x c a v a t u s , A p o c h a e t e h l s p l d a ( s o - c a l l e d ' i n c r e a s e r l ' s p e c i e s ) '
'decreaser'species).
Lesserpercentages
E. capansls(so-called
racemosa,
Dominatedby palatableperennialgrassessuchas Themedatriandra,Eragrostis
of variousincreaserspectestypes
'increaser
bareground,and many
2'species),withsubstantial
(so-called
caffra,setariaflabel/ata
Microchtoa
state ///. Dominatedby grassessuchas Adsfidaco ngesta,
grasses).
(short
annualsand microperennials
'increser3' species)with littlebare
Elyonurusargenfeus(so-called
j ,r"ru ,u. Dominatedby large,established
grassessuchas Aristidaiunciformis,
tufs of unpalatable
L
o r o u n d .L e s s e r b u t s i o n i f i c a n t a m o u n t s o f d e c r e a s e r a n d i n c r e a s e r 2 s p e c i e s ( s e eaSntdaltlel )s l l
t
"
i Statey. Vigorousfull coverof increaser3 species(seeStatelV).
State Y/. Baregroundand annuals.
i Catalogueof Transitions
'overresting'othersregardStateI as a variantof Statell perhapsdue to localsoileffects;othersagainwouldgroup
t,
7. Accordingto one hypothesisis due to
Transition
Statelwith StatelV
Transition2.
Lightgrazing.
Transition3.
relaxationof grazingpressure.
Completeor nearly-complete
species
grazingimposedin a way whichdoes not allowanimalslo avoideatingunpalatable
Moderate-to-heavy
dominanceby the unpalatable
in thefaceof established
grassesare notcapableof increasing
doesnotoccur,sincepalatabre
Accordingto one hypothesis
Transition4.
Transition 5.
relativecompetitive
perennials.Others believethis transitiondoes occur given total destockrng,but is very slow. There is also a hypothesisthat
U
n
d
e
r
t
h
i
s
h
y
p
o
t
h
e
s
i
s
,
w
h
i
c
h
g
r
a
s
s
g
r
o
w
sbeslvariesfromyearto
advantagecanbeshiftedbyexacttimingofgrazingatthebeginningofawetseason.
years in which the
selecting
by
be
assisted
could
Transition
5
Thus
rains.
early
of
year,dependingon when the first rain falls and on the sequence
growth.
period
of
early
this
grazing
lightly
during
very
grow
and
best,
palatablegrassesare favouredand
Transition 6.
z.
Transition
species;by this meanscompetitiveadvantageshiftsto the
Moderategrazingwhichailowsanimalsto choosepalatablespeciesand avoidunpalatable
M
o
s
t
c
o
m
m
o
n
l
y
t
h
i
s
w
o
u
l
d
c
o
m
e
a
b
o
u
t
u
n
d
e
r
m
o
d
e
r
a t e s e l s t oAcnkoi nt hg e. r f a c t o r m i g h t b e e a r l y - s e a s o n g r a z l n g l n
unoalatable,increaser3,species.
by the patternof rainfall(seeTransition5).
yearswhen palatablegrassesare disadvantaged
and groundcoveraccumulatein all plant
comes about if grazingpressureis relaxedbut not as completelyas for Transition3, so that while biomass
groups,thereis selectionagainstpalatablespecies'
of heavygrazingor fire can counterthe
B. Very heavygraztngin shortbursts,and/orburning.it is not well understoodwhat exactamountsor sequences
Transition
perennials
regenerate
palatable
to
of
the
capacity
the
specieswithoutdemolishing
"ompetitiveadvantageof unpalatable
grassesis complete
9. Sameprocessesas Transition6, continuingto the pointwheredominanceby unpalatable
Transition
virtually
all the swardis occupiedby large,vigorous,established
v
in
state
because
yery
transition,
not
a
feasible
practical
terms
manage
stow,or In
Transition10.
i
I
t
i
I
grasses
tussocksof unpalatable
I
grassesremain,andse
o ri lo s i o n i s s e r i o u s '
l T r a n s i t i o n T TC. o n t i n u e d h e a v y g r a z i n g t o t h e p o i n t w h e r e n e i t h e r t u s s o c k s n o r s e e d b a n k o f p e r e n n i a l
I
I Transition12. Only possiblewith soil reclamationwork and reseeding'
I
lOpportunitiesand Hazards
downthe routefrom Statell to Statelll and
One is simpleovergrazing,
]tn.r" ur.2 principalroutesby whichthe productivecapacityofthe rangelandcan be degraded
serioushazardboth becauseTransition6
is
a
more
v.
This
to
state
lV
and
ultimately
ll
to
State
from
state
route
ultimatelyto state vl. The mostserioushazardis the
thanfromStatelll An importantvariant
is
much
slower
lV
from
State
recovery
4,
and
because
to
Transition
quite
compared
of
stocking
moderatelevels
I can be madeat
byreducinggrazingpressure,andifthatisdoneinsuchawaythattheremaininggrazingisselectiveagainst
lhazardisthatifoneseekstorecoverfromstatellltostatell
palatablespecies,thereis a seriousriskof makingTransition7 ratherthanthe desiredTransition3.
thatthe returncan be mademuchmorequicklyvia Transition8
for returningfromstate lv to state ll deservementioning.one is the possibility
lrwo typesot opportunity
time
rn someyearsat the beginningof growingseasonsin which
possibility
that thereexistwindowsof
I totto*"d by Transition3 than by Transition5. The otheris the
suchyearsand grazingheavilyduringsuch
years
By identifying
versa
in
other
grasses,
vice
and
grassesare morevulnerableto grazingthan palatable
I unpalatable
t
.
species
unpalatable
pressure
against
strongly
I windowsof time it mightbe possibleto directgrazing
l
Allied Situations
Nardusif$azed in a way whichselectstoo stronglyagainst
lRanoelandswith similarfeaturesoccurin Britishhillpastures,whichbecomedominatedby the unpalatable
t
species.
palatable
Festuca
and
Agroslis
J
l
_
for tall grassveldin south Africawith a catalogueof statesand transitionsas well
Figure4. A State-andTransition-Model
and opportunities(Westobyet al.' 1989).
52
as managementhazards
AGRICOLA2OOO
O F O P P O R T U N I S T IR
CA N G E
S U G G E S T E DP R I N C I P L E S
MANAGEMENT
lf acceptanceof the state-andtransitionmodelby the scientific
communityleadsto a changein managementstyleof rangeland
managersfrom rigid,pre-plannedto flexible,pro-activeand
thenscientists
mustalsosupplysomeguidelines
opportunistic,
rangelandmanagement.
as to what constitutesopportunistic
The followingprinciplesare thereforeofferedfor discussionon
whethertheyare relevantto the currentsituation.
Flexibilitymeansto adjustquicklyto changingconditions,but
managementrefersto the abilityof the manager
opportunistic
appearinggood
to make use of suddenlyand unpredictably
opportunitiesbecausehe was preparedfor this eventuality
occurring,with the only uncertaintybeingexactlywhenit would
occur. Similarly,the managerhas alternativeaction plans
ready for sudden hazards and is able to apply pro-active
d a m a g e - c o n t r o l . P r i n c i p l e so f o p p o r t u n i s t i cr a n g e
managementshouldincludethat stockingratesshouldtrack
the rainfall,flexibleherd composition,a grazingsystemthat
simulatesnaturalpatternsof rangelanduse, fodderbanking,
purposefulrotationalrestingof the veld,preventingsuccessive
grazingof perennialgrassesat the same phenophase,
using
as managementtools,
fire and hay-makingopportunistically
mixinggrazingand browsingspeciesof livestockand using
indigenous
breedsas baselinebreeds.Surely,otherprinciples
couldbe addedto this list and prioritiescan be reassigned.
Probablythe most importantconclusionthat arisesfrom the
model is that livestocknumbersshould
state-and-transition
trackthe rainfall(Behnke& Scoones,1992;Behnke& Kerven,
'1994). Since rangelandproductivityand conditiondepend
primarilyon rainfall,livestocknumbersshould be adjusted
accordingto the rainreceived,with as shorta delayperiodas
possibleto reducestresson the environmentin the faceof an
approachingdroughtor minimiselost opportunitywhen the
rainsresumeagain. Namibianfarmerswill profitfrom a habit
of measuringthe carryingcapacityof theirveld on at leastan
a n n u a lb a s i s ,s i n c e t h i s w o u l d e n a b l et h e m t o d e s t o c ko r
restockrapidlyaccordingto the availablefodder and be in
harmonywith an ever-changing
environment.This increases
the sustainability
of the farmingenterprise,reducesgrazing
pressureon drought-stricken
veld and exploitsopportunities
presentedby good rainsand rapidlygrowingveld. Thereare
many satisfactorymethodsof measuringthe conditionand
p r o d u c t i v i to
y f v e l d , s o m e t a i l o r e de s p e c i a l l yt o N a m i b i a n
c o n d i t i o n (sL u b b e , '9l 9 7 ) .
H o w e v e r ,t o b e a b l e t o r e s p o n dq u i c k l yt o i n c r e a s e so r
decreasesin the foddersupplyby increasingor decreasing
a farmer
the numberof livestockon the range respectively,
has to have access to stock reservoirswhen restockingand
processingfacilitieswhich can cope with a suddeninfluxof
disposed livestockwhen destocking. lt is probablymore
difficultto obtainlivestockat the end of a drought,when most
phase,than it is to get rid of
farmersare in a herd-rebuilding
surplus livestockat the onset of a drought.Fortunately,a
droughtseldom strikesall of Namibiaat once and with the
pocketsof
same severity(Hutchinson,1993). District-sized
productive
good grazingremain
even while the countryis in
AGRICOLA2OOO
the grip of a droughtand may serye as a poolfrom which to
restockonce the droughthas passed. A large number of
commercialbeeffarmersfollowa weanerproductionsystem
that suppliesfeedlotswith younggrowingstockfor fattening.
After a drought,when the price of grains used in fattening
dietsis stillhighbecauseof recentcropfailuresbut rangeland
productivity
is alreadyincreasingrapidly,it is conceivable
that
a grazier could compete successfullywith the big feedlot
c o m p a n i e sf o r t h e p u r c h a s eo f w e a n e r s f r o m w e a n e r
productionsystemsand use them to grow out on his newly
productiverangeland.
Whenfarmersarewarnedin advanceof an impendingdrought,
as theywerethisyearof the El Ninodrought,theycan dispose
o f s u r p l u sa n i m a l si n g o o d t i m e , w h i l e t h e y a r e s t i l l i n a
marketableconditionand can obtaina fair orice. lf the farmer
holdson to his livestockfor too long,they will not only have
lostcondition,but he willalso be sellingat a stagewhen most
farmersare forcedto sell,and the marketis saturated,prices
are low and the farmersuffersa loss on his investment.The
commercial
farmerin Namibiaat leastis servedby an existing
(Rawlinson,1994)and
marketingand processinginfrastructure
profitably,
to
shouldbe able destock
butthe communalfarmer
is not in the same position(Holtzman& Kulibaba,1995). In
the communalareas,such structuresstillhaveto be created
or are in the processof beingcreated,but the attachmentof
the communalfarmerto his livestock,whichis his wealthand
status,presentsan additionalpsychological
barrierto thistype
of flexibility.Traditionalpastoralistsusedto be nomadic,simply
e s c a p i n gt h e e f f e c t o f a l o c a l i s e dd r o u g h t t h r o u g h
transhumance(Behnke& Scoones,1992; Dahlberg,1994),
but this optionis increasinglyunavailabledue to increasing
, 994).
h u m a np o p u l a t i odne n s i t y( A n o n . 1
Apart from the farmer'smarketingand supportsystems,his
herd has to be flexibleenoughto enablehim to destockand
restockrapidlyin the first place. Most conventionallivestock
enterprises
are notgearedtowardsmarketinga sizeablenumber
of animalsat an unforeseenstage,sincemost herdscontain
too high a proportionof breedinganimals to possessthe
requireddegree of flexibility. While any emergencysale of
livestockhelpsto postponeor alleviatethe effectof drought,it
is empirically
estimatedthata farmershouldreducehis herd's
feedconsumptioncapacityby at leastone-thirdin orderto make
a significantsavingon the reducedavailability
of rangeland
feed, althoughthe graziercan selectthe probabilitylevel best
(Danckwerts
suitedto his conditions
& Tainton,1996).Setting
the levelof breedinganimalsat a low butstableleveland filling
the remainingcarryingcapacitywith readilydisposableanimals
such as young,growing-outstock,castratesand replacement
femalesenablesthe grazierto reactto dry spellsby disposing
of filler livestockwithouthavingto cut into his real capital,the
breedingherd(exceptif conditionsdeterioratecatastrophically)
and reactto wet cyclesby retainingall home-bredprogenyand
purchasingadditionalfillers. However,the herd has to be
activelymanagedto increasethe proportionof fillersand the
degreeof flexibility
this provides.
A systemof controlledselectivegrazing(CSG),makinguse
of a relativelylow stockingrateand longgrazingperiods,has
53
been used in Namibiawith a fair amountof success(Bester,
1993). However,when comparedto the way wildlifeutilizes
the range,it is doubtfulthat CSG simulatesnaturalutilization
patterns.Beforethe adventof commercialfarming,huge herds
usedto roar!rthe veld(Skinner& Smithers(1990)
of herbivores
m e n t i o na h e r do f s p r i n g b o k1 2 0 k m l o n ga n d 1 8 k m w i d e ! ) ,
exertingenormousgrazing pressureon the range but for
r e l a t i v e l ys h o r t p e r i o d s o f t i m e . W i l d h e r b i v o r e sw e r e
constantlyon the move:the morea speciesrelieson grazing,
, 979). Traditional
t h e m o r e m i g r a t o r yi t i s ( E l t r i n g h a m 1
(shiftingpeople
pastoralism,
with its patternof transhumance
exhaustedand
time
between
and
in
space
livestock
and their
patternsfar
utilization
natural
resembles
resources),
fresh
more accuratelythan most commercialgrazingpractices.
A grazingsystem based on the principleof short duration
grazing(SDG) is possiblymuch more in line with natural
rangelanduse than the CSG advocatedcurrently.However,
becauseit demandsmoreintensive
SDG hascostimplications
f e n c i n g . I n u n s k i l l e dh a n d s , i t s d e s t r u c t i v ep o t e n t i a li s
of livestockrestrictedto a
frightening:a large concentration
small camp can irreparablydamagethe vegetation.Even in
the late 1970's,it was still possiblefor Namibiancommercial
to thatof traditional
farmersto usea similarescapemechanism
to governmentpastoralists,
by movingtheirherdstemporarily
owneddroughtgrazingreseryes.The notionthat all landhas
to be in production(i.e.nonecan lie in reserve)and increasing
put paidto thislastescapemechanismand
commercialisation
now farmershave to endurea droughton their own farms,
allowingtheirveld hardlyany opportunityto recover.When a
farmeris ableto evacuatehisfarmduringa drought'and return
only once his veld has recovered,the grazingsystem(whether
CSG or SDG) is possiblyless crucialthan when the veld has
to enduregrazingeven duringa drought.
Fodderbankingis a principleof opportunisticmanagement
thatis alreadywidelyadoptedby Namibianfarmers.Whenever
the rainsare good and resultin a surplusof grazing,farmers
put aside some of the surplusin the form of hay or foggage
(deferredgrazing)to be utilisedduringthe next dry spell. In
fact, deferred grazing is an integral part of most grazing
systemsadvocatedin Namibia(Joubert,1974;Bester,1993),
servingat oncethe needto accumulatea fodderbankand to
rest a proportionof the farm each year for a full growing
season.The proportionof restedveld increaseswith the aridity
of the farm, from as littleas 10% of the farm in the northern
regionsto as much as 33% in the dry southof Namibia.
Similarly,purposefulrestingof veld is an integralpartof many
of the grazingsystemsadvocatedin Namibiatoday (Bester'
of the most
the ecologicalrequirement
1993),acknowledging
duringthe
importantgrazingplantsto be sparedoccasionally
most criticalstagesof their lifecycle,when grazingwould be
at its most harmful. lt is of courseonly possibleto restveld if
there is sufficientotherveld availablefor grazingat the same
phenophase.Rotationalgrazingsystemswere designedto
achievethis,sincea merewithdrawalof a campfromgrazing
(e.g. during the vegetativedormant phenophasein winter)
does not necessarilyconstitutean effectiverestingopportunity
for the olants.
54
grazingsystemsin widespread
Anothereffectof the rotational
u s ei n N a m i b i ai s t o a v o i dg r a z i n gt h e s a m ec a m pa t a s i m i l a r
s t a g e o f d e v e l o p m e n ft o r s e v e r a l c o n s e c u t i v es e a s o n s .
duringthe mostsensitivephenophases
defoliation
Successive
( c o m m e n c e m e ngt r o w t h i n s p r i n g / e a r l ys u m m e r a n d
mustbe avoidedto retain
in latesummer/autumn)
translocation
the vigourof the naturalvegetation.A grazingsystemwhich
"forgets"this aspect is the otherwiseprogressive
regularly
systemof open rotationgrazing. However,this is probably
less a fault of the systemthan its improperimplementation
Eventhe best grazingsystemcan be corruptedby improper
whereascapablemanagementcan rescuea
implementation
poorsyslem.
T h e a b o v e f o u r p r i n c i p l e so f o p p o r t u n i s t i cr a n g e l a n d
management(the type of grazingsystem,fodder banking,
rotationalrestingand preventingsuccessivegrazingat the
are partof mostgrazingsystemsalready
same phenophase)
i n u s e i n N a m i b i a ,h a v e b e e n d i s c u s s e db y t h e f a r m i n g
populationfor many years and find widespreadapplication
(Versveldet al., 1988). One is left with the impressionthat
farmersthinkthey havenow doneenoughand neednot adapt
furtherto ourvariableenvironment.However,someimportant
p r i n c i p l erse m a i n :
Fire is the declaredenemy of most commercialfarmers in
so consideringits short-term
Namibiaand understandably
However,fire is also a naturaleventin arid
destructiveness.
and highlyseasonalrangeland(Trollope,1993)and playsan
the balancebetweenwoodyand
importantpartin maintaining
plants
in the Africansavanna(Smitet al., 1996)'
herbaceous
It modifiessavannavegetationin a way which cannot be
explainedby the range successionmodel (Teague& Smit'
the largeamountof effortand moneyspent
1992).Considering
of bush control(especiallychemical
means
on more artificial
it seems logicalto suggestthat
measures),
and mechanical
from preventingfire at all costs
change
the emphasisshould
to
to utilizingit constructively achievecertainmanagement
objectives.
The foremostrequirementof a constructiveveld fire is that it
killsmall-andmedium-sized
shouldbe hotenoughto effectively
of bush encroachment.
plants,
components
main
the
woody
dry
2
Uhaof combustible
least
possible
is
at
if
there
Thisis only
is
load
the
fuel
grass)
veld,
othenrvise
the
on
(primarily
matter
an
accumulation
Such
fire.
a
hot-enough
to
cause
insufficient
following
of surplusgrassdry matterwillonlyoccuroccasionally,
which
veld
fires
(witness
the
uncontrolled
rains
exceptional
season
rainy
1
997/98
of
the
the
start
at
Witvlei
area
the
ravaged
'1996/97
rains,causinglossof livestock
followingthe exceptional
shouldmakeuseof these
farmers
lives)
and
human
and several
tool ratherthan an
management
fire
as
a
to
enlist
rareevents
be
usedconstructively
fire
can
a
underwhich
Conditions
enemy.
(e.9.Trollope,
known
widely
are
and
researched
well
been
have
1993),yet the widespreadfear of fire persists.An alternative,
is to
but withoutthe beneficialeffecton bush encroachment,
stackthe surplusgrassawayas hay.
rangelandmanagementshouldemploy
Finally,opportunistic
breeds
speciesand use indigenous
a mixof domesticlivestock
AGRICOLA2OOO
morewidely.A widespectrumof herbivorespeciesutilizearid
rangelandin the wild,separatedfrom each otherecologically
while occurringside by side,therebypreventingcompetition
for feedand increasingthe efficiencyof utilization
of the available
vegetation(Eltringham,
1979). The mostcommonspeciesof
d o m e s t i cl i v e s t o c ki n N a m i b i aa r e c a t t l ea n d s h e e o .b o t h
grazers,while goats (the only browsingspecies)are really
n u m e r o u so n l y i n t h e c o m m u n a la r e a s ( M A W R D ,1 9 9 7 ) .
Effectively,
a largeproportion
of Namibianrangelandis utilised
by a monoculture
of grazers,quiteunlikethe naturalsituation
and with devastatingresultsfor the balancebetweenwoody
and herbaceousolantsin the savanna.
In addition,indigenousbreedsof livestockare much better
adaptedto our variableenvironment,survivedroughtsin a
betterconditionand are more oroductivethan exoticbreeds
( H e t z e l 1, 9 8 8 )a n d s h o u l db e m u c hm o r ew i d e l yu s e d ,i f o n l y
programmewith exoticbreedswith more
in a crossbreeding
d e s i r a b l ep r o d u c t i o nc h a r a c t e r i s t i c (sM o y o e t a l . , 1 9 9 6 ) .
lndigenousbreeds have had up to 2000 years to adapt to
local conditionsand have an indisputableadvantageover
exoticbreedswhen it comesto animaloutputper unitarea in
a n u n f a v o u r a b l e n v i r o n m e n t .A l t h o u g ht h e p o p u l a r i t yo f
browsingspeciessuchas the goat(helpedalongby the growth
i n t h e g a m e f a r m i n gs e c t o r )a n d o f i n d i g e n o u sb r e e d si s
increasingsteadily,muchmorecan stillbe donein this regard
t o i n c r e a s et h e f l e x i b i l i t ya n d s u s t a i n a b i l i t yo f N a m i b i a n
rangeland
management.
This listof principlesof opportunistic
rangelandmanagement
i s c e r t a i n l yn o t c o m p l e t ea n d m u c h o f t h e p r o o f i s s t i l l
outstanding.lts purposeis to encouragediscussionand a
thoroughrethinkingof our attitudetowardsa highlyvariable
primaryresourceof great importanceand how we utilizeit.
Degradation
of the Namibianrangeis widespread,
irrespective
o f w h e t h e rt h e l a n d i s u s e d c o m m e r c i a l l yo r c o m m u n a l l y
( B e s t e r& R e e d , 1 9 9 7 ) a n d h a s t o b e h a l t e d b e f o r et h i s
valuableresourceis damagedbeyondrepair.
REFERENCES
ANONYMOUS
1994. Understanding
the OshanaEnvironment.
DesertResearch
Foundation
of Namibia.
Gamsberg
MacMillan,
W i n d h o e kN, a m i b i a .
BEHNKE,R. 1997. Carryingcapacityand rangelanddegradation
in
s e m i - a r i dA f r i c a : C l e a r i n ga w a y c o n c e p t u a lr u b b l e . P r o c .
RangelandDesertification
Workshop,Sept. 1997, Reykjavik,
lceland/ 6thAgrison
4 - 611111997
Congress,
, Windhoek,Namibia.
B E H N K E ,R . & A B E L , N . 1 9 9 6 a . R e v i s r t e dT: h e o v e r s t o c k i n g
controversy
in semi-arid
Africa.1: Intensification
or overstocking:
When are theretoo manyanimals? WrldAnim. Rev.87: 4 - L
B E H N K E ,R . & A B E L , N . 1 9 9 6 b . R e v i s i t e dT: h e o v e r s t o c k i n g
controversyin semi-aridAfrica.2: Stockingrates for African
pastoralsystems. WrldAnim. Rev. 87: 9 - 17.
BEHNKE,R. & KERVEN,C. 1994. Redesigningfor risk:Tracking
and buffering environmental variability in Africa's rangeland.
NaturalResourcePerspective
no. 1, ODl, London,UK.
B E H N K E ,R . & S C O O N E S ,l . 1 9 9 2 . R e t h i n k i n g
r a n g ee c o l o g y :
lmplications
for rangelandmanagementin Africa. lssuesPaper
n o . 3 3 , O D l , L o n d o nU
, K.
B E S T E R ,F . V . 1 9 9 3 . H o w r a n g e l a n de v o l v e di n N a m i b i aw i t h
referenceto drought.In: R. MOORSOM& A. PFOUTS(eds.)
Drought Impacts and Preparednessin Namibia p. 104 - 124.
NEPRUW
. i n d h o e kN. a m i b i a .
AGRICOLA2OOO
BESTER,F.V.& REED, E. 1997. Bush encroachment:
A thorny
problem. Spotlighton Agricultureno. 1, MAWRD, Windhoek,
Namibia.
C H R I S T I A N l,. 1 9 9 8 . G r a z i n gm a n a g e m e nst t u d y f o r t h r e e o f
NOLIDEP'spilotcommunities.Unpublishedreport,NOLIDEP,
W i n d h o e kN, a m i b i a .
DAHLBERG,A. 1994. Contestingviewsand changingparadigms.
The landdegradation
paper
debatein southern
Africa.Discussion
no. 6, NordiskaAfrikainstitutet,
Uppsala,Sweden.
DANCKWERTS
J ., E .& T A I N T O NN, . M .1 9 9 6 . R a n g em a n a g e m e n t :
Optimizingforage productionand quality. Bul/. Grass/d Soc.
SthAfr. 7 (Suppl.1): 36 - 43.
ELTRINGHAM,S.K. 1979. The Ecologyand Conservationof Large
AfricanMammals.MacMillanPress.London.UK.
FRASER,A.K. & LUGG,G.W. 1962. WorkStudyin Agriculture.Land
Books,London,UK.
productivity
HETZEL,D.J.S.1988. Comparative
of the Brahmanand
some indigenousSanga and Bos lndicusbreeds of East and
southernAfrica. Anim. Br. Abstr. 56:243 - 255.
H O L E C H E C KJ,. 1 . ,P I E P E R R
, . D .& H E R B E L C
, .H.1995. Range
Management:Principlesand Practice(2"ded.).PrenticeHall,New
Jersey,USA.
HOLTZMAN,J.S. & KULIBABA,N.P.1994. Livestockmarketingin
pastoralAfrica:Policiesto increasecompetitiveness,
efficiency
and flexibility. In: l. SCOONES (ed.). Living with Unceftainty.
New Directionsin Pastoral Developmentin Africa p. 79 - 94.
Intermediate
Technology
Publications,
London,UK.
H U T C H I N S O NP
, . 1 9 9 3 . T h e c l i m a t o l o g yo f N a m i b i aa n d i t s
r e l e v a n c et o t h e d r o u g h ts i t u a t i o n I. n : R . M O O R S O M& A .
PFOUTS(eds.) Droughtlmpactsand Preparednessin Namibia
p . 1 - 3 2 . N E P R UW
, i n d h o e kN, a m i b i a .
JOUBERT,J.G.V.1974. Weidingsbeheer
in Suid-en Suidwes-Afrika.
UUB,Stellenbosch,
SouthAfrica.
LUBBE,L. 1997. A criticalevaluationof the criterialaid down to
evaluaterangelandconditionin Namibia.M.Sc. thesis,Arizona
StateUniversity,
Arizona,USA.
MAWRD1997.Agricultural
Statistics
Bulletin.Dir. Planning,
MAWRD,
W i n d h o e kN, a m i b i a .
McNAUGHTON,S.J. 1979. Grazingas an optimizationprocess:
Grass- ungulaterelationships
in the Serengeti.Am. Nat. 'l'13:
6 9 1- 7 0 3 .
M O Y O ,S . , S W A N E P O E LF,. J . C&
. R E G E ,J . E . O .1 9 9 6 . E v a l u a t i o n
of indigenous,
exoticand crossbredcattlefor beef productionin
a semi-aridenvironment:Reproductiveperformanceand cow
productivity.
Proc. Aust. Soc. Anim. Prod. 21:204-206.
OLSZEWSKI,
J. 1993. The historyof drought.In: R. MOORSOM&
A. PFOUTS (eds.) Drought lmpacts and Preparedness ln
Namibiap. 33-58.NEPRU,Windhoek,Namibia.
RAWLINSON,J. 1994. The Meat lndustryof Namibia 1835to 1994.
G a m s b e r gM a c M i l l a nW, i n d h o e kN, a m i b i a .
SCOONES,l. 1994.Newdirections
in pastoraldevelopment
inAfrica.
ln: l. SCOONES(ed.).Llvtngwith Uncertainty.New Directionsin
PastoralDevelopmentin Africap. 1 - 36. Intermediate
Technology
Publications.
London.UK.
SKARPE,C. 1991.lmpactof grazingin savannaecosystems.
Ambio
2 0 : 3 5 1- 3 5 6 .
SKINNER,J.D. & SMITHERS,R.H.N. 1990. The Mammalsof the
SouthernAfricansubregion.Univ. Pretoria,Pretoria,SouthAfrica.
S M I TG
, . N . ,R E T H M A NN, . F . G&. M O O R EA
, . 1 9 9 6 .R e v i e wa r t i c l e :
Vegetativegrowth,reproduction,
browseproductionand response
to treeclearingof woodyplantsin Africansavanna.Afr. J. Range
F o r . S c i . 1 3 : 7 8- 8 8 .
SWEET,R.J. 1997a.A rainfallmodelfor estimating
carryingcapacity.
Unpublished
report,NOLIDEP,Windhoek,Namibia.
SWEET,R.J. 1997b. Towardssustainablerange managementin
communalareas. Proc. 6rhAgrisonCongress,4 - 611111997,
W i n d h o e kN, a m i b i a .
TEAGUE,W.R.& SMll G.N. 1992. Relationsbetweenwoodyand
h e r b a c e o u sc o m p o n e n t sa n d t h e e f f e c t o f b u s h - c l e a r i n g
in
southernAfrican
savannas.J. Grass/.Soc. soufh. Afr. 9:6071.
TROLLOPE,W.S.W.1993. Effectand use of fire in the savanna
publication,
areasof southern
Africa.Occasional
Univ.FortHare,
Alice,SouthAfrica.
V E R S V E L D ,W . v . R . ,B E S T E R ,F . V . & S T E H N , H . C . 1 9 8 8 .
Benaderings
tot veldbestuur.Agricola5: 53 - 58.
55
WALTER,H. & VLOK, O.H. 1954. GrundlagenderWeidewirtschaft
in Sidwestafrika. Eugen Ulmer,Stuttgart,Germany.
WESTOBYM. 1980. Elementsof a theoryof vegetationdynamics
in arid rangeland.lsraelJ. Bot. 28:169 - 194.
WESTOBY M., WALKER,B. & NOY-MElR,1 1989. Opportunistic
for rangelandnotat equilibriumJ. RangeManage'
management
42:266-274.
56
AGRICOLA2OOO