Ecoviolence? Links between population growth, environmental scarcity and violent conflict in Thomas Homer-Dixon's work (1).

• Author: Gleditsch, Nils Petter

"Qualitative degradation or quantitative depletion reduces the total size of the pie. A growing number of people sharing the pie implies that each share of the pie shrinks. And finally, if the pie is distributed in pieces of unequal sizes, some may be too small for people to survive on."

Thomas Homer-Dixon has published extensively on population, environment and conflict. His theoretical framework first appeared in several seminal articles in the early to mid-1990s, (2) and research by Homer-Dixon and his colleagues on the relationship between population, environment and violent conflict has been influential in the field of political science. (3) In view of the widespread nature of human conflict (4) and the prevailing pessimism about population growth and environmental destruction, this linkage is clearly both important and policy-relevant. In addition to outlining what he believes to be the main causal mechanisms, Homer-Dixon has also examined a number of cases in detail.

Homer-Dixon's work is far removed from the simplifications of some of the popular literature on the theme of population, environment and conflict. There is little if any of the sensationalism of Robert D. Kaplan (5) or the doomsday predictions of Paul R. Ehrlich and Anne H. Ehrlich. (6) Homer-Dixon never asserts that population pressure and environmental degradation are the sole source of violent conflict. On the contrary, he emphasizes again and again the close interrelationship between demographic/environmental, social and political factors in the generation of violent conflict.

In the following, the basic theoretical scheme of Thomas Homer-Dixon's work on population, environment and violent conflict is presented, and then some of the main criticisms of his work are explored and summarized in five points. These criticisms relate both to his theoretical model and to his empirical studies. Lastly, a brief introduction to some of the recent comparative empirical studies aimed at testing Homer-Dixon's hypotheses more broadly is given.

THE LINKS BETWEEN POPULATION, ENVIRONMENT AND CONFLICT

Like other neo-Malthusian scholars, Homer-Dixon focuses on population variables. (7) He views population pressure as closely linked to the potential scarcity of renewable resources. While he argues that resource scarcities can cause violent intrastate conflict under unfavorable conditions, he believes that such scarcities are less likely to cause interstate conflict. (8)

Homer-Dixon and Jessica Blitt distinguish among three main causes of resource scarcity. (9) Supply-induced scarcity results from degradation or depletion of natural resources. Non-sustainable use may not allow a resource to regenerate. (10) In some cases this process causes a resource to become irreversibly and permanently degraded even though the human activities that led to degradation are halted. Demand-induced scarcity is primarily caused by population growth. If a resource base is constant, the availability of resources per person diminishes as the number of persons sharing it increases. Such scarcity can also arise from an increase in demand per capita. A third form, structural scarcity, applies only to certain groups who, relative to other groups, are excluded from equal access to particular resources. Such unequal social distribution of a resource does not presuppose actual scarcity if the resource were to be distributed evenly. Figure 1, below, illustrates Homer-Dixon's view of the links among these forms of scarcity and armed conflict.

Figure 1. Sources and Consequences of Environmental Scarcity (11)

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One of Homer-Dixon's strengths and one of the reasons why he has attracted so much attention is that he presents his notion of environmental scarcity in a very simple and intuitively appealing way. A prime example is his pie metaphor to describe the three forms of resource scarcity. Qualitative degradation or quantitative depletion reduces the total size of the pie. A growing number of people sharing the pie implies that each share of the pie shrinks. And finally, if the pie is distributed in pieces of unequal sizes, some may be too small for people to survive on.

WHAT RESOURCES?

What natural resources are potential bones of contention? Most armed conflicts and wars are over objectives that can broadly be defined as resources. (12) Neo-Malthusians are primarily concerned with resources that are linked to food production. Homer-Dixon and Blitt argue that large populations in many developing countries are highly dependent on four key resources that are especially crucial to food production: fresh water, cropland, forests and fisheries. (13) The availability of these resources determines people's well-being, and scarcity of such resources can lead to violent conflict under certain conditions.

FROM SCARCITY TO CONFLICT

Homer-Dixon predicts that greater resource scarcity tends to have social effects that increase the likelihood of internal violent conflict (see Figure 1, above). Resource scarcities can lead to constrained agricultural and economic productivity, causing widespread poverty. Migration can occur either because the environmental quality of a habitat has become unlivable (push factors) or, more commonly, because the migrants' economic outcome is likely to be better in areas with greater resource availability (pull factors). Both constrained productivity and migration are likely to strengthen the segmentation around already existing religious, class, ethnic or linguistic cleavages in a society. Increased competition and tensions reduces the interaction between such segments and makes non-violent articulations of interest less likely.

Acknowledging that objective deprivation--the mere fact that people are poor--seldom produces strong grievances, Homer-Dixon relies on the theory of relative deprivation. (14) Individuals and groups can experience relative deprivation when they perceive a gap between the situation they believe they deserve and the situation that they have actually achieved. But the deprivation hypothesis significantly overpredicts the likelihood that violent conflicts may occur from grievance; it proves insufficient in explaining the incidence of such events. For grievances to erupt into violent conflict, Homer-Dixon and Blitt therefore assume the presence of two other factors. (15) First, the aggrieved individuals must participate in some sort of collective capable of violent action against the authorities, such as ethnicity, religion and class. People must also feel the relevance of their group identity to their grievances--that they are aggrieved as a group. Second, the political structure must fail to give these groups the opportunity to express their grievances peacefully at the same time as it offers them openings for violent action.

THE ROLE OF INGENUITY

Homer-Dixon acknowledges that the human ability to generate ideas, what he terms ingenuity, is a crucial factor that can help people overcome resource scarcities. (16) But he sees it as a huge obstacle that many societies, especially in poor countries, are in limited supply of ingenuity. While most neo-Malthusians focus on the absolute physical limits to growth in a society, Homer-Dixon is more concerned about those societies that are "locked into a race between a rising requirement for ingenuity and their capacity to supply it." (17) As the supply of ingenuity shrinks relative to resource scarcity, societies will eventually experience a "critical ingenuity gap." This raises social dissatisfaction, increasing the risk of violent conflict.

Three factors especially limit the supply of ingenuity in poor countries. First, market mechanisms meant to increase the supply of ingenuity as resources decline often fail to work properly. The second factor is social friction. This phenomenon arises with the existence of "narrow distributional coalitions" that are able to attract a large share of the resources for the use of their members only. (18) Finally, shortages of financial and human capital reduce the supply of ingenuity in many poor countries.

Homer-Dixon admits that the main weakness of the ingenuity approach is the current inability among researchers to measure ingenuity quantitatively and thereby predict where and when critical ingenuity gaps will appear. (19) This also implies that it is impossible to verify empirically post facto whether it is the lack of ingenuity that causes some countries to experience resource scarcity.

CRITIQUE OF THE HOMER-DIXON MODEL

Along with the volume of attention that Homer-Dixon has drawn, he has also received a fair amount of criticism. (20) We will discuss five main challenges to Homer-Dixon's work.

Humanity Can Adapt to Scarcity

Members of a broad research tradition of technological optimists, generally referred to as cornucopians, have criticized Homer-Dixon and other neo-Malthusian theorists for being too pessimistic about the relationship between population and natural resources. To cornucopians, scarcity exists by definition when a resource is not in infinite and unconditional supply, but they refuse to see resources as pies of a fixed size. They give primacy to the human ability to overcome resource scarcity through technology and the application of knowledge. The level of technology influences the size of the...