Here's a paradox for you. Most ecologists would agree that we're ravaging the Earth's natural resources at an unsustainable rate—and pushing up against some dangerous thresholds in the biosphere. (See my old piece on planetary boundaries for the gloomy version of this tale.) Broadly speaking, the planet's ecosystems are in terrible shape, and this is widely believed to have negative consequences for humanity. And yet, at the same time, human well-being has never been better. People are living longer, healthier, and richer lives. If you could rev up a time machine and choose to be plopped at any point in history, 2010 would be a sound choice.

So what gives? Why the disparity? And does this mean that we shouldn't worry too much about global warming, ocean acidification, and other ecological crises-in-waiting, since it sure looks like we'll just continue to get richer even as we cause irreversible damage to the planet? (Jim Manzi has argued a version of this position in our debates on climate change.) Those are all good questions. And in the September issue of BioScience, a team of researchers led by McGill's Ciara Raudsepp-Hearne tried to come up with an explanation for the "environmentalist's paradox." Here are their four big hypotheses:

Maybe humanity isn't really better off. That's one possibility. Maybe the decline of ecosystem services is having an adverse effect on us and we just haven't noticed. Except that this is really hard to believe. It's true, natural disasters seem to be walloping more people than ever before—likely due to the fact we're heating up the planet with all our carbon pollution. But, the authors point out, that's vastly outweighed by the fact that things like life expectancy and per capita GDP have never been higher. Check out the Human Development Index. There's still inequality and poverty and disease, but on the whole, the trend's up and up. So much for that theory.

Advances in food production are more important than anything else. It's hard to think of a technological advance that has done more for humankind than the Green Revolution. Modern-day farming may dump chemicals all over the place, it may disrupt the nitrogen cycle, and it may deplete water tables, but there's no question that the invention of artificial fertilizer (and other assorted techniques) have enabled the world to feed itself even as the population has ballooned. And food is far more important than any of those other things. Of course, whether the benefits of industrial agriculture can continue to outweigh the downsides is an open question.

Technology makes us less dependent on ecosystem services. This is an attractive idea. We've been able to grow more crops on less land. We've been able to desalinate water. We've been able to shelter ourselves from heat waves. After Britain chopped down all its forests, it developed another energy source (coal) and kept on chugging. So maybe technology will continue to allow us to thrive even as ecosystem services decline. That's possible, although it's hard to imagine what technologies will shield us from widespread ocean acidification or the collapse of fishing stocks. Which brings us to the fourth hypothesis…