PUNDITS, JOURNALISTS and Sunday morning news show commentators sometimes say silly things about the links between resources and war. "Iraq is all about oil" or "Global warming caused the Darfur genocide." And, sometimes, NGO leaders and policymakers say similar silly things when they want the media to pay attention to a particular region or issue. It's easy to criticize these statements. But thoughtful commentators, of whom David Victor is normally one, know they contribute little by doing so. Yet, in this case, he's pulled together several oft-heard arguments about why threats from resource wars are overblown. Some of the skeptical positions have merit, but many are deeply misleading. No serious scholar of this issue says that resource stress causes violence by itself; almost none asserts that the causal links between resource stress and violence are direct; and very few argue that interstate war is the most likely outcome. Resource stresses are security dangers, though they are one among many. They will not be the only cause of conflict, but they will add to the risk of war.

If you listen to Victor, though, you might just get lulled into a false sense of security. He beats down straw-man arguments, in the end offering nothing but false reassurances about the security risks posed by resource stress. If the author had been willing to take on nuance, he wouldn't have been able to write the kind of simplistic and ideologically charged article that appeared in these pages. That's because serious scholars who have spent years studying the links between resources and mass violence-and I count myself in that group-rarely, if ever, make the kinds of arguments Victor so boldly attacks.

Rather, we argue that resource stress always interacts in complex conjunction with a host of other factors-ecological, institutional, economic and political-to cause mass violence. Also, causation is almost always indirect. People, groups and countries rarely fight over natural resources directly; instead, resource stress causes various forms of social dislocation-including widening gaps between rich and poor, increased rent-seeking by elites, weakening of states and deeper ethnic cleavages-that, in turn, make violence more likely. And, finally, this violence is almost always sub-national; it takes the form of insurgency, rebellion, gangsterism and urban criminality, not overt interstate war.

The claim that resource stress is sufficient by itself to cause violence is easily refuted. One simply has to identify cases where resource stress was present but violence didn't occur. Likewise, the claim that resource stress is a necessary cause of violence is easily refuted by finding cases of violence not preceded by resource stress. At various points in his article, Victor uses exactly these strategies to debunk the link between resources and war.

If resource stress causes violence in complex interaction with other factors, a much more nuanced refutation than what Victor offers is required. It's all about context. Careful analyses of specific cases are needed. Darfur is just one example. Here, the host of factors contributing to the violence and the tangled relationships among these factors are carefully identified, one by one. A critic who wants to refute this kind of claim needs to take on the facts of the case itself and marshal empirical evidence to challenge the claim's specifics. This exercise is hard, and it takes time.

Victor doesn't engage with this type of voluminous work. My research team and others around the world have undertaken painstaking analyses of cases as diverse as the Philippines, Pakistan, Haiti and South Africa. This research has shown that severe resource stress-including water scarcity, forest loss, land degradation and collapse of coastal fisheries-multiplies the impact of a society's existing vulnerabilities, including its ethnic cleavages and skewed distribution of land, wealth and power. Rural folk who depend directly on the local environment for their day-to-day livelihoods become poorer, while powerful elites manipulate laws to gain control of-and extract exorbitant rents from-increasingly valuable land, forests and water. As these resources dwindle in the countryside, people sometimes join local insurgencies against landowners and government officials. Other times, they migrate in large numbers to regions where resources seem more plentiful, only to fight with people who already inhabit those regions. They might also migrate to urban slums, where unemployed young men, especially, can be primed to join criminal gangs or radical political groups.

In light of these findings, Victor too quickly dismisses the security dangers of climate change. "Serious thinking about climate change", he writes, "must recognize that the ‘hard' security threats that are supposedly lurking are mostly a ruse." Yet, the recent report of Working Group II of the Intergovernmental Panel on Climate Change identifies multiple pathways through which global warming will hurt poor people in the Third World and hinder economic development there more generally. Large swaths of land in subtropical latitudes-zones inhabited by billions of people-will experience more drought, more coastal damage from storms, higher mortality from heat waves, worse outbreaks of agricultural pests and an increased burden of infectious disease. The potential impact on food output is a particular concern: In semi-arid regions where water is already scarce and cropland overused, climate change could devastate agriculture. Also, many cereal crops in tropical zones are already near their limits of heat tolerance, and even a couple degrees warming could lead to much lower yields.

By weakening rural economies, boosting unemployment and dislocating people's lives, global warming will increase the frustrations and anger of hundreds of millions of people in vulnerable poor countries. Especially in Africa, but also in some parts of Asia and Latin America, climate changes will undermine already frail governments-and make challenges from violent groups more likely-by reducing government revenues, increasing the economic clout of rent-seeking elites, overwhelming bureaucracies with problems and revealing how incapable these governments are of helping their citizens. We've learned in recent years that this kind of societal failure can have consequences around the world and that great powers can't always isolate themselves from these consequences. So climate change could readily produce "hard security threats" by any reasonable definition of the phrase.

At one point, Victor does acknowledge the reality of such complex causation: "Resource-related conflicts are multi-causal", he writes. But then he immediately draws a misleading conclusion from this fact: Because resource-related conflicts are multi-causal, he goes on, "primal ‘resource wars' can never exist." Here he sets up, once again, a straw man. No serious analyst of resource-related conflict would say any conflict is exclusively about resources.

Implicit in Victor's argument here is the notion that if a conflict has multiple causes, and if resource stress is one of these causes, then resource stress is probably not particularly important. The real cause is probably "deeper" and likely involves governmental or institutional failure. For instance, he writes:

Some analysts have pointed to conflicts over resources, including water and valuable land, as a cause in the Rwandan genocide. . . .Recently, the UN secretary-general suggested that climate change was already exacerbating the conflicts in Sudan. But none of these supposed causal chains stays linked under close scrutiny-the conflicts over resources are usually symptomatic of deeper failures in governance. . . .Climate is just one of many factors that contribute to tension.

Yet Victor provides absolutely no evidence or argument to justify either his substantive claims about Rwanda or Darfur or his sweeping assertion that failures in governance are ultimately the most important cause of these conflicts. How can he speak with such confidence? Is he an expert on these cases? What metric is he using to differentiate between the causal "weight" of different factors-resource, governmental, institutional or otherwise?

On the specifics of Rwanda, he is, in fact, decisively wrong: Several exacting and penetrating studies have now shown conclusively that cropland scarcity in Rwanda strongly affected rural grievances that were exploited by radical Hutus in the lead-up to the 1994 genocide. And regarding Darfur, the case is by no means closed one way or the other. We're still waiting for a close on-the-ground analysis of causation. But many reputable scholars have argued, on the basis of substantial evidence, that a long-term decline in rainfall in the Darfur region contributed to a breakdown-which the Khartoum government exploited, to be sure-of traditional relations between nomads and pastoralists.

Victor's unsubstantiated assertions here betray a too-common bias of social scientists: The forces of nature are ultimately subordinate to the forces of society. But the world is now too complex-and too multifactoral-for such social-science grandstanding. All this can't hide that we'll have war, social dislocation, weakening of rural economies, widening gaps between rich and poor, deepening ethnic cleavages-and that resource stresses play an important role.

Thomas Homer-Dixon holds the George Ignatieff Chair of Peace and Conflict Studies at the Trudeau Centre for Peace and Conflict Studies at the University of Toronto. He is the author of The Upside of Down: Catastrophe, Creativity, and the Renewal of Civilization (Island Press, 2006).