1 00:00:33,992 --> 00:00:36,286 A Perfect Planet. 2 00:00:41,708 --> 00:00:46,755 There is only one planet in the universe, as far as we know, 3 00:00:46,880 --> 00:00:49,007 where there is life. 4 00:00:49,132 --> 00:00:50,509 The Earth. 5 00:00:50,634 --> 00:00:52,094 Our home. 6 00:00:53,428 --> 00:00:55,973 The perfect planet. 7 00:00:59,226 --> 00:01:02,437 Life here is only possible 8 00:01:02,563 --> 00:01:07,067 because of a unique balance of natural forces. 9 00:01:11,446 --> 00:01:16,201 Energy from the sun powers the living world. 10 00:01:22,791 --> 00:01:27,129 Weather systems transport fresh water around the globe. 11 00:01:32,801 --> 00:01:38,765 And powerful ocean currents circulate life's essential nutrients. 12 00:01:43,186 --> 00:01:45,105 This series will reveal 13 00:01:45,230 --> 00:01:48,108 how these global forces have worked together 14 00:01:48,233 --> 00:01:52,446 to create our planet's fragile life-support system. 15 00:01:56,700 --> 00:02:00,412 One of these forces is so important 16 00:02:00,537 --> 00:02:05,792 that life would never have even started without it. 17 00:02:27,981 --> 00:02:30,609 Across the surface of our planet, 18 00:02:30,734 --> 00:02:34,946 there are over 1,500 active volcanoes. 19 00:02:46,958 --> 00:02:51,213 This is the most active - Kilauea in Hawaii. 20 00:03:06,561 --> 00:03:12,025 Here, magma - liquid rock from the planet's hot interior - 21 00:03:12,150 --> 00:03:16,071 bursts out through fractures in the Earth's crust. 22 00:03:16,196 --> 00:03:19,950 And it's been flowing for months. 23 00:03:31,086 --> 00:03:34,381 Nothing can stand in the lava's way. 24 00:03:46,017 --> 00:03:49,479 Volcanoes are certainly destructive, 25 00:03:49,604 --> 00:03:53,650 but without these powerful underground forces, 26 00:03:53,775 --> 00:03:56,570 there would be no breathable atmosphere. 27 00:03:58,864 --> 00:04:00,782 No oceans. 28 00:04:06,246 --> 00:04:08,039 No land. 29 00:04:09,958 --> 00:04:11,376 No life. 30 00:04:15,505 --> 00:04:17,507 We can't control volcanoes, 31 00:04:17,632 --> 00:04:21,595 but they're vital for all living things on Planet Earth. 32 00:04:30,270 --> 00:04:34,733 This is Cl Doinyo Lengai in Tanzania. 33 00:04:37,736 --> 00:04:40,322 It's one of Africa's most active volcanoes, 34 00:04:40,447 --> 00:04:45,285 and has erupted over 15 times in the last hundred years. 35 00:04:50,373 --> 00:04:54,127 On its northern flank lies Lake Natron, 36 00:04:54,252 --> 00:04:56,671 400 square miles in extent, 37 00:04:56,797 --> 00:05:01,343 and one of the world's most corrosive bodies of water. 38 00:05:06,223 --> 00:05:08,266 The water wells up from deep below, 39 00:05:08,391 --> 00:05:13,188 carrying such a concentration of chemicals that it can burn skin. 40 00:05:26,952 --> 00:05:29,788 But one animal thrives here. 41 00:05:35,168 --> 00:05:37,587 Volcano birds. 42 00:05:39,297 --> 00:05:44,219 Nearly two million lesser flamingos live in East Africa 43 00:05:44,344 --> 00:05:47,138 and all of them come here to breed. 44 00:05:53,562 --> 00:05:58,316 But they can only nest here when the lake's level drops so far 45 00:05:58,441 --> 00:06:01,444 that in the centre its bed is exposed. 46 00:06:03,738 --> 00:06:06,283 And that rare moment is now. 47 00:06:15,667 --> 00:06:19,462 How they know when the conditions are right is a mystery. 48 00:06:19,588 --> 00:06:24,050 But some have flown thousands of miles to be here. 49 00:06:26,553 --> 00:06:29,556 The flamingos head for the middle of the lake, 50 00:06:29,681 --> 00:06:34,436 where the intense evaporation has created islands of salt. 51 00:06:37,355 --> 00:06:40,901 It's here that the birds build their nests, 52 00:06:41,026 --> 00:06:43,653 over three miles from the lake's edge 53 00:06:43,778 --> 00:06:47,908 and safe from land predators, which are unable to cross 54 00:06:48,033 --> 00:06:50,869 the surrounding moat of caustic soda. 55 00:07:02,380 --> 00:07:05,967 The single egg is laid on a mount of hardened salt 56 00:07:06,092 --> 00:07:08,011 built by the adults, 57 00:07:08,136 --> 00:07:10,805 its height an insurance against 58 00:07:10,931 --> 00:07:12,682 a sudden rise in water level... 59 00:07:14,100 --> 00:07:17,145 which often happens on Lake Natron. 60 00:07:21,858 --> 00:07:24,653 As the centre dries and enlarges, 61 00:07:24,778 --> 00:07:29,157 more and more flamingos arrive to nest on it. 62 00:07:31,117 --> 00:07:33,703 In good years, such as now, 63 00:07:33,828 --> 00:07:36,790 as many as half a million pairs breed here. 64 00:07:47,425 --> 00:07:50,136 After 28 days of incubation, 65 00:07:50,261 --> 00:07:54,599 a chick emerges into Natron's harsh glare. 66 00:07:57,310 --> 00:08:02,857 Here, temperatures can rise to 55 degrees Celsius. 67 00:08:09,197 --> 00:08:13,201 Mother's wing, however, can serve as a sun-shield. 68 00:08:17,872 --> 00:08:21,084 The chick is fed a rich liquid 69 00:08:21,209 --> 00:08:24,170 made of the lake's barely digested algae 70 00:08:24,295 --> 00:08:26,923 and traces of its parent's blood. 71 00:08:35,056 --> 00:08:39,394 After a few days, the chick is strong enough to stretch its legs. 72 00:08:47,110 --> 00:08:52,782 It then joins a growing creche made up of chicks of different ages. 73 00:08:57,037 --> 00:09:01,624 Soon, the need for fresh water will force the infant birds 74 00:09:01,750 --> 00:09:04,461 to trek to springs on the lake's edge... 75 00:09:06,504 --> 00:09:10,008 a journey they have to make on foot, as their flight feathers 76 00:09:10,133 --> 00:09:12,343 have yet to develop. 77 00:09:18,224 --> 00:09:23,063 Every day, the adults fly to these springs to feed. 78 00:09:27,067 --> 00:09:31,154 Here, on the lake's margins, they collect algae that flourish 79 00:09:31,279 --> 00:09:36,409 in the volcanic water - vital food for the flamingos. 80 00:09:44,167 --> 00:09:48,963 It's the algae that turn the flamingos' feathers pink. 81 00:09:49,089 --> 00:09:51,716 It even colours their eyes. 82 00:09:56,513 --> 00:10:00,475 The adults spend most of their day at the springs, 83 00:10:00,600 --> 00:10:04,187 and now their chicks are going to join them there. 84 00:10:18,743 --> 00:10:21,496 No-one wants to get left behind. 85 00:10:27,627 --> 00:10:31,881 It's a three-mile march over razor-sharp flakes of soda 86 00:10:32,006 --> 00:10:34,425 and sticky, caustic mud... 87 00:10:38,054 --> 00:10:42,559 a life-threatening trial, especially for the youngest chicks. 88 00:10:47,939 --> 00:10:51,526 The groups merge into one giant creche. 89 00:11:26,269 --> 00:11:30,315 For some, the challenges are just too great. 90 00:11:33,985 --> 00:11:37,447 Exhaustion overcomes the weakest. 91 00:11:47,832 --> 00:11:51,586 And now there is yet another threat. 92 00:11:56,507 --> 00:11:59,719 Marabou storks. 93 00:11:59,844 --> 00:12:03,139 They have long legs like a flamingo, 94 00:12:03,264 --> 00:12:07,018 but a beak like a Roman sword. 95 00:12:11,439 --> 00:12:16,110 And they are patient, waiting for an easy target. 96 00:12:29,624 --> 00:12:33,253 Their very presence creates panic among the chicks. 97 00:12:39,217 --> 00:12:42,595 The smallest avoid being trampled underfoot 98 00:12:42,720 --> 00:12:45,181 by travelling on the outside of the group. 99 00:12:48,142 --> 00:12:51,896 But that exposes them to attack. 100 00:12:55,775 --> 00:12:58,319 Their only defence is to run. 101 00:13:03,074 --> 00:13:04,951 But you have little chance 102 00:13:05,076 --> 00:13:07,578 when you're barely ankle-high to your pursuer. 103 00:13:42,113 --> 00:13:45,241 Stragglers will almost certainly be taken. 104 00:13:48,369 --> 00:13:53,124 But there comes a point when every stork has had its fill. 105 00:14:07,722 --> 00:14:12,894 This little chick is very lucky. 106 00:14:19,942 --> 00:14:23,738 At last, the youngsters reach the freshwater springs 107 00:14:23,863 --> 00:14:27,658 at the lake's margin to rejoin their parents. 108 00:14:29,494 --> 00:14:34,332 Almost unbelievably, each chick has a unique call 109 00:14:34,457 --> 00:14:37,085 that its parent can recognise. 110 00:14:59,315 --> 00:15:03,694 It's not just lesser flamingos that depend on volcanoes. 111 00:15:06,823 --> 00:15:10,701 Ultimately, so do all living things. 112 00:15:18,000 --> 00:15:20,878 Over 80% of the Earth's surface 113 00:15:21,003 --> 00:15:25,675 is the result of magma bursting up from the molten interior. 114 00:15:34,058 --> 00:15:37,770 The process started four billion years ago 115 00:15:37,895 --> 00:15:40,940 and it still continues today. 116 00:15:45,987 --> 00:15:50,450 When lava cools, it solidifies into rock 117 00:15:50,575 --> 00:15:55,746 and eventually weathers into land that can support life. 118 00:16:03,754 --> 00:16:09,093 All the Galépagos Islands in the Pacific are volcanic, 119 00:16:09,218 --> 00:16:12,638 and Fernandina is the youngest of them... 120 00:16:14,390 --> 00:16:16,225 and still growing. 121 00:16:24,901 --> 00:16:30,323 At its centre, a volcanic crater four miles wide... 122 00:16:32,241 --> 00:16:35,077 and over 800 metres deep. 123 00:16:41,209 --> 00:16:45,880 It seems dormant, but it was erupting only two weeks ago. 124 00:16:52,845 --> 00:16:58,309 Even so, there are some who depend on the heat from this volcano. 125 00:17:04,524 --> 00:17:09,862 A female land iguana, heavy with eggs, approaches the crater's rim. 126 00:17:12,740 --> 00:17:16,160 It took her ten days to climb up here, 127 00:17:16,285 --> 00:17:19,956 but the toughest part of her journey is still ahead. 128 00:17:21,374 --> 00:17:25,044 She's going to descend into the crater itself. 129 00:17:38,349 --> 00:17:42,603 Frequent tremors make the crater walls unstable. 130 00:17:51,696 --> 00:17:54,282 More people have travelled in space 131 00:17:54,407 --> 00:17:58,953 than have visited the bottom of Fernandina's crater. 132 00:18:01,956 --> 00:18:04,250 But instinct drives her on. 133 00:18:07,253 --> 00:18:09,463 The warm volcanic ash on the crater floor 134 00:18:09,589 --> 00:18:14,176 has the perfect temperature for incubating her eggs. 135 00:18:16,512 --> 00:18:19,557 But there are no clear paths down. 136 00:18:21,392 --> 00:18:26,022 Any made last year have been destroyed by rockfalls. 137 00:18:47,376 --> 00:18:50,338 The slope is steep and unstable. 138 00:18:51,797 --> 00:18:56,469 Tumbling rocks quickly become an avalanche. 139 00:19:10,066 --> 00:19:12,693 With the boulders falling down away from her, 140 00:19:12,818 --> 00:19:15,279 she's not in immediate danger. 141 00:19:19,158 --> 00:19:22,244 But behind her, higher up, 142 00:19:22,370 --> 00:19:25,915 two other females have also started the descent. 143 00:19:33,923 --> 00:19:36,217 And now she is in the firing line. 144 00:20:01,200 --> 00:20:03,536 She's safe. 145 00:20:08,749 --> 00:20:11,877 Others before her haven't been so lucky. 146 00:20:15,464 --> 00:20:17,049 But she's undeterred. 147 00:20:45,286 --> 00:20:49,123 At last, after an eight-hour descent, 148 00:20:49,248 --> 00:20:51,709 she reaches the crater floor. 149 00:20:56,005 --> 00:21:00,176 Now she must find a suitable place to dig her nest. 150 00:21:07,266 --> 00:21:11,145 The best sites are already taken. 151 00:21:16,108 --> 00:21:19,653 And nesting females are very aggressive. 152 00:21:26,911 --> 00:21:30,790 A nodding head means keep away. 153 00:21:32,374 --> 00:21:33,834 Push off! 154 00:21:38,297 --> 00:21:43,177 Ignored warnings are met with force. 155 00:22:03,531 --> 00:22:07,827 But she's come a long way, and she's not going to give up now. 156 00:22:15,084 --> 00:22:20,631 She, too, starts to dig a hole in which to lay her eggs. 157 00:22:25,886 --> 00:22:28,973 That done, she will head back, 158 00:22:29,098 --> 00:22:32,768 leaving the volcano to provide the warmth her eggs need 159 00:22:32,893 --> 00:22:34,520 if they are to hatch. 160 00:22:38,023 --> 00:22:41,485 Sometimes, of course, the volcano erupts 161 00:22:41,610 --> 00:22:45,948 and destroys not only eggs, but many nesting adults. 162 00:22:52,788 --> 00:22:58,586 But for the iguanas, the benefits of nesting in the crater are so great 163 00:22:58,711 --> 00:23:00,796 that it's worth all the risks. 164 00:23:06,010 --> 00:23:11,682 Volcanic islands make up just 5% of the planet's land, 165 00:23:11,807 --> 00:23:16,770 but they're home to nearly 20% of its species. 166 00:23:19,565 --> 00:23:23,986 Animals often evolve very swiftly on islands, 167 00:23:24,111 --> 00:23:27,489 cut off from their mainland relatives 168 00:23:27,615 --> 00:23:30,576 and faced with the challenges of isolation. 169 00:23:35,205 --> 00:23:39,043 This is Wolf, an extinct volcano 170 00:23:39,168 --> 00:23:43,589 and one of the most remote islands of the Galépagos, 171 00:23:43,714 --> 00:23:46,842 800 miles from the nearest large landmass 172 00:23:46,967 --> 00:23:49,386 and over a million years old. 173 00:23:52,848 --> 00:23:54,099 A finch. 174 00:23:55,476 --> 00:23:57,728 A female. 175 00:23:57,853 --> 00:24:02,775 Its ancestors doubtless were blown here by storms many centuries ago. 176 00:24:04,693 --> 00:24:09,156 Like most finches, they feed on seeds, nectar and insects. 177 00:24:11,742 --> 00:24:14,995 But there's little food of any kind on Wolf. 178 00:24:18,374 --> 00:24:21,627 And since they aren't strong enough fliers to leave the island, 179 00:24:21,752 --> 00:24:26,215 they've had to find food from a very unusual source. 180 00:24:29,134 --> 00:24:33,013 They depend on another of the island's inhabitants. 181 00:24:39,812 --> 00:24:41,772 Nazca boobies. 182 00:24:46,902 --> 00:24:50,072 Every day, these seabirds commute 183 00:24:50,197 --> 00:24:53,826 between the island and their fishing grounds out in the open ocean. 184 00:24:57,913 --> 00:25:01,000 Each time a pair meet, they renew their bond... 185 00:25:03,377 --> 00:25:07,631 and then catch up with the neighbours. 186 00:25:13,762 --> 00:25:16,306 Now is the time... 187 00:25:16,432 --> 00:25:18,350 to hop into action. 188 00:25:41,623 --> 00:25:42,958 Blood. 189 00:25:45,335 --> 00:25:49,965 They are vampire finches. 190 00:25:54,136 --> 00:25:59,475 These little birds have become one of the world's newest species. 191 00:26:04,855 --> 00:26:07,232 She cuts the quill of a large flight feather, 192 00:26:07,357 --> 00:26:09,526 and the blood flows. 193 00:26:13,113 --> 00:26:16,867 The sight of it attracts the attention of others. 194 00:26:23,290 --> 00:26:28,504 Blood is very nutritious - worth fighting for. 195 00:26:42,142 --> 00:26:45,521 So, with this never-ending supply of food, 196 00:26:45,646 --> 00:26:48,482 the vampire finches can flourish on an island 197 00:26:48,607 --> 00:26:51,902 where otherwise they could not survive. 198 00:26:57,282 --> 00:27:02,412 Why the boobies don't object, nobody knows. 199 00:27:05,124 --> 00:27:07,918 Perhaps the finches' behaviour started 200 00:27:08,043 --> 00:27:12,131 when they helped the boobies to remove parasites from their plumage. 201 00:27:15,134 --> 00:27:18,220 Maybe the boobies think that the little vampires 202 00:27:18,345 --> 00:27:20,722 are still providing a service. 203 00:27:20,848 --> 00:27:22,516 Who can tell? 204 00:27:28,355 --> 00:27:32,067 Volcanic islands don't last forever. 205 00:27:32,192 --> 00:27:37,447 Changes deep in the Earth's crust bring their eruptions to an end, 206 00:27:37,573 --> 00:27:41,493 and the forces of erosion then begin to wear them down. 207 00:27:51,128 --> 00:27:54,506 But the coral around them continues to grow, 208 00:27:54,631 --> 00:27:58,510 sea levels change, and eventually all that is left 209 00:27:58,635 --> 00:28:04,725 is a ring-shaped island of coral rock surrounding a lagoon. 210 00:28:04,850 --> 00:28:06,643 An atoll. 211 00:28:17,446 --> 00:28:21,074 There are hundreds of atolls in tropical seas, 212 00:28:21,200 --> 00:28:24,995 all remnants of vanished volcanoes. 213 00:28:32,002 --> 00:28:35,589 This is one of the largest and most pristine - 214 00:28:35,714 --> 00:28:38,342 Aldabra, in the Indian Ocean. 215 00:28:41,136 --> 00:28:44,556 20 million years ago, it was an island 216 00:28:44,681 --> 00:28:47,809 with a volcanic crater in its centre. 217 00:28:53,065 --> 00:28:55,275 Now it's an atoll. 218 00:28:56,735 --> 00:29:00,822 Mangroves took root and seabirds came to nest. 219 00:29:03,742 --> 00:29:06,870 One land animal in particular... 220 00:29:06,995 --> 00:29:09,081 reached here before man. 221 00:29:12,793 --> 00:29:14,711 A giant tortoise. 222 00:29:16,046 --> 00:29:18,048 These creatures can float 223 00:29:18,173 --> 00:29:22,844 and live without food or fresh water for long periods of time. 224 00:29:27,349 --> 00:29:31,103 This isolated atoll is the perfect refuge. 225 00:29:32,271 --> 00:29:35,774 Their only enemy is the sun. 226 00:29:40,862 --> 00:29:46,994 Without shade, a tortoise risks being boiled in his shell. 227 00:29:50,747 --> 00:29:54,501 So, after feeding in the cool of the morning, 228 00:29:54,626 --> 00:29:57,587 and before the sun becomes too crushingly hot, 229 00:29:57,713 --> 00:29:59,548 they have to find cover. 230 00:30:01,008 --> 00:30:02,384 All of them. 231 00:30:09,141 --> 00:30:11,184 There is very little vegetation, 232 00:30:11,310 --> 00:30:13,478 but caves in the coral rock 233 00:30:13,603 --> 00:30:16,481 can provide the shade they so badly need. 234 00:30:24,698 --> 00:30:27,326 He's nearly there. 235 00:30:27,451 --> 00:30:32,706 All that is left is a white-knuckle ride to the bottom. 236 00:30:36,668 --> 00:30:38,754 And he's in. 237 00:30:42,632 --> 00:30:45,260 Thousands of others are still out in the sun. 238 00:30:46,887 --> 00:30:51,767 This tree could shade a couple of hundred, if they pack tight. 239 00:31:07,240 --> 00:31:09,868 It's bumper-to-bumper parking. 240 00:31:15,999 --> 00:31:20,128 Within an hour or so, all must find shade of some sort 241 00:31:20,253 --> 00:31:22,964 if they're to survive. 242 00:31:56,998 --> 00:31:58,625 Safe. 243 00:32:01,002 --> 00:32:06,091 But the future for Aldabra's tortoises is far from certain. 244 00:32:07,676 --> 00:32:12,013 The climate is changing, sea levels are rising, 245 00:32:12,139 --> 00:32:16,893 and Aldabra's tortoises may soon have to find a new refuge... 246 00:32:17,018 --> 00:32:18,937 or drown. 247 00:32:26,236 --> 00:32:29,948 In some places, volcanoes erupt not in the ocean, 248 00:32:30,073 --> 00:32:33,660 but in the very middle of a continent. 249 00:32:37,956 --> 00:32:41,042 North America, and in its very heart, 250 00:32:41,168 --> 00:32:45,172 a volcanic hot spot - Yellowstone. 251 00:32:52,012 --> 00:32:54,556 The last major eruption here 252 00:32:54,681 --> 00:33:00,854 came to an end about 650,000 years ago, 253 00:33:00,979 --> 00:33:04,024 but this volcano is only sleeping. 254 00:33:05,525 --> 00:33:10,030 Not far below ground, there is still magma. 255 00:33:10,155 --> 00:33:14,242 And that heats the groundwater to boiling point. 256 00:33:19,414 --> 00:33:21,333 Geysers. 257 00:33:24,503 --> 00:33:31,176 Some spout boiling water and steam to heights of 9O metres or so. 258 00:33:32,594 --> 00:33:37,599 Elsewhere, the scalding waters liquefy the ground sediments, 259 00:33:37,724 --> 00:33:40,727 creating pots of boiling mud. 260 00:33:46,942 --> 00:33:52,989 And this underground heating has proved a lifeline for some. 261 00:33:59,120 --> 00:34:01,039 River otters. 262 00:34:05,168 --> 00:34:08,838 They need a constant supply of food if they're to keep warm 263 00:34:08,964 --> 00:34:11,883 in these freezing temperatures. 264 00:34:16,346 --> 00:34:21,142 And this close-knit family know exactly where to find it. 265 00:34:38,743 --> 00:34:40,078 The springs are so hot 266 00:34:40,203 --> 00:34:43,999 that the rivers never freeze, even in the coldest winters... 267 00:34:50,463 --> 00:34:54,676 so the otter family can fish the year round. 268 00:35:14,613 --> 00:35:16,531 Trouble. 269 00:35:18,825 --> 00:35:21,620 This coyote knows that in the middle of winter 270 00:35:21,745 --> 00:35:25,123 a thermal river means otters, 271 00:35:25,248 --> 00:35:28,084 and otters mean fish. 272 00:35:33,381 --> 00:35:37,385 The question is... how to steal their catch? 273 00:36:01,910 --> 00:36:06,498 Perhaps the thing to do is to pretend you're not interested... 274 00:36:08,083 --> 00:36:13,088 and hope that they wander close enough for a snatch-and-run raid. 275 00:36:25,850 --> 00:36:28,645 It seems the cool-under-fire otters 276 00:36:28,770 --> 00:36:32,524 can outwit the not-so-wily coyote. 277 00:36:44,285 --> 00:36:47,372 Many animals benefit from the volcanic heat 278 00:36:47,497 --> 00:36:48,957 coming up from below. 279 00:36:52,669 --> 00:36:58,383 And we do as well, but not nearly as much as we could. 280 00:37:01,761 --> 00:37:07,434 The volcanic heat could provide us with much of the energy that we need, 281 00:37:07,559 --> 00:37:09,811 and then we could stop burning gas and coal 282 00:37:09,936 --> 00:37:13,648 that is now changing the climate worldwide. 283 00:37:25,118 --> 00:37:27,036 Deep in the Earth's crust, 284 00:37:27,162 --> 00:37:29,914 below both the oceans and the continents, 285 00:37:30,039 --> 00:37:34,711 there are lines of weakness along which rises liquid rock. 286 00:37:39,924 --> 00:37:44,304 The Kamchatka Peninsula in the north-west Pacific 287 00:37:44,429 --> 00:37:46,473 lies along one of them. 288 00:38:01,529 --> 00:38:05,325 There are only a thousand known geysers in the world, 289 00:38:05,450 --> 00:38:10,205 and many of them are here in this isolated valley. 290 00:38:22,675 --> 00:38:26,513 Steam from superheated water fills the air. 291 00:38:27,972 --> 00:38:32,185 But the danger from the scalding pools does little to deter. 292 00:38:32,310 --> 00:38:35,980 Kamchatka's most famous residents. 293 00:38:44,864 --> 00:38:49,619 In May, when the rest of Kamchatka is still covered by snow, 294 00:38:49,744 --> 00:38:51,412 this valley is free of it, 295 00:38:51,538 --> 00:38:56,668 and bears, having just woken up from their winter sleep, know that. 296 00:39:04,175 --> 00:39:07,887 The grass is fertilised by mineral-rich water 297 00:39:08,012 --> 00:39:09,848 spraying from the geysers... 298 00:39:12,559 --> 00:39:19,148 much-needed forage for a large male bear that hasn't eaten for several months. 299 00:39:24,863 --> 00:39:27,365 And he's not the only one. 300 00:39:38,960 --> 00:39:42,589 The bears haven't seen one another for seven months, 301 00:39:42,714 --> 00:39:44,549 since the start of winter. 302 00:39:47,302 --> 00:39:51,764 And it seems that right now they would prefer to keep it that way. 303 00:39:53,308 --> 00:39:58,271 Nothing should come between a bear and his first meal of the year. 304 00:40:03,568 --> 00:40:06,738 And in one place, Kamchatka's underground forces 305 00:40:06,863 --> 00:40:11,117 provide its bears with even more nutritious meals. 306 00:40:18,833 --> 00:40:22,879 Kurile Lake lies within the crater of an immense volcano 307 00:40:23,004 --> 00:40:28,551 that long ago produced one of the greatest eruptions in the planet's history. 308 00:40:32,138 --> 00:40:35,600 The lake is still circled by active vents... 309 00:40:38,019 --> 00:40:41,814 and mineral-rich ash from their regular eruptions 310 00:40:41,940 --> 00:40:45,109 has made these waters particularly fertile. 311 00:40:48,571 --> 00:40:51,950 Millions of salmon come here from the Pacific Ocean 312 00:40:52,075 --> 00:40:54,285 in order to spawn in these fertile waters, 313 00:40:54,410 --> 00:40:59,707 which will provide their newly hatched young with abundant food... 314 00:41:05,296 --> 00:41:11,427 so grass soon ceases to be top of the menu for Kamchatka's bears. 315 00:41:14,973 --> 00:41:17,600 By the time spring has turned to summer, 316 00:41:17,725 --> 00:41:22,438 Kurile Lake contains the most dense assembly of bears 317 00:41:22,563 --> 00:41:25,191 to be found anywhere on Earth... 318 00:41:29,654 --> 00:41:32,907 all hungry for salmon. 319 00:41:44,544 --> 00:41:49,966 But this early in the season, the fish are still strong and swift. 320 00:42:06,649 --> 00:42:08,985 Nothing seems to work. 321 00:42:17,452 --> 00:42:20,788 But one old bear knows that right now 322 00:42:20,913 --> 00:42:23,291 there is an easier meal to be had. 323 00:42:26,753 --> 00:42:30,798 He remembers that if he paddles out into the lake, 324 00:42:30,923 --> 00:42:34,093 away from the shoals of newly arrived salmon, 325 00:42:34,218 --> 00:42:37,847 there's food that doesn't need chasing. 326 00:42:58,201 --> 00:43:01,537 Some of the first fish to arrive have died, 327 00:43:01,662 --> 00:43:04,207 and their bodies can be easily collected... 328 00:43:04,332 --> 00:43:07,043 from the bottom of the lake. 329 00:43:13,341 --> 00:43:18,221 Diving for them at leisure doesn't use many calories. 330 00:43:24,102 --> 00:43:27,063 And he can take his time. 331 00:43:39,992 --> 00:43:44,497 A couple of weeks later, the salmon are beginning to spawn 332 00:43:44,622 --> 00:43:46,124 and are less wary. 333 00:43:49,085 --> 00:43:52,547 Now it's worth running. 334 00:44:09,313 --> 00:44:11,482 The fish are so abundant... 335 00:44:13,651 --> 00:44:15,778 that there is plenty for all... 336 00:44:17,738 --> 00:44:20,700 even those with no previous experience. 337 00:44:25,163 --> 00:44:26,956 There are now so many fish, 338 00:44:27,081 --> 00:44:31,502 it's difficult to know which one to chase. 339 00:44:45,975 --> 00:44:49,937 In a single day, a bear can consume 340 00:44:50,062 --> 00:44:52,315 100,000 calories, 341 00:44:52,440 --> 00:44:56,110 50 times more than the average human being does. 342 00:44:57,445 --> 00:45:01,657 And one part is particularly delicious. 343 00:45:06,370 --> 00:45:07,830 Caviar. 344 00:45:07,955 --> 00:45:11,000 80 calories in every mouthful. 345 00:45:19,133 --> 00:45:22,762 By supporting huge concentrations of salmon, 346 00:45:22,887 --> 00:45:27,141 mineral ash from Kurile Lake's volcanoes 347 00:45:27,266 --> 00:45:31,646 has made life surprisingly easy for these bears. 348 00:45:45,785 --> 00:45:50,581 Our planet depends on minerals brought up by volcanoes 349 00:45:50,706 --> 00:45:53,125 from the Earth's molten core. 350 00:45:56,754 --> 00:46:02,385 A single ash cloud can carry billions of tonnes of minerals. 351 00:46:15,815 --> 00:46:20,069 And as a consequence, the lands surrounding volcanoes 352 00:46:20,194 --> 00:46:22,488 are among the world's most fertile. 353 00:46:28,202 --> 00:46:31,205 Those in East Africa's Rift Valley 354 00:46:31,330 --> 00:46:34,667 support the most dynamic ecosystem on Earth. 355 00:46:41,048 --> 00:46:42,800 The Serengeti. 356 00:46:46,595 --> 00:46:52,393 This is the most productive of all natural grasslands anywhere. 357 00:46:54,729 --> 00:46:57,690 Every year, over a million wildebeest 358 00:46:57,815 --> 00:47:01,235 assemble in this particular corner of the Serengeti 359 00:47:01,360 --> 00:47:06,032 to feed on grass specially rich in calcium and phosphorus - 360 00:47:06,157 --> 00:47:11,037 essential minerals for the pregnant females. 361 00:47:13,456 --> 00:47:15,708 In just three weeks, 362 00:47:15,833 --> 00:47:20,087 half a million calves are born on these ash-rich plains. 363 00:47:21,839 --> 00:47:24,967 That's 24,000 a day, 364 00:47:25,092 --> 00:47:28,637 a thousand an hour. 365 00:47:32,558 --> 00:47:36,187 Calves stand up within a few minutes of being born... 366 00:47:39,732 --> 00:47:43,736 though some need a little more time to find their feet. 367 00:47:56,874 --> 00:47:59,418 But a mother won't let her calf suckle 368 00:47:59,543 --> 00:48:02,880 until it's mastered a few physical skills. 369 00:48:06,467 --> 00:48:08,010 Walking. 370 00:48:09,345 --> 00:48:10,721 Trotting. 371 00:48:12,098 --> 00:48:14,100 And running. 372 00:48:24,402 --> 00:48:28,948 Wildebeest calves must run if they're to stay alive... 373 00:48:45,423 --> 00:48:47,800 for these plains also support 374 00:48:47,925 --> 00:48:53,305 the greatest assembly of hunters on the planet. 375 00:48:56,058 --> 00:48:59,979 Each species has its own special hunting technique. 376 00:49:01,355 --> 00:49:03,023 But all have the same aim... 377 00:49:06,026 --> 00:49:11,240 to make the most of this brief super-abundance of life. 378 00:50:12,218 --> 00:50:15,638 Only one in ten wildebeest calves 379 00:50:15,763 --> 00:50:18,557 will survive to adulthood. 380 00:50:18,682 --> 00:50:21,393 But that is enough to maintain 381 00:50:21,519 --> 00:50:24,021 the million-strong herd of wildebeest... 382 00:50:25,689 --> 00:50:30,194 and the planet's highest density of predators. 383 00:50:33,155 --> 00:50:35,199 Volcanoes fertilise the planet, 384 00:50:35,324 --> 00:50:39,036 but they're the source of something else so important 385 00:50:39,161 --> 00:50:42,540 that life could not have started without it. 386 00:50:47,711 --> 00:50:51,882 The first carbon dioxide in the Earth's atmosphere 387 00:50:52,007 --> 00:50:56,720 was brought by volcanoes from deep in the Earth's crust. 388 00:51:00,432 --> 00:51:04,270 And this gas is the foundation of life. 389 00:51:04,395 --> 00:51:07,356 Every plant needs it to grow, 390 00:51:07,481 --> 00:51:10,025 and absorbs it from the air. 391 00:51:13,153 --> 00:51:17,116 Volcanoes continue to release carbon dioxide today, 392 00:51:17,241 --> 00:51:19,827 and for the last 10,000 years 393 00:51:19,952 --> 00:51:25,207 its presence in the atmosphere has suited life perfectly. 394 00:51:28,419 --> 00:51:32,089 Its greenhouse properties have kept our planet's climate 395 00:51:32,214 --> 00:51:34,341 stable and warm. 396 00:51:41,682 --> 00:51:43,517 But too much carbon dioxide 397 00:51:43,642 --> 00:51:46,353 would make the planet's temperature rise to levels 398 00:51:46,478 --> 00:51:52,192 that would upset the Earth's long-established ecological balances. 399 00:52:08,375 --> 00:52:13,255 Today, humanity itself has become a new kind 400 00:52:13,380 --> 00:52:15,132 of supervolcano. 401 00:52:22,056 --> 00:52:27,311 Now, every year, we ourselves release 100 times more carbon 402 00:52:27,436 --> 00:52:30,522 than all the Earth's volcanoes combined. 403 00:52:31,982 --> 00:52:35,653 And that has brought climate chaos. 404 00:52:40,324 --> 00:52:43,118 We can't control volcanoes. 405 00:52:43,243 --> 00:52:48,415 But we can limit the amount of carbon dioxide that we produce. 406 00:52:50,209 --> 00:52:53,337 And if we do that, there will still be time 407 00:52:53,462 --> 00:52:56,340 to restore the ecological balance 408 00:52:56,465 --> 00:53:00,844 that once made this Earth our perfect planet.