♪ this is "nightline." >> tonight, the last tepui. >> it's like this mythical place where there's stuff that's wilder than anything you could make up. >> deep inside the amazon. >> i guarantee that it's going to be a wild adventure. >> a famed biologist and one of the world's best climbers on the trek of a lifetime. >> the terrain's getting steeper and more complicated. >> to protect a biodiversity hot spot. >> dude, this is so sick. >> this is insane.

♪ good evening. thank you for joining us. on earth day 2022, the 52nd anniversary of the pledge to support protecting the environment. tonight, famed biologist bruce means and world-class climber alex hannold team up to protect the amazon by bringing attention to the so-called islands in the sky. here's a preview of nat geo's "explorer: the last tepui."

>> this morning, free soloist alex hannold climbing an unexplored rock formation deep in the amazon known as tepui. they brought along bruce means, who believes these tepuis are teeming with biodiversity like a hidden galapagos full of undiscovered species, he wants to see them protected. >> it's like this mythical place where there's stuff that's wilder than anything you could make up, and it really exists. >> hopefully by assessing the species richness of this particular area may compel government leaders and the people of guyana to want to conserve this fabulous, beautiful place. >> you are going onto, in this case, a piece of rock no human has ever touched. and so you really don't know what you're going to find. you have to rein in the fear, rein in the uncertainty, just

remain calm as you literally step into the unknown. >> we're on an expedition into the glorious heart of south america, the tepuis. >> when bruce and i get our first expedition here, i witnessed this passion that he had for science. i think he found nine new species. and i was like, oh. he's basically on a one-man mission to save this entire area by finding and cataloging enough new species to prove to the world that it's this unrivaled biodiversity hot spot that must be protected. but he's nearly 80 years old now. and there's one final place he has never been able to get to, to complete his work. high on the cliff walls themselves.

so i called alex honnold. alex is one of the boldest if not the single boldest climber in the world. i told him what we were going to try to do, and alex loved the idea of getting bruce up the cliff. alex is a can-do kind of guy. >> a trip like this with a renowned biologist, with a great team, with a cool objective, it's something that i've always wanted to do in my life. my role on the trip is to make sure we successfully climb the wall, and i think that, you know, particularly with an 80-year-old man, we're going to be pretty careful about it. >> 4,000 feet, i had us veering off at 3,750, the closest to the wall. >> that's 2,000 feet of vertical, huh? bruce, is that adequate for you? >> oh, yeah, i should be able to get specimens. >> if we can just get you to the top. >> yeah. >> you can do the full survey. >> the very best-case scenario would be that the wall is steep

enough that the rope basically hangs freely down in a plumb line. he'd be sitting on a chair, slowly levitating up the wall, enjoying the view, looking for species. >> being with bruce in the jungle is an incredible way of appreciating the diversity of life around. he knows the backstory of everything. it's like going to a party with somebody who knows everyone. oh, that guy used to date that girl, then they hung out, and that person -- you know. he knows all the relationships. as you appreciate the complex web of relationships and the jungle more, it makes it much more engaging. >> oh, oh! something good, y'all. spiders are predacious, and they usually eat each other so they're usually solitary. there are some that are colonial and this is one of them. that is cool, wow. >> hiking through the jungle to approach the tepuis is sort of an interesting experience. you start in the rain forest which is stepping over roots, crossing streams. each day it gets harder and harder as you get closer to the actual tepuis because the terrain gets steeper and most of

more vegetated. you're like, oh, it just keeps getting worse. >> getting a little tiring now. i think i've been doing this today -- almost six hours. >> i'm a little concerned about bruce. because the terrain's getting steeper. and more complicated. >> bruce is just moving more slowly than we all anticipated. with more difficulty. i think even he's surprised how hard he's getting his butt kicked. >> you okay there, bruce? >> i'm okay. >> you all right? >> yeah. >> it's hard, you know, not to worry whether we're going to be able to pull this off. >> so i've been promising bruce that he's going to get up the wall. but i don't really know how it's going to happen yet. >> my biggest fear would be that my age and my physical ability might deter or might somehow slow up the expedition.

that bothers me, worries me a lot. >> we could move forward with the porters, with the line cutters, and we blaze the trail to the base of the cliff, while bruce stays and does his stuff at double drop. then the trail is in, and then either we double back, maybe to spend some time with him, or we just start working on the climb. and he's catching up. >> i think half camps make sense, at least for the majority of the team. you know, because safety i think is the -- really has to be a priority. >> i'm for whatever you guys want to do. i'm not pushing for anything. i'm 80, almost 80. yesterday i had several potential bone-breaking falls. >> we need to reduce that down to nil. >> yeah, yeah. >> seems like we're going to split legs, you're going to pace yourself, it's going to be great. so we have a plan for the next couple of days.

>> you look out to the distance, it's like a whole little island. getting to the wall is incredibly complicated. >> watch out for holes. >> you're balancing on this skinny little log. if you slip, you're falling down into this steep crevasse. >> i don't know how we're going to get through this. >> just simply the most treacherous stuff that i've ever had to move through. opens up.sudden, the jungle - and this wall of rock appears. >> holy [ bleep ]. >> like dude, this is so sick! >> this is insane. >> it was crazy. it was crazy. but -- there we are deep in the jungle, so i guess at this point, i guess we're actually going to climb the wall. need long-lasting freshness? try febreze unstopables touch fabric spray.

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think, for us to feel good about you moving up through it. we're just worried, you know, that you could get hurt. there's no real way for us to evacuate you. over. >> i understand. not happy about it. but the success of the expedition depends on me and everybody else not getting terribly injured. you guys can continue the elevational transect. so i will send a drawing of a species of stequamie up there that is new to science and you're very likely to get. so anything and everything that you guys do while you're on the wall and on the summit will benefit our expedition greatly. >> packing for the wall. we're finally launching. >> fuka, guy just came up with the porters, take a look. >> that's the sketch for the frog we're looking for? >> yep. >> oh, wow. >> oh, that's so cool.

>> this cliff has never been climbed. so the plan is to work our way up the rock and find the route as we go. after about 800 feet, there's a ledge where we can hopefully set up camp. from there, we'll traverse the ledge all the way to the summit plateau, searching for frogs and other creatures all along the way. >> on a first ascent, there's going to be loose rocks. that's probably the biggest hazard that you face when you're pioneering a new route. i mean, we're talking things that can be huge, like pieces of rock the size of a school bus. something like that comes off when you're climbing, could definitely kill you. >> one of the most challenging things in climbing in general is fear of the unknown. basically, keeping your mind under control as you encounter difficulties. and first ascents are basically an amplified version of that experience, because when you're doing a first ascent, you really don't know what's there.

could be anything above you. who knows what's going to happen? >> all right, mike, here we go, this is the crux. >> now where the [ bleep ] do i go? >> just because you have a rope and equipment doesn't mean you're actually safe. you are way out there. you or a remote wall in the far corners of guyana. if you injure yourself, there's no real way you're going to be rescued or helped. >> how is it down there, fuka? >> [ bleep ]. >> did something rip? did you pull gear out or just fall off? >> just fell off. >> cool. >> slippery. >> this expedition, unfortunately, this is probably my last trip involving, you know, jungle hiking.

i just want to be quiet and love it. let it sink in. i'll be leaving the planet -- sometime. and i'll miss it. >> fuka and i have belayed here, fuka is belaying mark, can you see him? there he is, still climbing up out of the crazy clouds. i guess this is why they call it a cloud forest. >> all right, [ bleep ]. did it, we're on the ledge.

>> at the elevations where the vegetation occurs, it's very wet and prime habitat for l nds of frogs and other animals. you'll find a vertebrate animal that's endemic to the cliffs themselves would be outstanding, would be a wonderful find. >> i'm going to go up to this little tunnel here, get along. i think the key is stay near the base of the cliff. holy creepy crawlie. tarantula city. there was spots where it was just impenetrable, thickets like this where you're just tearing your way through. then eventually we popped out onto the wayasapu summit plateau. >> look at that tree right

there, that's full-on dr. seuss. we're up on the plateau, we're not on the highest point, but we've basically made it to the top. keep your eyes out. we're definitely in froggy terrain. this is where now we really need the weather to be good, because now we have no shelter and we're out in the open. and of course, the clouds just come up over the side of the tepui, then we're back into the fog. we can't see anything. and it starts raining. >> are you cold? come sit right here, fuka. >> i was almost hypothermic. i had to curl with mark inside a poncho beneath a rock. >> yeah, this isn't exactly the summit glory we were hoping for. and we haven't been able to find the frog, and i'm soaked to the bone.

sort of like finding a needle in a haystack. bruce seems to find them no problem. it's not that easy. oh! holy [ bleep ]. creatures! >> what kind? >> tadpoles. got one. oh my god. i found a tadpole. i mean, obviously that's a sure sign that there's frogs around here. hey, bruce, it's mark. we found a puddle that was just absolutely filled with tadpoles. >> ha ha! fantastic. if you can grab it and bag it for me, when you get back down here, we will have completed the entire transept. be safe. over and out. >> the goal was to get bruce up to the top of the cliff. it didn't go, you know, perfectly according to plan. but we did the climb. >> a first ascent up a tepui

that has never been climbed before. we got to the top. we completed the elevational transept. we found the tadpoles to bring down to bruce which might be a new species. that's what we came here for. and that's really important to me. because i have seen what happens in other places out here. the logging and the mining. and i think if people know about this place and how magical it is, they'll protect it. hey, guys. >> hey! >> hey! >> good to see you. high five. >> hey, bud. >> don't get too dirty, i'm so wet. >> hey, dude, how are you, bud? >> hey! >> i'll take the tadpole. >> so good to see you. >> likewise. this elevational transept has been truly successful. we have the entire transept now. this part of it from the summit

to devil drop is the part we needed to establish, and boy did we do that in spades. i wish i'd been up there with you. that was something i had deep in my heart. however, you did it, and you did it for us. >> i feel like we did something that matters. to collect new species, to study them, to take dna samples, to basically see something that no one has ever seen before. >> the tepuis are special places on the planet. they're part of my life, my love, my career. and so this trip is one of the great gifts to me. and i'd love to do more, but if i don't get to do it, this will be a highlight of my life. >> we'll be right back. feeling sluggish or weighed down? it could be a sign that your digestive system isn't working at its best. taking metamucil

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♪ that's "nightline" for this evening. nat geo's "explorer: the last tepui" is streaming on disney plus, owned by our parent company, disney. thanks for the company, america.

good night.