At one time, most wars between states were fought over disputed borders or contested pieces of land. Today, most boundaries are fixed by international treaty and few wars are fought over territory. But a new type of conflict is arising: contests over disputed maritime boundaries in areas that harbor valuable subsea resources, particularly oil and natural gas deposits. Such disputes have already occurred in the Persian Gulf, the Caspian Sea, the East and South China Seas, and other circumscribed bodies of water. In each case, the surrounding states claim vast offshore tracts that overlap, producing — in a world that may be increasingly starved for energy — potentially explosive disputes.

One of them is between China and Japan over their mutual boundary in the East China Sea. Under the United Nations Convention on the Law of the Sea, which both countries have signed, each is allowed to exercise control over an “exclusive economic zone” (EEZ) extending 200 nautical miles (about 230 standard miles) from its coastline. But the East China Sea is only about 360 miles across at its widest point between the two countries. You see the problem.

In addition, the U.N. convention allows mainland states to claim an extended EEZ stretching to their outer continental shelf (OCS).  In China’s case, that means nearly all the way to Japan — or so say the Chinese.  Japan insists that the offshore boundary between the two countries should fall midway between them, or about 180 miles from either shore.  This means that there are now two competing boundaries in the East China Sea.  As fate would have it, in the gray area between them houses a promising natural gas field called Chunxiao by the Chinese and Shirakaba by the Japanese.  Both countries claim that the field lies within their EEZ, and is theirs alone to exploit.

For years, Chinese and Japanese officials have been meeting to resolve this dispute — to no avail. In the meantime, each side has taken steps to begin the exploitation of the undersea gas field. China has installed drilling rigs right up to the median line claimed by Japan as the boundary between them and is now drilling for gas there; Japan has conducted seismic surveys in the gray area between the two lines. China claims that Japan’s actions represent an illegal infringement; Japan says that the Chinese rigs are sucking up gas from the Japanese side of the median line, and so stealing their property. Each side sees this dispute through a highly nationalistic prism and appears unwilling to back down. Both sides have deployed military forces in the contested area, seeking to demonstrate their resolve to prevail in the dispute.

Here, then, is Scenario #4: It’s 2022. Successive attempts to resolve the boundary dispute through negotiations have failed. China has installed a string of drilling platforms along the median line claimed by Japan and, according to Japanese officials, has extended undersea drill pipes deep into Japanese territory. An ultra-nationalistic, right-wing government has taken power in Japan, vowing finally to assert control over Japanese sovereign territory. Japanese drill ships, accompanied by naval escorts and fighter planes, are sent into the area claimed by China. The Chinese respond with their warships and order the Japanese to withdraw. The two fleets converge and begin to target each other with guns, missiles, and torpedoes.

At this point, the “fog of war” (in strategic theorist Carl von Clausewitz’s famous phrase) takes over. As a Chinese vessel steams perilously close to a Japanese ship in an attempt to drive it off, the captain of that vessel panics, and orders his crew to open fire; other Japanese crews, disobeying orders from superior officers, do the same. Before long, a full-scale naval battle ensues, with several sunken ships and hundreds of casualties. Japanese aircraft then attack the nearby Chinese drill rigs, producing hundreds of additional casualties and yet another deep-sea environmental disaster. At this point, with both sides bringing in reinforcements and girding for full-scale war, the U.S. president makes an emergency visit to the region in a desperate effort to negotiate a cease-fire.

Such a scenario is hardly implausible. Since September 2005, China has deployed a naval squadron in the East China Sea, sending its ships right up to the median line — a boundary that exists in Japanese documents, but is not, of course, visible to the naked eye (and so can be easily overstepped). On one occasion, Japanese naval aircraft flew close to a Chinese ship in what must have seemed a menacing fashion, leading the crew to train its antiaircraft guns on the approaching plane. Fortunately, no shots were fired. But what would have happened if the Japanese plane had come a little bit closer, or the Chinese captain was a bit more worried? One of these days, as those gas supplies become even more valuable and the hair-trigger quality of the situation increases, the outcome may not be so benign.

These are, of course, only a few examples of why, in a world ever more reliant on energy supplies acquired from remote and hazardous locations, BP-like catastrophes are sure to occur. While none of these specific calamities are guaranteed to happen, something like them surely will — unless we take dramatic steps now to reduce our dependence on fossil fuels and speed the transition to a post-carbon world. In such a world, most of our energy would come from renewable wind, solar, and geothermal sources that are commonplace and don’t have to be tracked down a mile or more under the water or in the icebound north. Such resources generally would not be linked to the sort of disputed boundaries or borderlands that can produce future resource wars.

Until then, prepare yourselves. The disaster in the Gulf is no anomaly. It’s an arrow pointing toward future nightmares.