Sir David Attenborough has been documenting nature for more than six decades. His various television series — such as “Life on Earth,” “The Living Planet” and “Planet Earth” — have taken viewers to every corner of the globe, capturing the beauty and complexity of the natural world.

At 92, the renowned British naturalist is hardly finished.

In recent years, Attenborough increasingly has used his spellbinding whisper of a voice not only to describe the courtship rituals of birds of paradise or the mass migration of millions of Christmas Island red crabs, but also to repeatedly sound the alarm about climate change.

Last fall at a global climate conference in Poland, he told world leaders that “if we don’t take action, the collapse of our civilization and the extinction of much of the natural world is on the horizon.” Earlier this year at the World Economic Forum in Switzerland, Attenborough again pushed for action, warning, “The Garden of Eden is no more."

“The only conditions modern humans have ever known are changing and changing fast,” he said at the time, adding, “It is tempting and understandable to ignore the evidence and carry on as usual or to be filled with doom and gloom. … We need to move beyond guilt or blame and get on with the practical tasks at hand."

Attenborough’s latest project, an eight-part Netflix series produced in partnership with the World Wildlife Fund, is full of sobering reminders about how climate change is threatening significant parts of the natural world, coupled with the hope that humans might find the collective willpower to avert the most catastrophic consequences.

“Our Planet” was filmed over four years and across every continent, taking viewers to the remote Arctic wilderness, the vast plains of Africa and the depths of the world’s oceans to explore how much of nature is changing — and, in many ways, vanishing — in the age of climate change. Its central message is one of urgency.

“What we do in the next 20 years will determine the future for all life on Earth,” Attenborough intones in the first episode of “Our Planet.”

Before a screening this week at the Smithsonian National Museum of Natural History, Attenborough spoke with The Post about the project, his reasons for optimism and what keeps him motivated. What follows has been edited for length and clarity:

Washington Post: You’ve been documenting the natural world for six decades now. And often with this very distinctive sense of wonder. And while a lot of your series have talked about the concerns with the state of the environment, only in more recent years have you been more outspoken about climate change and about the threat that it poses. What changed for you?

Sir David Attenborough: Well, not quite true. For example, 20 years ago, I was on Easter Island explaining [how] Easter Island was an example of a culture that destroyed its own environment and eventually killed itself, as it were. And I ended that series by saying that unless [we avoid that], we’re going to do it for the whole planet. The funny thing is people took no notice. They said, “Oh, yeah, you’re wrong about that.” Well, that was over 20 years ago. But now, of course, we are absolutely explicit about it because the scientists worldwide are absolutely unanimous about this. There’s no question that the world is warming. No question about that. The degree to which we are responsible is argued about by some, but most are absolutely agreed that humanity — we are the prime cause of this latest rise.

WP: In the parts that I’ve seen in this latest series, “Our Planet,” there’s this inescapable sense of loss — whether it’s the loss of habitat, or the loss of forests in Borneo or coral reefs in Australia. As a viewer you’re kind of left to ponder all that’s disappearing from the natural world. I assume that’s on purpose. And my question is: What do you and the producers want people to take away from this? What do you want people to come away thinking about?

Attenborough: A number of things. One is that we are totally dependent upon the natural world for every mouthful of food we eat and every lungful of air that we breathe. If we damage the natural world, we reduce that, so we damage ourselves. That’s the first. The second thing is that they should see — because the United Nations tell us that most people these days are urbanized, out of touch with the natural world, to some degree — that they should see the complexity, the beauty and the wonder of the natural world on which we depend. And finally, they should see that we have got to do something to look after it because the way things are going, we are running into serious trouble.

WP: You mentioned the United Nations. I was there in Poland last fall when you came and addressed the climate conference there and said, “If we don’t take action on climate change, the collapse of our civilization and the extinction of much of the natural world is on the horizon.” You called it one of the greatest threats in thousands of years. And you had a pretty simple message for the leaders there, which is, “You must lead.” So how’s the world doing? Who’s leading? Is there a lack of leadership?

Attenborough: Well, it’s a big problem. It’s not easy. It’s not easy to get all the nations in the world, of all kinds, [in agreement]. It’s hardly ever happened before. It happened when we saved whales. But that was just a section of humanity. Those maritime nations and people who fished — they could see the problem and they dealt with it. What we’re dealing with now is the entire globe, and that is a very big thing to do. People in Africa and Australia and China and Europe and South America and so on — we’ve all got to get together. And we all come from different backgrounds. So it’s not easy for people to understand why it’s damaging to cut down the Amazonian rain forest, for example. Lots of people will tell them no. But do the people who live there think so? Well, there are problems. And not just only in South America. In Australia at the moment, there are problems. And, of course, there are problems here in the United States.

WP: And since we are here in the United States, and especially in Washington, what do you make of the reversal of this country on climate action and what that means for the broader world?

Attenborough: Well, I mean, it’s a big blow. Can’t deny that. This country, the United States, consumes more and takes more from the natural world per capita than anybody in the entire globe. So to have people here denying it is a huge problem, and we have to do our best [despite that]. It doesn’t mean to say, “Well, in that case we’ll forget about it.” We can’t. It makes it more and more urgent that we keep going.

WP: This series certainly tries to highlight the problems facing the natural world and the dangers posed by climate change, and it carries this conservation message. Maybe less clear — to all of us — are what the solutions are. And I wonder what you see as some of the main solutions? And more important, how optimistic are you that we as a people can act?

Attenborough: I mean, the main problem, of course, is carbon. And a high proportion of our energy — the dominant source — has been from dealing with carbon, and we have to get out of that. We have the technology. There are problems — problems in storage, for example, storing electricity and power. It’s a difficult one to do. We haven’t done it properly ... Think if it cost almost nothing to take energy from the Sahara in the middle of Africa, for example, and feed it to, say, southern Europe for nothing? I mean [the sun] is up; we’ve got it all the time. Why aren’t we using it? And if you get the scientific brains of the world to turn themselves to that problem — if this country can send men to the moon, you know, I’m jolly sure that if it put its mind to it, it could solve that particular problem of electricity.

WP: On a personal note, do you have any intentions of winding down in any way? Is there always a next project? What gets you out of bed each day?

Attenborough: What’s getting me out of bed initially, of course, is that I can think of nothing nicer than spending my time looking at the natural world. But what gets me out of bed, too, is the knowledge that I have grandchildren — I don’t have great-grandchildren yet, but I hope I will have — I care about what’s going on with the next generation. And the great source of comfort I have is that younger people today are more activated than they have ever been. And if you want to take a section of the population and see where is the anxiety — it is them. It is their world. We have messed it up. My generation certainly have messed it up, and we’re giving it to them.

WP: When you see young people recently, just few weeks ago, marching basically all over the world — when you look at that, what do you see, as someone generations ahead of them?

Attenborough: I mean, strikes are a way of expressing a strong feeling that you have, but they don’t solve it. You don’t solve anything by striking. But you do change opinion, and you do change politicians’ opinions. And that’s why strikes are worthwhile.