Sunday is Earth Day, which typically means a flurry of stories about “green” cat litter and cleaning products. Here at Wonkblog, though, it’s an excuse to revisit a favorite old research paper — one that explores what’s known as the “environmentalist’s paradox.”

A real paradox, this one. (NASA)

So why the disparity? And does this mean that we shouldn’t fret too much about global warming, ocean acidification and other budding ecological crises, since recent history suggests that people will just continue to grow more prosperous even as we cause irreversible damage to the planet? (Indeed, some economists have tried to make exactly this point.)

Back in 2010, a team of researchers led by McGill’s Ciara Raudsepp-Hearne tried to figure out how to resolve the “environmentalist’s paradox,” in a paper for the journal Bioscience. Here were their four big hypotheses:

Maybe humanity isn’t actually better off. That’s one possibility to consider. Perhaps the decline of ecosystem services is having an adverse effect on us and we just haven’t noticed. But this is hard to square with the data. 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. The Human Development Index has plenty of data on this. There’s still inequality and poverty and disease, but on the whole, the trend’s heading upward. So this probably isn’t the answer.

Advances in food production are more important than anything else. It’s hard to think of a broad technological advance that has done as much for humanity as the Green Revolution. Modern-day farming may be extremely chemical-intensive, it may disrupt nature’s nitrogen cycle, and it may deplete water tables, but there’s no question that the widespread use of synthetic nitrogen fertilizers and other assorted farming techniques have enabled the world to feed itself even as the population has ballooned to 7 billion. And food, the authors note, just might override all those other concerns. (That said, it’s still an open question.whether the benefits of industrial agriculture will continue to outweigh the downsides in the decades ahead.)

Technology makes us less dependent on ecosystem services. This is another possible way to resolve the paradox. 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 in the eighteenth-century, it developed another energy source (coal) and kept on chugging. So perhaps technology will continue to allow us to thrive even as ecosystem services decline. That’s possible, although it’s still hard to imagine what technologies will shield us from widespread ocean acidification or an increasingly likely 4°C rise in global temperature. Which brings us to the fourth hypothesis. . .

The worst impacts of ecosystem degradation are yet to come. This is one of the more plausible explanations for the paradox. We’ve put a lot of carbon into the atmosphere, but it takes a few decades for those effects to fully manifest themselves in the climate. There’s a lag in the system, and our ecological debts haven’t come due yet. Likewise, a number of researchers have suggested that certain trends in environmental degradation — like the disruption of the nitrogen cycle or extinction rates — may have “tipping points,” whereby things seem to be crumbling slowly until suddenly, rapid and potentially irreversible shifts take hold.

What’s interesting about the BioScience study is its emphasis on the fact that researchers still don’t seem to have a solid grasp on the relationship between ecosystem services and human well-being. (In the two years since it was published, follow-up papers have stressed the need for better data on this link.)

For the moment, human existence keeps improving — in genuine and meaningful ways — even as we inflict damage to the planet. But it’s not clear the current path can or will last forever.