A few days ago I interviewed a former smoker. She asked that I protect her identity, and though I agreed, she was still very reluctant to discuss her old habit. Why the secrecy? "Sheila" has built a career in the U.S. on anti-smoking advocacy. Before she quit, she would start and end each day with a cigarette, and fight the good fight in between. A contradiction, yes, but it took me a while to grasp the extent of her discomfort. After I badgered her with questions like "I'm writing an article about hypocrisy. Can I use you as an example?" and "Did all these lies make you feel like a liar?" Sheila finally blurted, "I could lose my job!" That's the worst case, she conceded, but certainly she could lose standing with her peers. The tobacco industry could use this to discredit her work.

Though the stakes aren't as high for me, I can relate because I'm a hypocrite too. Despite identifying and working as an environmentalist, I am steadily trashing the planet. Whether it's small acts of consumption like printing off documents or bigger ones like flying across the world for a wedding, it seems like I'm always tripping up on my values, and unlike Sheila, I can't cite addiction in my defense.

Critics delight in accusing environmentalists of hypocrisy. They take deep satisfaction in forwarding emails about Al Gore's colossal home energy bills or the veranda he built of old-growth redwood. If they like that, they'll be delighted to learn that people like me and Al who identify as environmentalists aren't so green on average. Sure, we're keen recyclers (but maybe not much more than other people), and according to some studies we're less likely to drive (or not), but we're often unwilling to budge on big ticket items like having babies or taking vacations abroad. All in all, our lifestyles are a lot like those of our non-environmentalist peers: unsustainable.

Environmental professionals are aware of these contradictions and come up with justifications. A bit of consumption is needed for doing our work. We need to fly to conferences to exchange ideas. We need new computers every few years because they don't last long. Flights and PCs have environmental costs, but our net impact as people is good, and anyway, we're working within the constraints of our current society.

These are somewhat valid points. To abstain from any consumption, we'd have to stop cold. The planet needs heroes right now, and they're not going to be effective crouched catatonic in their bedrooms, or as some harsher critics recommend, dead. But this argument only goes so far. First, it's often hard to quantify the benefits of our work, and even a net benefit isn't necessarily a win. If we prevent three tonnes of CO2 by emitting two, but could have accomplished the same result with half the emissions, we've been wasteful -- and we can't really afford to be reckless with emissions right now.

Second, these explanations don't account for many of our eco-foibles, since lots of what we do isn't in the service of the cause. We take vacations, eat meat, and buy iPods because we want to, just for us. My fellow environmentalists might chafe at the accusation, but most of us are hypocrites.

It's not the worst thing to be. We're hypocrites because we're not immune to the allure of shiny new things or the pleasure and status that come with being well-travelled or the biological imperative of reproduction, and yet we have values that run counter to those desires. "Hypocrisy is the gap between your aspirations and your actions..." wrote George Monbiot in the Guardian, "But the alternative to hypocrisy isn't moral purity (no one manages that), but cynicism. Give me hypocrisy any day."

It's tempting to chalk up this aspiration-action gap to our humanity and just let ourselves off the hook, but we shouldn't. However unfairly, critics will use our inconsistencies to discredit our message. The fact that Sheila smoked doesn't make smoking any less dangerous. Al Gore's energy bills don't disprove climate change. Being hypocrites doesn't mean we're wrong, but people might choose to read it that way.

Still, one could argue that those bent on denying environmental threats will find ways no matter how us environmentalists behave. But addressing our hypocrisy isn't just about optics; it's a learning opportunity. If even those who have committed their careers to the green movement can't practice what they preach, clearly the current strategy isn't working. We need to go a whole lot deeper than climate change awareness and green living tips and even tinkering with efficiencies. We need to look at how we can satisfy, in less damaging ways, the basic desires that urge us to buy bigger houses, multiple cars, and to accumulate wealth in general, by examining cultures that achieve more happiness with less, as well as the forces that have historically driven shifts from one status system to another.

This is our challenge. It's our job to tackle this, but not because us environmentalists need to be less hypocritical. We have no more of an ethical obligation to protect the environment than anyone else. Everyone gains that responsibility by virtue of living on this planet, not by expressing concern for it.