1 00:00:27,163 --> 00:00:31,538 We are entranced by the beauty of our planet. 2 00:00:31,563 --> 00:00:34,098 Just take in this view for a moment. 3 00:00:34,123 --> 00:00:39,138 Lush green meadows, thick forest, jagged mountain peaks - 4 00:00:39,163 --> 00:00:40,858 it's magnificent. 5 00:00:45,843 --> 00:00:48,258 But whilst we appreciate that beauty, 6 00:00:48,283 --> 00:00:53,018 I think sometimes we forget that all of this is so fleeting. 7 00:00:53,043 --> 00:00:56,178 For the last four-and-a-half billion years, 8 00:00:56,203 --> 00:01:00,738 our Earth has been a constantly changing ball of rock, 9 00:01:00,763 --> 00:01:05,418 transforming itself over and over again. 10 00:01:05,443 --> 00:01:09,058 It's more fragile than we like to acknowledge. 11 00:01:09,083 --> 00:01:12,458 It's more indifferent to us than we care to admit. 12 00:01:15,843 --> 00:01:19,738 Now, thanks to pioneering new science, 13 00:01:19,763 --> 00:01:25,218 we can explore our planet's four-and-a-half-billion-year story 14 00:01:25,243 --> 00:01:26,698 like never before. 15 00:01:29,843 --> 00:01:34,378 In this series, we'll witness five pivotal moments 16 00:01:34,403 --> 00:01:36,018 in Earth's history... 17 00:01:39,043 --> 00:01:41,098 ...moments of drama... 18 00:01:42,683 --> 00:01:44,178 ...of crisis... 19 00:01:45,523 --> 00:01:47,778 ...and of rebirth... 20 00:01:51,563 --> 00:01:55,338 ...events that shaped the planet we live on. 21 00:01:58,043 --> 00:02:02,858 Wherever you are, you have beneath your feet the most precious object 22 00:02:02,883 --> 00:02:04,658 in the universe - 23 00:02:04,683 --> 00:02:08,938 a living, breathing, life-sustaining world. 24 00:02:08,963 --> 00:02:11,578 And this is its story. 25 00:02:48,083 --> 00:02:53,778 It can feel as if our living world was somehow inevitable... 26 00:03:00,123 --> 00:03:03,698 ...that ours is a planet with all the right ingredients 27 00:03:03,723 --> 00:03:06,258 for a rich assortment of life... 28 00:03:08,203 --> 00:03:13,098 ...not only to arise, but to flourish and endure. 29 00:03:14,643 --> 00:03:19,938 But, in fact, it's death that is the only true inevitability. 30 00:03:21,283 --> 00:03:25,298 There's an uncomfortable truth about life on Earth. 31 00:03:25,323 --> 00:03:29,338 You see, this great diversity, this weird, wonderful 32 00:03:29,363 --> 00:03:33,218 and beautiful mix of species, of plants, animals and fungi 33 00:03:33,243 --> 00:03:38,098 are all only here because something else has died - 34 00:03:38,123 --> 00:03:43,258 in fact, because an enormous number of other things have died. 35 00:03:43,283 --> 00:03:47,498 If we were to take the sum total of every living thing 36 00:03:47,523 --> 00:03:52,698 on our planet today, it would add up to less than 1% of those 37 00:03:52,723 --> 00:03:55,818 that have ever existed on Earth. 38 00:03:55,843 --> 00:04:00,698 But this colossal loss of life is not a tragedy. 39 00:04:00,723 --> 00:04:04,018 Extinction is a vital part of evolution. 40 00:04:07,363 --> 00:04:09,778 If nothing ever went extinct, 41 00:04:09,803 --> 00:04:13,098 there would be no room for new species to evolve. 42 00:04:14,523 --> 00:04:19,538 Over time, extinction helped create our rich living world. 43 00:04:21,003 --> 00:04:23,818 But our planet walks a tightrope. 44 00:04:25,643 --> 00:04:28,338 If extinction goes unchecked, 45 00:04:28,363 --> 00:04:31,938 the complex web of life crumbles. 46 00:04:36,923 --> 00:04:41,858 Imagine 90% of species suddenly dying - 47 00:04:41,883 --> 00:04:46,218 not just a few endangered plants or animals becoming extinct, 48 00:04:46,243 --> 00:04:48,818 or a handful of ecosystems disappearing, 49 00:04:48,843 --> 00:04:54,098 but nine out of ten living things wiped off the face of the Earth. 50 00:04:58,723 --> 00:05:03,418 Imagine what that Earth would look like in the aftermath - 51 00:05:03,443 --> 00:05:07,898 shattered, broken, bereft of the beautiful complexity 52 00:05:07,923 --> 00:05:09,858 that we take for granted today. 53 00:05:13,283 --> 00:05:18,658 We may think modern climate change is our planet's darkest hour, 54 00:05:18,683 --> 00:05:21,338 or the loss of the dinosaurs, 55 00:05:21,363 --> 00:05:24,058 but the Earth has seen worse. 56 00:05:25,843 --> 00:05:30,058 This is the story of the greatest mass extinction event 57 00:05:30,083 --> 00:05:31,618 in Earth's history. 58 00:05:36,603 --> 00:05:42,498 Something caused our planet's life-support systems to fail, 59 00:05:42,523 --> 00:05:47,218 wiping out most of the species on Earth. 60 00:05:48,683 --> 00:05:51,618 And this is not an apocalyptic vision, 61 00:05:51,643 --> 00:05:53,578 not a doomsday prophesy. 62 00:05:53,603 --> 00:05:56,138 This actually happened. 63 00:05:56,163 --> 00:05:59,818 252 million years ago, 64 00:05:59,843 --> 00:06:04,978 the Earth turned on the life that it had nurtured for so long. 65 00:06:09,123 --> 00:06:14,298 What does it take to destroy almost all life on Earth? 66 00:06:18,163 --> 00:06:20,138 And could it happen again? 67 00:06:25,843 --> 00:06:29,338 Well, the answer lies in Earth's deep history... 68 00:06:35,643 --> 00:06:40,218 ...in a time long before humans transformed the planet's surface... 69 00:06:45,803 --> 00:06:48,378 ...before the last Ice Age... 70 00:06:53,203 --> 00:06:57,258 ...before the asteroid impact wiped out the dinosaurs... 71 00:07:03,203 --> 00:07:07,178 ...in fact, back to a time before dinosaurs 72 00:07:07,203 --> 00:07:09,258 even existed at all. 73 00:07:28,563 --> 00:07:34,658 From space, the Earth in the Late Permian is a strange sight. 74 00:07:34,683 --> 00:07:38,018 From one side, a water world, 75 00:07:38,043 --> 00:07:39,658 no land in sight. 76 00:07:45,323 --> 00:07:50,538 But as the planet turns, something else creeps into view... 77 00:07:54,003 --> 00:07:58,778 ...all the Earth's major landmasses clustered as one. 78 00:08:00,603 --> 00:08:03,378 This is Pangea... 79 00:08:08,483 --> 00:08:12,058 ...a super continent rich with life. 80 00:08:18,723 --> 00:08:23,218 Coastal waters teem with weird and wonderful creatures. 81 00:08:25,963 --> 00:08:28,418 At once both alien, 82 00:08:28,443 --> 00:08:31,098 yet eerily familiar. 83 00:08:34,963 --> 00:08:41,458 And in lush forests, a cacophony of animal cries fill the air. 84 00:09:09,323 --> 00:09:12,618 In many ways, the Earth in the Late Permian 85 00:09:12,643 --> 00:09:14,938 was like the Earth we have today - 86 00:09:14,963 --> 00:09:18,058 millions of species of plants and animals, living together 87 00:09:18,083 --> 00:09:20,538 in complex, interconnected webs 88 00:09:20,563 --> 00:09:23,818 which are nurturing and self-sustaining. 89 00:09:23,843 --> 00:09:28,418 But in other ways, it was a very alien world. 90 00:09:28,443 --> 00:09:35,298 This was a time long before mammals or even dinosaurs walked the Earth. 91 00:09:35,323 --> 00:09:39,338 But life was no less remarkable. 92 00:09:39,363 --> 00:09:42,218 Scuttling around in the scrub of the Late Permian, 93 00:09:42,243 --> 00:09:44,338 you might have found one of these. 94 00:09:44,363 --> 00:09:48,858 This is the cast of a beautiful fossil of Nycteroleter. 95 00:09:48,883 --> 00:09:53,738 It's part of an extinct group of reptiles, and fed on things 96 00:09:53,763 --> 00:09:57,298 like pro to-cockroaches, dragonflies, millipedes. 97 00:09:57,323 --> 00:09:58,618 It's got quite large eyes, 98 00:09:58,643 --> 00:10:00,778 suggesting that it might have been nocturnal, 99 00:10:00,803 --> 00:10:04,778 and we also know that it had really good hearing - 100 00:10:04,803 --> 00:10:07,418 something quite unique for animals of that time. 101 00:10:08,603 --> 00:10:10,818 But then, look at this chap. 102 00:10:10,843 --> 00:10:12,578 It's Dvinia. 103 00:10:12,603 --> 00:10:14,458 It would've grown to about 50 centimetres. 104 00:10:14,483 --> 00:10:16,658 Looked like a small dog. 105 00:10:16,683 --> 00:10:20,738 Neither a mammal, nor a reptile, it's got forward-facing eyes. 106 00:10:20,763 --> 00:10:23,578 It was perhaps a predator of some kind. 107 00:10:23,603 --> 00:10:27,178 But, look, from the top, you can see it's got really wide cheeks, 108 00:10:27,203 --> 00:10:30,498 and the remains here of perhaps a sagittal crest, 109 00:10:30,523 --> 00:10:34,098 suggesting that it had very powerful muscles, a powerful bite. 110 00:10:34,123 --> 00:10:38,098 In fact, it might have been fishing for shellfish down on the beach 111 00:10:38,123 --> 00:10:41,898 and crunching them up with its powerful jaws. 112 00:10:41,923 --> 00:10:44,978 But last, and perhaps most impressive, 113 00:10:45,003 --> 00:10:51,538 this is a magnificent specimen of a super predator, Inostrancevia. 114 00:10:51,563 --> 00:10:52,938 What an animal. 115 00:10:52,963 --> 00:10:56,218 Just look at those sabre-tooth teeth there. 116 00:10:56,243 --> 00:10:57,858 Now, those are slashing tools. 117 00:10:57,883 --> 00:11:01,698 Those are for wounding prey, waiting for it to bleed to death, 118 00:11:01,723 --> 00:11:06,138 and then catching up with it and swallowing large chunks whole. 119 00:11:06,163 --> 00:11:08,938 This animal would've grown to about 3 metres in length 120 00:11:08,963 --> 00:11:10,858 and very fast-moving 121 00:11:10,883 --> 00:11:14,938 and been terrorising the large herbivores of its time. 122 00:11:14,963 --> 00:11:17,658 What a fantastic beast it must have been. 123 00:11:20,363 --> 00:11:22,298 But by the end of the Permian, 124 00:11:22,323 --> 00:11:25,858 along with nearly every other living thing on Earth, 125 00:11:25,883 --> 00:11:28,058 they would be dead. 126 00:11:49,843 --> 00:11:52,698 We're not certain how it started, 127 00:11:52,723 --> 00:11:56,138 but deep inside the ancient Earth, 128 00:11:56,163 --> 00:11:59,378 superheated rock is rising... 129 00:12:01,723 --> 00:12:05,298 ...pushing upwards against the solid outer crust... 130 00:12:09,123 --> 00:12:12,418 ...until it can take no more. 131 00:12:17,043 --> 00:12:18,978 The crust fails. 132 00:12:29,563 --> 00:12:32,938 The landscape physically torn apart, 133 00:12:32,963 --> 00:12:35,378 as lava floods onto the surface... 134 00:12:36,603 --> 00:12:39,698 ...forming great curtains of fire. 135 00:12:44,883 --> 00:12:49,658 This is just the beginning of the most deadly volcanic event 136 00:12:49,683 --> 00:12:51,058 in Earth's history. 137 00:13:01,563 --> 00:13:05,338 We can get clues to what these ancient eruptions were like 138 00:13:05,363 --> 00:13:07,778 by studying modern volcanoes. 139 00:13:15,963 --> 00:13:19,698 This is Tajogaite Volcano, in the Canary Islands, 140 00:13:19,723 --> 00:13:23,618 and in September of 2021, the ground here split 141 00:13:23,643 --> 00:13:28,138 and tonnes of lava, ash and toxic gases exploded, 142 00:13:28,163 --> 00:13:30,738 shaking the entire island. 143 00:13:39,803 --> 00:13:41,578 Over three months, 144 00:13:41,603 --> 00:13:48,498 170 million cubic metres of lava poured onto the surface. 145 00:13:50,963 --> 00:13:54,818 It was the first eruption on the island in 50 years. 146 00:14:02,803 --> 00:14:07,138 More than 7,000 people had to flee their homes. 147 00:14:19,643 --> 00:14:22,978 This volcano spewed out enough lava to fill around 148 00:14:23,003 --> 00:14:26,018 70,000 Olympic-sized swimming pools, 149 00:14:26,043 --> 00:14:29,938 and that lava covered an area around ten square kilometres - 150 00:14:29,963 --> 00:14:32,098 which sounds pretty impressive, 151 00:14:32,123 --> 00:14:38,098 but it's just a teaspoon compared to those at the end of the Permian. 152 00:14:38,123 --> 00:14:40,778 252 million years ago, 153 00:14:40,803 --> 00:14:47,338 around four million cubic kilometres of lava, ash and toxic gases 154 00:14:47,363 --> 00:14:50,938 erupted in a series of volcanic explosions 155 00:14:50,963 --> 00:14:55,018 that went on for 2 million years. 156 00:14:55,043 --> 00:14:59,538 The Permian eruptions were 1,000 times greater than 157 00:14:59,563 --> 00:15:01,618 any witnessed by humans. 158 00:15:03,363 --> 00:15:07,178 And the ancient lava is still with us. 159 00:15:07,203 --> 00:15:09,338 In Northwestern Siberia, 160 00:15:09,363 --> 00:15:13,618 beneath a landscape of swamps and flood plains, 161 00:15:13,643 --> 00:15:18,258 scientists have discovered a colossal lava field, 162 00:15:18,283 --> 00:15:22,778 dated a little over 250 million years old... 163 00:15:25,083 --> 00:15:28,578 ...lava that covers over two-and-a-half million 164 00:15:28,603 --> 00:15:30,098 square kilometres... 165 00:15:32,803 --> 00:15:37,818 ...enough to bury the entire continent of Australia 166 00:15:37,843 --> 00:15:39,818 hundreds of metres deep. 167 00:15:46,203 --> 00:15:53,378 252 million years ago, Northern Pangea was hell on Earth. 168 00:15:57,643 --> 00:16:02,778 Fire fountains blast volcanic material over six miles up 169 00:16:02,803 --> 00:16:04,138 into the atmosphere... 170 00:16:08,043 --> 00:16:11,818 ...burning millions of square miles of forests. 171 00:16:21,523 --> 00:16:25,498 And clouds bloom high into the atmosphere, 172 00:16:25,523 --> 00:16:27,178 blocking out the sun. 173 00:16:32,163 --> 00:16:34,738 Plants wilt and die... 174 00:16:40,003 --> 00:16:42,418 ...ash falls like snow... 175 00:16:46,643 --> 00:16:52,338 ...as vast swathes of Northern Pangea lie in ruins. 176 00:17:01,563 --> 00:17:06,098 These eruptions are on a scale almost beyond imagination. 177 00:17:08,403 --> 00:17:15,338 But lava still only covers less than 1% of Pangea's surface. 178 00:17:15,363 --> 00:17:19,698 And elsewhere, something curious is happening. 179 00:17:24,483 --> 00:17:28,138 A strange haze hangs in the air. 180 00:17:34,723 --> 00:17:38,538 Nutrient-rich volcanic ash and sulphur, 181 00:17:38,563 --> 00:17:44,178 transported thousands of miles, reflect the sun's rays... 182 00:17:45,843 --> 00:17:48,978 ...pushing global temperatures down... 183 00:17:56,043 --> 00:18:01,098 ...and in places, causing a surge of plant life to flourish. 184 00:18:07,283 --> 00:18:09,818 But death is coming. 185 00:18:25,963 --> 00:18:29,258 I've come to an outcrop in Northern Italy, 186 00:18:29,283 --> 00:18:34,978 made of rock that formed at the same time as those ancient eruptions. 187 00:18:38,043 --> 00:18:41,258 It's a fossilised crime scene 188 00:18:41,283 --> 00:18:44,178 with a chilling tale to tell. 189 00:18:46,443 --> 00:18:52,298 Look at this thin, black seam that runs all the way down here. 190 00:18:55,123 --> 00:18:57,378 It looks like coal to me, 191 00:18:57,403 --> 00:19:00,178 which would indicate that at one point... 192 00:19:02,043 --> 00:19:03,618 ...it was full of plant life. 193 00:19:03,643 --> 00:19:05,658 Probably full of lots of other life, too. 194 00:19:07,643 --> 00:19:10,978 Coal is little more than ancient organic matter 195 00:19:11,003 --> 00:19:14,538 that's been subjected to extreme temperatures and pressures 196 00:19:14,563 --> 00:19:16,858 over millions of years. 197 00:19:16,883 --> 00:19:19,378 So, where we find coal today, 198 00:19:19,403 --> 00:19:22,338 we know there was once life. 199 00:19:22,363 --> 00:19:26,218 But the rocks above it here tell an altogether different story. 200 00:19:32,763 --> 00:19:35,818 They're grey, dull, look a bit boring, 201 00:19:35,843 --> 00:19:38,338 a bit of a geological mush. 202 00:19:38,363 --> 00:19:40,538 But that's the point - 203 00:19:40,563 --> 00:19:44,658 because, aside from a few fossil microorganisms, 204 00:19:44,683 --> 00:19:50,338 scientists have found very little evidence of life in these rocks. 205 00:19:50,363 --> 00:19:55,898 So, what they are telling us is that 252 million years ago, 206 00:19:55,923 --> 00:19:59,618 the landscape here was almost devoid of life. 207 00:20:02,203 --> 00:20:08,738 In a geological blink of an eye, almost all life here vanished. 208 00:20:08,763 --> 00:20:12,538 You can't help but feel a certain sense of sadness. 209 00:20:12,563 --> 00:20:15,978 Holding this makes it so tangible. 210 00:20:19,083 --> 00:20:23,298 This was death on an unimaginable scale. 211 00:20:25,003 --> 00:20:29,058 But there's no evidence of lava here at all. 212 00:20:30,803 --> 00:20:34,298 When these rocks were laid down in this part of Italy, 213 00:20:34,323 --> 00:20:38,178 they were thousands of miles away from the eruptions in the north - 214 00:20:38,203 --> 00:20:41,858 certainly too far away for any direct impacts. 215 00:20:41,883 --> 00:20:44,498 But what's interesting is that geologists 216 00:20:44,523 --> 00:20:49,178 have found this line of death all over the planet - 217 00:20:49,203 --> 00:20:52,218 China, Australia, South Africa. 218 00:20:52,243 --> 00:20:55,898 And no matter how far away from the lava fields, 219 00:20:55,923 --> 00:20:58,538 there's a deathly silence in the fossil record. 220 00:21:01,003 --> 00:21:06,818 The question is, what could have killed this many creatures? 221 00:21:06,843 --> 00:21:11,778 What could have wiped out almost all life on Earth? 222 00:21:31,443 --> 00:21:35,218 Something more than lava was emerging from the Earth 223 00:21:35,243 --> 00:21:36,938 in Northern Pangea. 224 00:21:41,803 --> 00:21:47,138 Billions of tonnes of gases are injected high into the atmosphere. 225 00:21:56,003 --> 00:21:59,138 Water vapour, sulphur dioxide... 226 00:22:01,003 --> 00:22:05,978 ...but primarily a gas we all know too well - 227 00:22:06,003 --> 00:22:09,658 the greenhouse gas carbon dioxide. 228 00:22:29,963 --> 00:22:33,298 We're all becoming depressingly familiar with what happens 229 00:22:33,323 --> 00:22:39,018 when you pump huge quantities of carbon dioxide into the atmosphere. 230 00:22:39,043 --> 00:22:41,298 It's an experiment we've been running ourselves 231 00:22:41,323 --> 00:22:43,418 for more than 100 years. 232 00:22:43,443 --> 00:22:47,738 And the more the CO2, the more the heat is locked in, 233 00:22:47,763 --> 00:22:50,658 and the hotter our Earth becomes. 234 00:22:51,803 --> 00:22:55,298 Global warming isn't a localised effect. 235 00:22:55,323 --> 00:22:57,858 The whole planet feels the burn. 236 00:22:59,123 --> 00:23:00,698 Here we are, yeah, dead ahead. 237 00:23:00,723 --> 00:23:02,778 No creature is safe. 238 00:23:02,803 --> 00:23:06,058 You've got a little feeding party taking place here at the moment. 239 00:23:06,083 --> 00:23:08,258 Oh, look at that! 240 00:23:09,283 --> 00:23:11,658 Oh, yes, yes! 241 00:23:15,083 --> 00:23:18,138 Sorry to be a child, but it's always... 242 00:23:18,163 --> 00:23:20,658 Oh, oh, oh, oh! 243 00:23:20,683 --> 00:23:23,058 Oh, I just saw it catch a fish! 244 00:23:23,083 --> 00:23:24,138 Oh! 245 00:23:25,683 --> 00:23:28,018 There are several species here. 246 00:23:28,043 --> 00:23:29,458 Bottlenose... 247 00:23:31,683 --> 00:23:35,698 ...common, rough tooth, spotted. 248 00:23:37,363 --> 00:23:41,498 And dolphins, of course, can live in much warmer waters than these. 249 00:23:41,523 --> 00:23:44,098 So, you might imagine they're not the sorts of creatures 250 00:23:44,123 --> 00:23:47,218 that would be harmed by global warming. 251 00:23:47,243 --> 00:23:51,378 But sadly, I've got to tell you, these dolphins are in trouble. 252 00:23:57,803 --> 00:24:02,538 It's not always the temperature that poses a danger to life. 253 00:24:02,563 --> 00:24:05,858 In fact, for some, the heat is a blessing. 254 00:24:08,163 --> 00:24:10,778 Let's see what I've managed to catch. 255 00:24:12,243 --> 00:24:14,578 Wow, rather a lot. 256 00:24:14,603 --> 00:24:18,778 This mass of detritus here is plankton, 257 00:24:18,803 --> 00:24:21,978 much of it phytoplankton, algae. 258 00:24:22,003 --> 00:24:25,378 Now, most of the organisms wouldn't hurt anything, 259 00:24:25,403 --> 00:24:28,818 but there is one species, Karenia Brevis - 260 00:24:28,843 --> 00:24:31,578 well, that's an algae with a superpower. 261 00:24:31,603 --> 00:24:34,018 You see, when the water warms up here, 262 00:24:34,043 --> 00:24:37,458 it goes into a reproductive frenzy, 263 00:24:37,483 --> 00:24:41,058 producing blooms many hundreds of times greater 264 00:24:41,083 --> 00:24:42,978 than it normally would. 265 00:24:43,003 --> 00:24:45,218 But what's good for the algae, it turns out, 266 00:24:45,243 --> 00:24:47,778 is not so good for the dolphins. 267 00:24:47,803 --> 00:24:52,538 Because recent research has shown that this is extremely toxic. 268 00:24:52,563 --> 00:24:54,938 So, the small fish eat the algae, 269 00:24:54,963 --> 00:24:57,018 the bigger fish eat the small fish, 270 00:24:57,043 --> 00:24:59,658 the dolphins the larger fish. 271 00:24:59,683 --> 00:25:02,858 And this organism has been implicated 272 00:25:02,883 --> 00:25:05,738 in the deaths of dozens of dolphins, 273 00:25:05,763 --> 00:25:08,178 found dead floating in the sea here. 274 00:25:10,203 --> 00:25:14,578 Rising temperatures affect different parts of the food chain 275 00:25:14,603 --> 00:25:16,738 in different ways, 276 00:25:16,763 --> 00:25:20,538 throwing ecosystems out of balance... 277 00:25:20,563 --> 00:25:23,338 ...often with deadly results. 278 00:25:24,883 --> 00:25:27,178 You see, when it comes to global warming, 279 00:25:27,203 --> 00:25:30,298 it's not the actual heat that kills those creatures. 280 00:25:30,323 --> 00:25:34,498 It's the increases or decreases in plant or animal populations 281 00:25:34,523 --> 00:25:40,298 which disrupt those long-evolved, stable, beautiful ecosystems. 282 00:25:40,323 --> 00:25:45,898 Death by global warming is not short, sharp, and painless. 283 00:25:45,923 --> 00:25:48,658 It's prolonged and torturous. 284 00:26:06,683 --> 00:26:09,658 As the temperatures rise across Pangea... 285 00:26:16,323 --> 00:26:18,378 ...trees begin to die. 286 00:26:33,483 --> 00:26:37,178 Holes appear in the once-thick canopy, 287 00:26:37,203 --> 00:26:40,218 bathing the ground in sunlight. 288 00:26:45,563 --> 00:26:48,138 For some, it's an opportunity. 289 00:26:49,163 --> 00:26:51,178 Weed-like plants flourish, 290 00:26:51,203 --> 00:26:53,458 like spore-bearing lycophytes. 291 00:26:56,843 --> 00:26:59,298 No longer struggling in the shadows, 292 00:26:59,323 --> 00:27:02,018 in times of stress, they thrive. 293 00:27:05,883 --> 00:27:08,698 And foreign species appear. 294 00:27:08,723 --> 00:27:13,298 Woody, seed-bearing cycads that once only grew in the tropics 295 00:27:13,323 --> 00:27:16,018 are now abundant closer to the Poles. 296 00:27:21,203 --> 00:27:25,778 Surprisingly, some areas are now more diverse 297 00:27:25,803 --> 00:27:28,058 than before the warming began. 298 00:27:29,363 --> 00:27:33,618 But this is an ecosystem out of balance. 299 00:27:36,883 --> 00:27:39,018 A few more degrees' warming, 300 00:27:39,043 --> 00:27:41,738 and the living world will crumble. 301 00:27:56,923 --> 00:28:00,578 But then something strange happens. 302 00:28:03,163 --> 00:28:06,338 Red hot rivers of lava... 303 00:28:06,363 --> 00:28:08,978 ...turn to solid rock. 304 00:28:10,963 --> 00:28:13,738 Just as quickly as they started, 305 00:28:13,763 --> 00:28:16,898 the eruptions fall silent. 306 00:28:30,083 --> 00:28:33,218 The CO2 released from the Permian lavas 307 00:28:33,243 --> 00:28:36,498 likely dwarfed human emissions to date. 308 00:28:38,923 --> 00:28:43,138 But even that may have been just part of the story. 309 00:28:47,043 --> 00:28:48,858 These eruptions would have produced 310 00:28:48,883 --> 00:28:51,498 an inordinate amount of carbon dioxide - 311 00:28:51,523 --> 00:28:53,138 gig a tons of the stuff, 312 00:28:53,163 --> 00:28:55,978 certainly enough to manifest some global warming, 313 00:28:56,003 --> 00:29:00,018 perhaps in the realm of an increase of 5 or 6 degrees Celsius, 314 00:29:00,043 --> 00:29:01,898 something like that. 315 00:29:01,923 --> 00:29:04,938 Now, that's a substantial amount of heating, 316 00:29:04,963 --> 00:29:08,538 but it's not significant enough to account for all of the deaths 317 00:29:08,563 --> 00:29:10,978 that we see in the fossil record. 318 00:29:11,003 --> 00:29:13,218 Yes, there would have been extinctions, 319 00:29:13,243 --> 00:29:16,938 but not 90% of all life on Earth. 320 00:29:28,843 --> 00:29:32,778 The effects of carbon dioxide can be lethal. 321 00:29:32,803 --> 00:29:36,298 But some scientists think there was another killer. 322 00:29:39,563 --> 00:29:42,538 The volcanism hadn't stopped. 323 00:29:42,563 --> 00:29:46,618 It had just entered a terrifying new phase. 324 00:29:49,523 --> 00:29:52,098 Beneath the desolate lava field... 325 00:29:53,123 --> 00:29:56,898 ...hot magma still flows, 326 00:29:56,923 --> 00:30:00,538 forming great reservoirs underground... 327 00:30:00,563 --> 00:30:04,698 ...and slowly baking the Earth's crust. 328 00:30:17,723 --> 00:30:20,298 The rocks underground were older - 329 00:30:20,323 --> 00:30:24,178 hundreds of millions of years older than the land above. 330 00:30:24,203 --> 00:30:26,418 And amongst them, 331 00:30:26,443 --> 00:30:29,578 there was plenty of this stuff - 332 00:30:29,603 --> 00:30:33,098 coal and other rocks rich in carbon. 333 00:30:33,123 --> 00:30:36,218 Now, what happens when magma meets coal? 334 00:30:36,243 --> 00:30:42,058 Well, the coal burns, releasing yet more dangerous carbon dioxide. 335 00:30:42,083 --> 00:30:44,018 But that was just the half of it. 336 00:30:44,043 --> 00:30:46,618 You see, it wasn't just coal. 337 00:30:46,643 --> 00:30:50,338 There was also lots of salt. 338 00:30:50,363 --> 00:30:56,578 And salt like this can form when ancient lakes and seas dry up. 339 00:30:56,603 --> 00:30:59,658 And when magma comes into contact with salt, 340 00:30:59,683 --> 00:31:01,938 things get really nasty. 341 00:31:04,643 --> 00:31:06,938 The salt begins to bake, 342 00:31:06,963 --> 00:31:12,338 releasing toxic halogen gases rich in bromine and chlorine - 343 00:31:12,363 --> 00:31:17,178 archenemies of the Earth's fragile ozone layer, 344 00:31:17,203 --> 00:31:23,698 that thin layer that protects us from the sun's most harmful rays. 345 00:31:23,723 --> 00:31:28,018 So, what I'm trying to say here is that the magma had found its way 346 00:31:28,043 --> 00:31:32,458 into the worst possible place on the planet. 347 00:31:32,483 --> 00:31:35,018 It had created a time bomb. 348 00:31:41,363 --> 00:31:45,258 That magma begins to heat up the coal and salt 349 00:31:45,283 --> 00:31:48,818 to a temperature of 800 degrees Celsius. 350 00:31:53,163 --> 00:31:56,338 A poisonous cocktail of gases begins to build... 351 00:32:03,363 --> 00:32:07,018 ...until the land above can take no more. 352 00:32:40,243 --> 00:32:43,178 More CO2 floods the atmosphere, 353 00:32:43,203 --> 00:32:45,898 pushing global temperatures even higher. 354 00:32:48,163 --> 00:32:53,578 But this time, there were also those toxic halogen gases. 355 00:33:01,243 --> 00:33:06,378 We've seen the Earth's ozone layer damaged in recent history, 356 00:33:06,403 --> 00:33:11,338 when artificial chemicals created a so-called ozone hole. 357 00:33:12,843 --> 00:33:15,858 But in the Permian, the halogens may have eroded 358 00:33:15,883 --> 00:33:18,618 the ozone layer away entirely... 359 00:33:21,323 --> 00:33:26,098 ...bathing all life in deadly UV radiation. 360 00:33:28,163 --> 00:33:31,818 Scientists have noticed something strange going on with the pollen 361 00:33:31,843 --> 00:33:34,098 at the end of the Permian. 362 00:33:34,123 --> 00:33:35,858 Take a look at this. 363 00:33:35,883 --> 00:33:41,818 This is a highly-magnified image of a modern pine pollen grain. 364 00:33:41,843 --> 00:33:44,578 And you can see it's got two essential parts to its structure - 365 00:33:44,603 --> 00:33:47,338 the central circular part here, the corpus, 366 00:33:47,363 --> 00:33:49,658 and then these winged sacchi. 367 00:33:49,683 --> 00:33:53,618 These are wind-pollinated pollen species, 368 00:33:53,643 --> 00:33:56,098 and these help it float through the air. 369 00:33:56,123 --> 00:33:58,458 But have a look at this. 370 00:33:58,483 --> 00:34:01,938 This is an image of a fossilised coniferous pollen grain 371 00:34:01,963 --> 00:34:04,098 from the time of those eruptions. 372 00:34:04,123 --> 00:34:07,778 It's got three of these wing structures. 373 00:34:07,803 --> 00:34:10,738 This one has four. 374 00:34:10,763 --> 00:34:14,818 These pollen grains are malformed, misshapen and, in fact, 375 00:34:14,843 --> 00:34:16,898 if you look at this last one, 376 00:34:16,923 --> 00:34:20,738 this appear to have been in the process of dividing, 377 00:34:20,763 --> 00:34:23,178 but somehow it's failed. 378 00:34:23,203 --> 00:34:26,258 These are mutant pollen grains, 379 00:34:26,283 --> 00:34:29,538 and it's thought that the mutation was caused by 380 00:34:29,563 --> 00:34:32,378 the excessive UV radiation - 381 00:34:32,403 --> 00:34:38,578 evidence that those gases had really damaged the Earth's ozone layer. 382 00:34:38,603 --> 00:34:40,778 Now, other theories are available. 383 00:34:40,803 --> 00:34:43,338 Others believe that, in fact, it was acid rain 384 00:34:43,363 --> 00:34:47,978 that caused these mutations, or merely the extreme heat. 385 00:34:48,003 --> 00:34:50,098 But whatever the cause, 386 00:34:50,123 --> 00:34:54,818 what's clear is that at this point, life was on the brink. 387 00:35:10,283 --> 00:35:14,938 At first glance, it seems nothing has changed. 388 00:35:14,963 --> 00:35:18,298 But this already fragile ecosystem 389 00:35:18,323 --> 00:35:23,138 has taken a lethal dose of UV radiation. 390 00:35:23,163 --> 00:35:26,818 Healthy-looking plants are now sterile. 391 00:35:29,403 --> 00:35:33,218 As individuals die, they aren't replaced. 392 00:35:37,843 --> 00:35:42,338 Once-lush forests become ravaged wastelands. 393 00:35:49,443 --> 00:35:54,098 The collapse in the oceans is even more dramatic. 394 00:35:54,123 --> 00:35:57,018 Carbon dioxide reacts with sea water, 395 00:35:57,043 --> 00:35:59,378 which begins to turn to acid. 396 00:36:04,323 --> 00:36:07,218 And oxygen levels plummet - 397 00:36:07,243 --> 00:36:10,458 in some places, dropping to zero. 398 00:36:13,363 --> 00:36:15,938 Algae blooms across the planet. 399 00:36:17,723 --> 00:36:20,898 As it decomposes, it poisons the ocean 400 00:36:20,923 --> 00:36:23,858 with toxic hydrogen sulphide... 401 00:36:33,843 --> 00:36:40,218 ...until the seafloor becomes a foetid bed of slime. 402 00:36:44,043 --> 00:36:47,538 Sulphurous tides lap barren shores, 403 00:36:47,563 --> 00:36:50,898 and a smell like rotten eggs hangs in the air. 404 00:36:53,243 --> 00:36:57,978 The Earth's rich complexity has vanished, 405 00:36:58,003 --> 00:37:00,218 seemingly for good. 406 00:37:13,323 --> 00:37:15,418 It's been called many things - 407 00:37:15,443 --> 00:37:19,778 the Great Dying, the mother of all mass extinction events 408 00:37:19,803 --> 00:37:23,778 or, simply, when life nearly died. 409 00:37:23,803 --> 00:37:26,938 The details are still a bit hazy. 410 00:37:26,963 --> 00:37:30,618 Was it a single short, sharp, giant catastrophe, 411 00:37:30,643 --> 00:37:34,018 or a wave of smaller catastrophes? 412 00:37:34,043 --> 00:37:37,138 To what extent did the extinctions occur on land 413 00:37:37,163 --> 00:37:40,258 versus extinctions in the water? 414 00:37:40,283 --> 00:37:42,538 The fossil record is patchy, 415 00:37:42,563 --> 00:37:44,818 so there's plenty of room for academic debate. 416 00:37:44,843 --> 00:37:48,978 But the one thing that almost everyone agrees upon 417 00:37:49,003 --> 00:37:52,778 is that these ancient eruptions caused extinctions 418 00:37:52,803 --> 00:37:55,738 on an unprecedented scale. 419 00:37:55,763 --> 00:38:01,578 Figures frequently cited suggest that 70% of land vertebrates 420 00:38:01,603 --> 00:38:05,858 and 96% of marine life 421 00:38:05,883 --> 00:38:09,498 vanished off the face of the Earth forever. 422 00:38:12,003 --> 00:38:15,338 By the time the eruptions finally stop, 423 00:38:15,363 --> 00:38:20,538 the average global temperature has risen by over 10 degrees Celsius. 424 00:38:23,243 --> 00:38:29,578 Vast areas of the Earth's surface are completely uninhabitable, 425 00:38:29,603 --> 00:38:33,178 and nearly all species are gone. 426 00:38:41,843 --> 00:38:47,058 The End-Permian extinction has a virtually undisputed claim 427 00:38:47,083 --> 00:38:51,618 to being the worst moment in the history of the Earth. 428 00:38:52,803 --> 00:38:57,418 But from the ashes, there was a glimmer of hope, 429 00:38:57,443 --> 00:39:00,338 because life had survived somewhere. 430 00:39:00,363 --> 00:39:04,698 It must have. Otherwise, we wouldn't be here. 431 00:39:06,243 --> 00:39:10,978 In a way, we are all survivors of the Great Dying. 432 00:39:11,003 --> 00:39:17,498 You see, every living organism on the planet has an ancient ancestor, 433 00:39:17,523 --> 00:39:21,178 perhaps millions, perhaps billions of generations back, 434 00:39:21,203 --> 00:39:24,618 that not only survived that mass extinction event 435 00:39:24,643 --> 00:39:28,338 but then went on to prosper in the aftermath 436 00:39:28,363 --> 00:39:31,418 and then to repopulate the Earth. 437 00:39:34,483 --> 00:39:38,218 The Great Dying may have been the end of one world, 438 00:39:38,243 --> 00:39:42,018 but it was also the beginning of a new one. 439 00:39:52,963 --> 00:39:57,018 The Triassic Earth is a shadow of its former self. 440 00:40:01,803 --> 00:40:04,858 Many creatures seek refuge underground... 441 00:40:10,843 --> 00:40:13,658 ...sheltering from blistering temperatures 442 00:40:13,683 --> 00:40:16,018 and lethal UV radiation. 443 00:40:21,443 --> 00:40:26,738 Above ground, a single plant species dominates the landscape. 444 00:40:28,003 --> 00:40:32,258 Pleuromeia - a weed-like plant lucky enough to make it 445 00:40:32,283 --> 00:40:36,858 through the apocalypse and find itself with few competitors. 446 00:40:40,883 --> 00:40:43,818 It helps provide sustenance for the cockroaches, 447 00:40:43,843 --> 00:40:46,658 who also made it through unscathed. 448 00:40:51,683 --> 00:40:54,938 But just because the eruptions have stopped 449 00:40:54,963 --> 00:40:58,978 doesn't mean that life's troubles are over. 450 00:41:11,963 --> 00:41:15,618 The Early Triassic was dominated by extreme heat. 451 00:41:15,643 --> 00:41:18,978 The fossil record shows us that ocean temperatures could have been 452 00:41:19,003 --> 00:41:21,818 up to 14 degrees centigrade warmer 453 00:41:21,843 --> 00:41:24,178 than they were prior to the eruptions. 454 00:41:24,203 --> 00:41:28,538 In some places, the water was as warm as it is in a hot tub - 455 00:41:28,563 --> 00:41:31,458 too extreme for most marine organisms. 456 00:41:35,323 --> 00:41:38,778 And on land, things weren't faring much better. 457 00:41:38,803 --> 00:41:42,858 There were probably heatwaves of up to 60 degrees centigrade - 458 00:41:42,883 --> 00:41:47,298 a temperature that would have seriously inhibited photosynthesis. 459 00:41:47,323 --> 00:41:52,898 In fact, for the 10 million years following the mass extinction event, 460 00:41:52,923 --> 00:41:58,098 we see no significant coal reserves laid down anywhere on Earth. 461 00:41:58,123 --> 00:42:02,218 There simply weren't enough trees. 462 00:42:02,243 --> 00:42:07,218 For life to bounce back, the planet needed to cool down. 463 00:42:14,763 --> 00:42:18,618 In normal times, the Earth can cool itself - 464 00:42:18,643 --> 00:42:21,938 over thousands of years, removing carbon dioxide 465 00:42:21,963 --> 00:42:26,258 from the atmosphere, in part through reacting with rainwater. 466 00:42:27,563 --> 00:42:31,738 But vast areas of Pangea are desert. 467 00:42:31,763 --> 00:42:33,378 Little rain falls. 468 00:42:36,683 --> 00:42:41,218 So, it takes millions of years for temperatures to drop. 469 00:42:52,683 --> 00:42:56,658 And even then, recovery is slow. 470 00:43:00,763 --> 00:43:05,738 The living world's struggling to regain the diversity it once knew. 471 00:43:16,763 --> 00:43:19,338 But salvation was coming. 472 00:43:24,963 --> 00:43:31,218 High in the Dolomite Mountains is evidence for a bizarre event, 473 00:43:31,243 --> 00:43:34,778 one that may have helped life rebound. 474 00:43:38,123 --> 00:43:40,018 Look at this. 475 00:43:40,043 --> 00:43:43,098 Absolutely stunning. 476 00:43:43,123 --> 00:43:48,898 And these mountains were formed very shortly after the extinction event, 477 00:43:48,923 --> 00:43:52,258 and they're made up of sedimentary rock - 478 00:43:52,283 --> 00:43:55,138 layers of sediment on top of one another, 479 00:43:55,163 --> 00:43:58,778 each corresponding to a time in the Earth's history. 480 00:43:58,803 --> 00:44:01,058 The oldest rocks are at the bottom, 481 00:44:01,083 --> 00:44:03,298 around 238 million years old. 482 00:44:03,323 --> 00:44:05,098 The youngest at the top, 483 00:44:05,123 --> 00:44:08,058 about 200 million years old. 484 00:44:08,083 --> 00:44:11,218 Now, you might imagine that if we wanted to uncover the secrets 485 00:44:11,243 --> 00:44:14,018 in these rocks, we'd take some, break them open 486 00:44:14,043 --> 00:44:16,938 and look for some details - but not here. 487 00:44:16,963 --> 00:44:21,738 The secrets in these rocks are held in plain view. 488 00:44:21,763 --> 00:44:25,138 The key is the shape of the mountains. 489 00:44:25,163 --> 00:44:30,058 It hints at a planetary intervention that, just a few decades ago, 490 00:44:30,083 --> 00:44:33,258 we had no idea happened. 491 00:44:33,283 --> 00:44:38,258 Look, it starts steep at the bottom, rises sharply, 492 00:44:38,283 --> 00:44:40,578 and then there's a shallow shelf, 493 00:44:40,603 --> 00:44:44,218 and then it rises steeply again to the peak, 494 00:44:44,243 --> 00:44:46,298 currently in the clouds. 495 00:44:46,323 --> 00:44:50,818 But the bit that we're interested in is that shallow slope, 496 00:44:50,843 --> 00:44:56,218 which corresponds to about 2 million years in the Earth's history, 497 00:44:56,243 --> 00:44:59,098 and to a very strange period of time. 498 00:45:00,883 --> 00:45:05,298 This shallow slope is evidence of a softer rock type 499 00:45:05,323 --> 00:45:07,698 that's been eroded over the years. 500 00:45:10,123 --> 00:45:11,418 Here we go. 501 00:45:15,483 --> 00:45:18,178 This is a lump of sandstone. 502 00:45:18,203 --> 00:45:20,978 It's a soft sedimentary rock. 503 00:45:21,003 --> 00:45:23,138 The key is in the name. 504 00:45:23,163 --> 00:45:27,498 It's made up of sediments, like sand, which wash off of the land, 505 00:45:27,523 --> 00:45:30,978 down into the rivers and then down into the sea. 506 00:45:31,003 --> 00:45:34,458 So, what I'm holding here is evidence of rain - 507 00:45:34,483 --> 00:45:36,098 rather a lot of rain, 508 00:45:36,123 --> 00:45:40,698 because in places, this layer is about 80 metres deep. 509 00:45:42,403 --> 00:45:44,658 Sandstone is a common rock, 510 00:45:44,683 --> 00:45:47,658 but scientists have discovered similar layers 511 00:45:47,683 --> 00:45:50,098 right across the planet, 512 00:45:50,123 --> 00:45:55,098 leading some to think this was the result of a global deluge. 513 00:45:56,643 --> 00:45:59,498 Now, we're not precisely sure why it started. 514 00:45:59,523 --> 00:46:02,378 It could have been underwater volcanic activity 515 00:46:02,403 --> 00:46:04,418 disrupting the water cycle. 516 00:46:04,443 --> 00:46:06,978 But at some point in the Triassic, 517 00:46:07,003 --> 00:46:11,658 a time famed for being excruciatingly hot and arid, 518 00:46:11,683 --> 00:46:13,858 it started to rain. 519 00:46:13,883 --> 00:46:17,458 And, boy, did it rain - because that rain 520 00:46:17,483 --> 00:46:22,658 defined the Earth's climate for almost 2 million years. 521 00:46:36,283 --> 00:46:40,738 18 million years after the mass extinction, 522 00:46:40,763 --> 00:46:42,458 the heavens open... 523 00:46:44,843 --> 00:46:48,698 ...a sudden increase in rainfall across Pangea. 524 00:46:51,243 --> 00:46:53,858 The rain causes more extinctions... 525 00:46:55,763 --> 00:46:58,138 ...but the planet is reborn. 526 00:47:06,643 --> 00:47:09,578 Where arid shrub land once stood... 527 00:47:11,123 --> 00:47:13,778 ...lush forests now grow. 528 00:47:15,443 --> 00:47:19,658 It's been called the greening of Triassic Earth, 529 00:47:19,683 --> 00:47:24,218 and it marked the beginning of much of the life we know today. 530 00:47:36,243 --> 00:47:38,618 There were new species of crocodiles... 531 00:47:40,763 --> 00:47:42,698 ...amphibians... 532 00:47:45,923 --> 00:47:49,458 ...even early ancestors of modern mammals. 533 00:47:59,843 --> 00:48:03,178 But the mammals would have to wait in the wings. 534 00:48:03,203 --> 00:48:07,418 Other creatures were set to inherit this renewed world. 535 00:48:14,643 --> 00:48:15,938 Look at this. 536 00:48:17,643 --> 00:48:19,338 See this impression in the rock here? 537 00:48:19,363 --> 00:48:24,458 Look, there are one, two, three toes. 538 00:48:24,483 --> 00:48:27,258 This is a dinosaur footprint, 539 00:48:27,283 --> 00:48:30,858 and I love the fact that I can put my hand 540 00:48:30,883 --> 00:48:33,898 where a dinosaur once put its foot. 541 00:48:33,923 --> 00:48:37,498 Now, whether dinosaurs existed before the rains, we can't be sure. 542 00:48:37,523 --> 00:48:40,738 If they did, it was only as an obscure group 543 00:48:40,763 --> 00:48:42,538 in the south of Pangea. 544 00:48:42,563 --> 00:48:45,138 But in the millions of years after the rains, 545 00:48:45,163 --> 00:48:46,658 they certainly prospered. 546 00:48:46,683 --> 00:48:52,938 In some places, 90% of the vertebrate fossils are dinosaurs. 547 00:48:52,963 --> 00:48:55,138 Why did they suddenly do so well? 548 00:48:55,163 --> 00:48:56,818 Well, it could be down to the food. 549 00:48:56,843 --> 00:49:00,898 They could use it more efficiently to grow bigger more quickly. 550 00:49:00,923 --> 00:49:03,058 But whatever the reason, 551 00:49:03,083 --> 00:49:06,138 dinosaurs went on to dominate the Earth. 552 00:49:07,243 --> 00:49:08,418 I love this! 553 00:49:15,083 --> 00:49:17,338 By the end of the Triassic, 554 00:49:17,363 --> 00:49:21,498 the stage is set for the reptiles to rule supreme. 555 00:49:25,883 --> 00:49:31,858 This will be their world for the next 140 million years. 556 00:49:35,323 --> 00:49:38,378 The age of the dinosaurs is dawning. 557 00:49:51,323 --> 00:49:54,858 In one way, the End-Permian extinction 558 00:49:54,883 --> 00:49:59,218 exposed the fundamental fragility of life. 559 00:49:59,243 --> 00:50:02,298 Countless species of plants and animals were wiped out 560 00:50:02,323 --> 00:50:04,258 by those volcanic eruptions, 561 00:50:04,283 --> 00:50:07,418 and it took millions of years to recover. 562 00:50:07,443 --> 00:50:11,218 But perhaps the event also taught us another lesson 563 00:50:11,243 --> 00:50:13,778 about the tenacity of life - 564 00:50:13,803 --> 00:50:18,178 because the living world did bounce back, to be just as complex 565 00:50:18,203 --> 00:50:22,538 and just as beautiful, in fact, maybe even more so. 566 00:50:29,323 --> 00:50:33,098 But there's a big unspoken question here. 567 00:50:33,123 --> 00:50:36,978 For over 100 years, we've been pumping carbon dioxide into 568 00:50:37,003 --> 00:50:41,538 the atmosphere and watching as global temperatures creep up. 569 00:50:43,283 --> 00:50:49,658 So, what can the mass extinction 252 million years ago teach us 570 00:50:49,683 --> 00:50:52,618 about our own climate change event? 571 00:50:58,403 --> 00:51:03,138 I think the big lesson we've just learned is that the living world 572 00:51:03,163 --> 00:51:05,538 will ultimately be fine. 573 00:51:05,563 --> 00:51:09,698 Even if we don't address our climate and biodiversity crisis, 574 00:51:09,723 --> 00:51:13,378 if we burn every last lump of coal and drop of oil, 575 00:51:13,403 --> 00:51:16,898 if we leave this place as a complete hellscape, 576 00:51:16,923 --> 00:51:21,298 whilst we might perish, life will bounce back, 577 00:51:21,323 --> 00:51:25,418 and this will all be beautiful again - 578 00:51:25,443 --> 00:51:27,178 which begs the question, 579 00:51:27,203 --> 00:51:30,978 "Should we bother to preserve and protect it?" 580 00:51:31,003 --> 00:51:35,578 Well, that extinction event 252 million years ago 581 00:51:35,603 --> 00:51:37,658 was part of a planetary process. 582 00:51:37,683 --> 00:51:40,338 It was a chance volcanic eruption. 583 00:51:43,283 --> 00:51:45,178 Think of all of that suffering. 584 00:51:45,203 --> 00:51:47,298 Think of all of that wastage. 585 00:51:49,963 --> 00:51:54,258 Do we want those sorts of extinctions on our conscience? 586 00:51:55,923 --> 00:51:57,138 I don't think so. 587 00:52:16,323 --> 00:52:20,898 In this episode, we saw how an Earth-shattering eruption 588 00:52:20,923 --> 00:52:24,178 destroyed almost all life on Earth. 589 00:52:29,083 --> 00:52:31,738 This is the closest our planet has ever been 590 00:52:31,763 --> 00:52:33,418 to going back to square one. 591 00:52:35,683 --> 00:52:37,818 To understand the scale of the event, 592 00:52:37,843 --> 00:52:41,338 scientists mapped the Permian lava fields of Russia - 593 00:52:41,363 --> 00:52:44,378 known as the Siberian Traps. 594 00:52:46,283 --> 00:52:49,978 I have actually been to the Siberian Traps 595 00:52:50,003 --> 00:52:52,778 and flown helicopters. 596 00:52:54,163 --> 00:52:58,498 The helicopter is right, mm.. there. 597 00:52:58,523 --> 00:53:02,578 Floated on boats, hiked, 598 00:53:02,603 --> 00:53:07,338 ridden on trains all over Arctic Siberia, 599 00:53:07,363 --> 00:53:10,578 looking for remnants of the Siberian Traps. 600 00:53:11,963 --> 00:53:17,618 And these lava flows go distances that boggle the mind. 601 00:53:17,643 --> 00:53:23,258 The 1 million cubic miles that we have is probably a minimum number, 602 00:53:23,283 --> 00:53:26,378 and it's a minimum because not all of the rocks 603 00:53:26,403 --> 00:53:28,538 are exposed at the surface. 604 00:53:28,563 --> 00:53:31,858 We also sampled the rocks of the Siberian Traps 605 00:53:31,883 --> 00:53:34,938 with sledgehammers and rock hammers 606 00:53:34,963 --> 00:53:36,738 and a lot of hard work. 607 00:53:38,843 --> 00:53:41,738 The rock samples were key to understanding 608 00:53:41,763 --> 00:53:45,738 why the Earth's climate changed so dramatically. 609 00:53:45,763 --> 00:53:48,818 When magma comes up from deep within the Earth, 610 00:53:48,843 --> 00:53:51,898 it has gases dissolved in it, 611 00:53:51,923 --> 00:53:55,738 gases like carbon dioxide and sulphur dioxide. 612 00:53:55,763 --> 00:53:58,858 These gases come out into bubbles, 613 00:53:58,883 --> 00:54:03,738 a bit like when you take the lid off a soda bottle and it fizzes. 614 00:54:03,763 --> 00:54:08,538 But these gases told a contradictory story. 615 00:54:08,563 --> 00:54:12,058 Sulphur dioxide and carbon dioxide have opposite effects 616 00:54:12,083 --> 00:54:13,938 on the Earth's atmosphere. 617 00:54:13,963 --> 00:54:17,538 Sulphur dioxide reflects sunlight back into outer space, 618 00:54:17,563 --> 00:54:19,178 causing global cooling, 619 00:54:19,203 --> 00:54:21,698 whereas carbon dioxide is a greenhouse gas 620 00:54:21,723 --> 00:54:23,298 and can lead to global warming. 621 00:54:25,803 --> 00:54:29,298 It turns out that different volcanic gases hang around in our atmosphere 622 00:54:29,323 --> 00:54:30,858 for different amounts of time 623 00:54:30,883 --> 00:54:35,178 because of their different chemical properties. 624 00:54:35,203 --> 00:54:37,418 Sulphur dioxide tends to stay in the atmosphere 625 00:54:37,443 --> 00:54:39,618 for a shorter period of time, 626 00:54:39,643 --> 00:54:41,538 because it can get rained out. 627 00:54:42,683 --> 00:54:45,818 But carbon dioxide can stay in the Earth's atmosphere for hundreds, 628 00:54:45,843 --> 00:54:47,298 if not thousands of years. 629 00:54:48,803 --> 00:54:52,738 Scientists think that heat-trapping carbon dioxide 630 00:54:52,763 --> 00:54:56,578 would have built up in the atmosphere, warming the planet. 631 00:54:59,283 --> 00:55:03,538 And there were other clues in the fossil record. 632 00:55:03,563 --> 00:55:06,258 So, we can measure what temperatures were like in the past 633 00:55:06,283 --> 00:55:08,018 by the study of fossils, 634 00:55:08,043 --> 00:55:10,298 and particularly fossil bone material. 635 00:55:10,323 --> 00:55:11,938 So, when the bone is formed, 636 00:55:11,963 --> 00:55:14,458 it's partly controlled by the temperature. 637 00:55:14,483 --> 00:55:16,938 And so by studying these bones, we're able to see 638 00:55:16,963 --> 00:55:19,378 what the temperatures were like back in the past. 639 00:55:23,243 --> 00:55:29,618 Temperature rises of up to 7 degrees brought a deluge of rainfall. 640 00:55:29,643 --> 00:55:32,938 Known as the Carnian Pluvial Episode, 641 00:55:32,963 --> 00:55:36,858 some scientists think these conditions were essential 642 00:55:36,883 --> 00:55:39,058 to the success of the dinosaurs. 643 00:55:40,443 --> 00:55:45,738 My research suggests that more rain means it's better for the plants. 644 00:55:45,763 --> 00:55:51,138 This era of warm, wet conditions really boosted plant diversity. 645 00:55:51,163 --> 00:55:54,418 More plants equals more insects, more plant-eaters, 646 00:55:54,443 --> 00:55:57,098 and then you get more meat-eaters as well, 647 00:55:57,123 --> 00:55:59,018 and dinosaurs are part of that growth. 648 00:56:01,443 --> 00:56:02,978 So, this is Herrerasaurus. 649 00:56:03,003 --> 00:56:05,578 This is one of the first dinosaurs to appear. 650 00:56:05,603 --> 00:56:08,298 And as you can see by the sharp teeth here, 651 00:56:08,323 --> 00:56:12,058 this was a meat-eater, one of the top predators. 652 00:56:12,083 --> 00:56:16,578 The evidence for this growth is written in the rock record. 653 00:56:16,603 --> 00:56:19,898 The success of the dinosaurs after this event is seen in 654 00:56:19,923 --> 00:56:23,618 just an abundance of their fossils, but also in their sort of indirect 655 00:56:23,643 --> 00:56:27,378 records that they leave in the forms of their footprints as well. 656 00:56:27,403 --> 00:56:29,698 Before the Carnian Pluvial Episode, 657 00:56:29,723 --> 00:56:32,698 dinosaurs and their relatives only made up around 5% of the footprints 658 00:56:32,723 --> 00:56:35,138 at these different fossil sites. 659 00:56:35,163 --> 00:56:38,578 After the Carnian Pluvial Episode, we see a big increase - 660 00:56:38,603 --> 00:56:40,378 it jumps up to 70%. 661 00:56:42,043 --> 00:56:45,258 The explosion in the population of dinosaurs 662 00:56:45,283 --> 00:56:48,738 is a brand-new area of research. 663 00:56:48,763 --> 00:56:51,738 We can see that the ecosystems were changing, 664 00:56:51,763 --> 00:56:53,898 but what actually would've affected the dinosaurs, 665 00:56:53,923 --> 00:56:56,258 what would've caused them to be successful, 666 00:56:56,283 --> 00:56:58,098 we don't know yet. 667 00:56:58,123 --> 00:57:00,058 This is why there's so many palaeontologists 668 00:57:00,083 --> 00:57:01,818 doing active research. 669 00:57:08,283 --> 00:57:09,578 Next time... 670 00:57:13,003 --> 00:57:16,778 ...we journey deeper into the past, 671 00:57:16,803 --> 00:57:20,538 to witness one of the strangest moments in history... 672 00:57:22,443 --> 00:57:25,338 ...a global deep freeze.. 673 00:57:27,003 --> 00:57:29,898 ...that transformed the Earth... 674 00:57:29,923 --> 00:57:31,778 ...into an ice world. 675 00:57:37,043 --> 00:57:39,938 If the Earth could talk, what would it tell us? 676 00:57:39,963 --> 00:57:42,458 Well, the Open University imagine how it might answer 677 00:57:42,483 --> 00:57:43,978 some of our questions. 678 00:57:44,003 --> 00:57:46,578 To experience this interactive presentation, 679 00:57:46,603 --> 00:57:49,098 go to the website on the screen and follow the links 680 00:57:49,123 --> 00:57:50,978 to The Open University.