知道么？異地戀者間的距離有多遠，地球因此而受的痛就有多嚴重，異地戀者到底為地球造成了多大的傷害，看看本文的數據吧。

You're sitting in the airport terminal, rolling your copy of the Economist into a sweaty tube and waiting to see a significant other who lives far away. You're excited. You're aroused. But there's something else, a nagging feeling that gurgles in your stomach and won't go away. Is it pangs of guilt? It should be: The planet is about to suffer for your love.

Perversely, we live in a world where the sustainability consultant in San Francisco is willing to fly in an exotic boyfriend every month from Washington, D.C. All day, she helps companies "green their supply chains" and "internalize core social costs," yet that eco-savvy seems to vanish at night, when she e-mails: Come visit!!! You might say she's willing to be a locavore but not a locasexual.

Consider what happens when these two fly to see each other once a month. Since greenhouse gases emitted from high-altitude airplanes are thought to have several times the impact of ground transport, a carbon offset company would pin their romantic travels with the equivalent of 35 metric tons of CO2 each year. If that responsibility were divided evenly between the two, our sustainability consultant's lifestyle would be about six times worse for the environment than that of the average gas-guzzling American—and up to 10 times worse than that of the average San Franciscan. (Indeed, for her, breaking up would be about 10 times better for the environment than going vegetarian.)

Or let's say she finagles a transfer to New York, so she can be within driving distance of her sweetie. Now the happy couple can see each other every couple of weeks—while their long, solo trips down I-95 spit out an extra 3.6 metric tons of CO2 every year.

What's the aggregate impact of all this travel? The Census tells us there are about 100 million single people in America over the age of 17. We don't know how many of those folks are in long-distance relationships, but the available research suggests that at least a quarter of all college students are dating out of town. Since the rate is going to be much lower among the general population, we'll make a conservative estimate of 1 in 15 for all single adults. That gives us around 6.7 million unmarried Americans in long-distance relationships. Add in the 3.4 million married people who told the Census that they live separately but aren't "separated," and our total rises to more than 10 million individuals—or 5 million LDRs.

If all of these people made like our two-career couple and drove the distance from D.C. to New York City every two weeks, they would produce a total of about 18 million metric tons of CO2 a year. For comparison, 6.9 million metric tons would be added to the atmosphere if we suddenly eliminated all the public transportation in the United States. Eighteen million metric tons of CO2 is a third of what a national renewable energy standard (PDF) would save over 10 years—or 60 percent of the yearly emissions saved by "moderate adoption" of hybrid vehicles. And if even a small percentage of those relationships were bi-coastal—or even New York-Chicago or Los Angeles-Denver—the total would grow even more astronomical. Love lifts us up where we belong, as they say, but it does so at a steep price to the planet.

The same type of environmental logic has already been applied to our eating habits. The Local Food movement encourages us to cut CO2 emissions by calculating food miles—the distance a meal travels from production to the dinner table—and eating only what's produced within a 100-mile radius. Isn't it time for a Date Local movement, too? Let's start thinking about "sex miles": Just how far was this person shipped to hook up with you? And how many times more efficient would it be to date someone within a 100-mile radius? If the movement spread globally, mirroring either the decentralized development of Local Food co-ops or the manifesto-and-chapter model that built up to the Slow Food movement's mega-confab this summer, its environmental benefits could multiply many times.

A robust Date Local movement wouldn't just help the environment. Like other forms of economic localization, the decision to swear off Orbitz romance creates important spinoff benefits. For one, it makes people less anti-social. By spending all their free time out of town or staring at a webcam—that is, in their apartments or airline cabins, rather than in parks, bowling alleys, and pubs—long-distance lovers erode civic commitment and social support networks. They have fewer chances to meet new people. And they make their cities more stratified by inflating an über-class bubble of jet-set shut-ins who are—understandably, given their lifestyle—more worried about conditions at O'Hare than things going on outside their front door.

What's more, out-of-town daters have less sex than local couples—and long stretches of abstinence between visits could lead to negative health outcomes and thus higher health care costs. Distance also magnifies the impact of negative feelings like longing and suspicion; according to one study, intercity lovers are more likely to be depressed (PDF) and less likely to share resources or take care of each other when sick. And they spend money on travel that they might otherwise save and invest—leaving them vulnerable to economic shocks and wearing away their future standard of living. Every one of these demons could be banished by simply dating local.

Of course, like many eco-conscious attempts to instill social virtue, this proposal runs the risk of killing romance. Many a true human thrill—the high-octane cheeseburger! the long shower! the Chevy Suburban!—has been deflated by green evangelists out to render the personal political. And, in a way, long-distance dating is romantic precisely because it expends so much in the way of resources and effort. It's less exciting to date someone based on your shared love of canvas shopping bags than it is to pine for a partner who wants to meet in Arizona.

No, our Date Local movement won't be overbearing. It shouldn't try to break up every cross-country love odyssey. Instead, it will discourage this special type of conspicuous consumption at the margins, nudging people toward the realization that breaking up is in their own, and enlightened, economic self-interest.

For example, with fuel prices likely to whipsaw upward for the foreseeable future, many people currently in LDRs will end up questioning whether they want to keep timing their liaisons to coincide with oil underconsumption troughs—or whether it's better to call it splits. (The coming death of lucrative, globalized post-college jobs may force similar reconsiderations.) Date Local could educate them about the environmental and social benefits of breaking up and nudge them in the right direction. And the group would be there to cushion the brokenhearted by imparting newly minted locasexuals with a sense of noble self-sacrifice—not to mention a pool of cute, like-minded enviros who happen to live in the neighborhood.

So let's give it a try. Date Local's message is a simple one, in the best traditions of liberal reform. All you have to do is date here. Date now. Date sustainably. And if you absolutely have to date long-distance, do it via Amtrak.