1 00:00:27,300 --> 00:00:29,500 A Perfect Planet. 2 00:00:44,340 --> 00:00:48,580 We live in a world with a violent atmosphere. 3 00:00:51,860 --> 00:00:53,900 Rain clouds form, 4 00:00:53,900 --> 00:00:58,140 and powerful winds carry their fresh water around the globe. 5 00:01:00,620 --> 00:01:06,020 Without this, our perfect planet simply couldn't function... 6 00:01:06,020 --> 00:01:10,820 ...for all life on land depends on the weather. 7 00:01:23,580 --> 00:01:27,020 We all know that the weather can change on a daily, 8 00:01:27,020 --> 00:01:29,140 even hourly, basis. 9 00:01:31,460 --> 00:01:35,540 But annual weather patterns have been stable for millennia... 10 00:01:36,980 --> 00:01:41,620 ...and it's this reliability on which life depends. 11 00:01:41,620 --> 00:01:43,420 ANIMALS AND BIRDS CALL 12 00:01:47,420 --> 00:01:52,260 Every year in October, the weather brings a dramatic transformation 13 00:01:52,260 --> 00:01:55,620 to this tiny patch of forest in Zambia. 14 00:02:00,500 --> 00:02:03,140 Storm clouds begin to build. 15 00:02:06,780 --> 00:02:08,660 THUNDER CRASHES 16 00:02:11,500 --> 00:02:17,500 And right on cue, straw-coloured fruit bats start to appear. 17 00:02:23,300 --> 00:02:27,980 They've travelled hundreds, if not thousands, of miles to be here. 18 00:02:35,660 --> 00:02:39,540 And they always arrive at exactly the same time. 19 00:02:42,300 --> 00:02:46,420 They know that these rains will transform this forest, 20 00:02:46,420 --> 00:02:50,060 allowing countless fruit trees to ripen. 21 00:02:54,340 --> 00:02:58,700 And the bats gorge on the new-found abundance. 22 00:03:17,420 --> 00:03:20,620 For just 12 weeks every year, 23 00:03:20,620 --> 00:03:25,740 this forest becomes home to ten million fruit bats. 24 00:03:29,500 --> 00:03:33,460 One of the greatest gatherings of mammals on Earth, 25 00:03:33,460 --> 00:03:38,380 all crowding into an area no bigger than a dozen football pitches. 26 00:03:41,980 --> 00:03:45,020 From this hub, the bats fan out, 27 00:03:45,020 --> 00:03:48,980 consuming more than 300,000 tonnes of fruit, 28 00:03:48,980 --> 00:03:52,820 spreading the seeds and regenerating the forests. 29 00:04:11,980 --> 00:04:18,060 Africa's largest wildlife migration entirely dependent on the rain 30 00:04:18,060 --> 00:04:21,660 that comes to this small corner of Zambia 31 00:04:21,660 --> 00:04:24,700 at the same time each year. 32 00:04:40,460 --> 00:04:44,660 Every second, over 13 million tonnes of water 33 00:04:44,660 --> 00:04:49,300 evaporate from our oceans, forming clouds. 34 00:04:55,820 --> 00:04:58,740 The spin of the Earth and the prevailing winds 35 00:04:58,740 --> 00:05:01,580 determine where these clouds blow. 36 00:05:03,420 --> 00:05:06,980 As a consequence, some places get less rain... 37 00:05:08,620 --> 00:05:10,620 ...and others much more. 38 00:05:13,220 --> 00:05:15,300 The Amazon rainforest... 39 00:05:16,740 --> 00:05:18,260 THUNDER CRASHES 40 00:05:18,260 --> 00:05:21,380 ...one of the wettest places on Earth. 41 00:05:31,380 --> 00:05:33,860 It gets three metres of rain a year... 42 00:05:35,660 --> 00:05:41,140 ...so life has learned to deal with the near-daily downpours. 43 00:05:46,540 --> 00:05:49,580 Every year, for thousands of years, 44 00:05:49,580 --> 00:05:54,300 the persistent rains have flooded vast tracts of the Amazon... 45 00:05:56,380 --> 00:06:00,980 ...turning the jungle into a seasonal wetland. 46 00:06:02,860 --> 00:06:07,940 Anything living here must either climb or swim. 47 00:06:12,420 --> 00:06:16,620 But there's one extraordinary animal that has turned this deluge 48 00:06:16,620 --> 00:06:20,500 from a disaster into an opportunity. 49 00:06:26,260 --> 00:06:30,980 This fire ant has reached the edge of her known world. 50 00:06:34,580 --> 00:06:39,260 Her way forward has now become blocked by the rising waters. 51 00:06:45,780 --> 00:06:48,740 She's one of many, and in a few minutes 52 00:06:48,740 --> 00:06:51,780 their underground home will be submerged. 53 00:06:58,500 --> 00:07:04,900 Forced to evacuate, workers and soldiers try to save the larval young. 54 00:07:06,660 --> 00:07:11,260 As their nest floods, the colony seems to be doomed. 55 00:07:19,180 --> 00:07:22,860 But from chaos comes order. 56 00:07:24,860 --> 00:07:29,540 The fire ants band together, each locking legs with its neighbours. 57 00:07:32,180 --> 00:07:35,140 They're building a living raft. 58 00:07:37,820 --> 00:07:43,260 Each ant is covered in fine hairs that trap air against its body. 59 00:07:47,660 --> 00:07:53,540 As the raft forms, this air creates a cushion for them all to float on. 60 00:07:56,300 --> 00:07:58,820 This is the power of the colony. 61 00:08:00,260 --> 00:08:03,620 By working together, they've become unsinkable. 62 00:08:08,060 --> 00:08:10,380 And no-one gets left behind. 63 00:08:23,420 --> 00:08:28,180 Pulled from the shallows, the colony is now at the mercy of the flood. 64 00:08:33,940 --> 00:08:36,220 Holding tight to the larvae 65 00:08:36,220 --> 00:08:39,460 and keeping their queen hidden at the centre of the raft, 66 00:08:39,460 --> 00:08:43,060 the colony drifts into deeper water... 67 00:08:48,380 --> 00:08:50,860 ...where they're vulnerable to fish 68 00:08:50,860 --> 00:08:53,860 that now swim through the flooded forest. 69 00:09:00,180 --> 00:09:05,220 Those that lose their grip must get back to the safety of the raft. 70 00:09:16,860 --> 00:09:20,860 With jaws that join to become a surgical needle, 71 00:09:20,860 --> 00:09:24,540 this pond skater could suck an ant dry. 72 00:09:35,900 --> 00:09:38,980 But together the colony is strong, 73 00:09:38,980 --> 00:09:41,780 and it's time to repel boarders. 74 00:09:53,380 --> 00:09:56,620 The ants can travel like this for weeks. 75 00:09:59,620 --> 00:10:03,020 They've even come to depend on the flood to carry them 76 00:10:03,020 --> 00:10:05,380 to new feeding grounds. 77 00:10:18,380 --> 00:10:22,620 At last, the ants can make their raft secure. 78 00:10:28,140 --> 00:10:31,380 Surging forward, they claim their new home... 79 00:10:32,620 --> 00:10:36,020 ...evicting current tenants without hesitation. 80 00:10:39,820 --> 00:10:43,340 One of the first to safety is their larval queen, 81 00:10:43,340 --> 00:10:45,780 carried from the heart of the raft. 82 00:10:52,740 --> 00:10:56,780 This palm will be their home for the next three months, 83 00:10:56,780 --> 00:11:01,220 until the floodwaters recede and they can head back underground. 84 00:11:14,500 --> 00:11:18,060 The average temperature of our planet hasn't varied 85 00:11:18,060 --> 00:11:22,820 by more than a single degree Celsius in 10,000 years. 86 00:11:24,460 --> 00:11:27,260 This has made our climate stable, 87 00:11:27,260 --> 00:11:30,380 allowing animals to fine-tune their behaviour 88 00:11:30,380 --> 00:11:33,500 around predictable weather patterns. 89 00:11:36,740 --> 00:11:38,980 October in the Amazon. 90 00:11:40,860 --> 00:11:43,340 The heaviest rains have come to an end, 91 00:11:43,340 --> 00:11:47,700 and the falling river level exposes a new landscape. 92 00:11:50,580 --> 00:11:55,660 Three weeks ago, these mile-wide sand bars didn't exist. 93 00:11:57,980 --> 00:12:02,180 In another three months, they'll be back under water. 94 00:12:04,820 --> 00:12:10,900 But now they provide a crucial opportunity for giant river turtles. 95 00:12:13,740 --> 00:12:18,460 They've been coming here at precisely this time of year for generations. 96 00:12:24,340 --> 00:12:28,580 50,000 of them - a quarter of the world's population. 97 00:12:32,820 --> 00:12:34,860 They're all here for one reason. 98 00:12:36,540 --> 00:12:39,380 But their window of opportunity is short, 99 00:12:39,380 --> 00:12:42,020 so timing is everything. 100 00:12:46,660 --> 00:12:50,940 Scaling the three-metre-high banks will take this female 101 00:12:50,940 --> 00:12:54,980 higher and drier than she's been for months. 102 00:12:57,620 --> 00:13:01,180 She's come here to lay her eggs. 103 00:13:02,300 --> 00:13:04,500 But others have beaten her to it. 104 00:13:14,900 --> 00:13:18,060 The early arrivals have already claimed 105 00:13:18,060 --> 00:13:20,580 nearly every inch of the beach... 106 00:13:21,820 --> 00:13:24,420 ...and there are still many more turtles to come. 107 00:13:30,780 --> 00:13:33,940 Wherever she turns, the space is taken. 108 00:13:33,940 --> 00:13:35,820 SAND PATTERS 109 00:13:42,820 --> 00:13:46,980 But being fashionably late does have an advantage. 110 00:13:49,860 --> 00:13:53,460 Had she arrived earlier, her eggs might have been 111 00:13:53,460 --> 00:13:56,940 dug up by those searching for somewhere to lay. 112 00:14:02,620 --> 00:14:04,660 She's found her spot. 113 00:14:11,540 --> 00:14:16,620 Settling down, she lays nearly 100 eggs. 114 00:14:21,140 --> 00:14:24,460 Burying them keeps them safe from predators, 115 00:14:24,460 --> 00:14:27,660 and the warm sand incubates the clutch. 116 00:14:34,940 --> 00:14:40,380 They must hatch before the river rises again and floods the sandbar. 117 00:14:44,620 --> 00:14:48,580 Any turtles that lay after her may have left it too late. 118 00:14:55,860 --> 00:14:59,100 Hopefully, she has got her timing right. 119 00:15:12,540 --> 00:15:17,780 Two months on, and the hatchlings emerge into the world. 120 00:15:27,540 --> 00:15:31,180 They were laid at the perfect time. 121 00:15:31,180 --> 00:15:33,420 Hundreds scramble for the river 122 00:15:33,420 --> 00:15:35,860 just as the water starts to rise. 123 00:15:37,900 --> 00:15:41,140 Those still to hatch aren't so lucky. 124 00:15:47,260 --> 00:15:50,460 This year, the heavy rains have returned early. 125 00:15:50,460 --> 00:15:52,340 THUNDER RUMBLES 126 00:16:12,260 --> 00:16:15,260 The nesting beach is beginning to flood. 127 00:16:23,060 --> 00:16:26,420 Most hatchlings can escape in time. 128 00:16:34,020 --> 00:16:36,420 Those still below ground... 129 00:16:37,780 --> 00:16:39,820 ...will drown in their nests. 130 00:16:44,900 --> 00:16:49,820 For thousands of years, giant river turtles have timed their breeding 131 00:16:49,820 --> 00:16:53,860 around the Amazon's reliable cycles of rain. 132 00:16:57,300 --> 00:17:00,820 But today, our weather is changing. 133 00:17:05,260 --> 00:17:12,060 Disastrous early floods like this used to happen once every 20 years. 134 00:17:12,060 --> 00:17:16,820 Now the turtles have to deal with them every four. 135 00:17:31,260 --> 00:17:35,460 Winds may carry huge amounts of rain to the Amazon, 136 00:17:35,460 --> 00:17:40,340 but they don't provide this service to every corner of the planet. 137 00:17:42,100 --> 00:17:48,700 A third of the land receives less than 25cm of rain a year. 138 00:17:52,900 --> 00:17:58,460 Deserts are scarred by desiccating winds and baked by the sun. 139 00:18:01,340 --> 00:18:06,660 But even weather as challenging as this can be perfect for the locals. 140 00:18:12,300 --> 00:18:15,900 As darkness falls in the coastal deserts of South Africa, 141 00:18:15,900 --> 00:18:18,500 the dunes come alive... 142 00:18:18,500 --> 00:18:20,420 HIGH-PITCHED CALL 143 00:18:20,420 --> 00:18:24,260 ...with the call of a surprising desert dweller. 144 00:18:25,940 --> 00:18:28,700 HIGH-PITCHED CALL 145 00:18:32,300 --> 00:18:33,900 CALL CONTINUES 146 00:18:44,420 --> 00:18:47,420 A rain frog. 147 00:18:47,420 --> 00:18:54,300 Not what you'd expect in a place that gets just 7cm of rain a year. 148 00:18:58,820 --> 00:19:02,740 To survive here, she has to avoid the heat of the day 149 00:19:02,740 --> 00:19:04,780 buried in the sand. 150 00:19:07,020 --> 00:19:10,060 But each night, she heads out... 151 00:19:10,060 --> 00:19:12,780 ..on her hunt for moisture. 152 00:19:16,340 --> 00:19:20,700 Short, stumpy legs and a plump body are ideal for digging... 153 00:19:23,820 --> 00:19:27,020 ...but not so good for getting around. 154 00:19:31,100 --> 00:19:36,980 She can't hop, so she waddles across the dunes. 155 00:19:44,100 --> 00:19:48,340 The world's slowest steeplechaser. 156 00:19:52,540 --> 00:19:56,860 Obstacles are tackled with dogged perseverance. 157 00:20:03,660 --> 00:20:08,100 She can travel a whopping 38 metres a night. 158 00:20:08,100 --> 00:20:13,700 No mean feat when you're the same size and shape as a marshmallow. 159 00:20:19,260 --> 00:20:21,260 Termites. 160 00:20:21,260 --> 00:20:25,220 They are 75% water - 161 00:20:25,220 --> 00:20:28,780 a meal and a drink in one. 162 00:20:32,860 --> 00:20:37,060 But she's not the most agile predator. 163 00:20:38,660 --> 00:20:42,780 Maybe if they just came a little closer...? 164 00:20:46,860 --> 00:20:48,860 Oh, dear. 165 00:20:50,900 --> 00:20:53,940 Perhaps if they stop moving...? 166 00:21:14,580 --> 00:21:16,220 At last. 167 00:21:17,500 --> 00:21:21,220 But now she has another challenge. 168 00:21:21,220 --> 00:21:25,220 To swallow her food, she must squash in her eyeballs 169 00:21:25,220 --> 00:21:27,740 to push it down her throat. 170 00:21:36,380 --> 00:21:38,620 Termites may be juicy, 171 00:21:38,620 --> 00:21:42,300 but they don't provide her with quite enough water to survive. 172 00:21:46,060 --> 00:21:48,620 It rarely rains here, 173 00:21:48,620 --> 00:21:54,060 but coastal deserts do get another reliable source of moisture. 174 00:22:04,900 --> 00:22:09,580 At night - cool, moist air is blown in from the ocean, 175 00:22:09,580 --> 00:22:13,940 forming fog banks that shroud the desert in mist. 176 00:22:25,740 --> 00:22:30,340 It condenses on vegetation, wetting the sand beneath. 177 00:22:30,340 --> 00:22:35,700 So it's here that she waits, absorbing moisture through her skin. 178 00:22:43,660 --> 00:22:48,340 Rain frogs are so dependent on this water that they can only survive 179 00:22:48,340 --> 00:22:53,180 in places with at least 100 days of fog a year. 180 00:22:55,420 --> 00:22:57,700 And on the foggiest nights, 181 00:22:57,700 --> 00:23:00,700 when other frogs have emerged onto the dunes, 182 00:23:00,700 --> 00:23:04,780 she takes her opportunity to find love. 183 00:23:12,300 --> 00:23:16,180 Male rain frogs are smaller than the females, 184 00:23:16,180 --> 00:23:21,420 and his stubby legs make it hard to hold on... 185 00:23:21,420 --> 00:23:25,460 ..so he glues himself onto her back. 186 00:23:35,980 --> 00:23:38,420 Still locked in their embrace, 187 00:23:38,420 --> 00:23:42,940 the pair head back beneath the sand, where they'll lay their eggs, 188 00:23:42,940 --> 00:23:46,180 safe from the heat of the desert sun. 189 00:23:54,780 --> 00:23:58,420 But there's one desert that gets so cold 190 00:23:58,420 --> 00:24:02,260 that liquid water simply can't exist. 191 00:24:05,020 --> 00:24:09,060 Winter in Mongolia's Gobi Desert. 192 00:24:10,580 --> 00:24:13,460 40 degrees below freezing. 193 00:24:16,180 --> 00:24:20,740 One of the driest and most extreme environments in the world. 194 00:24:27,500 --> 00:24:31,180 Most animals can't survive weather like this... 195 00:24:33,540 --> 00:24:36,220 ...but there's one unique mammal 196 00:24:36,220 --> 00:24:39,420 that manages to eke out a living here. 197 00:24:42,100 --> 00:24:48,740 The Gobi is home to the last 1,000 wild Bactrian camels on Earth... 198 00:24:50,820 --> 00:24:53,620 ...surviving at the very edge of what's possible. 199 00:24:54,860 --> 00:24:57,100 CAMEL GRUNTS 200 00:24:57,100 --> 00:24:59,580 Even camels need moisture, 201 00:24:59,580 --> 00:25:03,380 but any water here is now frozen solid. 202 00:25:07,060 --> 00:25:10,140 It's down to the bull to find a solution. 203 00:25:12,940 --> 00:25:14,780 BULL GRUNTS 204 00:25:17,620 --> 00:25:19,700 Setting off with his herd, 205 00:25:19,700 --> 00:25:23,100 his search could cover thousands of square miles. 206 00:25:29,020 --> 00:25:33,700 Driving them forward, he can keep going for days on end. 207 00:25:44,260 --> 00:25:47,660 Herds come together from across their vast range... 208 00:25:49,140 --> 00:25:51,340 ...all looking for the same thing. 209 00:26:00,100 --> 00:26:06,380 These long-distance specialists can smell moisture from 30 miles away... 210 00:26:06,380 --> 00:26:08,620 ...and they've picked up a scent. 211 00:26:13,700 --> 00:26:18,100 Even in the Gobi, one of the driest places on Earth, 212 00:26:18,100 --> 00:26:22,020 wind can provide a rare source of moisture. 213 00:26:24,100 --> 00:26:28,380 Snow is blown to this desert from Siberia. 214 00:26:30,180 --> 00:26:33,460 Where it settles is impossible to predict, 215 00:26:33,460 --> 00:26:35,620 and it may not last long. 216 00:26:42,620 --> 00:26:47,820 But for now, at least, this bull has found what he's been searching for. 217 00:26:57,740 --> 00:26:59,980 In the cold, dry air, 218 00:26:59,980 --> 00:27:02,020 snow doesn't melt... 219 00:27:03,900 --> 00:27:06,420 ...so it must be eaten. 220 00:27:15,660 --> 00:27:19,540 The Gobi's windblown snow is a lifeline 221 00:27:19,540 --> 00:27:22,940 that will sustain his herd throughout the winter. 222 00:27:30,660 --> 00:27:33,980 Even in this most hostile of places, 223 00:27:33,980 --> 00:27:38,380 weather still provides just enough for survival. 224 00:27:50,220 --> 00:27:54,260 The largest, most unpredictable weather on the planet 225 00:27:54,260 --> 00:27:57,300 starts far out at sea. 226 00:28:03,180 --> 00:28:07,020 Hurricanes, typhoons and tropical cyclones 227 00:28:07,020 --> 00:28:10,660 are violent, short-lived megastorms. 228 00:28:12,140 --> 00:28:15,100 But there's a far more reliable weather system 229 00:28:15,100 --> 00:28:17,380 that originates over the ocean... 230 00:28:18,700 --> 00:28:23,140 ...one that is eagerly anticipated by all in its path. 231 00:28:26,140 --> 00:28:32,420 Monsoons are seasonal winds that blow at the same time each year... 232 00:28:34,900 --> 00:28:39,700 ...and they carry colossal amounts of water from the ocean to the land. 233 00:28:47,140 --> 00:28:48,660 Christmas Island. 234 00:28:50,140 --> 00:28:53,580 A remote speck of rock in the Indian Ocean. 235 00:28:58,060 --> 00:29:04,460 For the last four months, its forest interior has remained dry and dusty. 236 00:29:07,740 --> 00:29:11,620 Life here is waiting for change. 237 00:29:14,500 --> 00:29:19,500 In November, the first storms of the monsoon reach the island. 238 00:29:19,500 --> 00:29:21,940 THUNDER CRASHES 239 00:29:37,060 --> 00:29:41,420 They're a welcome relief for those that have suffered through the dry. 240 00:29:45,780 --> 00:29:50,900 And they are vital for the island's most numerous residents. 241 00:30:05,020 --> 00:30:08,380 The red crabs of Christmas Island. 242 00:30:12,580 --> 00:30:15,780 They've spent the dry season sheltering in damp burrows 243 00:30:15,780 --> 00:30:17,820 beneath the leaf litter. 244 00:30:21,140 --> 00:30:25,340 Crabs breathe through gills that must be kept moist. 245 00:30:29,780 --> 00:30:33,660 So it's only with the return of the annual monsoon 246 00:30:33,660 --> 00:30:37,540 that these land crabs can finally emerge. 247 00:30:44,660 --> 00:30:46,900 With the humidity now high enough, 248 00:30:46,900 --> 00:30:50,540 they can begin an epic trek to the coast. 249 00:31:03,180 --> 00:31:07,780 Every red crab comes together from across the island, 250 00:31:07,780 --> 00:31:10,460 and they do so in their millions. 251 00:31:12,860 --> 00:31:15,740 50 million, to be precise. 252 00:31:30,140 --> 00:31:35,420 They've come to release their eggs that can only develop in the ocean. 253 00:31:36,860 --> 00:31:39,300 There's just one small problem. 254 00:31:40,500 --> 00:31:43,380 They may be crabs... 255 00:31:43,380 --> 00:31:45,580 ...but they can't swim. 256 00:31:49,220 --> 00:31:51,500 They're scared of the sea. 257 00:32:05,420 --> 00:32:07,740 But they don't have a choice. 258 00:32:09,140 --> 00:32:13,620 They must release their eggs on the highest tide. 259 00:32:19,500 --> 00:32:23,580 Each carries around 100,000 eggs, 260 00:32:23,580 --> 00:32:26,260 so over just two or three nights, 261 00:32:26,260 --> 00:32:29,380 trillions are released into the ocean. 262 00:32:31,700 --> 00:32:35,340 Though some are more successful than others. 263 00:33:00,580 --> 00:33:05,180 Once their work is done, the crabs will return to the forest. 264 00:33:22,100 --> 00:33:24,900 Then, four weeks later, 265 00:33:24,900 --> 00:33:27,140 on the next highest tide... 266 00:33:32,580 --> 00:33:34,900 ...having hatched out to sea, 267 00:33:34,900 --> 00:33:39,940 a new generation of red crabs returns to the same beach. 268 00:33:42,180 --> 00:33:44,060 In good years like this one, 269 00:33:44,060 --> 00:33:47,860 countless millions arrive back on the shores of Christmas Island, 270 00:33:47,860 --> 00:33:50,500 turning the beaches red. 271 00:34:07,580 --> 00:34:12,260 Like their parents, they also need moisture in the air to breathe. 272 00:34:14,900 --> 00:34:17,180 So before the rains move on, 273 00:34:17,180 --> 00:34:22,860 the young crabs must undertake their own epic journey into the forest, 274 00:34:22,860 --> 00:34:26,660 where they'll wait out the next few months of dry. 275 00:34:46,780 --> 00:34:49,060 The Christmas Island crab - 276 00:34:49,060 --> 00:34:53,380 entirely reliant on the return of the monsoon. 277 00:35:04,300 --> 00:35:10,340 The annual rhythms of the weather shape life across our planet. 278 00:35:12,780 --> 00:35:15,020 In some parts of the world, 279 00:35:15,020 --> 00:35:19,260 seasonal cycles of wet and dry can bring dramatic change. 280 00:35:21,900 --> 00:35:24,780 And there are few places where this is more apparent 281 00:35:24,780 --> 00:35:26,980 than southern Africa. 282 00:35:34,020 --> 00:35:36,340 The Zambezi River. 283 00:35:38,020 --> 00:35:44,300 It flows across six countries and drains half a million square miles. 284 00:35:58,340 --> 00:36:00,940 At the peak of the wet season, 285 00:36:00,940 --> 00:36:07,540 5,000 tonnes of water cascade over Victoria Falls every second. 286 00:36:10,100 --> 00:36:13,500 And yet, each year when the rains stop, 287 00:36:13,500 --> 00:36:16,780 these falls run dry. 288 00:36:24,500 --> 00:36:28,460 It's almost as if someone turns off the tap. 289 00:36:33,620 --> 00:36:35,060 May... 290 00:36:38,460 --> 00:36:40,100 ..December. 291 00:36:43,220 --> 00:36:44,980 Wet season... 292 00:36:48,460 --> 00:36:50,260 ..dry season. 293 00:36:53,180 --> 00:36:56,980 It's happened like this for thousands of years. 294 00:37:03,100 --> 00:37:08,140 But there are signs that the weather here is changing. 295 00:37:08,140 --> 00:37:12,900 In recent years, the volume of water flowing over Victoria Falls 296 00:37:12,900 --> 00:37:15,460 has dropped by half. 297 00:37:19,660 --> 00:37:23,020 A concern for animals that have come to rely on 298 00:37:23,020 --> 00:37:26,620 the natural rhythms of wet and dry. 299 00:37:39,700 --> 00:37:45,540 Zambia's Luangwa River is a major tributary of the Zambezi. 300 00:37:47,380 --> 00:37:50,500 Every year, as the dry season takes hold, 301 00:37:50,500 --> 00:37:53,660 it dwindles into pools. 302 00:37:57,100 --> 00:38:00,540 Accommodation starts to get tight for the locals. 303 00:38:00,540 --> 00:38:02,380 HIPPO SNORTS 304 00:38:04,460 --> 00:38:09,500 With no other water around, the river becomes a magnet for visitors. 305 00:38:15,420 --> 00:38:20,060 Millions of red-billed quelea flock to the water's edge. 306 00:38:24,380 --> 00:38:28,180 These seed eaters need to drink every day... 307 00:38:47,140 --> 00:38:49,860 ...and Nile crocodiles know it. 308 00:38:51,380 --> 00:38:53,700 They may not have eaten for six months. 309 00:38:54,940 --> 00:38:59,820 For them, the dry season is the start of the good times. 310 00:39:09,380 --> 00:39:14,140 And they are not the only ones to depend on this time of year. 311 00:39:19,420 --> 00:39:23,140 Carmine bee-eaters have flown hundreds of miles 312 00:39:23,140 --> 00:39:25,460 from the rainforests of the Congo... 313 00:39:27,140 --> 00:39:30,380 ...arriving at the peak of the dry season, 314 00:39:30,380 --> 00:39:35,300 when steep sandbanks are exposed by the falling water. 315 00:39:41,700 --> 00:39:44,420 They're a perfect place to nest, 316 00:39:44,420 --> 00:39:47,260 out of reach of predators from above. 317 00:39:56,580 --> 00:40:02,020 Bee-eater burrows can extend for two metres into the soft river sand. 318 00:40:03,620 --> 00:40:06,460 Already home to 6,000 nests, 319 00:40:06,460 --> 00:40:11,100 real estate at Bee-eater Towers is in high demand. 320 00:40:15,060 --> 00:40:18,900 But it pays not to build too close to the neighbours. 321 00:40:29,500 --> 00:40:34,460 As more birds arrive, competition for the best nesting sites heats up. 322 00:40:45,500 --> 00:40:47,500 It's thirsty work. 323 00:40:58,340 --> 00:41:02,180 In the sudden commotion, they're vulnerable from below... 324 00:41:04,180 --> 00:41:05,820 ...and above. 325 00:41:09,740 --> 00:41:12,300 African fish eagles. 326 00:41:20,660 --> 00:41:23,740 They are permanent residents here. 327 00:41:23,740 --> 00:41:27,700 But at this time of the year, they don't just eat fish. 328 00:41:32,660 --> 00:41:36,220 The safest place to be is inside a burrow. 329 00:41:37,940 --> 00:41:43,540 But an eagle fly-by sends shock waves of panic through the colony. 330 00:41:56,420 --> 00:42:01,260 The eagles' strategy is to pin their prey against the river bank. 331 00:42:05,340 --> 00:42:08,100 With the colony in disarray, 332 00:42:08,100 --> 00:42:10,460 the predators have the advantage. 333 00:42:50,700 --> 00:42:55,100 These fish eagles also choose to breed in the dry season, 334 00:42:55,100 --> 00:42:59,340 because they need the bee-eaters as food for their chicks. 335 00:43:06,620 --> 00:43:11,540 But this year's dry season shows no sign of letting up. 336 00:43:19,180 --> 00:43:22,540 Parts of the river are now bone-dry, 337 00:43:22,540 --> 00:43:26,380 forcing huge male hippos from their home. 338 00:43:36,740 --> 00:43:39,020 With nowhere left to turn, 339 00:43:39,020 --> 00:43:42,420 they must converge on the few remaining patches of water... 340 00:43:42,420 --> 00:43:44,300 HIPPO GRUNTS 341 00:43:44,300 --> 00:43:47,100 ..but these are already occupied. 342 00:43:59,940 --> 00:44:03,540 The resident bull here can't tolerate another big male 343 00:44:03,540 --> 00:44:06,060 in his shrinking pool. 344 00:44:08,500 --> 00:44:10,460 HIPPO BELLOWS 345 00:44:36,500 --> 00:44:39,420 The newcomer is banished. 346 00:44:50,500 --> 00:44:53,580 Still the sun bakes the land... 347 00:44:56,660 --> 00:44:59,820 ...with devastating consequences. 348 00:45:31,740 --> 00:45:34,740 Hundreds of nests are wiped out. 349 00:45:43,140 --> 00:45:47,180 Southern Africa has experienced dry seasons 350 00:45:47,180 --> 00:45:49,340 for thousands of years. 351 00:45:50,860 --> 00:45:53,860 But this is something different. 352 00:45:58,940 --> 00:46:04,620 Record high temperatures and the lowest rainfall in nearly 40 years 353 00:46:04,620 --> 00:46:09,700 have thrown parts of Africa into one of the worst droughts in a century. 354 00:46:17,060 --> 00:46:18,860 THUNDER CRASHES 355 00:46:25,540 --> 00:46:30,820 Across the planet, our once stable climate is changing. 356 00:46:35,700 --> 00:46:37,940 Weather is less reliable... 357 00:46:40,380 --> 00:46:43,580 ...and is getting more extreme. 358 00:46:47,300 --> 00:46:50,140 Wildfires are becoming more frequent. 359 00:47:05,900 --> 00:47:08,540 Droughts are more intense. 360 00:47:19,380 --> 00:47:23,500 And storms are more ferocious. 361 00:47:27,740 --> 00:47:32,980 All this from a recent rise in global temperatures 362 00:47:32,980 --> 00:47:35,820 of just a single degree Celsius. 363 00:47:37,620 --> 00:47:40,940 Yet if climate change continues unchecked, 364 00:47:40,940 --> 00:47:46,980 we may see a rise of almost five degrees by the end of the century. 365 00:47:48,940 --> 00:47:53,500 We can only imagine what this will do to our weather. 366 00:48:12,220 --> 00:48:15,660 There are a few things more daunting for the wildlife film crew 367 00:48:15,660 --> 00:48:20,540 than the prospect of finding a very rare animal in a vast area. 368 00:48:24,700 --> 00:48:28,660 But that is the mission in Mongolia's Gobi Desert - 369 00:48:28,660 --> 00:48:32,220 to film an animal numbering less than 500 370 00:48:32,220 --> 00:48:35,940 in a wilderness of half a million square miles. 371 00:48:41,860 --> 00:48:45,060 We're all loaded up. We got 40 cases of gear, we got nine vehicles. 372 00:48:45,060 --> 00:48:47,340 We're off, we're heading to the Gobi. 373 00:48:50,820 --> 00:48:53,260 DAVID ATTENBOROUGH: From the capital, Ulaanbaatar, 374 00:48:53,260 --> 00:48:56,260 it'll take the team five days to cross Mongolia 375 00:48:56,260 --> 00:48:58,740 in the depths of winter - 376 00:48:58,740 --> 00:49:02,580 travelling in a convoy of large camping trucks, 377 00:49:02,580 --> 00:49:04,580 home for the next five weeks. 378 00:49:22,500 --> 00:49:28,340 1,000 miles later, the convoy reaches the Gobi and makes camp. 379 00:49:32,620 --> 00:49:35,700 Well, we have woken up on our first morning, 380 00:49:35,700 --> 00:49:38,580 and it's about an hour-and-a-half before sunrise, 381 00:49:38,580 --> 00:49:43,260 and rather foolishly we let the fire go out last night, so it's... 382 00:49:43,260 --> 00:49:45,460 ..a cool minus 20 in here. 383 00:49:45,460 --> 00:49:49,100 Everything's frozen solid - toothpaste, hot sauce for breakfast, 384 00:49:49,100 --> 00:49:51,140 even the AP's pee bottle... 385 00:49:51,140 --> 00:49:52,940 ..so that's nice. 386 00:49:55,620 --> 00:49:59,020 Finding a scarce animal in an area the size of Belgium 387 00:49:59,020 --> 00:50:01,900 is clearly no small task... 388 00:50:01,900 --> 00:50:04,980 GARBLED RADIO CONVERSATION 389 00:50:04,980 --> 00:50:08,860 ...but impossible without the help of local researchers. 390 00:50:10,700 --> 00:50:15,100 Each day, the team scour thousands of square miles. 391 00:50:15,100 --> 00:50:17,540 It's a huge area, and there's only 450 camels, 392 00:50:17,540 --> 00:50:20,860 so it really is a bit like a needle in a haystack. 393 00:50:22,100 --> 00:50:25,300 A truly enormous haystack. 394 00:50:29,540 --> 00:50:31,620 450 camels... ADIYA LAUGHS 395 00:50:31,620 --> 00:50:33,140 ...28,000 square miles. 396 00:50:33,140 --> 00:50:35,220 Easy, yeah? Yeah. 397 00:50:35,220 --> 00:50:38,260 And when scanning the horizon for camels, 398 00:50:38,260 --> 00:50:40,260 mistakes are all too easy. 399 00:50:40,260 --> 00:50:41,700 Another bush. 400 00:50:42,780 --> 00:50:45,060 A bush. Sorry. 401 00:50:46,580 --> 00:50:49,420 Sometimes there's not even a bush to look at. 402 00:50:49,420 --> 00:50:51,020 See anything? Nothing. 403 00:50:52,300 --> 00:50:54,300 Another hill climbed. 404 00:50:54,300 --> 00:50:56,100 Another trail followed. 405 00:50:56,100 --> 00:50:58,380 Another dead end. 406 00:50:58,380 --> 00:51:01,220 Thankfully, the experts remain positive. 407 00:51:01,220 --> 00:51:03,020 I hope you can see them soon. 408 00:51:03,020 --> 00:51:04,620 Yeah, yeah. Please. 409 00:51:07,500 --> 00:51:09,300 Two weeks since leaving the UK. 410 00:51:09,300 --> 00:51:11,780 I'm just hoping that we haven't... 411 00:51:11,780 --> 00:51:13,660 ...been slightly overambitious on this one. 412 00:51:13,660 --> 00:51:16,700 Getting slightly worried it might actually be impossible. 413 00:51:18,460 --> 00:51:20,180 ED SIGHS 414 00:51:22,100 --> 00:51:23,940 Hmm... Good support there, thanks. 415 00:51:25,300 --> 00:51:29,260 Eventually, the team spot their first camel... 416 00:51:29,260 --> 00:51:32,140 ..but, unfortunately, it spotted them first. 417 00:51:33,500 --> 00:51:35,540 Very far away. 418 00:51:35,540 --> 00:51:38,900 Poaching has made the surviving camels very nervous, 419 00:51:38,900 --> 00:51:42,780 and once they start running they can keep going for miles. 420 00:51:45,060 --> 00:51:47,300 WIND HOWLS 421 00:51:47,300 --> 00:51:49,740 And when the winter winds kick off, 422 00:51:49,740 --> 00:51:52,620 all signs of camel vanish. 423 00:51:52,620 --> 00:51:55,180 So, for about the past 24 hours, we've been experiencing 424 00:51:55,180 --> 00:51:58,100 the Gobi winds. It's been gusting up to 70mph hour all night, 425 00:51:58,100 --> 00:52:00,460 and the temps have probably been down to almost -50 426 00:52:00,460 --> 00:52:03,540 with the wind-chill. We just have to hunker down, we can't film in this. 427 00:52:07,660 --> 00:52:11,860 When the gale eases, the search reveals new hope. 428 00:52:13,340 --> 00:52:15,340 We got a load of fresh camel tracks here. 429 00:52:16,740 --> 00:52:20,140 And all tracks head one way - 430 00:52:20,140 --> 00:52:24,620 towards the even more remote mountainous southern Gobi. 431 00:52:28,780 --> 00:52:32,420 The team must decide if they should follow. 432 00:52:32,420 --> 00:52:36,180 Do you think that landscape is likely to be better for us? 433 00:52:36,180 --> 00:52:39,100 More camels and closer encounters or...? 434 00:52:39,100 --> 00:52:41,060 What's your gut telling you? 435 00:52:43,260 --> 00:52:45,420 Because of the wintertime, 436 00:52:45,420 --> 00:52:48,100 we need to see some snow... Mm. 437 00:52:48,100 --> 00:52:49,260 ...to see camels. 438 00:52:50,700 --> 00:52:55,300 To survive in this waterless desert, the camels depend on finding snow. 439 00:52:56,980 --> 00:52:59,300 So, with none in sight, 440 00:52:59,300 --> 00:53:03,660 the team decide to try their luck in the icy mountains to the south. 441 00:53:08,140 --> 00:53:09,980 Sure enough, there's snow - 442 00:53:09,980 --> 00:53:11,740 and lots of it. 443 00:53:15,100 --> 00:53:19,340 But the larger camping trucks struggle in the mountainous terrain, 444 00:53:19,340 --> 00:53:22,580 and the team are forced to go on without them, 445 00:53:22,580 --> 00:53:27,700 leaving them somewhat more exposed to the winter conditions. 446 00:53:27,700 --> 00:53:30,020 It's been down to -25 over the last week. 447 00:53:30,020 --> 00:53:33,380 So very thin canvas tents will be a whole new experience 448 00:53:33,380 --> 00:53:36,020 in the Gobi Desert for us. 449 00:53:36,020 --> 00:53:39,540 I'm wearing, currently, two pairs of trousers, thermals, 450 00:53:39,540 --> 00:53:43,420 thermals on top, two pairs of jumpers, three coats, two hats... 451 00:53:43,420 --> 00:53:45,940 So I THINK I should be all right. 452 00:53:45,940 --> 00:53:47,100 HE EXHALES 453 00:53:49,380 --> 00:53:51,020 TOBY: You all right, Eddie? 454 00:53:51,020 --> 00:53:52,700 Oh, I'm terrific, yeah. 455 00:53:52,700 --> 00:53:55,100 HE LAUGHS Really terrific! 456 00:53:55,100 --> 00:53:57,660 HE SIGHS CONTENTEDLY I'm all cosy. 457 00:53:59,140 --> 00:54:00,580 I'm not. I'm cold. 458 00:54:00,580 --> 00:54:02,020 Really cold! 459 00:54:06,420 --> 00:54:11,740 As Adiya predicted, with snow come camels. 460 00:54:11,740 --> 00:54:14,540 The signs are everywhere. 461 00:54:17,860 --> 00:54:19,700 But having travelled so far, 462 00:54:19,700 --> 00:54:22,740 they can't risk anything ruining this chance. 463 00:54:22,740 --> 00:54:26,220 HUSHED: Camels don't seem to like the cars so... 464 00:54:26,220 --> 00:54:27,700 ...now we walk. 465 00:54:29,860 --> 00:54:32,180 We've been walking for about five miles now, 466 00:54:32,180 --> 00:54:34,500 and hiking across this landscape, 467 00:54:34,500 --> 00:54:38,140 it really does give you a new-found respect for the camels. 468 00:54:43,660 --> 00:54:46,900 We've seen some camels way out on the plain here, 469 00:54:46,900 --> 00:54:51,300 but in order not to scare them, John's going to head out on his own. 470 00:55:04,140 --> 00:55:06,980 Yeah, yeah, I can see him. He's, um... 471 00:55:06,980 --> 00:55:08,620 ADIYA: Going to south? 472 00:55:08,620 --> 00:55:12,020 Yeah, he's going to the south, he's just this side of the ridge. 473 00:55:18,660 --> 00:55:20,620 The camels come to John. 474 00:55:20,620 --> 00:55:22,620 They are? The camels are coming to John? 475 00:55:22,620 --> 00:55:24,020 Yes! Really? 476 00:55:28,620 --> 00:55:31,900 JOHN OVER RADIO: Maybe grab the bags and come down to where I am now 477 00:55:31,900 --> 00:55:35,500 by these bushes, and we'll see if we can't slip down into the oasis. 478 00:55:40,940 --> 00:55:43,940 HUSHED: This is just amazing. It's hard fought... 479 00:55:43,940 --> 00:55:46,820 ..but the reward is so worth it. 480 00:55:46,820 --> 00:55:50,180 Because right now we're about 100 metres away... 481 00:55:51,580 --> 00:55:56,540 ...from some of the rarest and hardiest mammals on the planet. 482 00:55:59,180 --> 00:56:00,580 What a privilege. 483 00:56:02,900 --> 00:56:06,820 The team film behaviour very few people have seen. 484 00:56:08,340 --> 00:56:12,700 Rare images of one of the world's most endangered creatures. 485 00:56:14,220 --> 00:56:17,660 Once widespread across Central Asia, 486 00:56:17,660 --> 00:56:22,260 this uninhabited desert is the wild camels' final home. 487 00:56:24,180 --> 00:56:28,860 Were it not for Adiya's team, it might have disappeared altogether, 488 00:56:28,860 --> 00:56:33,860 but because of their work we may yet save this icon of the Gobi. 489 00:56:39,180 --> 00:56:41,580 Next time... 490 00:56:41,580 --> 00:56:42,980 ..oceans. 491 00:56:45,660 --> 00:56:49,740 All marine life depends on the continuous movement of water. 492 00:56:51,620 --> 00:56:54,820 Our oceans are linked by powerful tides... 493 00:56:56,660 --> 00:56:58,500 ..and where there are currents, 494 00:56:58,500 --> 00:57:00,260 there is life. 495 00:57:04,460 --> 00:57:07,500 The Open University has produced a free poster 496 00:57:07,500 --> 00:57:09,900 exploring our perfect planet. 497 00:57:09,900 --> 00:57:14,940 To order, please call 0300 303 0901. 498 00:57:14,940 --> 00:57:19,860 Or go to bbc.co.uk/perfectplanet 499 00:57:19,860 --> 00:57:23,060 and follow the links to the Open University.