In the last couple of years, there's been a surge of what you might call "cool PBS," by which I just mean social-media-friendly stuff like Sherlock and Downton Abbey that sort of expands people's ideas of what public television is and especially what its relationship to pop culture is.

But that's not a reason to overlook classic, documentary-making, nature-liking, animal-hugging PBS, which brings us to tonight's return of Nature, produced by WNET in New York, which debuts its new season Wednesday night with "Saving Otter 501." (8:00 pm in many places, but check your local listings, as always.)

This is the story of how the Monterey Bay Aquarium makes its 501st attempt to save an orphaned otter and release her back into the wild. They feed her, they teach her, they even place her with a surrogate mother. (The whole thing is narrated by Daniel Stern, which, for children of the '80s, gives it a whole nostalgic Wonder Otter Years quality that's downright diabolical.) While the special contains more adorable, awesome otter footage than you can shake a ... flipper? ... at, it doesn't take a monster to ask the question: Is this worth it, for one baby otter?

Well, as it turns out, California's wild otter population is pretty tiny and heavily concentrated, and there's that funny thing about ecosystems: otters are one of the few predators that urchins have, and urchins eat kelp, so if you follow the math, otters are necessary to protect kelp from being overrun in the creation of — no kidding — "urchin barrens." Yikes.

There's a nice line-straddling here between "Look at nature; nature is cool!" and "Look how much we're having to do just to keep from wiping out this entire animal, like, as a thing that exists." The scientists are careful to stress that this is only worth doing if it ultimately benefits the wild population, not if it results in a bunch of hand-raised otters being released into Monterey Bay to take food out of the mouths of the wild otters that remain.

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