commentary: debating environment, population, and conflict

7/31/2019 Commentary: Debating Environment, Population, and Conflict

1/307E N VI RO N M EN TALC H AN GE & S ECURITY P RO JECT REPORT , ISSUE 6 (SUMMER 2000)

Commentary

COMMENTARY : D EBATING ENVIRONMENT ,P OPULATION , AND CONFLICT

T he environment, population, and conflict thesis remains central to current environm ent and security de1990s, an explosion of scholarship and policy attention was devoted to unraveling the linkages among tW hile it can easily be argued that both the research and policy comm un ities have made significant adva findings and policy lessons remain the sub ject of in tense debate. T he recent publication of a host of significthis debate dictated a special commentary section to supplement the lengthy book reviews provided in thiEnvironmental Change and Security Project Report.

In the first art icle, leadin g figu re T hom as H omer-D ixon and his colleagues from the University of Toro prom inent crit ique enunciated by fellow peace researcher N ils Petter Gledi tsch from the Intern ational PeaceOslo (see box on Gleditschs critique). Richard M atthew of the Un iversity of California, Irvin e, comm e N AT O Comm ittee on the Challenges of M odern Society pilot study entitled Environmental Security in an InternationalContext.Geoffrey D. D abelko joins Richard M atthew to draw conclusions from a M arch 20 00 environmenconflict workshop with leading scholars. In the last commentary, University of California, Irvine researchercritiques Indra de Soysa and N ils Petter GleditschsTo Cultivate Peace: Agriculture in a World of Conflict,portions of whichwere reprinted in issue 4 of theECSP Report.

The Environment and Violent Conflict:A Response to Gleditschs Critique and Some Suggestions

for Future Research

by Daniel M . Schwartz, Tom D eligiannis, and T homas F. H om er-Di

IN T R O D U C T I O N

N ils Petter Gleditsch, senior researcher at the International Peace Research Institute, Oslo, has writtewidely noted critique of recent research in the new field of environmental security (Gleditsch, 19Gleditschs critique echoes and builds upon criticisms leveled by skept ics of environment-con flict rese(e.g., Deudney, 1991; Levy, 1995; and Rnnfeldt, 1997). H e identifies a numb er of specific problems of thconceptualization, and m ethodology, sometimes singling out the work of the team led by Thom as Hom er-Dixothe University of Toronto (henceforth referred to as the Toronto Group). In this article, we respond to these ccerns and propose avenues for future research.


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D an iel M . Schwartz and Tom D eligiannis are Ph.D . candidates at the U niversity of Toronto. T hom as Fis the Director of the Peace and Conflicts Studies Program at the University of Toronto and author of Environment,Scarcity, and Violence(Princeton University Press, 1999 ). T his article is drawn from the forthcomin g N oveedited volume by Paul F. Diehl and Nils Petter Gleditsch entitled Environmental Conflict(Westview Press). Published with permission of the pu blisher (Copyright W estviewPress). T he editors of theECSP Reportwish to thank Tad Homer- D ixon, D an Schwartz, Tom D eligiannis, Paul D iehl, N ils Petter Gledit sch, Leo A . W. W iegm an , and Iaassistance.

Norwegian peace researcher Nils PetterGleditsch makes a nine-point critique of envi-ronment, population, and conflict literature inhis seminal 1998 article, Armed Conflict andthe Environment: A Critique of the Literature.These nine points, summarized below, spurredThomas Homer-Dixon and his colleagues at theUniversity of Toronto to pen the response pub-lished here. Gleditsch, senior researcher at theInternational Peace Research Institute, Oslo,(PRIO) maintains the literature has the follow-ing characteristics.

1. There is a lack of clarity over what is meant

by environmental conflict;2. Researchers engage in definitional and po-lemical exercises rather than analysis;

3. Important variables are neglected, notablypolitical and economic factors, which havea strong influence on conflict and mediatethe influence of resources and environmen-tal factors;

4. Some models become so large and com-plex that they are virtually untestable;

5. Cases are selected on values of the depen-dent variable;

6. The causality of the relationship is reversed;7. Postulated events in the future are cited as

empirical evidence;8. Studies fail to distinguish between foreign

and domestic conflict; and,9. Confusion reigns about the appropriate level

of analysis.

Nils Petter Gleditsch. Armed Conflict and theEnvironment: A Critique of the Literature. Journal of Peace Research Vol. 35, no. 3, 1998: 381-400.

Meth odological issues underpin Gleditschs critique,and we therefore deal with them in detail. Gleditschasserts that m uch environment-conflict research is meth -odologically unsound and fails to qu alify as systematicresearch. H e contend s it violates the rules of quasi-experimental methodologyused by convent ional socialscientists in lieu of true experimental methods that arenot viable for many social scientific inquiries. This per-spective is his starting point for identifying many of thespecific problems in environment-conflict research. Asa result, he disregards th e detailed findings of the Toront oGrou p, the Swiss-based Environmental Conflicts project(EN CO P), and other research projects that do n ot meethis standard s of evidence. We argue th at G leditschs pro-posed approach is a methodological straightjacket thatwould, if widely adopted, severely constrain research inthe field. We do not take issue with the quasi-experi-mental methodology per se. Rather, we show that the

case-study method used b y the Toronto Group has quali-ties that com plement quasi-experimental m ethods.In Section One, we address some of the conceptual

and theoretical problems identified by Gleditsch anddiscuss his selective critique of the literature on the rela-tionship between environmental scarcity and conflict.Gleditschs critique does not address the validity of thespecific findings that emerged from ENCOP and theToronto Group. Instead, he treats these projects with abroad brush, at times associating them with other, lessrigorous, research. Section two examines underlyingmethodological issues and addresses Gleditschs concerns

arising from his methodological perspective. The finalsection of the article looks forward and suggests avenuesfor future research on the environment-conflict nexus.

I. CONCEPTUAL AN D T HEORETICAL ISSUES

Gleditsch identifies a number of common prob-lems with the literature on environmental stress andconflict. This section responds to conceptual and theo-retical criticisms aimed explicitly at the Toronto G roupsresearch.

B A C K G R O U N D


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Employing a Comprehensive D efin it ion of ScarcityDisputes amon g scholars about how to conceptual-

ize environm ental stress have long hindered research onthe links between this stress and violent conflict. Essen-tially, these are disputes about the delineation of theindependent, or causal, variable. Gleditsch faults muchof the literature for being unclear as to whether thecausal factor is absolute resource scarcity or environ-m ental degradation . H e criticizes H om er-D ixonsconcept of environm ental scarcitywhich integrates sup-ply, demand, and distributional sources of the scarcityof renewable resourcessuggesting it muddies the waters, althou gh he fails to explain why (Gleditsch, 1998387).

Following Stephan Libiszewski, Gleditsch adopts adistinction between conflicts that result from simpleresource scarcity and those that result from environ-mental degradation (Libiszewski, 1992). U nfortunately

however, Libiszewskis distinction is a wholly inadequatestarting point for research on the environmental causesof violence. First, as Gleditsch himself acknowledges,the two categories are not causally separate: degradationof an environmental resource, like cropland or freshwater supplies, can cause a straightforward or simplescarcity of that resource. Second, degradation of an en-vironmental resource is only one of two possible sourceof a decrease in a resources supply. D egradation referto a drop in the quality of the resource; but cropland,fresh water, and the like can also be depleted, whichmeans the resources quantity is reduced. If we restrict

our analysis to conflicts caused by degradation of envi-ronmental resources, we will omit a main source of thereduced supply of these resources in many poor coun-tries around the world.

Third, environmental degradation, th e phenomenonGleditsch wants us to emphasize, is exclusively a sup-ply-side prob lem: if we degrade a resource, then there iless of it available. Any hypothesis linking environm en-tal degradation to violence is linking, essentially, thereduction in t he resources supply to violence. H oweverif we want to explore the causes of violence, a resourcesabsolutesupply is not interesting. What we should in-vestigate, rather, is the resources supplyrelative to, first,demand on the resource, and, second, the social distri-bution of the resource. The relationships between supplyand demand and between supply and distribution de-termine peoples actual experience of scarcity, and underany practical hypothesis, it is these relationships thatinfluence the probability of violence. This is the reasonthat we include demand and distributional aspects inour definition of environmental scarcity.1

Fourth and finally, focusing on environmental deg-

This article The Environment and Violent Con-flict: A Response to Gleditschs Critique andSome Suggestions for Future Research byDaniel M. Schwartz, Tom Deligiannis, and Tho-mas Homer-Dixonis drawn from the forthcom-ing November 2000 edited volume by Paul F.

Diehl and Nils Petter Gleditsch entitled Environ- mental Conflict (Westview Press). This volumepromises to make a significant contribution tothe environment, population, and conflict litera-ture. Following, is the table of contents for Envi- ronmental Conflict :

Chapter 1. Controversies and QuestionsPaul F. Diehl & Nils Petter Gleditsch Chapter 2. The Case of South AfricaVal Percival & Thomas Homer-Dixon

Chapter 3. Causal Pathways to ConflictWenche Hauge & Tanja Ellingsen

Chapter 4. Demographic Pressure andInterstate ConflictJaroslav Tir & Paul F. Diehl

Chapter 5. Demography, Environment, andSecurity

Jack Goldstone Chapter 6. Water and Conflict

Steve Lonergan Chapter 7. Resource Constraints or

Abundance?Bjrn Lomborg

Chapter 8. Democracy and the EnvironmentManus Midlarsky

Chapter 9. The Limits and Promise ofEnvironmental Conflict Prevention

Rodger Payne Chapter 10. The Spratly Islands Conflict

David Denoon & Steven Brams Chapter 11. Environmental Cooperation and

Regional PeaceKen Conca

Chapter 12. Armed Conflict and theEnvironment

Nils Petter Gleditsch Chapter 13. The Environment and Violent

ConflictDaniel M. Schwartz, Tom Deligiannis &

Thomas Homer-Dixon

To order a copy of this book, please contactWestview Press at:

Westview PressPerseus Books Group Customer Service

5500 Central AvenueBoulder, CO 80301

(800) 386-5656; Fax: (303) 449-3356E-mail: [email protected]



Commentary

radation alone tends to lead researchers to overlook orneglect key interactionssuch as the processes we callresource captureand ecological marginalizationamongsupply, demand, and distributional pressures (Homer-D ixon, 1999 : 73-80). Resource captureoccurs when th edegradation and depletion of a renewable resource (adecrease in supp ly) interacts with popu lation growth (anincrease in demand) to encourage powerful groupswithin a society to shift resource access (that is, to changethe resources distribution) in their favor. These groups

tighten their grip on the increasingly scarce resource anduse this control to boost their wealth and power. Re-source capture in tensifies scarcity for poorer and weakergroups in society.Ecological marginalizationoccurs whenunequal resource access (skewed distribution) combineswith pop ulation growth (an increase in demand) to causelong-term migrations of people to ecologically fragileregions such as steep upland slopes, areas at risk of de-sertification, tropical rain forests, and low-quality pub-lic lands within urban areas. H igh popu lation densitiesin these regions, combined with a lack of knowledge

and capital to protect the local ecosystem, cause severeresource degradation (a decrease in supply) (Homer-Dixon, 1999: 177). Resource capture and ecologicalmarginalization are often intimately inter-linked, withone leading to the other.

Some might argue that by including distributionalissues in our definition of environmental scarcity, theToronto Group makes the concept so broad as to beuseless, because the group classes conflicts solely overresource distribution as environmental conflicts.2 Theargument is misguided. Un even d istribution never actson its own: its impact is always a fun ction o f its interac-tion with resource supply and demand. In practicalterms, the reason resource distribution is important isthat the resources people want (that are, in other words,in demand) are in finite supply. Indeed, the TorontoGroup found in its research that problems of decliningresource supp ly and rising resource demand were alwaysintimately entangled with u neven resource distribution.

For these four reasons, an exclusive focus on envi-ronm ental degradation in environm ent-conflict researchun reasonably restricts, distorts the scope of the research,

and misses crucial aspects of the environmental chal-lenges facing the developing world. It is better, we believe,to acknowledge explicitly that the fundamental issue isone of scarcity of renewable resources and that any t reat-ment of this scarcity should encompass the exhaustiveset of scarcitys sources: decreases in supply, increases indemand, and changes in distribution. The TorontoGroup incorporates these three facets of scarcity in itstripartite definition of scarcity.

Challenging Simonesque OptimismAt a more fundamental level, Gleditsch questions

the very idea that humanity is facing increasing envi-ronmental scarcities. His critique seems to be guided bythe assumption that the links between environmentalscarcity and violence are overstated, because humanityshows astonishing capacity to adapt to scarcities(Gleditsch, 1998: 383-384 and 395). Markets stimu-late human inventiveness and commerce that open upnew sources of scarce resources, encourage conservation,and create technologies that allow substitution of rela-

tively abun dant resources for scarce ones. Th ese adapt iveprocesses certainly operate in many cases, as we havepreviously noted (Homer-Dixon, 1995; Homer-Dixon,1999: 31-5 and 107-32). But Gleditsch does not ac-knowledge that societies often fail to adequately adjustto scarcity, with poverty, migrations, and institutionalfailure the result. Environmental scarcities unquestion-ably have profoundly debilitating effects on someeconomies, societies, and social groups.3 Just becausehumans are remarkably adaptive in some cases does notmean that they are always adaptive.

Gleditsch seems particularly influenced by JulianSimons cornucopian thesis that, based on the historicalrecord, human societies can bring to bear on their re-source scarcities sufficient ingenuity to prevent anydecline in well-being over the long run (Simon, 1996).But Simons techno-optimist arguments are too simplis-tic, for three reasons. First, he tends to project the trulyextraordinary improvements in human well-being overthe past two centuries linearly into the future, withoutmu ch qu estion ing or reflection . Yet, if we look back fur-ther th an two hundred years, it is clear that hum an affairs

W e argue that Gleditschs proposed approach is a methodologi-cal straightjacket that would, if widely adopted, severely con-strain research in the field.


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have my been marked by many non-linear eventssudden, sharp changes in economic and socialbehaviorsome of which have had decidedly negativeeffects on human well-being. The progress of the lasttwo centuries is not the only evidence we should use toestimate our trajectory into t he future.

Second, when Simon analyzes trend s in hum an well-being, he usually uses highly aggregated data, such asstatistical averages for all of hum ankind. Yet, when thesedata are disaggregatedthat is,broken into sub-categoriesSimons optimism is lesspersuasive. For example, althoughboth the percentage and absolutenumber of hungry people havefallen globally in the last twentyyears, Latin America, South Asia,and especially sub-Saharan Africa

have not seen reductions in theabsolute number of hungrypeople.4 Third and finally, closestudy of specific cases shows thatsocieties do n ot always generate th eingenuity they need when andwhere it is needed (Lele and Stone, 1989). Althoughenvironmental and demographic stress often drives upthe requirement for ingenu ity in poor countries, a num -ber of factorsincluding market failure, inadequatehuman capital, and political competition over scarcenatural resources among powerful groupscan impede

the flow of ingenuity (Homer-Dixon, 1999: 107-32).H omer-D ixon and others have responded with con-siderable theoretical and empirical detail to thearguments of Simon and other techno-economic opti-mists (Homer-Dixon, 1999: 28-44; Cohen, 1995;Ahlburg, 1998). Nowhere does Gleditsch acknowledgethese responses. The determinants of adaptation to scar-city are a major outstanding issue for researchers in thisfield. Gleditsch would better advance our understand-ing if he engaged with the various positions on the issue,rather than appearing to accept the arguments of theoptimists at face value.

Bringing Nature in to Social T heoryGleditschs skepticism about the seriousness of en-

vironmental scarcities is the starting point for a keyelement of his critique of the environment-conflict lit-erature. H e argues that the literature overstates the imp actof environmental scarcities on violent conflict and, inthe process, ignores other, perhaps more powerful causalvariables. Far too many analyses of conflict and theenvironm ent are based on overly simplistic reasonin g,

he writes. The greatest weakness in this respect is thatmuch of this literature ignores political, economic, andcultural variables (Gleditsch, 1998: 389). Bydeemphasizing environmental scarcities, Gleditsch cor-respondingly emphasizes other variables.

This approach implies that environmental stress maybe no more than an intermediate or intervening vari-able between dysfunctional political and economic in-sti tutions and conflict . Thus, Gleditsch asks if

environm ental conflict may beprimarily an underdevelopmentproblem, because environ-mental degradation or load isstrongly correlated with poverty(Gleditsch, 1998: 396). Heseems to argue that conflict indeveloping coun tries is best ex-plained by social causes, no t by

the physical influences of thenatural environment. In theprocess, like many scholars of comparative development,Gleditsch marginalizes thephysical circumstances of hu-

man society as explanatory variables; he app ears to con-sider them to be, at most, secondary causes of socialbehavior. When it comes to violent conflict, they aremerely aggravators of already existing social stresses. Ifthis is his position, Gleditsch is making a classicendogeneity mistake: he is claiming that environmental

problems are a consequence of, and endogenous to, thebroader social system and that, therefore, any conflictcaused by environmental problems is ultimately causedby social factors.

It is unquestionably true that social variables mustbe central to any adequate explanation of human con-flict, whether in rich or poor countries. The TorontoGroup discusses at length the political, economic, andcultural factors that interact with environmental scar-city to cause violence. The societies most vulnerable toenvironmentally-induced violence are those simulta-neously experiencing severe environm ental scarcity andvarious forms o f institu tional failure (especially failuresof states and markets) that hinder social adaptation tothe scarcity. The key role of social variables mu st th erefore be acknowledged. H owever, this requirement doesnot mean that physical variables should be made fullyendogenous to the social system and, consequently,turned into relatively uninteresting secondary causes ofsocial conflict and stress.5

As Homer-Dixon has noted, there are three reasonswhy environm ental scarcity should be considered at leas

Environmental scarci-ties unquestionablyhave profoundly debili-tating effects on some

economies, societies, andsocial groups.



Commentary

partly an exogenous factor in social behavior and con-flict and why, th erefore, environmental scarcity deservesresearch attention in its own right (H omer-Dixon, 199 9:16-18 and 104-6). First, environmental scarcity is notonly influenced by social variables like institutions andpolicies; it can itself affect these institutions and poli-cies in harm ful ways. This is the case when shor tages of a renewable resource, such as cropland or forests, moti-vate elites to seize control, through either legal or coer-cive means, of the resources remaining stocks (resourcecapture). In other words, we should not assume that so-cial variables are completely independent and externalstarting points in the causal chain; it turn s out that theycan be affected by environmental scarcity, sometimesnegatively. Second, the degree of environmental scar-city a society experiences is not , as it turns ou t, wholly aresult of economic, political, and social variables, likefailed institutions and policies; it is also partly a func-

tion of the particular physical characteristics of thesocietys surrounding environment. These characteris-tics are, in some respects, independent of human activi-ties. For example, the vulnerability of coastal aquifers tosalt intrusion from the sea and t he depth of upland soilsin tropical regions are physical givens of these envi-ronmental resources. Third, once environmental scar-city becomes irreversibleas when most of a countrysvital topsoil washes into the seathen the scarcity is,almost by definition, an external influence on society.Even if enlightened reform of institutions and policiesremoves the underlying social causes of the scarcity, be-

cause the scarcity itself is irreversible, it will remain acontinu ing burden on society.The claim that environmental scarcity can be, in

part , an exogenous variable, should not be confused withthe claim (which we do not make) that environmentalscarcity can have a direct impact on conflict. We arguethat the link between environmental scarcity and con-flict is most often indirect. Nevertheless, environmentalscarcity can still have an exogenous impact on the socialconditions that eventually lead to conflict.

Ident ifying Key Variab les

Gleditsch claims that the Toronto Group and otherresearchers overlook important variables like regime typeand democracy. H owever, the Groups full model doesintegrate regime-type variables into its analysis of thesocial and econom ic effects of environm ental scarcities.In the scholarly literature on the origins of revolutionsand civil violence, the variables of opportunity structurean d state capacity,which are central to the TorontoGroups model, are recognized as integral aspects of re-gime type (Goodwin, 1997; Tarrow, 1994; Skocpol,

1979). Fur thermore, in his recent work, C olin Kahl ex-plicitly builds on the Toronto Groups model to furtherour understanding of how regime type affects the linksbetween environmental scarcity and violence (Kahl,1998).

More specifically, however, Gleditschs suggestionthat the Toronto Group is blind to the importance of regime type is, on close reading, actually a call for theinclusion of ademocracyvariable in environment-con-flict models (Gleditsch, 1998: 389).6 We agree withGleditsch th at a more explicit focus on d emocracy couldbe beneficialas long as analysts are careful in their useof democracy. As H omer-Dixon has argued, the termdemocracyis used too loosely by lay commentators andexperts alike. It commonly encompasses an extraordi-narily variegated set of social phenomena and institut ionsthat have complicated and multiple effects on the inci-dence of social turmoil and violence (Homer-Dixon,

1999: 182).7

Gleditsch deserves credit for advancingenvironmental conflict literature along this importanttheoretical path. If future research can address the diffi-cult issues surrounding the precise definition andoperationalization of dem ocracy, importan t findings mayyet emerge.8

Using Historical EvidenceFinally, Gleditsch claims that the Toronto Groups

theory about the links between environmental scarcityand conflict is flawed, in part because it is founded oninferences about future scarcities. Gleditsch asserts that

Hom er-Dixon, and many other authors. . .have stressedthe potential for violent conflict in the futu re withoutproviding adequ ate empirical evidence of past or presentlinkages between environmental scarcities and violentconflict (Gleditsch, 1998: 393).9

Gleditsch is mistaken that the Toronto Group usesthe future as evidence to substantiate its claims thatthere are links between environmental scarcities andconflict. In the process of developing its model, theGroup has undertaken more than a dozen detailed his-torical case studies. These include studies of the C hiapasrebellion, the Rwandan genocide, violence betweenSenegal and M auritan ia, civil conflict in the Philippin es,and ethnic violence in Assam, India.10 The historicalanalyses in these case studies were informed by the richliteratures on the causes of revolution, insurgency, andethnic strife. Taken together, they are a foundation forthe Toronto G roups larger theoretical model abou t link-ages between environm ental scarcity and violent conflict.Non e of the hypotheses in this model depends on eventsyet to come; rather, the model is informed by eventsthat have already taken place.11


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To support his claim that the Toronto Group usesthe future as evidence for its model, Gleditsch takes is-sue with commentators who argue that water scarcity inthe M iddle East could lead to arm ed conflict in the fu-ture. Without referring to any research in particular, buthaving identified the Toronto Group by name at thebeginning of the paragraph, Gleditsch concludes thatthis is a hypothesis based on controversial theory anddebatable extrapolations, rather than data which mayconfirm the prediction (Gleditsch, 1998: 394).Gleditsch thus conflates the findings of the TorontoGrou p with largely unsubstantiated claims by other writ-ers regarding the potential for conflict over waterresources.

The specific findings of both the Toronto Groupand EN CO P are certainly worthy of detailed consider-ation in any discussion of links between environmentalscarcity and conflict. In this case, Gleditsch did not to

refer to the Toronto Groups thinking on the conse-quences of water scarcity. H ad he done so, he wouldhave noted a number of interesting hypotheses worthyof testing. Homer-Dixon argues that the world is notabout to witness a surge of water wars. Wars over riverwater between u pstream and downstream neighbors arelikely only in a narrow set of circumstances, H omer-Dixon writes. The downstream country must bethreatening to restrict substant ially the rivers flow; theremu st be a history of antagonism between the two coun-tries; and, most importantly, the downstream countrymust believe it is militarily stronger than the upstream

country. . . .There are, in fact, very few basins aroundthe world where all these conditions hold now or mighthold in the future (Homer-Dixon, 1999: 139). TheToronto Groups research on water scarcity is, in fact, atodds with sensationalist claims about water wars.

II. FINDIN G O U R W AY IN TH E W ILD ERNESS

Underpinning many of Gleditschs criticisms aredeeper methodological issues pertaining to the conductof social science inqu iry. G leditsch claims, for instance,that the Toronto Group fails to select cases appropri-ately, neglects to investigate the possibility of reversecausation, devises un testable mod els, overemph asizes thecomp lexity of ecological-political systems, and lacks thetools to weight causal variables. These criticisms can onlybe understood in the context of Gleditschs unduly nar-row perspective on what constitutes systematicresearch.

In this section, we first show that process-tracingwithin single cases shou ld be an integral part of system-

atic research in the social sciences; th is method com plements more conventional quasi-experimentalapproaches. Drawing a distinction betweencausal ef- fectsand causal mechanism s, we then show wh y Gleditschscriticisms of the Toronto Groups researchas identi-fied in the previous paragraphare unfounded. We alsorecap some of the key findings of the Toronto Groupthat G leditsch overlooked as a result of his methodological bias. In short, we show that there are more than afew lights in the wilderness to guide future researchinto the relationship between environm ent and conflict

Conducting Systematic ResearchGleditsch asserts that scholars have conducted little

systematic research to date on the link between envi-ronmental scarcity and violent con flict (Gleditsch, 1998384-7). By systematic research, he seems to mean ei-ther experimental or quasi-experimental analyses. (He

discusses statistical analyses and controlled-case com-parisons in particular, but quasi-experimental methodscan include coun terfactual analyses and con gruence pro-cedures.) Gleditsch additionally contends that pastresearch into the links between environment and con-flict consisted merely of exploratory case-studies thatfailed to demonstrate causal connections (Gleditsch,1998: 392).

In our opinion, Gleditsch has an overly circum-scribed view of what counts as systematic research inthe social sciences. Many social science methodologistshave long recognized that systematic research includes

not only experimental and quasi-experimental methodsbut single-case methods as well.12 Highly influentialstudies in the social sciencessuch as Graham AllisonsEssence of D ecision(1971) and Arend LijphartsT he Poli-tics of Accommodation(1975)have used single casestudies to build and test theories.13

At issue in this debate over the merits of the case-s tudy method are fundamental ontological andepistemological questions pertaining to the nature ofcausation. Among competing views on how causationcan be demonstrated, philosopher David Humes argu-ments remain influential.14 H ume asserted that causationcould be demonstrated only by showing a high degreeof covariance between types of event s, which he termedconstant conjunction. Humes notion of constant con- jun ction underpin s experim ental and qu asi-experim entamethodologies in the social sciences; many researchersincluding Gleditsch, appear to believe that it also viti-ates the single-case method.

However, Andrew Bennett (1997) shows convinc-ingly that H um es not ion of causality un derpin s not onlyexperimental and quasi-experimental methods but the



Commentary

single case-study method as well. Bennett notes thatHume recognized three sources of causality, only oneof which was constant conjunction. T he other two weretemporal successionand contiguity. Bennett argues thatwhile constant conjunction is related to what method-ologists term causal effect , temporal succession andcontiguity are related tocausal mechanism. The causaleffect of an explanatory variable is defined by Bennettas the change in probability and/or value of the depen-

dent variable that would have occurred if the explana-tor y variable had assum ed a different value. Causalmechanism, on the other hand, is defined as the causalprocess and intervening variables through which causalor explanatory variables produce causal effects (Bennett,1997: 18-19). Both causal effectand causal mechanismare therefore essent ial and complementary facets of cau-sality. While the experimental and quasi-experimentalmethods aim to gauge causal effect, they say little about

causal mechanism. The single-case method, conversely,helps reveal causal mechan ism bu t gives little indicationof causal effect. In short, neither the experimental andquasi-experimental nor the single-case method is suffi-cient to demonstrate causation with any finality. It isequally evident, however, that the single-case method isa necessary tool to demonstrate causation.

An example from the natural sciences illustrates thedistinction between causal effect and causal mechanism.Although the correlation between smoking and cancerhas been known for many years, only within the last fiveyears have researchers pinpointed exactlyhowsmokingengenders cancer. That is, the causal effects were alreadyknown, but until recently the causal mechanisms re-mained unknown. The recent identification of thesemechanisms has put the tobacco industry on t he defen-sive, because they now find it harder to retreat to theclaim that scientific proof is lacking.15

The distinction between causal mechanism andcausal effect is also cogent for the social sciences. Timo-thy McKeown notes that only by distinguishing betweencausal effect and causal mechanism can one begin to

understand why AllisonsEssence of a D ecisionan dLijphartsT he Politics of Accomm odationhad such mo-mentous impact on the field of political science. Bothseriously challenged long-standing theories: Allisonsanalysis of decision-making during the Cuban missilecrisis undermined the notion of the state as a unitary,rational actor; and Lijpharts analysis of politics in theNetherlands challenged prevailing ideas about the im-pact of political cleavages. The im portant p rocesses these

authors identified in their case studies would have beenoverlooked in a statistical analysis. McKeown (1999:172-174) asserts these case analyses had a large impactprecisely because they h ighlightedhowevents unfoldedby identifying their causal mechanisms.16

Several leading philosophers of science have madesimilar points. Wesley Salmon (1984: 121), for example,argues in favor of explicating causal mechanisms: T hemere fitting of regularities into p atterns has little, if any,

explanatory force. Andrew Sayer (1992: 106-7) statesthat what we would likeis a knowledge of howth eprocess works. Merely knowing thatC has generally beenfollowed byE is not enough: we want to u nderstand thecontinuous process by whichC produced E AndAbraham Kaplan (1964: 329) asserts that we see betterwhysomething happens when we see betterin moredetail, or in broader perspectivejustwhat does hap-pen.17

Bennett notes that the distinction between causaleffect and causal mechanism has prompted a debateamong methodologists about which of these two sourcesof causality is more important. Although some analystssuggest th at causal effects are logically prior t o the iden-tification of causal mechanisms (King, Keohane, andVerba, 1994: 86), others insist that causal mechanismsare ontologically prior to causal effect (Yee, 1996: 84).Bennett dismisses this controversy, arguing that cau-sality involves both causal effects and causal mechanismsand its study requires a diversity of methods, some of which are better adapted to the former and some to thelatter (Benn ett, 1997 : 25).

[A]n exclusive focus on environmental degradation in envi-ronment-conflict research unreasonably restricts, distortsthe scope of the research, and misses crucial aspects of the environ-mental challenges facing the developing world.


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Bennetts reluctance to confer priority on eithercausal effect or causal mechanism, however, does notsuggest that the identification of one should not pre-cede the identification of the other in terms of thepractical task of puzzle solving in the social sciences.Indeed, when a research program is in its early stagesand the underlying theory is still largely undeveloped,

focusing first on causal mechan isms is probably the beststrategy. O nce researchers have discovered these causalmechanisms and elaborated the theory, they can thenbegin to estimate causal effects.18 Thus George andMcKeown emphasize the role that single-case methods(involving process-tracing) can play in the developmentof theory (George and McKeown, 1985: 34-41).19

With this methodological underpinning, theToronto Group set out to perform a series of case stud-ies of the causal links between environm ent scarcity andconflict. Although the possibility of such links had been

recognized by previous scholarship, theory was rudim en-tary. Using a process-tracing approach, the TorontoGroup conducted over a dozen case studies to betterunderstand the causal mechanisms that might connectenvironm ental scarcity to conflict. T he results prod ucedby the Toronto Group reflect the methodology used:the Group does make general claims about causal mecha-nisms (for example, at the end of his second In ternation alSecurityarticle on the subject, Homer-Dixon says ex-plicitly that environmental scarcity causes violentconflict), but it has been careful to avoid making suchclaims about causal effects (nowhere in the Groups re-search reports are there any claims about the power of environmental scarcity relative to other potential causesof conflict).20

Without undertaking research into causal mecha-nisms, estimates of causal effect are far less illuminating,for two reasons. First, researchers will not know whichpotentially confounding variables they should controlin their statistical tests; and, second, researchers mayoverlook key processes and causal relationships that arehidden in the data. In quasi-experimental methods of

social science, it is impossible to control all variablesthat may affect the dependent variable under study;therefore, researchers must pick and choose their con-trol variables carefully. Process-tracing helps identifythose particularly worthy of control.21 Also, process-tracing reveals variables and causal patterns that maynot emerge from statistical analysis. For instance, the

patt erns of ecological marginalization and resource cap-ture, which were discovered by the Toronto Group usingprocess-tracing, are not obvious and would undoubt-edly have remained hidden from statistical analysis. TheGroups research suggests, however, that quasi-experi-mental and statistical methods should now be used toinvestigate these patt erns.22 This more inclusive under-standing of systematic research helps us address fivefurther concerns raised by Gleditsch about contempo-rary environment-conflict research: selection of cases onthe ind ependent and dependent variables; failure to con-

sider that the dependent variable may in fact be animport ant cause of the independent variable; a propen-sity to develop untestable models; overemphasis on thecomplexity of ecological-political systems; and an in-ability to gauge the relative power of environmentalscarcity as a cause of conflict.

Selecting Case StudiesFollowing Marc Levy (1995) and C arsten Rnn feldt

(1997), Gleditsch contend s that choosing cases in whichboth environmental scarcity and violent conflict wereknowna priorito exist, violates a fundamental principleof research design that applies to both qualitative andquantitative analyses. Consequently, Gleditsch(1998:391-92) asserts this practice produces nothingmore than anecdotal evidence to support its hypoth-eses.

Gleditschs approach to research design appears tohinge on the assump tion t hat causality is little more thancausal effect. Causal mechanism is regarded as less im-portant or is simply not considered at all. Although weagree that researchers must allow for variation on both

T he societies most vulnerable to environmentally-induced vio-lence are those simultaneously experiencing severe environmen-tal scarcity and various forms of institutional failure that hindersocial adaptation to the scarcity.



Commentary

the independent and dependent variable if they want toestimate casual effect, we contend researchers will findsuch an approach less helpful in identifying causalmechanisms. If causal mechanism is believed to be anintegral aspect of causality, then selecting case studieson the independent and dependent variable is hardly anegregious error in research design. Indeed, in order tounderstand whether there are causal links between envi-ronmental scarcity and violent conflictand, if thereare, howthese variegated links workit will be some-times necessary to select cases in this manner. TheToronto Group therefore intentionally selected cases inwhich environm ental scarcities and violent conflict wereknown a priorito exist (Homer-Dixon, 1999: 169-76).T he Group then u sed process-t racin gto determine if theindependent and dependent variables were actually caus-ally linked, and, if they were, to induce from a closestudy of many such cases the common mechanisms of

causality and the key interm ediate variables that charac-terized these links.A related objection to selecting cases on both the

independent and dependent variables is that the re-searcher might as a result, overlook possible confoun dingvariables and spurious relationships. The researchermight, for instance, believe that data show a causal linkbetween variables Aand B, a link that fits the researchershypothesis nicely. But the researcher might fail to lookfor variableC , a variable that is linked to both Aand Band is a cause of both . For example, environm ental scar-city might appear to be a cause of conflict, bu t, in reality,

not be a cause, if poverty is actually a cause of changesin both these variables. This concern, however, is mis-placed, because vigilant case-study researchers shoulddetect such situations. Eckstein (1975: 125-26) contendsthat such researchers can test countertheoriesthatis, theories about other likely causes of changes in thevalue of the dependent variable.23 Just as the quasi-ex-perimental researcher must anticipate variables tocontrol, the case-study researcher must anticipate po-tentially spurious causal mechanisms.

Investigat ing Reverse Causation

A distinction between causal effect and causalmechanism helps us address Gleditschs concern thatviolent con flict (the dependent variable in m ost research)may in fact be an important cause of environm ental scar-city (the independent variable). Gleditsch (1998: 393-3)claims that environment-conflict researchers have ne-glected this possibility of reverse causation and havelikewise failed to consider the possibility that environ-mental scarcity and violent conflict are related to eachother in a positive feedback loopthat is, a vicious circle.

We do not deny that conflict may exacerbate envi-ronmen tal scarcity, but this possibility was not the focusof th e Toronto Groups research. N evertheless, we wouldargue that process-tracing offers an excellent way to d is-cover reverse causality, because it unearths causalmechan isms. It allows researchers to t race causal mecha-nisms that unfold over long periods of time and therebyto investigate the impacts of past conflicts on subsequentenvironm ental conditions. An approach that focuses oncausal effects, however, cannot reveal reverse causationas easily. Although simultaneous equations can be usedto model reverse causation, and although quasi-experi-mental methods, using lagged variables or congruenceprocedures, can be used to span time, a far more intui-tive approach is to focus on causal mechanisms, becausethey will tell the researcher exactlyhowpast conflictsexacerbated environmental scarcity.

Moreover, the quasi-experimental method can pro-

duce ambiguous results when attempt ing to differentiatebetween cause and effect. Consider the following ex-ample: When a barometer falls, deteriorating weather islikely to follow. Although it precedes the change inweather, the falling barom eter clearly does not cause thischange. Thus, we can not distinguish between cause andeffect. If we understand the mechanism that causes thebarometer to fall, however, we understand that causeand effect can only be differentiated once weather con-ditions prior to the barometers fall are controlled (Miller,1987: 34).

Constructing Testable ModelsWhile Gleditsch contends that much of the envi-ronment-conflict literature to date is overly simplistic,he asserts that the Toronto Group is guilty of just theopposite mistakethat is, of developing overly com-plex models that are not testable (1998: 391-92). Webelieve that Gleditsch contradicts himself here by de-manding a strict adherence to conventional researchdesign while simultaneously agitating for an incremen-ta l and modular approach to theory bui lding.Conventional research design forbids the omission of variables that are correlated with the key independentvariable. Such an omission creates what Gary King,Robert Keohane, and Sidney Verba (1994: 168-176)term anomitted variable bias. Many of the variables con-sidered by the Toronto Group are correlated with thekey independent variable of environmental scarcity. If Gleditsch is suggesting that we drop these variables outof the equation in the name of testable models, he isalso suggesting that we contravene a fundamental canonof conventional research design.

Since the Toronto Group did not adopt such a re-


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search design, however, this internal contradiction doesnot directly concern us. N everth eless, G leditschs agita-tion for less complexity is disturbing. If environmentalscarcity were either a necessary or a sufficient cause of conflict, it would be possible to reduce our m odels com-plexity. O f course, environmental scarcity is neith er anecessary nor sufficient cause (there are few, if any, such

causes of conflict). If, th erefore, researchers are to make

a nom othetic claim about the relationship between en-vironmental scarcity and con flict, environm ental scarcitymust be part of what philosopher J. L. Mackie (1965)terms an IN US condition: it mu st be aninsufficient bu tnecessarycompon ent of a cond ition th at is itself anun-necessarybut sufficient cause of conflict.

Discovering IN US condition s is the goal of the case-study researcher. For environm ental-conflict researchers,this entails unearthing the myriad and variegated waysin which environmental scarcity interacts with othersocial, economic, and political factors to engender con-flict. We do not mean to suggest that a process-tracing

approach eclipses the important goal of parsimony.Rather, by focusing on relevant causal mechan isms, pro-cess-tracing helps the environment-conflict researcherdetermine the bound aries of the INU S condition . With-out a clear picture of these boundaries, simply droppingvariables in the name of parsimony becomes a haphaz-ard affair. O nce th ese boundaries have been defined,however, estimating causal effects becomes a more p re-cise procedure.

D ealing with Complex SystemsAccording to Gleditsch, t he Toronto Group claims

that ecological-political systems are more complex thanstrictly social or ph ysical systems. H e goes on t o arguethat this claim is unwarranted because any social sys-tem is as complex as the theory developed to study it(1998: 392). In other words, the complexity is in themind of the beholder, rather than in the phenomenonitself. Actually, the Toronto Group does not argue thatecological-political systems are m ore com plex. They ar-gue simply that these systems are, intrinsically,exceedingly complex. No doubt many social, biologi-

cal, and physical systems are just as complex or evenmore complex (althou gh some un questionably are not)

The problem of complexity exists in the real world.It cannot be wished away by assuming that it residesonly in the mind of the researcher. Gleditschs extraor-dinarily strong constructivist position on this issue isquestionable both empirically and philosophically

(Rescher, 1998). Researchers in a variety of fields in-

creasingly acknowledge the reality of comp lexity and aredeveloping powerful theories to understand complexsystems. These theories raise serious questions aboutconventional (often mechanistic) explanations of sociaphenomena and about the conventional methodologiesused to study these phenomena (Cowan, Pines, andMeltzer, 1994). Rather than denying complexitys existence, Gleditsch and other social scientists shouldexplicitly acknowledge the problems it creates for theirresearch and try to develop methodssuch as those fo-cusing on causal mechanismsfor dealing with it.

Weighting Causal VariablesGleditsch implies that process-tracing within singlecase-studies does not allow researchers to gauge the relative weights of causal variables (1998: 384-386). H e alsosuggests that th e quan titative analysis by Wenche H augeand Tanja Ellingsen (1998) is one of the few attempts totest systematically the relationship between environmen-tal scarcity and conflict. Th ese researchers, he not es, didfind a statistically significant relationship b etween envi-ronmental degradation and violent conflict, but theyconcluded that economic and political variables weremore important than environmental variables. Thus,Gleditsch implicitly accepts the notion that indepen-dent variables can be assigned weights that in dicate theirelative causal power. Gleditsch, of course, is hard ly alonehere. Causal weighting is widely considered to be theultim ate goal of statistical analyses, and the lack of ability to weight variables using single case studies isconsidered this methods foremost drawback.

The practice of causal weighting, however, has itsproblems. Elliott Sober (1988) contends that the stan-dard statistical technique of analysis of variance

[T ]he Toronto Group and EN CO P, among others, is not onlytheoretically and conceptually intact, but also rests on soundmethodological pillars.



Commentary

(ANO VA) does not actually yield causal weight s. Rather,it identifies thedifferencethat various causes can makein an observed effect. Ascertaining the difference, Sobermaintains, is distinct from ascertaining a causal weight.Similarly, Richard Lewont in (1976) argues that , althoughcausal weighting may be appropriate when the relation-ships amon g variables are additive, it is misguided whenthe relationships are interactive. Lewont in contends thatanalysis of variance produces uninterpretable resultswhen dealing with interactive variables.

If environmental scarcity is one component of anINUS condition, as argued above, then environment-conflict researchers are not dealing with additive relationsamong causal variables. Rather, these relationships areinteractive. Environmental scarcity, for example, inter-acts with a societys ability to supply social and technicalingenuity. If the society can supply abundant ingenuityin response to its environmental problems, then severe

social disrupt ions will probably be avoided; if it cann ot,then negative outcomes, including conflict, are muchmore likely.

Interactivity is hardly limited to the relationshipsamong variables in ecological-political systems. Mostsocial systems exhibit in teractivity am ong variables. T hatso many researchers treat the relationships among vari-ables in social systems as additive does not reflect thereality of these systems. Rather, it reflects misguided at-tempts by researchers to avoid dealing with the realityof thecomplexityof these systems.

III. SUGGESTIONS FO R FUTURE RESEARCH

In Gleditschs final section, entitled The WayAhead, he asserts that critique will serve to advancethe field only if it stimulates more satisfactory research(Gleditsch, 1998 : 395). Although we do n ot agree thatall work on environment and conflict has been unsatis-factory, we do agree that debates in the field, such as theone we are engaged in here, can provide the spark fornew research agendas. In this spirit, we draw on the above

remarks to m ake some suggestions for futu re work. Th esesuggestions fall in five categories: filling data gaps,operation alizing key variables, specifying con textual fac-tors, dealing with complexity, and encouragingmeth odological pluralism.

Filli ng D ata GapsWe agree with Gleditsch that serious data gaps im-

pede research on the links between environment andconflict. There is a particular lack of good data on the

extent and degree of soil, water, and forest degradationin developing countries; data on resource distributionand resource-use practices are also poor. The field th ere-fore needs a more systematic and rigorous approach todata collection. Because this research crosses so manydisciplinary boundaries, systematic data collection m ustinvolve intimate collaboration with experts in a widerange of disciplines, including soil science, hydrology,forest ecology, and the political economy of commu-nity resource use.

In ou r efforts to im prove the found ation of data onwhich we build our environm ent-con flict research, how-ever, we must recognize that not all good data arequantitative: process-tracing of single cases, in fact, gen-erates thick descriptions of environment-conflictlinkagesdescriptions rich withqualitativedata. Morelocal case studies are needed, which bu ild upon researchdone to date, and test and refine existing hypotheses at

the local level.Operationalizing Key Variables

If environment-con flict researchers want to estimatecausal effect, it is essential that they include in their analy-ses key variables identified by environment-conflictresearch. In order to includ e these variables, efforts mustturn towards their operationalization.

The Toronto Group has identified a n um ber of vari-ables that play a pivotal role in the link betweenenvironment and conflict. For instance, as noted above,the quantity of ingenuity a society supplies in response

to environmental scarcity can play a key role in deter-mining its ability to adapt to that scarcity. The supplyof ingenuity, then , is an independent variable that shouldbe included in any statistical analysis attempting tomeasure the causal effect of environmental scarcity onconflict (Homer-Dixon, 1999: 107-114).

But, operationalizing this variable is not a straight-forward task. Researchers need an adequate measure of ingenuity. Th e Toronto Group has identified other m ea-sures that should be included in any complete statisticalanalysisand that therefore require operational-izationincluding state capacity and socialsegmentation, as well as the aforementioned processesof resource capture and ecological marginalization(which can potentially be represented as single vari-ables).24

Specifying Contextual FactorsEmpirical research has now identified some causal

mechanisms linking environmental scarcity and violence.However, much more work remains to be done to de-termine precisely the intervening and interacting


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variablesthe contextual factorsaffecting t he strengthof these processes. Under what circumstances, exactly,do these processes un fold? In t he following, we refer tosome of the specific findings of the Toronto Group, andsuggest some contextual factors worthy of further in-vestigation.

By setting in motion processes of resource captureand ecological marginalization, environm ental scar-city often increases the wealth gap between thoseelites that take advantage of the opportunities scar-city offers and those marginal groups that suffer thebrunt of scarcity. H ow does the degree of state au-ton omy affect th ese two processes? To what extentwould better-defined and enforced property rightsreduce the predatory behavior of elites?

The m ultiple effects of environmental scarcity in-

crease demands on the state, stimulate intra-elitebehavior, and depress state t ax revenues. Such pres-sures can weaken the administrative capacity andlegitimacy of the state. H ow does institu tional de-sign affect state capacity in the presence of thesepressures? H ow do international econom ic forcesboth aggravate and mitigate these pressures?

Narrow distributional coalitions (e.g., coalitions of rent-seekers that work to redistribute the econom yswealth in their favor) often block institutional re-form including reform of markets, property rights,

judicial system s, and the stat es resou rce-manage-ment regimesessential to reducing environmentalscarcity or alleviating its harsh effects. To what ex-tent does scarcity provoke such behavior? Can arobust civil society counteract the obstructionistbehavior of these narrow distributional coalitions?

D ealing wit h ComplexityAt the m ethodological level, we need to explore how

causation works at the interface between the physical/ ecological and social worlds. Environment-conflict re-search brings us face to face with some of the mostintractable issues in philosophy of science, specificallywhether causal generalizations describing the social worldhave the same status as those describing the naturalworld. Because systems in both these domains are fun-damentally complexcharacterized by huge numbersof components, causal interactions, feedback loops, andnon linearityenvironment-conflict researchers can gaininsights from comp lexity theory. We urge greater recep-tivity to the concepts and findings of this rapidlydeveloping field.

Encouraging Methodological Plurali smIn order to deal with the research challenges de-

scribed above, we encourage our colleagues to accept adegree of methodological pluralism. The various meth-ods available to us make up a diverse set of arrows in thequiver of the social scientist, and we should choose thearrow most likely to hit our t arget. Statistical and quasi-experimental methodologies are needed to identifycorrelations and causal effects; process-tracing of singlecases is needed to specify causal mechanisms. These twogeneral approaches should not be used in isolation fromeach other; rather, we shou ld try to exploit the synergiesthat are possible when they are used in parallel by col-laborating researchers. For instance, statistical analysiscan identify outliers and anomalous cases that deservefocused attention using process-tracing; in turn, pro-cess-tracing can identify key interacting variables and

scope conditions that should be incorporated into sta-tistical tests of the environment-conflict hypothesis.Methodological pluralism, however, is not a license

for shoddiness. Researchers shou ld be held to high standards of evidence. Th is paper has demon strated th at theenvironm ent-conflict research of the Toronto Group andEN CO P, amon g others, is not on ly theoretically andconceptually intact, but also rests on sound method-ological pillars. We hope that futu re researchers will usethis body of evidence to deepen our understandings ofthe linkages between environmental scarcity and vio-lent conflict.

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Yee, Albert. The Effects of Ideas on Policies. In terna-tional O rganization50:2 (Winter 1996): 69-108.

1 The three main sources of environmental scarcity includereduced supply, increased demand, and skewed distribution.See Homer-Dixon (1999: 47-72).

2 An anonymous reviewer of this article raised this objec-tion, as well as David Dessler (1999: 100-101).

3 The literature supporting this claim is so vast it cannot besumm arized. An excellent survey can be found in , World Bank(1992). See also Midlarsky (1999) who provides compellingempirical evidence on the intimate connections between scar-city (including resource scarcity), inequality, and social conflict.Dasgupta (1993) provides an economic analysis of the effectof resource scarcity on commu nit ies in the developing world.Good and relatively current surveys of the state of the envi-ronm ent in Ch ina and India, which together constitute aboutforty percent of the worlds population, are Smil (1993) andRepetto (1994).

4 Recent data from the Food and Agriculture Organiza-

t ion (FAO , 1999a) shows that t he percentage of undernou rished people in all three regions has either remainedsteady (sub-Saharan Africa) or fallen (South Asia and LatinAmerica). H owever, the absolute num ber of undernourishedpeople over the past thirty years has either grown (sub-Sa-haran Africa and South Asia), or remained relatively stableoverall (Latin America). See also FAO, 1999b.

5 D an D eudney (1999), has recently coined the phraseso-cial-social theoryfor theories that presume social events haveonly social causes; he usesnature-social theoryfor theories in

which natu ral variables play a significant causal role.6 Gleditsch writes th at words such as democracy or au-

tocracy do not occur in the model. In view of the extensivetheoretical literature relating the degree of democracy to civilviolence . . . a d emocracy variable should have been in cludedexplicitly.

7 For an excellent treatment of the variegated nature of de-mocracy, see Collier and Levitsky (1997).

8 The differentiation of the democracy variable, in theState Failure Task Forces Phase II report, represents an at-tempt to move in this direction. See Esty, et al (1999: 52-53).

9 Much of the literature, Gleditsch writes, deals withconflicts of interest involving potentialviolence rather thanwith actualviolence. . . . The argument is entirely in terms of fu tu rewars, which may happen . (Italics in original.)

10 Several of the Toronto Groups historical case studies arereproduced in Homer-Dixon and Blitt (1998).

11 EN CO P similarly relied u pon a large num ber of histori-cal case studies during the course of the project research. Th esecase studies are published, along with their theoretical find-ings in a three volume work, Bchler, et al (1996). This volumecontains: M. Abdul H afiz and N ahid Islam, EnvironmentalDegradation and Intra/Interstate Conflicts in Bangladesh;Moh amed Suliman, Civil War in Sudan: the Im pact of Eco-logical Degradation; Moh amed Suliman, War in D arfur orthe Desert versus the Oasis Syndrome; Peter B. Okoh, En-

N O T E S


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vironmental Degradation, Conflicts, and Peaceful Resolutionin Nigeria and between Nigeria and Neighboring States;Stephan Klotzli, The Water and Soil Crisis in Central Asia:A Source for Fut ure C onflicts?; Stephen Libiszewski, WaterDisputes in the Jordan Basin Region and Their Role in theResolution of the Arab-Israeli Conflict; Gunther Bchler,Rwanda: T he Root s of Tragedy, Battle for Elimin ation on anEthn o-Political and Ecological Basis.

12 See, for example, Eckstein (1975); Campbell (1975);George (1979); George and McKeown (1985); Dessler(1991); Yee (1996); Bennett (199 7); and McKeown (1999).

13 T his point is made in McKeown (1999: 172-174). Non -experimental methods have also been widely used in thenatural sciences. See McKeown (1999: 171), and Eckstein(1975: 114-115).

14 H um e was, in fact, highly skeptical of our ability to showcausation. His analysis of causation was meant to ascertain

the bare epistemic facts that undergird our intuition of cau-sality.15 See Grad y (1996: 3). A similar distinction between causal

effect and causal mechanism has implications for other areasin the natural sciences as well. For instance, although scien-tists have known for n early a centu ry that aspirin relieves pain,it is only within the last few years that they have discoveredthe causal mechanisms behind this pain relief. See Garavito(1999: 108).

16 Although qualitative quasi-experimental methods, suchas the comparative case study, can also detect causal mecha-nisms, the single-case meth od is often a more efficient m eansof discovering these processes. Moreover, because control isextremely difficult to achieve in th e comparative meth od, it isquestionable if causal mechanisms can be more accuratelydetected than with t he single-case meth od.

17 Kaplan also argues that d escription s, which are often dif-ferent iated from explanat ion, m ay themselves be explanatory,because the how may provide a why and not just a what.Not ed philosopher of science, Rom H arr (1985: 40), m akesa similar point when he asserts, In practice we never restcontent with laws for which there is no explanation. O nenotable criticism of this approach is made by Kincaid (1994:

117), who argues that causal mechanisms can always be dis-covered at deeper levels (e.g. at psychological or evenneurophysiological levels). King, Keohan e, and Verba m ake asimilar point (1994: 86). We believe this criticism ultimatelyfails, however, because a researcher mu st always cond uct theirresearch at a chosen level of analysis, and the causal mecha-nisms they seek should correspond to the level of analysis of their research. M oreover, if deeper causal mechanisms are dis-covered, and if they support the theory, then the theory willonly be more robust.

18 Research is sometim es sparked b y a prelimin ary correla-tion analysis that offers a prom ising avenue for fur ther research(e.g. the Democratic Peace). Nevertheless, we maintain that afull-blown statistical analysis of these preliminary findingswould benefit greatly from case-study research into causalmechanism. The research process then, should be viewed asan iterativeone, with quasi-experimental and case-stud y meth-ods complementing one anot her.

19 Although the logic for separating the testing and build-ing of theories in quantitative methodologies is sound,Campbell (1975:178-193) shows that this partition is notnecessary in case-stud y research. C ampb ell convincingly demonstrates that the problem of ex post factohypothesizing isovercome in the pattern matching methodologyfrom whichprocess-tracing was conceived because this procedure op ensthe possibility that an hypot hesis initially generated b y a particular case could subsequently fail to be supported by thesame case. Also, see Collier (19 93: 1 15).

20 Although the above quote from Homer-Dixons In tern a-tional Securityarticle does not refer explicitly to causalmechanism, the underlying approach taken throughout thearticle consists of an explicit attempt to discover these pro-cesses. It is therefore reasonable to assum e that the nom etheticclaim made is this article refers to causal mechanisms.

21 The comm on m istake amon g researchers is to om it a vari-able that should be controlled in a statistical analysis. Thiscan result in what statisticians refer to as a Type I error, wherethe null hypothesis is true but researchers decide it is false.However, it can be equally dangerous to include a variable

that should not be controlled. This can result in a Type IIerror, where th e nu ll hypoth esis is false bu t researchers decideit is true. Cartwright (1979: 429-32) points out that an ir-relevant control variable can always be found that annuls orreduces a true relationship. A Type II error can also be com-mitted by failing to include a suppressor variable; that is, avariable that, once controlled for, unmasks a true relation-ship. To avoid both Type I an d Type II errors, we suggest thatresearchers use process-tracing to determine the appropriatecont rol variables.

22 A parable recounted by Diana Baurmind (1983:1297)illustrates why research into causal mechanisms can be in-valuable in discovering control variables. The number ofnever-married persons in certain British villages is highly in-versely correlated with the number of field mice in thesurrounding meadows. Marital status of humans was consid-ered an established cause of field mice by the village eldersuntil the mechanism of transmission were finally surmisedNever-married persons bring with them a disproportionatenu mb er of cats relative to the rest of the village populace andcats consum e field mice. With the generative mechanisms understood, village elders could concentrate their attention on



Commentary

increasing th e population of cats rather than t he proport ionof never-married persons. Glymour et al. (1987:19-2 1) op-pose Baumrinds generative account of causality. They arguethat in fact never-married personsdocause variation in fieldmice, even if the causation is indirect, and nothing in thestory prevents the use of covariance analysis on uncontrolledsamples to discover that the intervening variables is the den-sity of cats. But t his belies the process that social scientists useto discover control variables. Without an investigation of thecausal mechanisms, it is doubt ful that the d ensity of cats wouldhave been included in a statistical analysis.

23 Although it is not possible for case-study researchers toconsider all possible spurious relationships, neither is it pos-sible to include all possible confoun ding variables in a statisticalmod el. D avid D essler (1999: 101) adopt s this approach wh enhe suggests th at environment-con flict researchers Test causalclaims not against thenull hypothesisbut against rival sub-stantive account s of political violence in t he cases analyzed.

24 The State Failure Task Forces Phase II report makes sig-nificant strides in this direction. Unfortunately, datalimitations seriously impeded their ability to adequatelyoperationalize some key variables. See Esty, et al (1999).

P E C S N E W S

A TRI-ANNUAL NEWSLETTER ON ISSUES OF POPULATION, ENVIRONMENTAL CHANGE, AND SECURITY

PUBLISHED BY THE ENVIRONMENTAL CHANGE AND SECURITY PROJECT.

FEATURES O F EACH ISSUE:

M eeting reports from recent EC SP m eetingsPast synopses have covered meetings that explored thedemographic, environm ental, and food security conditions inWest Africa; the connection between population,consumption, and wood resources; and migration andenvironmental issues.

Book reviewA solicited review of a recently released publication looking at

popu lation, environm ent, and/or security issues. Lessons from the Field

This section is dedicated to sharing field reports from theUniversity of Michigan Population Fellows Programs.

Project NewsT his final section includes information on new EC SPpublications, website features, and staff activities.

Early feedback on the first issue of thePECS News:

You have really put together a first-rate piece. The layout is crisp, clean, highly readableYou have a fineassortment of articles, all at just t he right length for all-in-one-sitting readability. I loved the book review yousolicitedit was refreshing to read a true critique, with both positive and constructive comments I alsoespecially liked the report highlights and project news sectionsthey really give the reader a sense of thebreadth of your work at a glance.

T he next i ssue of PECS Newswill be published in October 2000. If you are interested in receiving a copy, pcontact the Project at [email protected] or by telephone at 202 -69 1-4 13 0. A ll issues of the newavailable on-line at h ttp://ecsp.si.edu/PEC S-N ews.


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Commentary

Environment and Security in an International Context:Critiquing a Pilot Study from N ATO s Com mittee on the

Challenges of Modern Society

by Richard A . M atthew

In Pakistans North-West Frontier Province, the combination of severe environmental stress and diffuse, vioconflict along the Afghanistan bord er might seem to provide an excellent examp le of the relationships examin the NATO Committee on the Challenges of Modern Societys (CCMS) new report onEnvironment andSecurity in an International Context .1 At first blush, one might conclude that environmental stress in this region escalating the conflict. H owever, on closer examination it seems that the effect of environm ental stress is miSometimes it acts to reinforce or trigger conflict, while other times it motivates people to reduce tensions cooperate to solve problems. It has proven very difficult to model the varying effects of environmental stress iaccurate way. The co-chairs of this CCMS pilot study have undertaken the arduous task of developing a genmodel of environmental stress and conflict applicable to the entire world. In my experience, modeling a smregion of a country abounding with many factors pulling in different directions is so complex that it is impossto be satisfied with the results.

Although the problem is an exceedingly complex one, the new CCMS report on environment and securitvery lucid an d well organized. It asks several explicit questions: What is environm ental security? H ow can we mit? What sort of information would be useful to policymakers? And what sort of responses are available?

Much of the value of the NATO/CCMS and Science Programme work on environmental issues is in process of bringing people together to focus on certain challenges, view them from new perspectives, and, perhcome to a shared understanding. These benefits may add value to the task force experience beyond what is wrin the report, but I shall consider only the text of the report, recognizing that it is a small part of a valuable important initiative.

In many ways, it is a bold report. It is bold not only in its recommendations but also in that it addressesquestion of complexity very directly, unlike many other policy documents. This is a source of strength, but it introduces some theoretical problems, which are the focus of my comments.

The report begins by noting that N ATO has a long-standing interest in non -traditional security issues, and environmental stresses are emerging as one of these issues. As anybody who studies environmental history knownumber of scholars believe that environmental stress has been the driving force behind many events in huhistory.2 T he report is not int roducing new issues. What is new is that a set of institutions that t raditionally havelooked at these issues are now starting to examine them.

Among the questions that have divided scholars and policymakers recently are whether security institut

Richard A. M atthew is Assistan t Professor of In ternation al Relat ion s an d En vironm ental Policy aCalifornia, Irvine.



Commentary

ought to be studying this set of issues, whether theseissues are best addressed by security institutions, andwhether these institutions bring a certain value to theprocess that is not found elsewhere. It is important tomention these concerns since many of the conclusionsin th is report are similar to t hose of work un dertaken bydevelopment organizations and other organizations.

One might be encouraged by the apparent conver-gence of thin king amon g institutions that ostensibly havelittle in common. Indeed, one possible value of rethink-ing security is that th is can provide a framework in whichdialogue can take place among different groups and in-stitut ions, largely free of preconcept ions and prejudices.Of course, one might also raise the concern that mili-tary institutions are moving into areas already occupiedby the development and other communities, and won-der if this will lead to better ou tcomes in the long run .

O ne of th e fears of those critical of security institu -

tions examining environmental stress is that they willstudy it from a p erspective or with a m indset that sim-ply reinforces or extends their traditional mandates.Critics worry that particular environmental issues willbe ident ified as important, while others will be neglectedbecause they do not fit well into a traditional securityframework. Environmental problems identified as se-curity issues, and hence likely to receive support fromgovernments and publics, could begin to monopolizeresources. Critics are concerned that the neglected is-sues might be those m

commentary: debating environment, population, and conflict

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