I recently visited a Vermont electronics recycling company, and wandered through a warehouse packed with obsolete, difficult-to-recycle devices: electric typewriters, video game consoles, reel-to-reel tape decks, guitar amplifiers, television, spectrometers, stereo speakers, and even some medical imaging consoles. I thought the mashup was interesting, so I took a picture with my iPhone and tweeted it. A few minutes later, Nathaniel Bullard, a renewable energy analyst (and friend), tweeted back at me: "How many of those single-function boxes are now just a module in a smartphone, I wonder?"

Most, I thought. But surely not the air conditioning unit-sized oscilloscope at the front of the picture? A device that large and specialized must remain that way, no? Wrong: a few minutes later Bullard tweeted a link to an oscilloscope app on the App Store.

Almost from the moment the iPhone was released, environmentalists and sustainable designers have criticized the device—and its breakneck upgrade cycle—as fundamentally unsustainable. And they have a point. Despite Apple's considerable efforts at promoting its recycling programs, most of the iPhone remains impossible to recycle. But since that tweeted conversation with Nat, I've begun to think that there's a more interesting way to look at the iPhone's environmental profile.

If, a decade ago, the world's most creative product designers had gathered to design a single object to reduce and even eliminate consumption of difficult-to-recycle, resource intensive devices like stereos, flashlights, televisions, typewriters, and even oscilloscopes, I don't think they could have come up with anything better than the iPhone and the smartphone models that followed and imitated it.

There's no data on how much copper, gold, steel, and other raw materials have been saved by opting for a (frequently upgraded) iPhone for a closet full of older generation electric and electronic devices. But I know (because I measured) it's possible to fit more than 100 iPhone 6's in that oscilloscope sitting in a Vermont recycling warehouse—and each of those iPhone 6 handsets can do far more than an oscilloscope. Of course, the cocktail of materials—copper, gold, rare earth elements, steel, glass and plastic—will be different. But each app installed into an iPhone is—in many cases—one less scoop of ore being refined into a separate device.

Is the iPhone sustainable? I guess it depends on how you define "sustainable." But especially for emerging market consumers in places like India, China, and across Africa, it's certainly more sustainable to buy a smartphone than the bevy of devices bought and eventually tossed aside by previous generations of consumers in developed countries. What is the iPhone? From an environmental standpoint, it's unexpected progress.