A ghostly green light, the aurora borealis, weaves and bobs through a slow dance above a dark winterscape of ice and snow in the opening moments of The Green Planet’s third hour, Seasonal Worlds, a subtle reminder that, even in normal times, our green planet is a world of climatic extremes — extreme heat and bitter cold, blinding light and extreme darkness. And yet, plants grow here too.

“This is the boreal forest,” David Attenborough says, in an almost reverential hush, “the largest forest on Earth, 750 billion trees, smothered by snow throughout the winter.”

It is hard to watch these gentle, serene images of a quiet, almost haunting beauty and not think of the conflagration of wildfires that, right now, as this episode of The Green Planet makes its US debut on public broadcaster PBS, is scorching its way across wide expanses of Western Europe, just as they have in recent summers across western Canada and the United States, and deep into Siberia. The true boreal forest, the line of trees that separates the temperate forest from the Arctic expanses, is the northernmost boundary of an extraordinary world, Attenborough reminds us, as he stands in an oversize blue parka and a tiny red woollen hat on the edge of the Arctic Circle. It’s a world dominated by relentless change, the gentleman naturalist tells us, and the change is not limited to just human-caused climate. Change is the very definition of a season world — winter is not like summer, and the plants and animals that live here have learned to adapt.

By now, midway through the series, The Green Planet’s template is clear. Eye-filling visuals, much of them captured from drones gliding over an endless canopy of green, coupled with a lush symphonic score and Attenborough’s familiar dulcet voiceover, features few stylistic surprises, but one of the great joys of The Green Planet is the way it reveals hidden surprises in the seemingly familiar: Nettles that sprint, brambles that hook their quarry — yes, plants can be predatory, too — and creepy crawlers that literally creep and crawl. “Soon, every inch of space and patch of light is tamed,” until, of course, it isn’t. Predatory plants, indigenous and invasive alike, stalk their prey and move and suffocate it, captured by time-lapse photography, in the same way a snake may stalk and suffocates an unwary rodent. Plants don’t have brains the way we think of brains, but it’s hard not to watch The Green Planet and not imagine that there is a kind of self-awareness at work — a virtual Little Shop of Horrors of tales of survival and adaptation. Thermal cameras alert the viewer to temperature swings inside a flower and the air immediately around it — the secret of pollination, and how it works. A later sequence shows how wildfires can lead to regeneration, given the proper conditions, and not everything is always as it seems.

Season Worlds holds its lens to nearly every temperate region on Earth, from Australia to the lower Arctic, from the Cape Province of South Africa to the coastal old-growth forests of Western Canada — dandelion wine and daffodil wine in equal measure. The cumulative effect of Seasonal Worlds is soul-stirring and life-affirming. At its best, and there are moments in Season Worlds that equal anything in the series, The Green Planet is a welcome balm for a troubled world, and a timely reminder that humankind — all of us — must do everything we can to protect and preserve nature’s bounty. The hour’s final scenes, filmed in California’s giant redwood sequoia forests, are enough to bring a tear to the eye.

The Green Planet: Seasonal Worlds premieres Wednesday, July 20 on PBS at 8E/7C. New episodes bow Wednesdays through Aug. 3, on PBS and the PBS app.