MEGAN JAMES

I was excited to tell you how much my family has loved watching “Life on Our Planet,” the new Morgan Freeman-narrated nature doc on Netflix — a great activity for the whole fam! But then we watched the final episode, and it wasn’t fun and fascinating anymore; it was terrifying.

I should have seen it coming.

The show is structured around the five mass extinctions Earth has endured over the last 500 million years. Each obliteration of ancient species gave rise to a new order of better-adapted survivors. It’s a story about how life finds a way.

Each episode alternates between CGI recreations of prehistoric creatures — a very silly fish with a mouth that can’t close; surprisingly cute, hairless mammals; and, of course, the dinosaurs — and gorgeous footage of animals alive today that exemplify key aspects of evolution: a flamboyance of flamingoes thriving in the desolate Atacama Desert; wolves hunting bison in subzero temperatures; a colorful spider doing a wacky dance to attract his mate.

It’s wild and thrilling, and we all looked forward to watching it together.

Then came the final episode, which charts the arrival of the planet’s most dangerous predator: humans.

We watched a group of prehistoric people use small stone walls to corner a herd of bison against a cliff before chasing them over the edge to their deaths. My 6-year-old did not like this, even though in previous episodes she had cheered on all the big cats as they hunted their prey. This situation with humans was different. It wasn’t a fair fight, she seemed to intuit.

We all perked up for a rousing scene on the advent of agriculture, but before we knew it humans had taken over every corner of the globe — and were messing it all up.

These kids know about climate change. We talked about it this summer when the air was smoky and the rain wouldn’t stop. It comes up at school and in the children’s book “Ada Twist, Scientist.” But this depiction was scarier: It left us teetering on the brink of a sixth mass extinction.

“Why can’t people just be good?” my 9-year-old asked with despair, while Morgan Freeman enumerated the ways in which we continue to harm the planet, over stark footage of a gigantic claw tearing down a mountaintop for coal.

I didn’t have an answer. I told her that this is the great challenge of our lifetime. And that lots of people are working very hard to save the planet. I reminded her of the things we do to help (even though they seem pointless and small by comparison): riding our bikes to school, planting wildflowers for pollinators.

She asked if it would happen in her lifetime, and I think she meant a mass extinction, so I said, no, no, absolutely not. But I know she and her sister will face the worsening effects of climate change throughout their lives.

I didn’t tell her that.

Instead I reiterated what Morgan Freeman said at the end of the show, which I found somewhat comforting: The dinosaurs didn’t understand what was happening to their planet, but we do. What are we going to do about it?