The application of agricultural land rating and crop models to C0 2 and climate change issues in Northern regions: the Mackenzie Basin case study
MichaelBrklacich,Patrick Curran andDouglasBrunt
DepartmentofGeography,Carleton University, 1125ColonelBy Drive, Ottawa, Ontario KIS586, Canada
The Mackenzie Basin in northwestern Canada covers approximately 1.8million km2 and extends from52“ N
to
70°N. Much of the Basin iscurrently toocool and remote from markets to support a viable agriculturalsector, but the southern portionof the Basin has the physical potential to support commercialagriculture.This case study employed agriculturalland rating and crop models to esti- matethe degreetowhichaC02-induced global warming mightalter thephysical potential forcom- mercialagriculture throughoutthe Basin. The two climate changescenarios consideredinthisanal- ysis would relax the currentconstraints imposed byashort and coolfrost-freeseason,but without adaptivemeasures, drier conditions and acceleratedcropdevelopmentrateswereestimated to offset potential gains stemmingfrom elevated C02levels and warmertemperatures.Inaddition tostriving for abetter understanding of the extent to whichphysical constraintsonagriculture mightbe modi-
fiedbyclimatechange,there isaneed toexpandthe research context and to consider thecapacityof agriculture toadapttoaltered climates.
Key words: agriculturallandsuitability, wheatyields,Northern Canada
Introduction
Research into the potential impacts of global cli- matechange onhuman activities has flourished over the last decade, and the relationships be-
tweenagriculture and climate change havere- ceived considerable attention. (For reviews of the effects of global climate change on world ag- riculture see Reilly etal. 1996, and Parry 1990.
Studieson the sensitivity of Canadian agricul-
ture to climate change are presented in Arthur 1988,Bootsmaetal. 1984,Brklacich and Stew-
art 1995, Singh and Stewart 1991, Smit et al.
1989, Williamsetal. 1988).
Inretrospect, agriculture waswell-positioned torespond tothe challenges that mightaccom- panyglobal climate change foratleast threerea- sons. First, weather is an important inputtoag- ricultural production on an annual basis and long-term climate trends exert considerable influence over the location of agriculture.
These indisputable linkages underpin the sensi- tivity of food production systems to a global climate change and have become part of the rationale for investigating the potential bio-
©Agricultural and Food ScienceinFinland ManuscriptreceivedFebruary 1996
physical impacts of climate changeon agricul-
ture.
Second,many of the climatechange scenar- ios thatwereadvanced throughout the
1980 s and
early
1990 s
suggested aless favourable climate for agricultural production (eg: drierconditions, greatervariability) (IPCC 1990)and oftencon- tributed to a general conclusion that climate change would result inaless secureglobal food supply. This potential decline in food security in combination with otherconcernsregarding the long-term potential for meeting planetary food requirements ledtoareframing of global climate changeconcerns, and contributedtoan explicit recognition of the economic, social and politi- cal dimensions of climate change impacts re- search(Brown etal. 1989, World ResourcesIn- stitute 1990).Third, agricultural research has investigated the relationships among food production, weath- erand climate for many decades,andas aresult addressing the agricultural impacts of climate change didnot hinge upon the development of new scientific methods. Existing agricultural research frameworks and methodswere ableto incorporate climate changescenarios,and agri- culture becameone of the first sectors toexam- ine impacts which might stemfrom global cli- mate change.
Overall,agricultureandagricultural research were and continue tobe well-positioned to in- vestigate the physical, biological, economic and social impacts stemming from global climate change. Much of this research into the agricul- tural impacts of climate change has, toa large extent, evolved from conventional agricultural research and it embraces the assumptions and contextwhich underpin agricultural research in the major food producing regions. For example, agricultural research often draws upon reliable soils and weather data, well-documented crop trials, and high quality farm management data.
However,reliable and complete biophysical and socio-economic data bases donotexist for many regions whichare near orbeyond thecurrentcli-
mate margin for commercial agriculture. As a result conventional approaches for gauging the
agricultural impacts of rising C02levels and glo- bal climate changecanbe difficulttoimplement in northern regions.
This paper focuses on assessing the impacts ofa potential global climate changeon agricul- tural opportunities in northern regions. It draws upona casestudy in the MackenzieBasin, Can- ada,and examines issues relating to:
model applicationsnear and beyond thecur- rent climate frontier for commercial agricul-
ture,
sparsedatacoverage, and
linking biophysical and socio-economic as- sessments.
The Mackenzie Basin context
An overview of the Mackenzie Basin
The Mackenzie Basin (Figure 1)is the world’s twelfth largest watershed witha drainage area of about 1.8 million km2.The main trunk of the Mackenzie River is the dominantfeature, and theLiard,Athabasca and Peace River watersheds represent significant areas in the southern half of the Basin. The Basin extends from 52°Nto 70°N,and includes portions of theArctic, Bore- al and Grasslands ecoclimate regions (Statistics Canada 1986).
Much of the Basin is currentlytoocool and remote from markets to support a viable agri- culturalsector, but the southern portion of the Basin has the physical potentialtosupport com- mercial agriculture. Commercial agricultural productionoccurs primarily in the Peace River region. Wheat and barleyarethe key cash crops, but canola (rapeseed) has become increasingly important in the last 10 years. During the 1980
s
anaverage of 335 800 ha ofbarley and 383 100 ha of wheatwere seeded in the Peace Riverre- gion. Forage production andpasture arethe oth- er main agricultural landuses. About 1.2 mil- lion ha of land in the Peace River region is cur- rently used for commercial agricultural produc- tion (Agriculture Canada 1986, 1990).
The Mackenzie Basin case study
With the Mackenzie Basin covering avastarea, much of which is beyond the current climate boundary for agriculture, it should not be sur- prising that existing data bases impose con- straintson the opportunitytoassess the agricul- tural impacts of climate change.
For example, detailed, high resolution soils maps have been compiled for only a limited number of sites within theBasin,and donotpro- vide afoundation for exploring the Basin’s ag- riculturalprospects.Basin-wide coverage of ba-
sic soils data is notavailable below the scale of
1:1
million. At this scale,the smallest recogniz- able land parcel is about 4000 ha and providesa foundation for reconnaissance levelassessments.There were 567 weather stations operating in the Mackenzie Basin between 1951 and 1980.
Since the study presented in this paper repre- sents one component of a multi-sector assess- mentofclimate change impactsonthe Macken- zie Basin (Cohen 1992),for consistency, allsec- toral studies contributing tothe Mackenzie Ba- sin project utilize the 1951-80 climate base line.
For many of the weatherstations,the record has Fig. 1.The Mackenzie Basin.
been compiled forarelatively short period(i.e.
less than a decade), and lengthy gaps in the record and/or observation ofa limited number of weather properties limit their utility. A com- parison of the data requirements of thecurrent generation of crop modelstothe observed weath- errecords revealed that the datarequired toim- plement these models could be satisfiedatless than20 sites throughout the Basin. Given this level of coverage, it is feasible to conductas- sessmentsof crop yield sensitivities to climate change for selected indicatorsites,but clearly it isnot possible toextrapolate from these select- ed assessments and draw conclusions about the Basin in general.
Crop trials supported by detailedweather, soils andmanagement data arerequired to cali- brate crop modelstolocal conditions. Data from crop trials are available for limitedareas, and allare within the southern reaches of the Basin.
Under theserestrictions, full calibration of crop models is simply not feasible.
The research framework developed for the Mackenzie Basin study recognized the limita- tions imposed by the available informationbase, and was designed to make the best use of the available information. The assessment began with aBasin-wide assessment of theextent to which possible changes in long-term climate averages mightalter agroclimate constraints and land suitability for commercial production of spring-seeded cereal grains. Regions identified as having a physical potential to support com- mercial agriculture under this initialassessment were targeted formore intensive investigations into the effects ofaC02-induced climate change on annual spring wheat yields.
An agricultural resource potential perspective
Resource rating scheme overview
The primary analytical tool usedtoestimate the climate change impacts on agricultural land
potential was the Land Suitability Rating Sys- tem for Spring-Seeded Small Grains (LSRS) (Agronomic Interpretations Working Group 1992). This rating scheme was selected for two reasons. Firstly, climate properties are consid- ered explicitly by the rating scheme and there- fore it could be appliedtoclimate change issues.
Secondly, implementation of the LSRS requires routinely collectedsoils,climate and landscape data and therefore itcanbe appliedtobroadre- gions.
The LSRS is based onrating the extent to whichsoil,climate and landscaperepresent lim- itations for the production ofcommon spring- seeded grains (e.g. wheat, oats,barley). Each of thecomponentsis rated separately and assigned aninitial value of 100. Then theextent towhich arange of factors(e.g. effective growing degree days, drainage class, topography) impair crop production is determined and points are deducted toreflect the severity of the limitation.The overall land suitability ratingranges from 0to 100,and is based on the most limiting component. An over- view of the analytical units upon which the land suitability assessmentsare founded andabrief de- scription of eachcomponentand the data usedto implement each componentfollows.
Units of analysis
The polygons defined for the Soil Carbon Data Base (Soil Carbon Base Working Group 1992) are compiled at a 1:1 million scale and repre- sentthe analytical units used in thisassessment.
These polygons are notnecessarily homogene- ous andcan includea Dominant Soil whichex- ceeds 40% of the polygon’s surfacearea, and a Subdominant Soil accounting for between 10%
and40% of the polygon area.About 1800 poly- gonscontaining mineral soilswereextracted for further analysis and account for about 57% of the Basin’s landarea.
Climate component
The climatecomponentconsidered theextent to which accumulated heat and moisture limit
spring-seeded cereal growth and development.
Growingdegree days above 5°C wasthe prime indicator of heat accumulation during the frost- free season.The May through September mois- turesupply, estimatedasthe difference between accumulated precipitation and potential eva- potranspiration, was used to calculate thesea- sonal moisture supply. The LSRS can consider the impacts of earlier than average fall frostson land suitability for commercial crop production, but insufficient data prohibited theuse of this component of the rating scheme. Detailsonpoint deductions associated with each of the climate parameters aredescribed in Agronomic Interpre- tations Working Group(1992).
The 10 km by 10 km baseline(1951-1980) of monthly mean temperatures and total precip- itation compiled by Environment Canada (Smith and Cohen 1993)was augmented with monthly normals for minimum and maximumtempera- tures. Many of the land units (i.e. Soil Carbon Data Base polygons) used in this analysis fol- low natural drainage systemsand thereforeare delineatedasrelatively long narrow polygons.
Several 10 km x 10 km climate grid cells inter- sect partially with these land units. The devel- opment of climate profiles for these land units basedon anaveraging ofclimate grid cells would have regularly included substantialareasof land outside the soil polygon and thereby contribut- edto unreliable estimates. To minimize theoc- currenceof thiserror source,baseline tempera- ture and precipitation data for the land units of analysis used in this assessment wereestimated as the climate associated with the 10 km by
10 km grid cell closest to the centroid of each soil polygon. The moisture supply wascalculat- ed using monthly data for the following climate properties: precipitation, maximum and mini- mum temperature, solar radiation at the top of the atmosphere. Solar radiation estimates atthe top of the atmosphere were obtained from Rus- selo et. al. (1974). The Brooks (1943) method was employed toestimate daily mean tempera- tures from monthly climatenormals, and these daily estimateswereused tocalculate theaccu- mulation of growing degree days.
Scenarios for long-term climate change were derived from the application of the Canadian Climate Centre (CCC) and Geophysical Fluid Dynamics Laboratory (GFDL) GCMsto2 xCO, atmosphere experiments(Boer et al. 1984 and Manabe and Wetherald 1987,respectively, as re- ported in Smith and Cohen 1993). Scenarios weregenerated by applying differencesbetween 2 x C02 and I x CO, GCM model runs to the 1951-80 monthly temperatureand precipitation means.
Warmertemperatures wereestimated for the entire Mackenzie Basin and for all seasons un- der the CCC scenario, but thegreatest tempera- ture deviations were estimated for the winter months and in the northerly portions of the Basin (Fig. 2).The regional climate changesce- nario derived from the GFDL GCMwas con- siderably different from the CCC scenario. Esti- matesunder the GFDL scenario ofsummertem- perature increases for the southern half of the Mackenzie Basin were in the 4°C to 6°C range whereas the CCC scenario estimates ranged from I°Cto 3°C. Estimated summer temperature in- creases for the northern half of the Mackenzie Basinwere similar under thetwo scenarios.
The estimated changes in wintertemperature also varied. The CCC-derived wintertempera- tureincreases tendedtobe in excess of 4°C for mostof theBasin. Estimated increases under the GFDL scenariowere considerably less, and in general did not exceed 3°C.
Changes in precipitation patterns were also considerably different between thetwoscenari- os (Fig. 3). Precipitation estimates under the CCC scenario for all seasons were in the +25%
range overmostof the Basin. Estimated devia- tions from thecurrentunder the GFDL scenario were more severe, especially during thesummer for which estimated precipitation changes ranged from decreases of up 25%toincreases inexcess of 100%.
Soils component
The rating of mineral soilswasbasedon theex- tent towhich moisture supply capacity, surface
factors, subsurface factors and drainage impose limitationsoncrop production. Limitationswere estimatedas afunction of depth oftop soil,tex- ture, drainage, soil structure and consistency,
organic carbon content, pH, depthtoan imped- ing layer, and bulk density. The required data were either extracted directly from the Soil Carbon Data Base orinformation from the Data Fig. 2. Temperaturechangesestimated under the Canadian Climate Centre (CCC) andGeophysicalFluidDynamicsLabo- ratory (GFDL) model-based2 x CO, scenarios.
GFDL Scenario
Base was used toinfer the required data. Point deductions for soil factors are presented in Agronomic Interpretations Working Group (1992).
Landscape component
The landscapecomponentconsidered slope and slope length, stoneremoval requirement and Figure 3. Precipitation changesestimated under the Canadian Climate Centre (CCC) and GeophysicalFluid Dynamics Laboratory(GFDL) model-based2 x C02scenarios.
coarsefragmentcontent.Lack of reliable infor- mation prohibited theuse of the flooding factor in this analysis. The data required to rate the landscape component were taken from the Soil Carbon DataBase,andwereeither used directly orused asproxy data. Detailsonthe implemen- tation of this component arefound in Agronom- ic Interpretations Working Group(1992).
Interpreting the overall rating
The lowestor mostlimiting score of the three components becomes the basis of determining the overall land suitability ranking for spring- seeded cereal crops, while the othertwocompo- nents areincludedassubfactors influencing ag- ricultural potential. This approach provides a preliminary estimate of the combined effects of soil, climate and landscape factors on agricul- tural land potential.
To assist with interpretation the overall score canbe grouped into three broad categories (Ag- ronomic Interpretations Working Group, 1992).
Lands witharating ranging from 60to 100points areconsidered highly suitable for sustained crop production. Ratings from 30to60 points repre- sentlands whicharemoderately suitable for ag- riculture, and scores less than30 points desig- natelands whichareunsuitable for commercial agriculture.
Climate change impacts on agro-climate potential
The current average frost-free period for the Basin of 132 days (Figure 4)represents a sub- stantial constrainttothe commercial production of crops. Each of the climate change scenarios impliesaconsiderable extension of the frost-free period, with thegreatest estimated increase of 29 days occurring under the GFDL scenario.
With the longer frost-free period and higher
temperaturesassociated with the climate change scenarios, itwas estimated that there would be substantial increases in effective growing degree
Fig.4. Impactsof climate changeonselectedagroclimate properties inthe Mackenzie Basin.
days (GDD) over the duration of the frost-free period. The current Basin-wide average falls short of 1000GDD,and represents a moderate tosevere constrainttothe production of spring- seeded cereals. Spring-seeded cereals typically require about 1600 GDD. and this threshold is reachedon average under both ofclimatechange scenarios considered in this study.
The estimated seasonal moisture supply, de- finedasthe differencebetween precipitation and potential evaporation, was also sensitive to the climate change scenarios. Substantial precipita- tion increases estimated under the GFDLsce- nario are offset by anticipated potential evapo- ration increases,resulting in only minor adjust- ments to the estimated seasonal moisture sup- ply. However,the CCC scenarioassumes only a
modest precipitation increase,and thiswas more than offset by the estimated potential evapora- tion increase. As a result,the estimated seasonal moisture supply decreased under the CCC cli- matechange scenario.
Climate change impacts on agricultural land suitability
Figure 5 illustrates the estimated impacts of the CCC and GFDL climate change scenariosonthe agricultural land suitability throughout the Mac- kenzie Basin. Undercurrentconditions,it ises- timated that nearly 6 million ha of mineral soils throughout the Mackenzie Basin are physically suitable for the production of spring-seeded small cereals. Moderately suitability agricultur- al lands accountfor nearly 36 millionha, while the remaining 62 million ha of mineral soilsare estimatedtobe unsuitable for spring-seededce- reals.
The largest adjustments in land suitability for agriculture stemming from global climate change are estimated under the GFDL scenario. A 41%
increase in the totalarea of land which is either highlyor moderately suitable for cereals is esti- mated under this scenario, and this includes an
estimated64% increase in highly suitable land. Fig. 5.
Climatechange impactsonagricultural land suita- bility.
Under the CCC scenario, the total area of lands highly and moderately suitable for spring- seeded cereals is estimated toincrease by 31%.
This aggregation of highly and moderately suit- able lands however masks an estimated29%
decline in land which is highly suitable for agri- culture. Under the CCCscenario, the estimated temperature increases relax constraints associ- ated with thecurrent short, cool frost-free sea- son, but this potential benefit is offset by esti- mated increases in moisture deficits. As aresult therewas anestimated decrease in the landarea with the highest potential for crop production.
A crop yield perspective
CERES-WHEAT overview
The primary analytical tool used in thiscompo-
nentof the studywasthe CERES-WHEAT crop growth and productivity model. Thiscropmod- elwasselectedasit isone of only afew models whichcan consider the combined effects ofCO, and climate changes on crop yields, and the model has been applied elsewhereathigher lat- itudes(Brklacichand Stewart 1995).
The version of the model used in this research is described in Ritchie and Otter (1985) and Godwinetal. (1989). CERES-WHEAT predicts cropgrowth and yields for individual wheatva- rieties, and the model employs simplified functions which advanceon adaily timestepto estimate crop growth and yield as afunction of plant genetics, daily weather (solarradiation, maximum and minimumtemperature,precipita- tion), soil conditions, and managementfactors.
Modelledprocesses include phenological devel- opment, growth of vegetative and reproductive parts, biomass production and partitioning amongplant parts, and root system dynamics.
The model also tracks moisture inputs and with- drawals,and estimates the impacts of soil-water deficitsonphotosynthesis and partitioning. For this analysis, seeding date (SD) was estimated
asthe first day of the frost-free season and soil moisture conditionsatseeding reflected theex- tent to which soil moisture reserves were re- chargedoverthe winter period.
The intensive data requirements of the CERES-WHEAT crop model limited the appli- cation of the modelto 16 sites scattered through- out the Mackenzie Basin. The remainder of this section summarizes the input data used in the cropyieldassessmentandpresentsselected find- ings fortwosites. Beaverlodge at55°N is in the Peace River region and within the area of the Basin which presentlysupportscommercial ag- riculture. Hay River at 61°N is beyond thecur- rent climate frontier for agriculture (Fig. I). This analysis focuses on isolating the sensitivity of spring wheat yields to climate change, and changes in production practices. The use of alternative crop varieties and other adaptive measures are beyond the study’s scope.
Model performance
Crop development aspects of the model track well with observedconditions, and differences between the estimated and observed times from sowingto maturity are minimal (Brklacich and Stewart 1995).This indicates that the model rep- licates crop development processes reasonably well and therefore can be applied in climate change studies. Model estimates of crop yields however often exceed observed yields, and the models provide little insight into the effects of poor weatheron cropquality. Overall, this sug- gests the modelcan be used to provide insight into the relative rather than absolute impacts of climate changeon wheat yields.
Atmospheric C0
2data
The current level of carbon dioxide in the at- mosphere is assumedtobe360 ppm. Future lev- elsare set at 555 ppm and are based uponan
“equivalent ofa2 x CO,” atmosphere. This ap- proach has been used elsewhere in climate im-
pactassessments (Rosenzweig and Parry 1994) and recognizes that increases in the atmospher- ic concentrations of othertrace gaseswill result inaradiative forcing of the atmosphere equiva- lentto that duetoa doubling of C02but occur- ring priortoactual C02doubling.
Climate data
Baseline climate data for the period 1951to 1980 were derived from the observed weather record ateach site. Recorded daily values for maximum and minimumtemperatureand precipitationwere employed. Solar radiation dataarenotcollected on aroutine basis and therefore the deJong and Stewart(1993)methodwasusedtoestimate dai- ly solar radiation values from temperature and precipitation data.
Scenarios for long-term climate change (Figs 2 and 3) were derived from the application of the CCC and GFDL GCMs to 2 x CO, atmos-
phere experiments (Smith and Cohen 1993).
These climate change estimates were then su- perimposedontothe daily baseline climate data.
Soils data
Soil datawere obtained from the Canada Soil Information System(CanSIS).The latitude-lon- gitude position of each weather stationwasused to locate the corresponding CanSIS soil poly- gon, and thefollowing soils data for the domi- nantsoil in the polygonwereutilized in the anal- ysis: texture, bulk density, organiccarbon, pH, coarse fractions, layer thickness,and soil clas-
sification.
Management data
Though many wheat varietiesare grown in the Peace River region, this study is based upon cv. Manitou. Many oftoday’s wheat varieties have been derived from cv. Manitou and it has been usedas arepresentative variety in previous stud- ies(Brklacich andStewart 1995).
The application offertilizer, particularly ni- trogen, on commercial crops is considered very
important for most agricultural regions in the Basin. The findings presented in this paper are based on 36 kg/ha N,which is consistent with recommended fertilizer application levels for wheat.
Climate change impacts on seeding date for wheat
The frost-freeseasonin the Mackenzie Basin is relatively short andcool,and therefore the esti- mated seeding date(SD)for spring-seeded crops was assumedtobe the first day of the frost-free period. At Beaverlodge, which is situated in the Peace River region, the estimatedmean SDoc- cursin the last week of April (Figure 6), but can
vary frommid-Aprilto mid-May. The estimated mean spring wheat SD for HayRiver, which is
located beyond the current climate frontier for agriculture,was about one week later than the meanSD atBeaverlodge but the range in SDs is similaratboth sites.
An earliest possible SD of mid-May repre- sentsarelatively late start tothe crop season. It israre undercurrentclimate conditions that the estimated SD atBeaverlodge occurs after this threshold, thereby reducing the risk associated with farming in a climateally marginal region.
Spring conditionsatHay Riverareconsiderably more risky,.and the estimated SD occurs after mid-May about 25% of the time.
Both climate change scenarios imply an ear- lierSD, however the magnitude of the estimated impacts are not uniform. Mean SD is advanced toagreaterextentunder the CCC scenario than under the GFDL scenario. A comparison of the
twoclimate change scenariossuggeststhat larg- erprecipitation increases and less pronounced temperatureincreases for the winter and spring seasons under the GFDL scenario would result in wetterand cooler soil conditions in the early spring, thereby limiting the impacts on seeding dates.Itshould benoted, however,that bothsce- narios leadtoadecline in production riskatHay
River. The estimated SD occursafter mid-May about25% of the time undercurrentclimatecon- ditions,however the risk associated with this rel- atively late SD is removed under the CCC sce- nario and reducedtoabout 10% of the yearsun- der theGFDLscenario.
Climate change impacts on wheat yields
The short, cool frost-free seasons and the potential for crop failures at Hay River tendto suppress cropdevelopment and yields. Estimat- edcurrent meanwheat yields at Hay River are about50% of themean yield estimated for Bea- verlodge (Figure7).
The estimated impact of the equivalent ofa 2 x C02 atmosphere in isolation (i.e. C02 in- creaseswithout climate change) was anincrease in wheat yields of about 30%. The potential ben- efits of increases in atmospheric C02tendedto be offset by the climate changes specified under the CCC and GFDL scenarios. Thewarmertem- peratures, especially during the later phases of cropdevelopment, shortened the time available for grain filling and therefore the climate change scenarios donotnecessarily implymore favour- able conditions for cereal crops. At HayRiver, it is estimated under both scenarios that thecom- bined effects of C02 increases and climate change would result in mean wheat yields that aresimilartoyields estimated under thecurrent Fig. 6.Climatechange impactsonestimated springwheat
seedingdates.
Fig. 7.Climatechange impactsonestimated springwheat yields.
climate. For Beaverlodge, this estimated trend also applies for the GFDLscenario, but it is es- timated that the expected increases in crop mois- ture stress associated with the CCC scenario would further reducemeanwheat yieldstoabout 75% of the currentestimatedmean.
Expanding the research context
The research framework used in this study was initiated by specifying scenarios for climate change, and then the implications of these pos- sible changes wereestimated for agriculturalre- sourcepotential and wheat yields in the Mac- kenzie Basin. This approach has been instrumen- tal in isolating the sensitivity of particular at- tributes of agricultural systems to a pre-speci- fied climate perturbation.
While the spatial displacement of conditions whicharephysically suitable for the production ofaparticular agricultural activity will undoubt- edly have considerable impact on the future of agriculture, this sortof information doesnot di- rectly address the vulnerability of agricultural systemstochanging conditions and the capacity of agriculture to adapt to change (Carter etal.
1994;HDP 1994; Smit 1993). In ordertoinves- tigate the adaptive capacity of agricultural sys- temstopotential changes in climate and other conditions which influence agriculture, there is a need to expand the conventional research framework employed in this analysis and also consider:
Do farmers perceiveachange (inclimate and/
or otherconditions)?
What role does climate play in agricultural de- cision-making relative toother influences in- cluding otherenvironmental, economic,polit- ical and socio-cultural factors?
• Is the farm vulnerabletothe changing conditions?
• If the farm is vulnerable,what is the perceived range ofadaptive responses?
Which of these adaptive responses could be implemented?
Which of the feasible adaptive responses comes closestto meeting the goals for farm- ing?
Conclusions
This study provided preliminary insights into the potential effects of global climate changeonag- riculturalprospects in the Mackenzie Basin. The relatively short and cool frost-free periods char- acterizing thecurrent climate impose consider- able constraintson spring-seeded cereal produc- tion in this region. The twoclimate change sce- narios considered in this analysis would relax theseconstraints,but it is importantto notethat, the magnitude and the geographical distribution of the estimated impacts arenotuniformacross the region. Furthermore, it was estimated that without adaptive measures, accelerated crop growthratesand drier conditions associated with the climate change scenarios could offsetpoten- tial gains associated with elevated C02levels and expanded frost-free seasons.
Improving upon these preliminary assess- mentshinges upon advances in atleast twoare- as.Incomplete data is clearly asubstantial limi- tation.The available dataon weather, soils,crop trials and farmmanagement aresufficientto sup- portreconnaissance levelassessments.Creative methods for supplementing the existing data basesarerequired.
Thisassessmentconsidered the physical po- tential for commercial production of cereals.
Logical extensions of this research would in- volve considering the role of climate relativeto other biophyscial and socio-economic factors which influence agricultural systems, and ad- dressing the capacity of agricultural systemsto adaptto climate change.
Acknowledgements.The authorsgratefully acknowledgethe supportprovided by theAtmospheric Environment Serv- ice,Environment Canada, and the Centre for Land andBi- ologicalResourcesResearch,Agriculture Canada.The pa- per has benefitted from the constructive reviewsby two anonymousreviewers.
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SELOSTUS
Viljelyvyöhykkeiden ja kasvumallien soveltaminen ilmastonmuutoksen tutkimisessa:
Mackenzien jokialue, Kanada
Michael Brklacich,Patrick Curranja Douglas Brunt Carleton University, Kanada
Mackenzienjokialue sijaitsee Kanadan luoteisosas- saja onlaajuudeltaan noin 1,8miljoonaakm2. Tällä hetkellä alue onliian viileäja etäisyydet ovat liian pitkiä, jottamaataloutta kannattaisi harjoittaamerkit- tävässä määrin. Jokialueen eteläosien luonnonolot ovatkuitenkinsellaiset, ettätaloudellisesti kannatta- valle maataloudelle on edellytyksiä. Tutkimuksessa selvitettin, miten ilmastonmuutoksesta aiheutuva maailmanlaajuisen lämpötilan nousu vaikuttaa Mackenzienjokialueen luonnonoloihin. Tutkimukses-
sasovellettiin maatalousmaan luokitustajakasvumal- leja, joiden avulla arvioitiin alueen potentiaalista maataloustuotantoa muuttuneissaolosuhteissa. Ana- lyysissä käytetyt kaksi ilmastonmuutosta kuvaavaa skenaariota viittaavat siihen, että lämpötilan nousu lyhentää nykyisin hyvin pitkää routajaksoa. Saman- aikaisesti kuitenkin kuivuusja viljan nopeutunut kas- vu vähentäväthyötyä, jokamaataloustuotannollekoi-
tuu lisääntyneestä hiilidioksidista ja kohonneesta lämpötilasta.
