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Political Geography xxx (2014) 1e5

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Political Geography

journal homepage: www.elsevier .com/locate/polgeo

Guest Editorial

Climate change and conflict: Making sense of disparate findings

Keywords:Climate changeConflictMeasurementWeatherWar

http://dx.doi.org/10.1016/j.polgeo.2014.10.0040962-6298/© 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Salehyan, Idx.doi.org/10.1016/j.polgeo.2014.10.004

a b s t r a c t

This introduction to the special issues starts with a general overview of the literature. The relationshipbetween climate, climate change, and conflict has been empirically tested in a wide variety of studies, butthe literature has yet to converge on a commonly accepted set of results. This is mainly due to poorconceptualization of research designs and empirical measurements. Data are often collected at differenttemporal, geographic, and social scales. In addition, “climate” and “conflict” are rather elusive conceptsand scholars have utilized different measures of each. The choice of measures and empirical tests is not atrivial one, but reflects different theoretical frameworks for understanding environmental influences onconflict. Therefore, results from different analyses are often not commensurable with one another andreaders should be wary of broad, sweeping characterizations of the literature. The individual contribu-tions to the special issue are also discussed. Articles herein focus on different geographic regions, tem-poral periods, and levels of conflict, adding additional layers of complexity to our understanding of theclimate/conflict nexus.

© 2014 Elsevier Ltd. All rights reserved.

In 2007, Political Geography published a highly influential specialissue on climate change and conflict. The contributions to that issuehave had an enormous impact on the field and rank among themost cited articles in this journal. At that time, the environmentalsecurity literature could still be considered a ‘niche’ within thebroader field of conflict studies, although it was a niche with enor-mous significance. While there was a broad scientific consensusabout the physical science, the social implications of climate changebecame the new frontier of academic as well as policy debates.From the decision to grant the 2007 Nobel Prize for Peace to AlGore and the Intergovernmental Panel on Climate Change, to theUS Department of Defense's assertion that climate change, “mayact as an accelerant of instability or conflict … (US Department ofDefense, 2010: 85),” the notion that the environment may have adirect or indirect influence on conflict could not be ignored. There-fore, many analysts turned their attention to how natural disastersand shifting weather patterns affect violent unrest.

While research on climate/weather and conflict has not yet fullymatured to the point of establishing well-accepted findings, it hascertainly progressed at a rapid pace and is now an important themein conflict research. Shortly after the 2007 special issue was pub-lished, I wrote in the Journal of Peace Research that there wasmismatch between alarmist claims made in media and policy cir-cles, and the (then) current state of scholarly research, which wasstill quite tentative (Salehyan, 2008). While some had found evi-dence of a link between past natural disasters and violence, othersfound weak or no evidence of such a relationship. Since 2007, animpressive array of qualitative and quantitative studies hasemerged, which examine everything from pastoral conflict in

., Climate change and conflict:

Kenya (Detges, 2014; Witsenburg & Adano, 2009) to major powerconflict in Europe over the last millennium (Tol & Wagner, 2010).While the early literature was still “testing the waters” to see ifthere are any robust effects at all, most scholars now agree thatthere is a climatic influence on conflict behavior. As of yet, however,there is still no consensus about exactly how or why climatic vari-ablesdalone or in conjunction with other factorsdmatter forviolence. In short, the discussion is no longer about whether ornot the climate influences conflict, but about when and how itdoes so.

In this introduction, I examine progress in the field and arguethat we may be at the cusp of a scientific breakthrough, althoughwe have yet to establish a definitive body of wisdom. The fieldcan be best described as what Kuhn (1966) calls the period of“immature science.” It is well-accepted that this is a promisingarea of inquiry, but the field has no commonly-accepted units ofobservation, temporal scales, definitions of ‘climate,’ or even defini-tions of ‘conflict.’ Collectively, we think something is going on, butwe do not know what that something is yet. While this looks likea confusing mess for casual readers of the literature, it presentsan important juncture for theoretical development. It affordsscholars a unique opportunity to develop frameworks for under-standing disparate findings and unifying a fragmented set ofstudies.

Inwhat follows, I will examine the current state of the literature,although I make no claim to conduct an exhaustive review. Rather,my point is to underscore key fault lines in the field with respect tomethods and findings. In order to narrow my scope somewhat, Iwill focus largely, but not exclusively, on the quantitative literature

Making sense of disparate findings, Political Geography (2014), http://

Guest Editorial / Political Geography xxx (2014) 1e52

(with which I am most familiar). I also argue that while scholarshave paid lots of attention to developing ever more sophisticatedempirical techniques, current debates will not be resolved throughgathering more data or refining estimation strategies. Rather, whathas been sorely lacking is attention to a carefully specified theoryabout causal relationships, scope conditions, and appropriate unitsof analysis. I will not develop such a theory here, but throughoutthis essay I hope to offer a set of conceptual tools and ideas forothers to consider. Finally, I will examine the contributions to thisspecial issue and assess how this group of articles helps advancethe scientific study of the climateeconflict nexus.

Climate change and conflict? One field or many

Fig. 1. Geographic, temporal, and social dimensions in conflict research.

No wonder, then, that in the early stages of the development ofany science different men confronting the same range of phe-nomena, but not usually all the same particular phenomena,describe and interpret them in different ways.

e Thomas Kuhn. 1996, The Structure of Scientific Revolutions.Chicago: University of Chicago Press. Third Edition, page 17.

Studies of the climate changeeconflict connection have adopteda broad array of methodological approaches, units of analysis, tem-poral scales, indicators of climate/weather, and definitions of con-flict. While this pluralism can sometimes be productive, it canalso lead to what seems like a cacophony of different findings.Recent reviews of the literature add to this confusion. In one over-view of the literature, Scheffran and Battaglini (2011: 37) concludethat, “The causal chain from climate stress to human and societalimpacts is complex and not fully understood.” Gleditsch (2012: 7)takes a firmer stance, stating that, “it seems fair to say that so farthere is not yet much evidence for climate change as an importantdriver of conflict.” Yet on the other side of the debate, Hsiang,Burke, and Miguel (2013: 1235367e12) conduct a meta-study of60 quantitative articles from a variety of disciplines and concludethat “past climatic events have exerted considerable influence onhuman conflict.” These authors are clearly reading the same bodyof work, but have very different interpretations of the state of thefield.

Why is there such a disparity in the reading of the literature?Partly, this stems from individual authors' own biases with respectto the findings. However, a more significant problem arises whentrying to digest extant work: while scholars are, in one form oranother, trying to understand causal linkages between climatic var-iables and conflict, they are approaching the problem from verydifferent angles. While studies of ‘climate’ and ‘conflict’ fall underthe same general category, we have many distinct and sometimesincommensurable research programs within it. In terms of inde-pendent variables, some scholars have used direct measures ofrainfall (e.g. Hendrix & Salehyan, 2012; Kevane & Gray, 2008) orrainfall as an instrument for growth (e.g. Bohlken & Sergenti,2012; Miguel, Satyanath, & Sergenti, 2004); others have looked attemperature (Burke, Miguel, Satyanath, Dykema, & Lobell, 2009;Zhang, Brecke, Lee, He, & Zhang, 2007); while still others haveused natural disasters such as storms and floods (Slettebak,2012). Some have even suggested that El Ni~no events are associatedwith conflict (Hsiang, Meng, & Cane, 2011). Dependent variablesrange from inter-communal violence at the local level (Theisen,2012; Witsenburg & Adano, 2009); to civil war events (Theisen,Holtermann, & Buhaug, 2011); to conflict between states(Gartzke, 2012). Often times, empirical data are used as stand-insfor more difficult to measure concepts such as “resource competi-tion” or “scarcity.” Yet rarely do scholars closely align the variables

Please cite this article in press as: Salehyan, I., Climate change and conflict:dx.doi.org/10.1016/j.polgeo.2014.10.004

selected with the theoretical concepts and causal processes theyare trying to shed light upon.

Theoretical and empirical models vary with respect to three di-mensions: geographic scales, temporal scales, and social scales (seeFig. 1). Much of the confusion in the literature stems from the factthat analyses are often conducted at different scales, making com-parisons across studies quite difficult. First, consider differences ingeographic scale. While some have looked at conflict using theentire country as the unit of analysis (Hendrix & Glaser, 2007;Hendrix & Salehyan, 2012), others have looked at subnational unitssuch as particular localities or even arbitrarily defined grid-cells(O'Loughlin et al., 2012; Raleigh & Urdal, 2007). The choice ofgeographic unit is not a trivial one. Take for instance attempts tooperationalize the more general concept of ‘water scarcity.’ Whilea 10 � 10 km grid cell might be useful for capturing how decliningrainfall affects individual farmers who do not have access to irriga-tion, for other purposes it may be more insightful to look at riverdrainage basins and water catchments that can span entire worldregions (Yoffe, Wolf, & Giordano, 2007). The geographic scale ofconflict is also important to consider. Aggregate statistics on foodand water availability at the national level in a country as large assay, India, maymask local-level variation; rainfall statistics for Indiamay not accurately reflect water availability in conflict-prone As-sam state. Yet, if there are reasons to believe that rural peopleaffected by drought or other natural disasters will take their pro-tests to the capital, migrate to urban areas, or join highly-mobilerebel organizations, then there is no reason to believe that local-level climatic variables will correlate with conflict in that samelocality.

Often, researchers are agnostic about the appropriategeographic scale to be used. Grid-cells can be drawn at any arbi-trary size; researchers can choose provinces, districts, or municipal-ities as the unit of analysis; and so on. The modifiable areal unitproblem (MAUP) suggests that the choice of unit boundaries canhave significant implications for statistical results (see Rød &Buhaug, 2008, for an application to conflict data). Ideally, onewould want to establish the robustness of findings across potentialunits when there is uncertainty about the appropriate geographicscale. Nonetheless, the MAUP is more than a mere statisticalnuisance. If a finding at one scale does not hold at a different scale,scholars should think carefully about how geography affects pur-ported theoretical mechanisms at that level of aggregation.

Making sense of disparate findings, Political Geography (2014), http://

Guest Editorial / Political Geography xxx (2014) 1e5 3

Second, studies vary with respect to their temporal scale. Natu-ral disasters such as cyclones and floods may unfold in a matter ofdays, droughts can span several years, and climate change itself im-plies long term changes in observed conditions over decades orcenturies. Much of the literature utilizes short-term “shocks” intemperature, rainfall, or other such climatic variables, usuallymeasured in monthly or annual changes (Couttenier &Soubeyran, 2014; Hendrix & Glaser, 2007; Landis, 2014). Othershave examined longer-term processes that can only be seen atmuch longer time intervals (Zhang et al., 2006, 2007). Again, thischoice has important implication for the development of theory.Short term deviations from normal weather patterns may matterfor some social processes, while longer term change can be moreimportant for others. For instance, farmers may take to the streetsin sporadic protests and riots in response to a weather shock thatdamages crops in the short-term. However, when faced withlong-term decline in rural incomes as the result of increasingaridity, pressure to abandon farming and move to the cities maymount, possibly leading to different types of social tension. Intensenatural disasters such as storms and floods may lead to differentoutcomes than slower processes such as sea-level rise and desert-ification, in which people have more time to adapt.

The third dimension onwhich research differs has to dowith thesocial scale that is being studied. By social scale, I mean the degreeof coordination among individuals and organizational resourcesneeded to undertake collective action. Environmental variablesmay affect an individual's propensity to resort to violence andcrime (Rotton & Cohn, 2003); relatively unorganized protests andriots (Hendrix& Salehyan, 2012); rebellion by organized, armed ac-tors (Burke et al., 2009); and international conflict between states(Tir & Stinnett, 2012). Results for one type of social phenomenonmay not be commensurable with other types of behavior. More-over, causal relationships are likely to differ; the causal chain lead-ing fromwater scarcity to communal conflict between farmers andpastoralists may look very different when examining conflict be-tween nation-states over water resources. The same variablesthat influence conflict between states, which are highly organizedentities, may not apply to conflict between individuals and vice-versa. To illustrate how social scale matters, take for example apair of studies by Hendrix and Salehyan (see Hendrix & Salehyan,2012; Salehyan & Hendrix, 2014). In the first study (Hendrix &Salehyan, 2012), we show that abnormally high and abnormallylow levels of rainfall, which can both disrupt normal agriculturalpractices, predict social conflict events such as sporadic protestsand riots. These types of unrest are usually short-lived, require rela-tively little sustained commitment, and have limited degrees of or-ganization. By contrast, armed conflictdwhich requires a long-termcommitment by ‘professional’ militant organizationsddeclinesduring periods of low rainfall and resource scarcity (Salehyan &Hendrix, 2014). Such groups need food and supplies in order tomaintain a rebel army, and find it more difficult to sustain their op-erations under conditions of environmental distress. Thus, in look-ing at different scales of social organization, the effect of a similarset of independent variables may differ.

Ultimately, the choice of appropriate units of analysis and mea-sures depend on one's research question and theoretical expecta-tions. Too often studies are simply framed as asking, “does theclimate affect conflict?” without carefully considering the theoret-ical underpinnings behind the choice of geographic, temporal, andsocial units. A finding that, say, sustained drought in a river basinsystem does not lead to conflict between states is not sufficient todisprove a climateeconflict relationship. It may be the case thatsustained drought leads to conditions ripe for communal conflictor interpersonal disputes instead. Likewise, urban consumers maynot be affected by food production levels in the domestic context,

Please cite this article in press as: Salehyan, I., Climate change and conflict:dx.doi.org/10.1016/j.polgeo.2014.10.004

but be very sensitive to fluctuations in global markets. It is criticallyimportant, therefore, for researchers to carefully match their choiceof units and measures to the causal process they hope to shed lightupon and not jump to conclusions about relationships that theirstudy is not designed to measure.

To illustrate this point, take the increasing trend towardgeographic disaggregation in conflict studies in general, and the cli-mateeconflict relationship in particular. A number of scholars haveexpressed dissatisfaction with the practice of using aggregate,country-level statistics to measure civil war dynamics and havecollected an impressive arrayof subnational indicators such as battlelocations and local resource availability (e.g. O'Loughlin et al., 2012;Raleigh & Urdal, 2007; Theisen, 2012). In short, these studies havechosen to reduce the geographic scale of analysis to a particularprovince, district, municipality, or grid-cell. Using a grid-basedapproach (Theisen et al., 2011) find that local indicators of droughtdo not predict civil war events in that locality and they thus concludethat “drought is unlikely to directly cause civil war” (page 106).However, such a study is only consistent with one underlying theo-retical mechanism: that local level drought and scarcity predict thatpeople will fight in areas where resources are scarce.1 Alternativetheories may suggest that aggrieved individuals are recruited fromresource-poor areas and attack areas that are resource-rich. Or,that resource scarcity drives migration to the cities, leading to con-flict in urban areas (Bhavnani & Lacina, n.d.). Or, that resource scar-city predicts recruitment into militant organizations, and theseorganizations determine where to launch attacks based solely ontactical considerations such as the availability of “soft” targets. Itwould be wrong to suggest that failure to reject the null hypothesisthat local scarcity has no relationship to local civil war events im-plies that there is no causal relationship between scarcity and civilwar more generally. It could very well be the case that other causalmechanisms at different geographic scales are at play.

Just as inferences from one scale cannot readily be used to makeinferences about another, it can also be problematic to bundle ap-ples and oranges when comparing across studies. In a meta-analysis by Hsiang et al. (2013), the authors include 60 different ar-ticles that measure a relationship between climatic variables andconflict. However, the individual research papers chosen for themeta-analysis are quite heterogeneous with respect to their tempo-ral and geographic units, the dependent variable measuring con-flict, and climatic indicators. They include a study on violence inbaseball games, for example, along with studies on civil war andimperial collapse. The articles included in the analysis, therefore,may not be commensurable with one another. While many of thepapers included show a relationship between some climatic vari-able and some violent outcome, measured at some level of analysis,it is difficult to develop a general theoretical understanding of suchdiverse phenomena. It may be very well be the case that there is acorrelation between temperature, rainfall and a variety of conflictoutcomes, but without some attention to mechanisms, it is hardto understand the underlying causal processes at work.2

In summary, the terms ‘climate’ and ‘conflict’ refer to generalconcepts but must be carefully operationalized at particulargeographic, temporal, and social scales. The choice of units of anal-ysis and operational indicators is not trivial, but should be informedby theory. Too often, researchers reach for data that is readily athand rather than selecting research designs that best match thetheory and concepts one wishes to explore. Fortunately, we nowlive in a data-rich world, inwhichmore information is readily avail-able than ever before. Data on rainfall and temperature have beencollected at weather stations and through remote-sensing; civilwar data exist at the local, subnational, and national levels; newdata on protests, riots, and communal conflict are now available;and so on. When theory suggests a particular unit of analysis or

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Guest Editorial / Political Geography xxx (2014) 1e54

type of conflict, researchers should ensure that data and theory fiteach other. When theory is agnostic about appropriate units ormeasurements, then scholars should, whenever possible, establishthe robustness of findings across the possibilities (see e.g. Landis,2014). Moreover, when interpreting results, scholars should takecare to be somewhat constrained in their conclusions and avoidsweeping generalizations. A finding, or lack thereof, at one levelof analysis does not necessarily translate well to other levels ofanalysis. “Climate change does (not) lead to conflict,” is rarely aninference that can be made from research designs that can onlycapture particular aspects of the climateeconflict nexus. Morenuanced and circumscribed conclusions are often moreappropriate.

Summary of the special issue

The contributions to this special issuemake significant strides inadding to a vibrant body of research on climate change, environ-mental disasters and conflict. Collectively and individually, the arti-cles herein offer theoretical advances and rigorous empiricalapproaches to the field. Each article tackles a slightly different ques-tion and utilizes distinct units of analysis. Therefore, the purpose ofthis enterprise is not to answer the elusive question, “will climatechange cause conflict?” but rather, to assess how, in particular con-texts, weather and climate variables influence a number of conten-tious actions. Each study is designed to assess one particular aspectof the climateeconflict relationship, although the articles collectedhere speak to more general themes in the literature.

First, Wischnath and Buhaug focus their analysis on subnationalvariation in violence in India and look at a particular mechanismleading from climate to conflict: food production. They use ageographically disaggregated approach using Indian states andunion territories rather than artificial grid cells. Rather than lookingat indirect measures such as temperature and rainfalldwhich areoften used as proxies for food and water availabilitydthey useactual data on inter-annual changes in grain production. Theyalso utilize a variety of different measures of conflict gleanedfrom different sources, all of which focus on deadly violence.They find that crop loss in one year is significantly associatedwith an increase in fighting the subsequent year, providing evi-dence that at least for India, food scarcity is linked to an increasein armed violence.

Second, Nina von Uexhull takes advantage of sub-nationally dis-aggregated data to assess the linkages between rain-fed agricul-ture, drought, and violence in Africa. The analysis utilizes a gridcell approach to maximize spatial resolution along with annual ob-servations, but looks at conflicts at a relatively sophisticated socialscale, namely, organized armed conflict. She distinguishes betweenthe occurrence of drought in a given year and a sustaineddroughtdmeasured by consecutive drought-yearsdand includessatellite derived data on the type of crop cover in a region. The re-sults suggest that both simple drought incidence and the number ofdrought years significantly increase the risk of violent confronta-tions in a locality, a result that is more pronounced in areas thatrely on rain-fed agriculture. This study adds considerable nuanceto the existing literature as it identifies a policy-relevant variablethat can help cut conflict risk; improving access to irrigation andwater storage can significantly reduce the risk of violence.

Next, Hendrix and Devlin examine conflict at a very high socialscaledmilitarized disputes between nation-statesdto examine therelationship between freshwater scarcity and conflict. Theyexamine different temporal scales in their analysis by distinguish-ing between long-term mean levels of precipitation and year-to-year shocks in rainfall. They find strong evidence that the choiceof temporal units reveals important differences between long

Please cite this article in press as: Salehyan, I., Climate change and conflict:dx.doi.org/10.1016/j.polgeo.2014.10.004

term trends and short term triggers. Interstate conflicts are lesslikely to occur when pairs of countries experience lower thanaverage rainfall in a given year; short term declines in water avail-ability have a pacifying effect. However, looking at longer termtrends yields different patterns. Countries that have lower meanlevels of rainfall and higher overall rainfall variability are morelikely to come into conflict with one other. Therefore, scarcity canhave a conflict-intensifying effect as well as a conflict-reducing ef-fect among pairs of states depending on the choice of time interval.

Then, the article by ColinWalchmoves beyond a simple conflict/no conflict dichotomy and asks why rebel organizations cooperatewith governments in providing disaster relief. Therefore, in aninteresting twist to the literature, rather than looking at how natu-ral disasters might lead to conflict and violence, this article looks atcooperative behavior among antagonists after a disaster. He exam-ines qualitative evidence from the Philippines to examine why theMoro Islamic Liberation Front collaborated with the governmentbut the National People's Army did not. This research is based onextensive field research in the Philippines and in-depth interviewswith actors on the ground, adding rich layers of complexity to ourunderstanding of disaster cooperation. The level of hostility be-tween the combatant parties as well as ties to the local populationhelp to explain the difference in response to the same typhoonevent.

Busby, Smith and Krishnan seek to produce high-resolutionmaps of where climate change vulnerability in Africa is most se-vere. They are most interested in examining subnational variationin risks to human populations. Rather than traditional hypothesistesting, they take existing assumptions regarding disaster expo-sure, population, household and community resilience, and state-level governance to create composite maps of where problemstend to overlap. Using a variety of indicators, they shed light onwhich areas in Africa, at the subnational level, are most likely tosuccumb to negative human security impacts given changes inclimate. The maps they produce provide a very useful, simple visu-alization of complex data, which can help guide policy efforts toplan for the future.

Ide et al. offer a similar mapping exercise, but focus their anal-ysis on Kenya and Uganda. Like Busby et al., they create a compositemap of climate change risks and vulnerability and include variablesfor exposure to natural hazards, sociological aspects of vulnerabilitysuch as infant mortality, and past conflict. They find that vulnera-bility is most severe on the Kenyan side of Lake Victoria and inthe northern parts of Uganda. Importantly, they take the additionalstep of correlating their maps with a number of different datasetson political and social conflict. Moreover, they present case narra-tives of three locations in their study area in order to “ground truth”or corroborate the results against the actual experiences of commu-nities. They find mixed evidence in support of their mapping exer-cisedat least as it relates to violencedalthough the combination ofqualitative and quantitative evidence to validate their risk assess-ments is a useful step forward.

Finally, Gleditsch andNordås dissect the Intergovernmental Panelon Climate Change 5th assessment report, focusing on statementstherein regarding the human impact of climate change. They notethat while the 4th assessment report was quite alarmist in its claimsregarding armed conflict, the latest IPCC report is more balanced andnuanced. One important conceptual issue in the report, they note, isthe distinction between ‘human security’ and ‘armed conflict.’Whilediscourse on human security has blossomed in recent decades, it isoften used vaguely to refer to any negative outcome of climatechange. Armed conflict, on the other hand, is a much more definedconcept, making it relatively easier to conduct empirical work. Theauthors conduct an exhaustive review of the IPCC report and provideone of the first, full-length critiques of its contents.

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Guest Editorial / Political Geography xxx (2014) 1e5 5

In all, the articles in this special issue represent the cutting edgeof research on the climateeconflict relationship. Collectively theyadd considerable nuance and richness to the academic debateand provide some useful direction to those in the policy domain.Yet, while adding to a cumulative body of wisdom, readers shouldtake care not to simplify this work into a simple “yes or no” dichot-omy when addressing the question, “will climate change leads tomore conflict?” Climatic influences on various forms of conflictare not simple and direct. Rather, this special issue offers an impor-tant set of findings related to a wide variety of climate/conflict link-ages and paints a varied picture of the relationship.

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Idean SalehyanDepartment of Political Science, University of North Texas, USA

E-mail address: idean@unt.edu.

Available online xxx

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