Natural Resources, Climate Change, and Conflict
Summary and Keywords
What is the relationship between resource scarcity and abundance, on the one hand, and intrastate conflict, on the other? Under what conditions do natural resources cause conflict? Which types of resources can better predict the onset, intensity, and duration of intrastate conflict? These questions and other related questions are needed to discuss how renewable as well as non-renewable resources influence the onset, intensity, and duration of intrastate conflict. In particular, there are two strands of the literature: the first strand deals with renewable resources, such as water, cropland, forests, fish stocks, etc., and examines how the scarcity of such resources leads to resource completion and subsequently to a greater risk of conflict. In this context, it also discusses the more recent literature on climate change and conflict. The second strand deals with non-renewable resources that tend to have a high value-to-weight ratio, such as fossil fuels and minerals, and evaluates how abundance of such resources affects potential “greed” and “grievance” motives of rebels to take up arms as well as a state’s capacity to put down a rebellion, both of which can lead to civil conflicts.
Overall, with the exception of the very recent empirical work on climate change as a “threat multiplier,” the bulk of the empirical evidence provides non-robust and often even contradictory results and thus does not allow for a clear-cut conclusion: while some studies support the link between resource scarcity/abundance and armed conflict, others find no or only weak links. The inconclusiveness of the results might be due to various factors, such as the inability/failure of the extant literature to adequately address the mechanisms via which resource scarcity and abundance could lead to conflict as well as which types of natural resources, including climatic changes, matter most. Moreover, empirical studies differ with regard to the type of conflict under study, ranging from violence against the government (civil wars [1,000 deaths], civil conflict [25 deaths], and low-intensity conflict [protests and riots]) to intercommunal violence (conflict that occurs between competing groups within a state), the operationalization and/or measurement of the types of resource scarcity and abundance, and the appropriate level of analysis (individual, household, subnational, national).
What is the relationship between resource scarcity and abundance, on the one hand, and intrastate conflict, on the other? Under what conditions do natural resources cause conflict? Equally important, which types of resources can better predict the onset, intensity, and duration of intrastate conflict?1 This article takes these and related questions as a motivation and discusses how scarcity of renewable resources (cropland, water, forest, fish stocks, etc.)—including climate change–induced scarcity of such resources—as well as the abundance of (mainly) non-renewable resources that tend to have a high value-to-weight ratio (fossil fuels and minerals, but also renewable resources such as timber) influence the onset, intensity, and duration of civil conflicts. As will be elaborated more thoroughly, there is a large body of literature that studies the resource–conflict nexus. The methods applied vary from qualitative analyses (comparative and individual case studies) to quantitative ones (econometric modeling and statistical regressions, cross-country and time-series analyses). A systematic review of this work serves to discuss strengths and potential weaknesses and ultimately to outline different avenues for further research.
This article begins with an overview of studies on resource scarcity and conflict. This literature starts from the premise that resource scarcity leads to resource completion and subsequently to a greater risk of violence. While early empirical studies, mainly qualitative ones, report a positive relationship between resource scarcity and conflict, large-N studies have failed to establish a connection. Hence the relationship between resource scarcity and conflict remains highly contested. It is worth noting that in the course of the recent climate change debate, the resource scarcity–conflict nexus has regained prominence, and consequently it is presented in detail below.
The article then discusses resource abundance and conflict. Advocates of this strand of research advance several arguments about how natural resource abundance could affect conflict. For example, it is argued that resource wealth increases the value of the state as target; that resource abundance reduces the opportunity costs for rebellion; that resource dependency reduces the ability of the state to prevent insurgency; and that resource wealth aggravates grievances. As in the case of resource scarcity, however, empirical evidence that natural wealth, in the form of oil, diamonds, or timber, is associated with conflict is by no means conclusive.
Finally, the article concludes by highlighting some of the theoretical and analytical problems in existing research. It also points to several avenues for further research, which mainly follow the recent trend toward relying on new disaggregated datasets, which make it possible to study more precisely the exact conditions under which scarcity or abundance of natural resources can trigger conflict.
Resource Scarcity and Conflict: Arguments
According to the neo-Malthusian2 perspective, increasing pressures on natural resources due to a growing population and/or degradation of resources result in violent conflict (Bächler, Böge, Klötzli, Libiszewski, & Spillmann, 1996; Homer–Dixon, 1994, 1999).3 In particular, Homer-Dixon (1999) identifies three paths via which scarcity of a resource might occur: demand-induced scarcity, which is a consequence of population growth and/or increased consumption per capita; supply–induced scarcity, i.e., reduced availability of renewable resources due to consumption and degradation/climatic changes that develop faster than regeneration processes; and structural scarcity caused by an unequal distribution of access to natural resources, which can be potentially exacerbated by elites’ manipulation of the access to these scarce resources (see also Kahl, 2008). According to Homer-Dixon, these three components interact and reinforce each other, resulting in two social processes, which he calls resource capture and ecological marginalization.4 Resource capture occurs when resource depletion and population growth cause unequal resource access. In such cases, powerful elites in their attempt to secure resources that they anticipate becoming scarce in the future manipulate state policies in their own favor, which in turn weakens institutional responses to grievances and consequently the risk of violence increases. Ecological marginalization occurs when unequal resource access and population growth cause resource degradation and depletion. Under such conditions, population groups faced with resource scarcity migrate into areas possibly characterized by a fragile eco-system, therefore further straining this system, and consequently the risk of violence between natives and newcomers increases (see also Barnett, 2000; Reuveny, 2007).
Cornucopians or “resource optimists,” on the other hand, argue that conflicts over resources can be prevented because resource scarcity can be overcome. While they acknowledge that resource scarcity may negatively affect human well-being, still they argue that humans can adapt to resource scarcity by using market mechanisms, such as pricing, technological innovation, international trade, and other means (Lomborg, 2001). In addition, political ecologists have also criticized the neo-Malthusian argument as being overly deterministic and for ignoring the importance of histories and context, for example, in the form of socio-economic and political processes (see, for example, Barnett, 2000; Barnett & Adger, 2007; Matthew, 2002). Consequently, these scholars propose a causal story in which scarcity of renewable resources (and climatic changes) are just one of several key factors in the overall relationship between resources and violent conflict, with political and economic factors playing an even more important role (Gleditsch, 1998; Theisen, 2008). In addition, political ecologists maintain that resource scarcity and violent conflict might be caused by other factors, such as weak political institutions, bad governance, and corruption, and that there might exist a feedback or a loop between the two. That is, while resource scarcity can trigger conflict, conflict can also lead to resource scarcity through loss of wildlife and habitat destruction, overexploitation of natural resources, and pollution (Matthew, Halle, & Switzer, 2002).
Resource Scarcity and Conflict: Empirical Evidence
The empirical literature on the resource scarcity–intrastate conflict nexus is quite broad due to the variety of resources that can be considered, and the empirical evidence is rather mixed.5 While some single or comparative case studies show that scarcity is likely to lead to violent conflict, as for instance in South Africa (Percival & Homer-Dixon, 1998), Kenya and the Philippines (Kahl, 2008), or Rwanda (Andre & Platteau, 1998), others find that resource scarcity plays only a minor role in causing conflict (Benjaminsen, 2008; Brown, 2010; Percival & Homer-Dixon, 1996). For instance, Benjaminsen (2008) reports that the drought in northern Mali was probably not a necessary condition for the Tuareg rebellion to take place. Similarly Brown (2010) did not find any evidence that there was worsening vegetation growth prior to the outbreak of the conflict in Darfur. While this type of research has produced important insights regarding the links between resource scarcity and conflict, still its near-exclusive selection of cases involving conflict fails to shed light on the absence of conflict in other countries with similar environmental conditions of resource scarcity. In addition, the social, economic, and political contexts in which scarcity and conflict take place are likely to differ considerably, rendering the generalization of case studies rather difficult. Thus the remainder of this section concentrates on the recent wave of empirical large-N research and presents the empirical results according to the type of resource (water, land, etc.) under study, including the recent literature on climate change.
The empirical evidence from large-N quantitative studies examining the effects of resource scarcity on intrastate conflict is rather inconclusive. On the one hand, there exist studies showing that land degradation, freshwater scarcity, and deforestation all significantly increase the risk of civil conflict/war (Gizelis & Wooden, 2010; Hauge & Ellingsen, 1998; Raleigh & Urdal, 2007). On the other hand, there are studies showing the exact opposite, namely that land degradation has no impact and that more, not less water per capita increases the risk of conflict (Hendrix & Glaser, 2007). In addition, soil degradation and water scarcity are shown to have a mixed impact on armed conflict (Raleigh & Urdal, 2007), whereas according to Benjaminsen, Alinon, Buhaug, and Buseth (2012), water scarcity is not an important driver of intercommunal conflicts in the Sahel. Moreover, Meier, Bond, and Bond (2007) find that increased vegetation rather than scarcity is positively associated with the incidence of organized raids, suggesting that an increase in vegetation creates strategic advantages by providing cover for these raids. In contrast, Urdal (2005) shows that land scarcity combined with high rates of population growth increases the risk of armed conflict somewhat. Similarly, scarcity of productive land is shown to increase the risk of violence when agricultural wages decline (Urdal, 2008), while high land scarcity combined with high population growth seems to decrease violence (Østby, Urdal, Tadjoeddin, Murshed, & Strand, 2011).6
Climate Change as a “Threat Multiplier”?
The recent emergence of climate change as a major item on policy agendas has revived the neo-Malthusian argument, and an extensive body of quantitative studies examines the possible links between climatic change and conflict. The first wave of empirical climate change-conflict studies focused mostly on Africa or countries/regions of it and relied almost exclusively on simple meteorological indicators, such as temperature and/or rainfall, as well as natural disasters as possible correlates of civil and intergroup conflict (e.g., Benjaminsen et al., 2012; Bergholt & Lujala, 2012; Böhmelt et al., 2014; Brückner & Ciccone, 2010; Buhaug, 2010; Burke, Miguel, Satyanath, Dykema, & Lobell, 2009; Fjelde & von Uexkull, 2012; Hsiang, Meng, & Cane, 2011; O’Loughlin et al., 2012; Theisen, Holtermann, & Buhaug, 2012). Most of this research, although it accounted for some contextual factors, such as economic development and differing political systems, provides little evidence for a strong direct link between climate change or climate variability and conflict (see Bernauer, Böhmelt, & Koubi, 2012; Buhaug, 2016; Gleditsch, 2012; Meierding, 2013; Salehyan, 2014; Scheffran, Brzoska, Kominek, Link, & Schilling, 2012; Theisen, Gleditsch, & Buhaug, 2013).7
Moreover, even research that finds significant effects does not agree on the direction of the relationship. For instance, whereas Burke et al. (2009) and Fjelde and von Uexkull (2012) report that drier years lead to significant increases in the probability of conflict in Africa, O’Loughlin et al. (2012) find that in East Africa, whereas drier periods do not affect the risk of conflict, wetter periods tend to decrease it. Theisen (2012), using a gridded analysis for Kenya, finds evidence that low rainfall seems to reduce conflict in the following year, while Hendrix and Salehyan (2012) and Raleigh and Kniveton (2012) find that wetter-8 and drier-than-normal conditions are associated with more conflict. Finally, a few scholars note that other factors (e.g., population pressure, low economic development, and ethno-political exclusion) are likely to have a stronger impact on conflict risk than climatic conditions (Böhmelt et al., 2014; Buhaug, 2010; O’Loughlin, Linke, & Witmer, 2014).
While climatic conditions per se are unlikely to cause conflict, still environmental changes could act as a “threat multiplier” (CAN, 2007) in that they have the potential to exacerbate a wide range of existing and often interacting conflict drivers such as high population growth, resource scarcity, unmanaged migration, poverty, and poor governance. Hence a second wave of research examines the climate–conflict nexus in a multiple-stage fashion in that they explicitly consider conditional effects and indirect links from climate to conflict mostly via economic conditions (Devitt & Tol, 2012; Koubi, Bernauer, Kalbhenn, & Spilker, 2012), food prices and production shocks (Bellemare, 2015; Buhaug, Benjaminsen, Sjaastad, & Theisen, 2015; Caruso, Petrarca, & Ricciuti, 2016; Smith, 2014; Weinberg & Bakker, 2015; Von Uexkull, Coicu, Fjelde, & Buhaug, 2016; Wischnath & Buhaug, 2014; see also van Weezel, 2016),9 livestock prices (Maystadt & Ecker, 2014), and to a lesser extent migration (Bhavnani & Lacina, 2015; Bohnet, Cottier, & Hug, 2014; Ghimire, Ferreira, & Dorfman, 2015; Koubi, Böhmelt, Spilker, & Schaffer, 2016). For instance, Von Uexkull et al. (2016), using a new conflict event dataset covering Asia and Africa for the period 1989–2014, report that a local drought increases the likelihood of sustained violence in regions with agriculturally dependent and politically excluded groups. Schleussner, Donges, Donner, and Schellnhuber (2016) also find evidence using global datasets that conflict onset is enhanced by climate-related disaster occurrence in ethnically fractionalized countries. Caruso et al. (2016) focus on Indonesia for the period 1993–2003 and find that an increase in the minimum temperature during the core month of the growing season (i.e., the past December) increases the number of violent incidents due to the reduction in rice production. This recent research thus provides some evidence that climatic changes could act as a “threat multiplier” in several of the world’s regions. While this work is a promising start to move the extant literature forward, it is still constrained in that it focuses on specific countries or regions and single problems, such as failed harvests or increasing food prices, which might be exacerbated by climate change, thus leading to conflict. However, even in these cases, the agricultural production shocks might not necessarily lead to conflict if they are managed well by capable governments. Hence there is room for future work to build on these very promising studies and strive for a better specification (theoretically and empirically) of the conditions under which climate change and climatic variability lead to conflict.
Except for the very recent work on climate change as a “threat multiplier,” most of the quantitative work in the field does not provide evidence for the resource scarcity–conflict thesis. Some studies even contradict the findings from many of the earlier case studies, and the generally inconclusive results point to a more complex relationship between scarcity and conflict than most resource scarcity theorists envisage. Several scholars argue that much of the empirical work addressing this relationship has been overly simplified in that it ignores the potential mediating roles of key economic and political variables, fails to address issues of endogeneity, and is unclear about the appropriate level of analysis (individual, household, subnational, national) (Bernauer et al., 2012; Buhaug, 2016; Gleditsch, 1998, 2012; Theisen, 2008). Moreover, empirical studies differ with regard to the type of conflict under study, ranging from violence against the government, such as large-scale civil war (1,000 deaths), civil conflict (25 deaths), and low-intensity types of conflict (e.g., protests and riots) to intercommunal violence (i.e., conflict that occurs between competing groups—e.g., “pastoralist violence” or “farmer–herder” violence). Furthermore, studies vary in the type of resource scarcity that they analyze, focusing on such different resources as land degradation, water scarcity, deforestation, climate change (i.e., temperature and/or precipitation changes), etc. Also the operationalization and/or measurement of the types of resource scarcity differ from study to study. And finally, the question of aggregation strongly affects empirical results: earlier studies especially tend to use both resource scarcity and conflict measures aggregated at the national level, even though scarcity does not usually affect a whole country in the same way/intensity and civil conflict/war is often a more local phenomenon.10 While more recent studies tend to address these shortcomings and thus deliver more consistent results, it seems that several important theoretical and analytical issues remain to be addressed.
Resource Abundance and Conflict: Arguments
While the link between renewable resources and conflict rests on scarcity, the link between non-renewable resources, such as fossil fuels and minerals, and conflict rests on abundance. Although natural resource can contribute to economic growth, employment, high fiscal revenues, and peace, many resource-rich countries are characterized by slow growth rates (Van der Ploeg, 2011), bad political and economic institutions (Acemoglu & Robinson, 2006), and rent-seeking (Besley & Persson, 2011; Torvik, 2002) and suffer from political violence (Collier & Hoeffler, 2004; Fearon, 2005). For these reasons natural resource wealth has been coined a curse for development rather than a blessing (Ross, 2004a, 2004b).
In the corresponding literature several explanations for the links between resource wealth11 and conflict have been advanced. Figure 1 provides a schematic overview of the different links. First, resource wealth could foster conflict by funding rebel groups since resource wealth can represent an opportunity to either finance a rebellion (feasibility mechanism) or to exploit it for personal enrichment. This argument is typically labeled the “greed” perspective (Chassang & Padró-i-Miquel, 2009; Collier & Hoeffler, 2004, 2005; Collier, Hoeffler, & Rohner, 2009; Rustad & Binningsbø, 2012). Second, resource wealth could weaken state institutions since resource wealth can diminish governments’ willingness to establish an effective apparatus for levying taxes and a capable bureaucracy to provide public goods and thus preserve peace (Fearon & Laitin, 2003; Snyder & Bhavnani, 2005; Torvik, 2002). Third, resource wealth can render the state a more attractive target for rebels since political power is associated with rents from resource extraction (Besley & Persson, 2011; Dal Bó & Powell, 2009; Fearon & Laitin, 2003 Mitchell & Thies, 2012). Fourth, resource wealth can facilitate trade shocks by making a country more dependent on global commodity markets (Dal Bó & Dal Bó, 2011; Humphreys, 2005; Ross, 2006). Fifth, resource wealth can make separatism financially attractive in resource-rich regions (Collier & Hoeffler, 2005; Sorens, 2011). And sixth, resource wealth can aggravate grievances, i.e., local citizens perceive the distribution of resource rents to be unfair, with too few benefits allocated to the resource-producing region (Humphreys, 2005; Murshed & Gates, 2005; Østby, Nordas, & Rod, 2009), and/or resources extraction leads to conflict where the local population is frustrated over negative externalities associated with the extraction process, such as pollution, land expropriation, and in-migration (Humphreys, 2005; Hunziker & Cederman, 2016; Ross, 2004a).
In contrast, some scholars have proposed a counterargument, the so-called “rentier state” argument, which suggests that governments use revenues from abundant resources to buy off peace through repression (Ross, 2012; Smith, 2004), patronage (Bjorvatn Naghavi, 2011; Fjelde, 2009; Le Billon, 2003), and large–scale distributed policies (Basedau & Lay, 2009; Le Billon, 2001). As a result, rentier states should be more stable politically and less prone to conflict. In particular, Fjelde (2009) posits that oil-rich governments can use political corruption to buy support from key segments of society, effectively outspending other entrepreneurs of violence. Similarly, Thies (2010) argues that rebels and rulers compete for primary commodities, the former to gain financially and the latter to sustain revenue flows. When rulers face opposition, they manipulate property rights to stay in power, effectively preventing conflict.
Resource Abundance and Conflict: Empirical Evidence
Similar to the empirical literature on the resource scarcity–intrastate conflict relationship, the resource abundance–interstate conflict is quite broad due to the variety of resources that can be considered. A large volume of empirical studies attempts to demonstrate that natural resources increase the risk of civil war onset, its duration, and its intensity.12 As one of the first studies on this topic, Collier and Hoeffler (2004) confirm the hypothesized link between resource endowments and the risk of civil war, reporting that rebellion was more likely to occur in countries with abundant natural resource deposits, supporting the greed argument. Subsequent studies have either supported (Ross, 2004b) or refuted this conjecture (Fearon, 2005; Hegre & Sambanis 2006; Humphreys, 2005). Fearon (2005) in particular shows that the empirical association between primary commodity exports and civil war outbreak is neither strong nor robust, and insofar as there is some association, this is due in part to the inclusion of fuel exports in the primary commodity measure, which are more robustly related to conflict onset. He further argues that high oil exports indicate a weaker state given the level of per capita income and possibly a greater “prize” for state or secessionist capture, both of which might favor civil war. In contrast, Bazzi and Blattman (2014) find little robust evidence supporting either the opportunity cost (greed) or the state-as-a-prize mechanism as a factor explaining the onset of conflict. They find that higher prices across all commodity types (i.e., agricultural goods, perennial tree crops, and extractive products) are associated with shorter and less intense conflicts rather than with new ones and conclude that this finding supports the idea that resource rents increase state capacity, which makes the end of conflict more likely.
In an effort to move beyond this indeterminacy, research has refined the highly aggregated measure of resource abundance (i.e., “primary commodity exports”) by focusing on the type of resource. Examples include oil and gas (Asal et al., 2016; Aslaksen, 2010; De Soysa & Neumayer, 2007; Lujala, 2010; Ross, 2012; Smith, 2015; Wegenast & Basedau, 2014), non-fuel minerals such as diamonds (Lujala, 2009; Lujala, Gleditsch, & Gilmore, 2005; Østby et al., 2009; Ross, 2006), forests (Buhaug & Rød, 2006; Rustad, Rød, Larsen, & Gleditsch, 2008), and agriculture (Dube & Vargas, 2013; Humphreys, 2005). In addition, research examines the impact of the natural and geographic characteristics of these resources on conflict in various forms: studies distinguish lootable (onshore) and non-lootable (offshore) resources as it is argued that lootable resources (e.g., diamonds) can be extracted and transported relatively easy by small groups and unskilled workers, while non-lootable resources (e.g., oil) require immense investment into extraction technologies (Le Billon, 2001; Lujala, 2009, 2010; Miodownik & Bhavnani, 2011; Ross, 2004b). Furthermore, studies distinguish physically diffuse from point-source resources13 and differentiate between those that are proximate and those that are distant to national capitals14 (Buhaug & Lujala, 2005; Buhaug & Rød, 2006; Buhaug et al., 2009). The typical expectation is that lootable, distant, and diffuse natural resources are usually more difficult for a government to control and thus represent a tempting booty for non-state actors, therefore leading to higher likelihood of conflict.
Taking this approach even further, fine-grained disaggregated analyses capture the local characteristics of resource variables rather than simply breaking these variables down into further categories. Research in this manner divides countries into grid cells, treating each cell separately (often in combination with nationwide predictors). Defined as a subnational event, conflict may affect certain parts of a country’s territory and not others, with the presence of resources increasing the size of the conflict zone and generating longer conflicts. Disaggregated studies consequently utilize measures of remoteness (Buhaug & Lujala, 2005; Buhaug & Rød, 2006), the location of resources in a conflict zone (Buhaug & Gates, 2002; Buhaug & Rød, 2006; Lujala, Rod, & Thieme, 2007), and the location of rebellion (Buhaug & Gates, 2002; Østby et al., 2009).
The picture emerging from these recent studies is that the relationship between resource abundance and conflict is neither clear-cut nor very robust. For example, Humphreys (2005), using information on yearly oil production, shows that a country’s oil production per capita is positively linked to its conflict risk. Similarly, Ross (2006), using exogenous indicators of oil and gas wealth, reports that oil and gas are robustly related to civil war onset before the 1970s and that rents from onshore oil and gas production are related to separatist civil war onset in particular. De Soysa and Neumayer (2007) reaffirm that oil is associated with civil conflict onset (25 casualties or less per year) but not with civil war (1,000 battle-related deaths). Lujala (2010) shows that oil-producing countries are 1.5 to 2 times more likely to experience armed civil conflict than non-producers. Østby et al. (2009) also find that oil in general is estimated to be positively associated with conflict, but the variable is insignificant in most model specifications. The location of oil and type of conflict also matter, with overlapping conflict and oil areas being associated with higher combatant deaths and longer governmental conflicts (over central government) but not with territorial (i.e., secessionist) ones (Lujala, 2010; Lujala et al., 2007). Lujala (2010) also reports that oil production increases the risk of conflict onset when located onshore, whereas offshore production has no effect on onset. In contrast, Smith (2015) reports that oil income does not have any substantial or significant impact on civil war onset. Similarly, Cotet and Tsui (2013) find no effect for oil wealth on civil war onset once country-fixed effects are accounted for. Brunnschweiler and Bulte (2009) also show that, controlling for endogeneity, oil no longer affects civil conflict onset. Recent studies pursuing the perspective that ethnicity may be a salient factor in the resource abundance–conflict nexus find strong evidence that the geographic overlap of politically excluded ethnic groups and local abundance of oil and gas increases the likelihood of conflict, particularly territorial secessionist ones (Asal, Findley, Piazza, & Walsh, 2016; Mähler & Pierskalla, 2015; Hunziker & Cederman, 2016; Sorens, 2011; Wegenast & Basedau, 2014).
Turning to the effects of diamonds on conflict, Lujala et al. (2005) explore the impact of two types of diamonds—“primary” (non-lootable) and “secondary” (lootable) diamonds)15—on two types of conflict—ethnic and non-ethnic. They find that while production of primary diamonds is related to a lower risk of conflict, secondary diamond production strongly and significantly increases the risk of conflict onset in the post–Cold War period (see also Østby et al., 2009). Humphreys (2005) finds that the volume of diamond production (measured per capita) is positively associated with the likelihood of civil war onset—both within Africa and more generally. Ross (2006) also reports that rents from secondary diamond production are related to separatist civil war onset. Furthermore, Lujala (2009) reports that lootable gemstones in conflict zones more than double the number of battle-related deaths. This finding is corroborated by Bellows and Miguel (2009), who demonstrate that chiefdoms with diamond mines in Sierra Leone during the 1991–2002 civil conflict witnessed more attacks and battles. Le Billon (2008), however, suggests that high diamond abundance and industrial exploitation seem to reduce armed conflict occurrence. Finally, while Humphreys (2005) shows that diamond wealth (i.e., abundance) tends to produce shorter wars by facilitating military victories by one side or the other, Buhaug and Lujala (2005), Lujala et al. (2005), and Lujala (2010) show that secondary diamonds are linked to longer conflicts instead.
The literature argues that forest resources can increase conflict because they offer economic benefits (opportunity) and the extraction of timber does not require advanced technology or specific know-how. Forest resources located in remote areas are more susceptible to looting or extortion, and the government’s ability to tax, exploit, or trade these resources is often minimal. Furthermore, forest resources are diffuse resources, meaning that they are widely spread and may be harvested by less capital-intensive industries with a large workforce. Finally, forests can provide cover for rebels, thus affecting the likelihood of conflict. In general, most studies do not find a significant effect of forest resources on conflict onset, but a few studies show that forest resources can play a role in conflict duration. Forest cover has also been included in a few disaggregated studies, although forest conflict was not a main focus of these studies. Buhaug and Rød (2006) analyze the onset of conflict using grid cells as the units of observation without finding any support for the forest and conflict argument. Similarly Collier, Hoeffler, and Söderbom (2004) find forest cover to be insignificant in accounting for the duration of civil war in 1960–2000. However, when analyzing the duration of conflict, Buhaug and Lujala (2005) find a negative relationship between forest resources and conflict duration. Rustad et al. (2008) study the effect of forest cover on both the onset and the duration of civil conflict. They find that at the national level there is very little support for a general and direct relationship. At a more disaggregated level, the authors examine the duration of conflict when forest resources are available in the conflict zone. Again, no general relationship is found. However, they find that a shorter distance to the coast tends to make the conflicts in forested conflict zones longer. It needs to be noticed that many of the significant results of this study are, however, driven by one or two cases, therefore calling the robustness of these findings into question (Rustad et al., 2008).
Regarding the effects of agriculture on conflict, Humphreys (2005) observes that the impact of agricultural commodities on conflict is underexamined and suggests that they would be positively correlated with a higher risk of conflict. Dube and Vargas (2013) examine how changes in the price of agricultural goods, such as coffee (which are labor-intensive), and natural resources, such as oil (which are capital-intensive), affect conflict. Using a dataset on civil war in Colombia, they find that that the sharp fall in coffee prices in the 1990s increased violence in regions growing coffee by lowering wages and the opportunity costs of joining army groups, while the sharp increase in oil prices fueled conflicts in oil regions by increasing municipal revenue through rapacity. Angrist and Kugler (2008) also examine the impact of upsurge in coca prices on violent death rates in Colombia and report increased violent death rates in growing areas after the increase in coca cultivation. Brückner and Ciccone (2010), using a data set of 39 sub-Saharan African states, find that a 20% decrease in a country’s commodity price index increases the probability of war onset by 2.8 percentage points (given an average civil war onset probability during 1980–2006 of 2.8%). Miodownik and Bhavnani (2011), on the other hand, show, using a computational model, that minority-led regimes that depend primarily on agricultural revenue are less prone to conflict than similar structured regimes that depend on lootable natural resources, such as diamonds. Finally, Bretthauer (2015) reports that high dependence on agriculture and low levels of tertiary education are important factors affecting local and regional conflicts. Overall there is thus some evidence that links income in the agricultural sector to the probability of rebellion.16
Empirical Evidence: Rentier Mechanisms
While there exists some evidence that resource abundance, in particular oil, increases the risk of conflict, several studies also find evidence that indeed some of the rentier mechanisms are present in oil states. Fjelde (2009), for example, shows that the interaction of high levels of corruption and appropriable resources (oil wealth) reduces the conflict-proneness of a country by offsetting the destabilizing effect of resource abundance. Basedau and Lay (2009) report an inverted U-shaped relationship between resource rents and the risk of conflict. This means that although an increase in resource rents increases incentives for rent-seeking and conflict by the opposition, it also provides credibility to extensive political patronage programs, which for sufficiently large resource rents lead to less violence. Similarly, Bjorvatn and Farzanegan (2015) find that resource rents in GDP can promote political stability, but only when political power is sufficiently concentrated. Ross (2012) and Wright, Frantz, and Geddes (2014) also find that oil income plays a stabilizing role in autocracies in that oil rents strengthen autocratic leaders from removal by other rebel groups. Finally, Thies (2010) shows that almost all primary commodities, including oil, strengthen states’ capacity but do not directly affect civil war onset.17
In concluding this section on the relationship of resource wealth and conflict, it is fair to say that despite notable progress, the now-voluminous body of research on the abundance–conflict relationship has not been able to disentangle the different possible mechanisms behind this relationship and has fallen short of reaching a definitive consensus. As in the case of the resource scarcity–conflict relationship, the inconclusiveness of the results might be due to various factors. First, there exist differences in the coding of civil war, with some studies focusing on civil war onset and others on its duration, severity, or recurrence. Second, the type of resource abundance whose effect is examined strongly varies, with some studies analyzing the effect of oil and others analyzing the effect of diamonds, agricultural commodities, etc. Third, the precise measure of resource abundance and dependence also differs. Some studies use a simple dummy variable indicating whether or not a country possesses natural resources (oil, diamonds, timber), whereas others rely on the value of the resource’s production and either relate it to a country’s GDP or its population or studies employing the value of primary exports as a share of GDP. Fourth and finally, several studies utilize national-level datasets, whereas more recent studies shift their focus to the subnational level, which is possible due to the recent collection of disaggregated and geo-referenced datasets.
This article surveys and summarizes the recent literature on the link between natural resources and conflict. Many studies have examined the relationship between natural resource scarcity or abundance/dependence, on the one hand, and civil conflict, on the other. While the bulk of this literature has failed to confirm a consistent positive relationship between these variables, recent studies provide evidence that under certain conditions both scarcity and abundance could lead to conflict. These recent studies, instead of analyzing the direct relationship between resource scarcity/abundance and conflict, investigate the different—mostly conditional—mechanisms that link the presence or absence of natural resources to the risk of civil conflict. For example, recent research on climate change and conflict provides some evidence that climate change–induced droughts can lead to violence in those regions in which the population is strongly dependent on agriculture and at the same time politically excluded (Von Uexkull et al., 2016) therefore supporting the idea that climatic changes can act as a “threat multiplier.” Similarly, research on resource abundance suggests that it is not necessarily the mere presence of these resources that it is important for conflict, but rather where exactly in a country they are located and how difficult they are to mine or harvest. Moreover, other studies focusing on the opposite question—namely on the conditions under which these resources can lead to stability instead of conflict—show that especially if power is concentrated and/or corruption is widespread, the presence of natural resources leads to a “rentier state” and thus political stability (Bjorvatn & Farzanegan, 2015; Fjelde, 2009; Thies, 2010).
These results underline the importance of further examining open questions in the literature regarding the precise mechanisms via which natural resources could lead to conflict and which types of resources, including climatic changes, matter most. For instance, why should one expect water scarcity, climate variability, or oil deposits, to lead to conflict if these resources were managed by political/economic institutions that “provided for the people” and “invested in people”? Furthermore, much of the resource-conflict literature concentrates on conflict (i.e., rebellion, guerrilla, civil conflict) interactions between states and rebel groups. However, local water scarcity, low agricultural production, or high food prices induced by changing climatic conditions should be more likely to lead to low-level conflicts (political violence) rather than full-scale armed conflict because of the corresponding collective action problem. While the focus on civil conflict could be justified to a great extent by the lack of more disaggregated data, recent advances in data collection can facilitate the investigation of a much broader range of conflict types such as protests, riots, strikes, and intercommunal conflict. The Armed Conflict Location and Event Data (ACLED) (Raleigh, Linke, Hegre, & Karlsen, 2010) provide information on communal conflicts, albeit only for Africa (1997–2013) and South Southeast Asia (2010–2015); the Social Conflict Analysis Database (SCAD) (Salehyan et al., 2012) offers information on social conflicts from 1990 to 2015 covering Africa, Mexico, Central America, and the Caribbean; and the Uppsala Conflict Data Program Geo-referenced Event Dataset (UCDP GED) (Sundberg & Melander, 2013) provides information on three types of organized violence—state-based conflict, non-state conflict, and one-sided violence—resulting in at least one direct death for Asia, Africa, and the Middle East (excluding Syria) for the period 1989–2014 and the Americas and Europe for the period 2005–2014. Consequently, further subnational studies that employ detailed disaggregated data for both resources and type of conflict may be particularly useful in improving our understanding of these open questions.
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(1.) The focus of this review is on intrastate conflict because the literature on the impact of natural resources on interstate conflict is quite limited.
(2.) Neo-Malthusian arguments, inspired by Thomas Malthus’s proposition that population increases geometrically while food production only grows arithmetically, grew in the late 1960s and 1970s and were presented in the 1972 book Limits of Growth (Meadows et al., 1972).
(5.) Resource scarcity could also trigger interstate conflict. However, extant quantitative work focuses almost exclusively on the effects of water scarcity on the probability of interstate conflict. Systematic empirical analyses suggest that transboundary waters are associated with low-level conflicts, but not with full-scale “water wars” (e.g., Brochmann & Hensel, 2009; Dinar, 2009; Gleditsch et al., 2006; Hensel et al., 2006; Katz, 2011). Moreover, several scholars report that states tend to cooperate rather than fight over their shared water resources (Dinar et al., 2007; Kalbhenn, 2011) and that institutionalized agreements (treaties) could offset the risk of conflict (Brochmann, 2012; Tir & Stinnett, 2012).
(6.) Binningsbo et al. (2007) use the ecological footprint index as a measure of resource scarcity/environmental degradation. They find that increasing a country’s ecological footprint reduces the risk of violent conflict. This result cuts against neo-Malthusian claims, suggesting that higher per capita consumption of natural resources is associated with lower probability of violent conflict.
(7.) However, Hsiang et al. (2013), based on a meta-analysis of 60 studies, report a “remarkable convergence of results” and “strong causal evidence” that climatic events are linked to social conflict at all scales and across all major regions of the world (see also Burke et al., 2015). Yet their meta-analysis has been criticized with respect to sample selection, selection of indicators, and interpretation of results (Buhaug et al., 2014).
(8.) The argument linking wetter conditions to conflict rests on the notion that wetter conditions provide strategic advantages in warfare and, due to resulting abundance, encourage wealth-seeking behavior that facilitates recruitment of people to participate in violence (Meier et al., 2007; Raleigh & Kniveton, 2012).
(10.) Recently, Selby (2014, p. 829) argues that a departure from the current positivist research program is necessary and that much of the current quantitative research is spurious and produces Northern stereotypes.
(11.) In the literature, resource abundance/wealth and resource dependence have often been treated as synonymous, even though they differ quite strongly and as a result might have different implications for conflict. Resource abundance means that there is a high production per capita of the resource(s) in question, whereas resource dependence implies that the resources constitute a high proportion of the country’s exports. Consequently, resource dependence might be especially violence-enhancing, especially at high levels, because it makes a country vulnerable to price shocks, which in return cause economic crisis, making conflict more likely (Basedau & Lay, 2009; Van der Ploeg, 2011). Whether or not high amounts of resources are conducive to peace might also depend on the institutional setting of the country (Acemoglu & Robinson, 2006).
(12.) With few exceptions (e.g., Caselli et al., 2015; Colgan, 2010; De Soysa et al., 2011; Hendrix, 2015), the literature on the impact of resource abundance for interstate conflict is still nascent.
(13.) Diffuse resources are spread over wide areas and produced by a large number of small operators (alluvial diamonds, gems, minerals, timber, coffee, rubber), whereas point resources are the exact opposite—concentrated in small areas and in the hands of a few producers (oil, gas, kimberlite diamonds, copper, iron). This implies that rebels may face fewer barriers in capturing and controlling resources dispersed across geographically remote regions of a state because they are usually not controlled by the government (Le Billon, 2001).
(14.) Proximate resources are located close to the center of power, while distant ones are located in remote areas that may be politically contested and/or near porous borders. Government control is stronger for proximate resources, making illegal trade more difficult.
(15.) “Primary” diamonds are extracted from deep-shaft mines and are generally controlled by large firms and governments and; thus they generally cannot be considered lootable. “Secondary” diamonds, on the other hand, are near the surface and are commonly mined by small teams of unskilled workers, and thus they are more lootable.