Brace yourself. You may not be able to tell yet, but according to global experts and the U.S. intelligence community, the earth is already shifting under you. Whether you know it or not, you're on a new planet, a resource-shock world of a sort humanity has never before experienced.

Two nightmare scenarios -- a global scarcity of vital resources and the onset of extreme climate change -- are already beginning to converge and in the coming decades are likely to produce a tidal wave of unrest, rebellion, competition, and conflict. Just what this tsunami of disaster will look like may, as yet, be hard to discern, but experts warn of "water wars" over contested river systems, global food riots sparked by soaring prices for life's basics, mass migrations of climate refugees (with resulting anti-migrant violence), and the breakdown of social order or the collapse of states. At first, such mayhem is likely to arise largely in Africa, Central Asia, and other areas of the underdeveloped South, but in time all regions of the planet will be affected.

To appreciate the power of this encroaching catastrophe, it's necessary to examine each of the forces that are combining to produce this future cataclysm.

Resource Shortages and Resource Wars

Start with one simple given: the prospect of future scarcities of vital natural resources, including energy, water, land, food, and critical minerals. This in itself would guarantee social unrest, geopolitical friction, and war.

It is important to note that absolute scarcity doesn't have to be on the horizon in any given resource category for this scenario to kick in. A lack of adequate supplies to meet the needs of a growing, ever more urbanized and industrialized global population is enough. Given the wave of extinctions that scientists are recording, some resources -- particular species of fish, animals, and trees, for example -- will become less abundant in the decades to come, and may even disappear altogether. But key materials for modern civilization like oil, uranium, and copper will simply prove harder and more costly to acquire, leading to supply bottlenecks and periodic shortages.

Oil -- the single most important commodity in the international economy -- provides an apt example. Although global oil supplies may actually grow in the coming decades, many experts doubt that they can be expanded sufficiently to meet the needs of a rising global middle class that is, for instance, expected to buy millions of new cars in the near future. In its 2011 World Energy Outlook, the International Energy Agency claimed that an anticipated global oil demand of 104 million barrels per day in 2035 will be satisfied. This, the report suggested, would be thanks in large part to additional supplies of "unconventional oil" (Canadian tar sands, shale oil, and so on), as well as 55 million barrels of new oil from fields "yet to be found" and "yet to be developed."

However, many analysts scoff at this optimistic assessment, arguing that rising production costs (for energy that will be ever more difficult and costly to extract), environmental opposition, warfare, corruption, and other impediments will make it extremely difficult to achieve increases of this magnitude. In other words, even if production manages for a time to top the 2010 level of 87 million barrels per day, the goal of 104 million barrels will never be reached and the world's major consumers will face virtual, if not absolute, scarcity.

Water provides another potent example. On an annual basis, the supply of drinking water provided by natural precipitation remains more or less constant: about 40,000 cubic kilometers. But much of this precipitation lands on Greenland, Antarctica, Siberia, and inner Amazonia where there are very few people, so the supply available to major concentrations of humanity is often surprisingly limited. In many regions with high population levels, water supplies are already relatively sparse. This is especially true of North Africa, Central Asia, and the Middle East, where the demand for water continues to grow as a result of rising populations, urbanization, and the emergence of new water-intensive industries. The result, even when the supply remains constant, is an environment of increasing scarcity.

Wherever you look, the picture is roughly the same: supplies of critical resources may be rising or falling, but rarely do they appear to be outpacing demand, producing a sense of widespread and systemic scarcity. However generated, a perception of scarcity -- or imminent scarcity -- regularly leads to anxiety, resentment, hostility, and contentiousness. This pattern is very well understood, and has been evident throughout human history.

In his book Constant Battles, for example, Steven LeBlanc, director of collections for Harvard's Peabody Museum of Archaeology and Ethnology, notes that many ancient civilizations experienced higher levels of warfare when faced with resource shortages brought about by population growth, crop failures, or persistent drought. Jared Diamond, author of the bestseller Collapse, has detected a similar pattern in Mayan civilization and the Anasazi culture of New Mexico's Chaco Canyon. More recently, concern over adequate food for the home population was a significant factor in Japan's invasion of Manchuria in 1931 and Germany's invasions of Poland in 1939 and the Soviet Union in 1941, according to Lizzie Collingham, author of The Taste of War.

Although the global supply of most basic commodities has grown enormously since the end of World War II, analysts see the persistence of resource-related conflict in areas where materials remain scarce or there is anxiety about the future reliability of supplies. Many experts believe, for example, that the fighting in Darfur and other war-ravaged areas of North Africa has been driven, at least in part, by competition among desert tribes for access to scarce water supplies, exacerbated in some cases by rising population levels.

"In Darfur," says a 2009 report from the U.N. Environment Programme on the role of natural resources in the conflict, "recurrent drought, increasing demographic pressures, and political marginalization are among the forces that have pushed the region into a spiral of lawlessness and violence that has led to 300,000 deaths and the displacement of more than two million people since 2003."

Anxiety over future supplies is often also a factor in conflicts that break out over access to oil or control of contested undersea reserves of oil and natural gas. In 1979, for instance, when the Islamic revolution in Iran overthrew the Shah and the Soviets invaded Afghanistan, Washington began to fear that someday it might be denied access to Persian Gulf oil. At that point, President Jimmy Carter promptly announced what came to be called the Carter Doctrine. In his 1980 State of the Union Address, Carter affirmed that any move to impede the flow of oil from the Gulf would be viewed as a threat to America's "vital interests" and would be repelled by "any means necessary, including military force."

In 1990, this principle was invoked by President George H.W. Bush to justify intervention in the first Persian Gulf War, just as his son would use it, in part, to justify the 2003 invasion of Iraq. Today, it remains the basis for U.S. plans to employ force to stop the Iranians from closing the Strait of Hormuz, the strategic waterway connecting the Persian Gulf to the Indian Ocean through which about 35% of the world's seaborne oil commerce passes.