One year ago, the U.S. government put on a dazzling display of incompetence. Despite pouring billions of dollars into homeland security, the Bush administration responded to Hurricane Katrina with all the rapidity and confidence of an anaesthetized elephant.

The problem lay not only with the preemptive failure to invest money in stronger New Orleans levees, which could have minimized the damage when the hurricane struck, nor just with the government's response, which took longer than the international community's action in the wake of the Southeast Asian tsunami. And the debacle was not merely a function of rampant corruption among the businesses that took government handouts to repair the damage. Rather, the flaws of the U.S. approach to Katrina run much deeper.

As we pass the one-year anniversary of the cataclysm, it has become increasingly clear that a hurricane that earlier would have had local or at most regional impact has become a matter of global concern. Hurricane Katrina is, ultimately, a foreign policy problem. U.S. policies abroad did not generate the hurricane winds. But Washington's attitude toward climate change and international cooperation certainly sowed the winds, and we continue to reap the whirlwind. It is blowback of the most literal kind.

America faces a situation unique in its history. After reaching its territorial limits and expanding overseas, the United States is now threatened by the very waters that previously sheltered us from world war and aerial devastation. Today, imperial overstretch has undercut our global influence, and an arrogant approach to the planet threatens to shrink our very territory.

Acquired from France in 1803, New Orleans was the prize of the Louisiana Purchase. The port connected the young American republic to the global economy of the time. The rivers of the Midwest converged to feed the Mississippi, and the Mississippi flowed into the Louisiana port, allowing American farmers to sell their surplus abroad. “Geopolitics created New Orleans,” wrote George Friedman in Stratfor shortly after the hurricane hit. For two centuries, through the marketing of agriculture and petrochemicals and oil, the city served as a nexus where the local and the global rubbed shoulders.

New Orleans was the first glimmer of what journalists and politicians would proclaim in the 1840s as America's “manifest destiny” to stretch from coast to coast. Over the course of the 19th century, in a pell-mell rush, the United States pushed its frontier westward, seizing a chunk of Mexico along the way for good measure.

By 1890, after much death and displacement of indigenous peoples, it was all over. The United States had reached its territorial limits. The frontier was suddenly no more.

Three years later, historian Frederick Jackson Turner transformed the closing of the American frontier into a provocative thesis on the national character of the United States. He contended that the frontier—its democratic nature, its seemingly unlimited resources, and the conflicts it generated—exerted an enormous influence on the American psyche. The end of the frontier would usher in a new era of competition within the United States. It was, to use Turner's words, the end of “the first period in American history.”

Turner's frontier thesis of 1893 came at a propitious time, for as one door closed, another was opening. Although Turner did not consider imperialism, his address came just as a second period in American history was beginning in earnest: overseas expansion. Turner's conception of social evolution as a sequence—from hunter to rancher to farmer to urbanite—lent itself to a more general application. Having evolved toward a more perfect union, the United States was ready to spread not simply westward but globally.

Historian Brooks Adams supplied the missing link in this grand scheme with his 1895 argument that democracy could only be preserved through expansion abroad. Thus did the architects of the new American empire acquire a suitable ideology. After 1898, the world was our frontier, and we ventured outward to extend dominion over Hawaii, Puerto Rico, Cuba, and the Philippines, followed quickly by Nicaragua, the Dominican Republic, and Mexico—all in the name of democracy. “There is in the ocean no constitutional argument against the march of the flag, for the oceans, too, are ours,” declared imperial cheerleader Albert Beveridge before the Senate in 1900 in a paean both to the “self-government” that the United States was imposing on the Philippines and to what the Indiana senator declared elsewhere to be the “commercial supremacy of the Republic.”

It took the insights of historian William Appleman Williams, in his famous 1955 essay “The Frontier Thesis and American Foreign Policy,” to trace this Turner-Adams hybrid ideology through Teddy's Roosevelt's directives, Wilson's 14 Points, and Truman's references to the “frontier of democracy.” Just as Turner had declared the frontier closed in 1893, Williams declared America's new global frontier closed during the Cold War. Nuclear weapons, he argued, put very definite limits on territorial expansion and the promotion of democracy. An escalation of the conflict between Moscow and Washington, he wrote, “would make the world a frontier for fossils.”

When the Cold War ended, approximately 100 years after the closing of the American frontier, a new set of options emerged. The possibility of an even-greater extension of U.S. influence—the unipolar moment—beckoned. Adams' notion of democracy through expansion became a hallmark of the neoconservative revolution. In Afghanistan, Iraq, and elsewhere, Washington has attempted to widen what it calls the “zone of democracy.” Turner might not have approved of the presumption that the United States should impose its social system on others. But he would have applauded the pioneer spirit that has overtaken the White House.

What had begun in New Orleans—the westward push and the linking of territorial expansion to increased global interaction—has come to an end in New Orleans. Hurricane Katrina marks the third and final closing of the American frontier. First we hit the Pacific Ocean. Then we butted up against the seemingly implacable power of the Soviet Union. And now we have reached the final frontier: the limits of the planet itself.

Hurricane Katrina was no anomaly. Climate change has transformed previously benign tropical storms into major disasters. A 2005 Science article reported a tremendous increase worldwide in the number of cyclones and monsoons over the last 35 years. Using 80 computer simulations, Lawrence Livermore National Laboratories concluded that human activity—the burning of fossil fuels—is the only logical cause for the ocean temperature increases that have made these storms more violent.

The rise in global temperatures in turn triggers the melting of the ice cap and a rise in sea levels. The U.S. government has itself conservatively estimated a one-foot rise in water levels by 2050. Major cities—such as Charleston, Miami, Long Beach, and San Jose—will be threatened by the rising water. Port operations will be disrupted. Millions of people will be displaced. Imagine Katrina, the industrial-strength version.

Thus, for the first time in its short history, the United States faces the very real possibility that its borders will contract rather than expand. And as writer Bill McKibben aptly noted in the aftermath of the Katrina disaster, “Our rulers have insisted by both word and deed that the laws of physics and chemistry do not apply to us.” This is American exceptionalism writ large.

It's not just the United States, of course. Environmental researcher Norman Myers estimates 150 million people worldwide will be displaced by the rising waters. NASA's Jim Hansen takes a more pessimistic look at geologic history and projects an 80-foot boost in sea level if the global mean temperature rises five degrees Fahrenheit. That would translate into 150 million displaced people in India alone. New Orleans is just the tip of the melting iceberg.

In the 1890s, Turner was fascinated by the dark heart of economics: scarcity. The frontier represented an abundance of land and resources; its closure suggested reaching not simply territorial limits but ecological ones as well. Today, Washington's putative expansion of democracy occurs hand in hand with an attempt to secure control over energy resources. Preserving access to Middle Eastern oil has come at the expense of serious energy conservation at home and any deliberate policy to control greenhouse gas emissions on either a national or global level.

This combination of democracy promotion and resource exploitation typifies a frontier ethos that has run amok. Climate change compels not simply a new U.S. approach to the environment but a fundamental rethinking of U.S. foreign policy as well.

Americans don't like to hear about limits. We're an all-you-can-eat nation. We're also a super-marathon nation. The obese and the hyperfit share a common belief that nothing can stop us, neither the length of our belts nor the capacity of our endurance.

Jimmy Carter tried to talk about limits back in the 1970s and was trumped by Reagan's morning-in-America optimism. The neoconservatives who helped frame U.S. foreign policy, particularly after September 11, 2001 revived Reagan's can-do spirit, but in a metastasized form. They envisioned a limitless expansion of U.S. democracy, military reach, and energy consumption. They recognized none of the limits of the realist tradition. And they certainly didn't heed any of the restrictions demanded by the international community—the Kyoto Protocol or the International Criminal Court—which might limit U.S. actions in the world.

The last three years of foreign policy failures have been a rude reminder that, our exceptionalist tradition notwithstanding, limits apply to America as well. The Iraq fiasco has demonstrated the limits of military power. The ballooning debt has revealed the budgetary constraints of U.S. imperialism. The rise of anti-Americanism underscores the limits to which others can be arm-twisted to follow Washington's lead.

Until Katrina, environmental limits had a speculative quality, for they were often expressed in terms of numbers (rising temperatures, mounting emissions, shrinking ozone). Debates raged in the popular press between apocalyptics and Pollyannas largely in the future tense. Katrina, however, was not hypothetical. Katrina was as real as it gets. Environmental limits set by climate change, like the territorial limits that brought continental expansion to an end, will ultimately render America's unipolar moment unsustainable.

The disappearance of the frontier in 1890 prompted deep soul-searching on the part of Frederick Jackson Turner, and through his writings, among Americans at large. If its implications are heeded, Hurricane Katrina should have a similar effect on the American body politic.

The United States should shift its attention back to our failing infrastructure, our eroding manufacturing base, our indebted economy, our schools and public transportation and health care system. This should not be a neo-isolationist turn. Rather, in a globalized age when all domestic decisions have foreign policy consequences and ecological events respect no borders, the frontier must be redefined. We must face, not flout, our limits. We must re-engage with the world in a different way, as good neighbors rather than frontier outlaws.

New Orleans 2005 was our generation's closing of the frontier, the final frontier. It's time to develop a new frontier thesis to limit the damage inflicted by the cowboys currently occupying the White House.

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