LISA DESJARDINS: In the last two years, National Geographic Explorer Paul Salopek traversed the Chinese countryside, marched along South Korea's demilitarized zone, and fended off grizzly bears in Alaska.

And he's done it on foot.

Now his expedition from Africa to the tip of Southern America -- of South America crosses into the Western Hemisphere.

Stephanie Sy checks in on his adventures to date.

STEPHANIE SY: Paul Salopek is more than halfway done with his journey dubbed the Out of Eden Walk.

His path began in the Great Rift Valley of Ethiopian 2013, winding through the Middle East and Asia before crossing the Pacific Ocean for Alaska.

Salopek's dispatches for National Geographic along the way bring readers with him stride for stride on this unprecedented trek.

And Paul joins us now.

Paul, welcome back to the "News Hour."

The last time we spoke was about two years ago.

You were winding your way through the Middle Kingdom, a 2.5 year walk through China.

What were the main takeaways, if you can give them in a few moments?

PAUL SALOPEK, Fellow, National Geographic: You know, it was 2.5 years, more than 4,000 miles.

This is much, much longer than the distance between Los Angeles and New York.

It's like walking actually from Chicago to Paris, from basically tropical rain forest at the foot of the Himalayan Mountains to the snowy forests of Manchuria near Russia.

So I covered all these different landscapes, big cities, high mountains, empty valleys, the deserts, and just sheer diversity of China really came through.

And it allowed me as a journalist to kind of get out of the bubble that many of us travel in when we go for quick, short hits to places like China and talk to ordinary people every single day.

It was quite a privilege.

STEPHANIE SY: Let's move on to the next parts of your journey, which take you to South Korea and then Japan, where, again, you're walking in the rural countryside, but I sense such a theme of emptiness and isolation and loneliness.

Were those your main takeaways from that region?

PAUL SALOPEK: It really was.

When I took a ferry boat from Northern China into South Korea and then another ferry into Japan, one of the most startling kind of discoveries for me was just how empty the countryside is.

The depopulation of the countryside in South Korea and Japan, as a product of hyper-urbanization and hyper-globalization, was just astonishing.

When I walked through the rural parts of Honshu, the main island, I one day walked almost 25 miles and saw three people.

I had to go back to my methodology of camping and going across the deserts of Central Asia or the deserts of Saudi Arabia.

I had to start carrying food.

I had to start thinking about sleeping out in a sleeping bag because there were no lodging.

It was kind of spooky.

It was like walking through almost a postapocalyptic rural landscape.

STEPHANIE SY: You leave Asia, and one of the rules of this journey is you can't get on motorized transit, right?

You can't take planes, trains and automobiles, but you can take ships.

And you end up on a container ship heading to Alaska.

So talk about the experience of being on a container ship.

PAUL SALOPEK: That's -- that was a first for me.

I mean, and the reason -- the whole reason -- I need to add why I'm on a container ship going 5,000 miles across the North Pacific - - is that following the pathways of the ancient first peoples who populated the world.

I got stymied at the Russian border with China.

I couldn't go through Russia because of Russia's invasion of Ukraine.

So that old Siberian migration route into Alaska was closed.

So the alternative was taking a ship across the Pacific.

A container ship took me for 11 days between Yokohama, Japan, to a tiny port in British Columbia and Canada called Prince Rupert.

We were traveling at about 15, 16 miles an hour, moving something like 4,000 containers of everything you can imagine.

And it was like a glimpse, Stephanie, of looking behind the scenes at how globalization works.

Who are these seafarers who move all of our stuff, all the clothes that we're wearing, all the stuff in our homes, the cars that we drive?

Moves on these giant moving warehouses.

This ship was 300 meters long.

That's like four city blocks.

It was colossal.

STEPHANIE SY: You have to tell me what the Lost Coast of Alaska was like and what the most remarkable moments there were.

PAUL SALOPEK: What I have said, Stephanie, before is that this is kind of a walk of a lifetime, a journey of a lifetime, in which there are walks of a lifetime inside of it.

And one of them was the Lost Coast, the outer coast of Alaska.

And where's that?

It's that long stretch of exposed coastline and that little kind of finger of Alaska that stretches out of the main chunk of it.

I think it was about 300 miles of empty wild beaches, of spruce forests coming down to wild surf, of glaciers spilling into inlets, of seeing grizzly bears, seeing moose on the beaches.

I never imagined these wild animals being on beaches, and there they were.

And it's also kind of soberingly, on a more serious note, beyond the kind of natural wonder and the joy of knowing that there are these landscapes still left on the planet, is, it's incredibly dynamic due to the climate change crisis.

These glaciers are melting.

It's changing the course of rivers.

It's affecting the ecology of salmon that migrate up the rivers.

As one of the experts that I talked to said: "This is the geography, Paul, of the future, right here."

It's kind of the laboratory of what's going to happen in different ways around the world.

STEPHANIE SY: So you're back in the Western Hemisphere, Paul.

And is it true that the last time you were in the U.S.

was a decade ago?

If that is the case, what are your reflections upon returning?

It's been quite a lot happening in the last decade.

PAUL SALOPEK: The last time I was in the U.S.

was December of 2012.

And that was like just before Obama was sworn in the second time, right?

Twitter had just gone public, when it was called Twitter back then.

It's both kind of exhilarating, but also a bit strange.

I have told my editors I feel a little bit like, I don't know, a guy who's been -- who's come back from, like -- like Rumpelstiltskin, come out, come awake under the tree after a lifetime, right, and the world has changed around him.

STEPHANIE SY: And where are you off to next?

PAUL SALOPEK: So I'm hunkered down for the winter, waiting for the worst of the winter storms to pass.

And my winter base is in Gustavus near Glacier Bay National Park in Southeastern Alaska.

In the springtime, the plan is to kind of do something very different.

After walking, I don't know, about 18,000 miles, I plan to get into a sea kayak and sea kayak about 1,000 miles south to Vancouver and the U.S.

border.

As archaeologists are discovering, the people I'm following, the first discoverers of the world back in the Stone Age, did use watercraft.

And I'm going to try to follow their pathway now.

I will be paddling in and out with paddling partners, instead of walking partners.

So that's the plan in the spring.

STEPHANIE SY: Well, we look forward to reading all of your future dispatches on your walk and on your canoe, Paul Salopek.

You can read all of Paul's writings and see his videos at outofedenwalk.com.