1 00:00:26,880 --> 00:00:29,080 A Perfect Planet. 2 00:00:43,840 --> 00:00:48,040 We live in a world with a violent atmosphere. 3 00:00:51,320 --> 00:00:53,320 Rain clouds form, 4 00:00:53,320 --> 00:00:57,640 and powerful winds carry their fresh water around the globe. 5 00:01:00,040 --> 00:01:05,480 Without this, our perfect planet simply couldn't function... 6 00:01:05,480 --> 00:01:10,360 ...for all life on land depends on the weather. 7 00:01:23,040 --> 00:01:26,560 We all know that the weather can change on a daily, 8 00:01:26,560 --> 00:01:28,600 even hourly, basis. 9 00:01:30,840 --> 00:01:35,080 But annual weather patterns have been stable for millennia... 10 00:01:36,360 --> 00:01:41,120 ...and it's this reliability on which life depends. 11 00:01:41,120 --> 00:01:42,920 ANIMALS AND BIRDS CALL 12 00:01:46,880 --> 00:01:51,680 Every year in October, the weather brings a dramatic transformation 13 00:01:51,680 --> 00:01:55,080 to this tiny patch of forest in Zambia. 14 00:02:00,000 --> 00:02:02,640 Storm clouds begin to build. 15 00:02:06,240 --> 00:02:08,200 THUNDER CRASHES 16 00:02:10,920 --> 00:02:17,000 And right on cue, straw-coloured fruit bats start to appear. 17 00:02:22,800 --> 00:02:27,520 They've travelled hundreds, if not thousands, of miles to be here. 18 00:02:35,160 --> 00:02:39,080 And they always arrive at exactly the same time. 19 00:02:41,760 --> 00:02:45,880 They know that these rains will transform this forest, 20 00:02:45,880 --> 00:02:49,560 allowing countless fruit trees to ripen. 21 00:02:53,720 --> 00:02:58,200 And the bats gorge on the new-found abundance. 22 00:03:16,880 --> 00:03:20,080 For just 12 weeks every year, 23 00:03:20,080 --> 00:03:25,280 this forest becomes home to ten million fruit bats. 24 00:03:28,920 --> 00:03:32,920 One of the greatest gatherings of mammals on Earth, 25 00:03:32,920 --> 00:03:37,920 all crowding into an area no bigger than a dozen football pitches. 26 00:03:41,480 --> 00:03:44,480 From this hub, the bats fan out, 27 00:03:44,480 --> 00:03:48,440 consuming more than 300,000 tonnes of fruit, 28 00:03:48,440 --> 00:03:52,280 spreading the seeds and regenerating the forests. 29 00:04:11,480 --> 00:04:17,520 Africa's largest wildlife migration entirely dependent on the rain 30 00:04:17,520 --> 00:04:21,240 that comes to this small corner of Zambia 31 00:04:21,240 --> 00:04:24,240 at the same time each year. 32 00:04:39,880 --> 00:04:44,120 Every second, over 13 million tonnes of water 33 00:04:44,120 --> 00:04:48,800 evaporate from our oceans, forming clouds. 34 00:04:55,280 --> 00:04:58,240 The spin of the Earth and the prevailing winds 35 00:04:58,240 --> 00:05:01,120 determine where these clouds blow. 36 00:05:02,880 --> 00:05:06,440 As a consequence, some places get less rain... 37 00:05:08,080 --> 00:05:10,200 ...and others much more. 38 00:05:12,680 --> 00:05:14,800 The Amazon rainforest... 39 00:05:16,160 --> 00:05:17,680 THUNDER CRASHES 40 00:05:17,680 --> 00:05:20,880 ...one of the wettest places on Earth. 41 00:05:30,880 --> 00:05:33,360 It gets three metres of rain a year... 42 00:05:35,160 --> 00:05:40,640 ...so life has learned to deal with the near-daily downpours. 43 00:05:46,000 --> 00:05:49,000 Every year, for thousands of years, 44 00:05:49,000 --> 00:05:53,840 the persistent rains have flooded vast tracts of the Amazon... 45 00:05:55,800 --> 00:06:00,560 ...turning the jungle into a seasonal wetland. 46 00:06:02,320 --> 00:06:07,520 Anything living here must either climb or swim. 47 00:06:11,840 --> 00:06:16,200 But there's one extraordinary animal that has turned this deluge 48 00:06:16,200 --> 00:06:20,000 from a disaster into an opportunity. 49 00:06:25,720 --> 00:06:30,480 This fire ant has reached the edge of her known world. 50 00:06:34,080 --> 00:06:38,800 Her way forward has now become blocked by the rising waters. 51 00:06:45,200 --> 00:06:48,160 She's one of many, and in a few minutes 52 00:06:48,160 --> 00:06:51,280 their underground home will be submerged. 53 00:06:57,880 --> 00:07:04,400 Forced to evacuate, workers and soldiers try to save the larval young. 54 00:07:06,080 --> 00:07:10,840 As their nest floods, the colony seems to be doomed. 55 00:07:18,640 --> 00:07:22,320 But from chaos comes order. 56 00:07:24,280 --> 00:07:29,000 The fire ants band together, each locking legs with its neighbours. 57 00:07:31,760 --> 00:07:34,640 They're building a living raft. 58 00:07:37,240 --> 00:07:42,800 Each ant is covered in fine hairs that trap air against its body. 59 00:07:47,040 --> 00:07:53,040 As the raft forms, this air creates a cushion for them all to float on. 60 00:07:55,760 --> 00:07:58,360 This is the power of the colony. 61 00:07:59,720 --> 00:08:03,120 By working together, they've become unsinkable. 62 00:08:07,600 --> 00:08:09,880 And no-one gets left behind. 63 00:08:22,840 --> 00:08:27,720 Pulled from the shallows, the colony is now at the mercy of the flood. 64 00:08:33,520 --> 00:08:35,680 Holding tight to the larvae 65 00:08:35,680 --> 00:08:38,920 and keeping their queen hidden at the centre of the raft, 66 00:08:38,920 --> 00:08:42,560 the colony drifts into deeper water... 67 00:08:47,880 --> 00:08:50,320 ...where they're vulnerable to fish 68 00:08:50,320 --> 00:08:53,360 that now swim through the flooded forest. 69 00:08:59,640 --> 00:09:04,800 Those that lose their grip must get back to the safety of the raft. 70 00:09:16,280 --> 00:09:20,280 With jaws that join to become a surgical needle, 71 00:09:20,280 --> 00:09:24,040 this pond skater could suck an ant dry. 72 00:09:35,480 --> 00:09:38,560 But together the colony is strong, 73 00:09:38,560 --> 00:09:41,320 and it's time to repel boarders. 74 00:09:52,800 --> 00:09:56,200 The ants can travel like this for weeks. 75 00:09:59,080 --> 00:10:02,520 They've even come to depend on the flood to carry them 76 00:10:02,520 --> 00:10:04,920 to new feeding grounds. 77 00:10:17,800 --> 00:10:22,120 At last, the ants can make their raft secure. 78 00:10:27,560 --> 00:10:30,880 Surging forward, they claim their new home... 79 00:10:32,000 --> 00:10:35,560 ...evicting current tenants without hesitation. 80 00:10:39,240 --> 00:10:42,760 One of the first to safety is their larval queen, 81 00:10:42,760 --> 00:10:45,320 carried from the heart of the raft. 82 00:10:52,200 --> 00:10:56,200 This palm will be their home for the next three months, 83 00:10:56,200 --> 00:11:00,760 until the floodwaters recede and they can head back underground. 84 00:11:14,000 --> 00:11:17,480 The average temperature of our planet hasn't varied 85 00:11:17,480 --> 00:11:22,320 by more than a single degree Celsius in 10,000 years. 86 00:11:24,000 --> 00:11:26,720 This has made our climate stable, 87 00:11:26,720 --> 00:11:29,920 allowing animals to fine-tune their behaviour 88 00:11:29,920 --> 00:11:33,120 around predictable weather patterns. 89 00:11:36,240 --> 00:11:38,520 October in the Amazon. 90 00:11:40,240 --> 00:11:42,800 The heaviest rains have come to an end, 91 00:11:42,800 --> 00:11:47,200 and the falling river level exposes a new landscape. 92 00:11:50,000 --> 00:11:55,200 Three weeks ago, these mile-wide sand bars didn't exist. 93 00:11:57,480 --> 00:12:01,760 In another three months, they'll be back under water. 94 00:12:04,240 --> 00:12:10,480 But now they provide a crucial opportunity for giant river turtles. 95 00:12:13,160 --> 00:12:18,000 They've been coming here at precisely this time of year for generations. 96 00:12:23,760 --> 00:12:28,080 50,000 of them - a quarter of the world's population. 97 00:12:32,280 --> 00:12:34,440 They're all here for one reason. 98 00:12:36,000 --> 00:12:38,920 But their window of opportunity is short, 99 00:12:38,920 --> 00:12:41,560 so timing is everything. 100 00:12:46,160 --> 00:12:50,440 Scaling the three-metre-high banks will take this female 101 00:12:50,440 --> 00:12:54,480 higher and drier than she's been for months. 102 00:12:57,080 --> 00:13:00,680 She's come here to lay her eggs. 103 00:13:01,760 --> 00:13:04,080 But others have beaten her to it. 104 00:13:14,400 --> 00:13:17,560 The early arrivals have already claimed 105 00:13:17,560 --> 00:13:20,080 nearly every inch of the beach... 106 00:13:21,240 --> 00:13:23,880 ...and there are still many more turtles to come. 107 00:13:30,280 --> 00:13:33,440 Wherever she turns, the space is taken. 108 00:13:33,440 --> 00:13:35,360 SAND PATTERS 109 00:13:42,240 --> 00:13:46,520 But being fashionably late does have an advantage. 110 00:13:49,280 --> 00:13:52,880 Had she arrived earlier, her eggs might have been 111 00:13:52,880 --> 00:13:56,400 dug up by those searching for somewhere to lay. 112 00:14:02,200 --> 00:14:04,200 She's found her spot. 113 00:14:10,960 --> 00:14:16,200 Settling down, she lays nearly 100 eggs. 114 00:14:20,520 --> 00:14:23,880 Burying them keeps them safe from predators, 115 00:14:23,880 --> 00:14:27,200 and the warm sand incubates the clutch. 116 00:14:34,400 --> 00:14:39,960 They must hatch before the river rises again and floods the sandbar. 117 00:14:44,080 --> 00:14:48,160 Any turtles that lay after her may have left it too late. 118 00:14:55,320 --> 00:14:58,600 Hopefully, she has got her timing right. 119 00:15:11,920 --> 00:15:17,200 Two months on, and the hatchlings emerge into the world. 120 00:15:27,080 --> 00:15:30,640 They were laid at the perfect time. 121 00:15:30,640 --> 00:15:32,880 Hundreds scramble for the river 122 00:15:32,880 --> 00:15:35,400 just as the water starts to rise. 123 00:15:37,440 --> 00:15:40,680 Those still to hatch aren't so lucky. 124 00:15:46,680 --> 00:15:50,000 This year, the heavy rains have returned early. 125 00:15:50,000 --> 00:15:51,920 THUNDER RUMBLES 126 00:16:11,680 --> 00:16:14,720 The nesting beach is beginning to flood. 127 00:16:22,560 --> 00:16:26,000 Most hatchlings can escape in time. 128 00:16:33,560 --> 00:16:35,920 Those still below ground... 129 00:16:37,240 --> 00:16:39,360 ...will drown in their nests. 130 00:16:44,320 --> 00:16:49,200 For thousands of years, giant river turtles have timed their breeding 131 00:16:49,200 --> 00:16:53,320 around the Amazon's reliable cycles of rain. 132 00:16:56,880 --> 00:17:00,360 But today, our weather is changing. 133 00:17:04,760 --> 00:17:11,480 Disastrous early floods like this used to happen once every 20 years. 134 00:17:11,480 --> 00:17:16,320 Now the turtles have to deal with them every four. 135 00:17:30,720 --> 00:17:34,920 Winds may carry huge amounts of rain to the Amazon, 136 00:17:34,920 --> 00:17:39,840 but they don't provide this service to every corner of the planet. 137 00:17:41,560 --> 00:17:48,200 A third of the land receives less than 25cm of rain a year. 138 00:17:52,320 --> 00:17:58,000 Deserts are scarred by desiccating winds and baked by the sun. 139 00:18:00,720 --> 00:18:06,160 But even weather as challenging as this can be perfect for the locals. 140 00:18:11,680 --> 00:18:15,480 As darkness falls in the coastal deserts of South Africa, 141 00:18:15,480 --> 00:18:18,000 the dunes come alive... 142 00:18:18,000 --> 00:18:19,880 HIGH-PITCHED CALL 143 00:18:19,880 --> 00:18:23,760 ...with the call of a surprising desert dweller. 144 00:18:25,440 --> 00:18:28,240 HIGH-PITCHED CALL 145 00:18:31,760 --> 00:18:33,400 CALL CONTINUES 146 00:18:43,960 --> 00:18:46,880 A rain frog. 147 00:18:46,880 --> 00:18:53,760 Not what you'd expect in a place that gets just 7cm of rain a year. 148 00:18:58,200 --> 00:19:02,240 To survive here, she has to avoid the heat of the day 149 00:19:02,240 --> 00:19:04,280 buried in the sand. 150 00:19:06,520 --> 00:19:09,560 But each night, she heads out... 151 00:19:09,560 --> 00:19:12,280 ..on her hunt for moisture. 152 00:19:15,800 --> 00:19:20,240 Short, stumpy legs and a plump body are ideal for digging... 153 00:19:23,280 --> 00:19:26,560 ...but not so good for getting around. 154 00:19:30,560 --> 00:19:36,480 She can't hop, so she waddles across the dunes. 155 00:19:43,600 --> 00:19:47,880 The world's slowest steeplechaser. 156 00:19:52,000 --> 00:19:56,320 Obstacles are tackled with dogged perseverance. 157 00:20:03,160 --> 00:20:07,520 She can travel a whopping 38 metres a night. 158 00:20:07,520 --> 00:20:13,200 No mean feat when you're the same size and shape as a marshmallow. 159 00:20:18,800 --> 00:20:20,840 Termites. 160 00:20:20,840 --> 00:20:24,720 They are 75% water - 161 00:20:24,720 --> 00:20:28,320 a meal and a drink in one. 162 00:20:32,320 --> 00:20:36,560 But she's not the most agile predator. 163 00:20:38,120 --> 00:20:42,320 Maybe if they just came a little closer...? 164 00:20:46,360 --> 00:20:48,360 Oh, dear. 165 00:20:50,400 --> 00:20:53,480 Perhaps if they stop moving...? 166 00:21:14,080 --> 00:21:15,760 At last. 167 00:21:17,000 --> 00:21:20,640 But now she has another challenge. 168 00:21:20,640 --> 00:21:24,720 To swallow her food, she must squash in her eyeballs 169 00:21:24,720 --> 00:21:27,240 to push it down her throat. 170 00:21:35,880 --> 00:21:38,040 Termites may be juicy, 171 00:21:38,040 --> 00:21:41,840 but they don't provide her with quite enough water to survive. 172 00:21:45,520 --> 00:21:48,080 It rarely rains here, 173 00:21:48,080 --> 00:21:53,640 but coastal deserts do get another reliable source of moisture. 174 00:22:04,400 --> 00:22:09,080 At night - cool, moist air is blown in from the ocean, 175 00:22:09,080 --> 00:22:13,440 forming fog banks that shroud the desert in mist. 176 00:22:25,120 --> 00:22:29,800 It condenses on vegetation, wetting the sand beneath. 177 00:22:29,800 --> 00:22:35,200 So it's here that she waits, absorbing moisture through her skin. 178 00:22:43,120 --> 00:22:47,800 Rain frogs are so dependent on this water that they can only survive 179 00:22:47,800 --> 00:22:52,720 in places with at least 100 days of fog a year. 180 00:22:54,920 --> 00:22:57,120 And on the foggiest nights, 181 00:22:57,120 --> 00:23:00,120 when other frogs have emerged onto the dunes, 182 00:23:00,120 --> 00:23:04,360 she takes her opportunity to find love. 183 00:23:11,760 --> 00:23:15,680 Male rain frogs are smaller than the females, 184 00:23:15,680 --> 00:23:20,920 and his stubby legs make it hard to hold on... 185 00:23:20,920 --> 00:23:24,920 ..so he glues himself onto her back. 186 00:23:35,480 --> 00:23:37,840 Still locked in their embrace, 187 00:23:37,840 --> 00:23:42,400 the pair head back beneath the sand, where they'll lay their eggs, 188 00:23:42,400 --> 00:23:45,720 safe from the heat of the desert sun. 189 00:23:54,240 --> 00:23:57,840 But there's one desert that gets so cold 190 00:23:57,840 --> 00:24:01,800 that liquid water simply can't exist. 191 00:24:04,480 --> 00:24:08,600 Winter in Mongolia's Gobi Desert. 192 00:24:10,120 --> 00:24:12,960 40 degrees below freezing. 193 00:24:15,640 --> 00:24:20,280 One of the driest and most extreme environments in the world. 194 00:24:26,960 --> 00:24:30,680 Most animals can't survive weather like this... 195 00:24:33,080 --> 00:24:35,680 ...but there's one unique mammal 196 00:24:35,680 --> 00:24:38,880 that manages to eke out a living here. 197 00:24:41,520 --> 00:24:48,240 The Gobi is home to the last 1,000 wild Bactrian camels on Earth... 198 00:24:50,280 --> 00:24:53,120 ...surviving at the very edge of what's possible. 199 00:24:54,400 --> 00:24:56,600 CAMEL GRUNTS 200 00:24:56,600 --> 00:24:59,000 Even camels need moisture, 201 00:24:59,000 --> 00:25:02,960 but any water here is now frozen solid. 202 00:25:06,480 --> 00:25:09,680 It's down to the bull to find a solution. 203 00:25:12,480 --> 00:25:14,320 BULL GRUNTS 204 00:25:17,120 --> 00:25:19,120 Setting off with his herd, 205 00:25:19,120 --> 00:25:22,560 his search could cover thousands of square miles. 206 00:25:28,440 --> 00:25:33,280 Driving them forward, he can keep going for days on end. 207 00:25:43,760 --> 00:25:47,120 Herds come together from across their vast range... 208 00:25:48,720 --> 00:25:50,920 ...all looking for the same thing. 209 00:25:59,560 --> 00:26:05,880 These long-distance specialists can smell moisture from 30 miles away... 210 00:26:05,880 --> 00:26:08,200 ...and they've picked up a scent. 211 00:26:13,160 --> 00:26:17,560 Even in the Gobi, one of the driest places on Earth, 212 00:26:17,560 --> 00:26:21,560 wind can provide a rare source of moisture. 213 00:26:23,560 --> 00:26:27,920 Snow is blown to this desert from Siberia. 214 00:26:29,640 --> 00:26:33,000 Where it settles is impossible to predict, 215 00:26:33,000 --> 00:26:35,120 and it may not last long. 216 00:26:42,080 --> 00:26:47,320 But for now, at least, this bull has found what he's been searching for. 217 00:26:57,320 --> 00:26:59,440 In the cold, dry air, 218 00:26:59,440 --> 00:27:01,520 snow doesn't melt... 219 00:27:03,400 --> 00:27:05,920 ...so it must be eaten. 220 00:27:15,120 --> 00:27:19,040 The Gobi's windblown snow is a lifeline 221 00:27:19,040 --> 00:27:22,440 that will sustain his herd throughout the winter. 222 00:27:30,160 --> 00:27:33,440 Even in this most hostile of places, 223 00:27:33,440 --> 00:27:37,840 weather still provides just enough for survival. 224 00:27:49,600 --> 00:27:53,800 The largest, most unpredictable weather on the planet 225 00:27:53,800 --> 00:27:56,880 starts far out at sea. 226 00:28:02,560 --> 00:28:06,560 Hurricanes, typhoons and tropical cyclones 227 00:28:06,560 --> 00:28:10,120 are violent, short-lived megastorms. 228 00:28:11,600 --> 00:28:14,560 But there's a far more reliable weather system 229 00:28:14,560 --> 00:28:16,920 that originates over the ocean... 230 00:28:18,120 --> 00:28:22,720 ...one that is eagerly anticipated by all in its path. 231 00:28:25,640 --> 00:28:31,920 Monsoons are seasonal winds that blow at the same time each year... 232 00:28:34,320 --> 00:28:39,160 ...and they carry colossal amounts of water from the ocean to the land. 233 00:28:46,640 --> 00:28:48,240 Christmas Island. 234 00:28:49,560 --> 00:28:53,160 A remote speck of rock in the Indian Ocean. 235 00:28:57,480 --> 00:29:03,960 For the last four months, its forest interior has remained dry and dusty. 236 00:29:07,240 --> 00:29:11,120 Life here is waiting for change. 237 00:29:14,000 --> 00:29:18,960 In November, the first storms of the monsoon reach the island. 238 00:29:18,960 --> 00:29:21,440 THUNDER CRASHES 239 00:29:36,520 --> 00:29:40,960 They're a welcome relief for those that have suffered through the dry. 240 00:29:45,280 --> 00:29:50,440 And they are vital for the island's most numerous residents. 241 00:30:04,480 --> 00:30:07,920 The red crabs of Christmas Island. 242 00:30:12,040 --> 00:30:15,280 They've spent the dry season sheltering in damp burrows 243 00:30:15,280 --> 00:30:17,280 beneath the leaf litter. 244 00:30:20,520 --> 00:30:24,880 Crabs breathe through gills that must be kept moist. 245 00:30:29,240 --> 00:30:33,040 So it's only with the return of the annual monsoon 246 00:30:33,040 --> 00:30:37,040 that these land crabs can finally emerge. 247 00:30:44,240 --> 00:30:46,360 With the humidity now high enough, 248 00:30:46,360 --> 00:30:50,080 they can begin an epic trek to the coast. 249 00:31:02,680 --> 00:31:07,280 Every red crab comes together from across the island, 250 00:31:07,280 --> 00:31:10,000 and they do so in their millions. 251 00:31:12,320 --> 00:31:15,240 50 million, to be precise. 252 00:31:29,560 --> 00:31:34,920 They've come to release their eggs that can only develop in the ocean. 253 00:31:36,360 --> 00:31:38,800 There's just one small problem. 254 00:31:40,000 --> 00:31:42,920 They may be crabs... 255 00:31:42,920 --> 00:31:45,120 ...but they can't swim. 256 00:31:48,720 --> 00:31:51,080 They're scared of the sea. 257 00:32:04,920 --> 00:32:07,240 But they don't have a choice. 258 00:32:08,560 --> 00:32:13,080 They must release their eggs on the highest tide. 259 00:32:19,080 --> 00:32:23,080 Each carries around 100,000 eggs, 260 00:32:23,080 --> 00:32:25,720 so over just two or three nights, 261 00:32:25,720 --> 00:32:28,920 trillions are released into the ocean. 262 00:32:31,120 --> 00:32:34,880 Though some are more successful than others. 263 00:33:00,000 --> 00:33:04,640 Once their work is done, the crabs will return to the forest. 264 00:33:21,640 --> 00:33:24,360 Then, four weeks later, 265 00:33:24,360 --> 00:33:26,760 on the next highest tide... 266 00:33:32,040 --> 00:33:34,280 ...having hatched out to sea, 267 00:33:34,280 --> 00:33:39,400 a new generation of red crabs returns to the same beach. 268 00:33:41,680 --> 00:33:43,520 In good years like this one, 269 00:33:43,520 --> 00:33:47,440 countless millions arrive back on the shores of Christmas Island, 270 00:33:47,440 --> 00:33:50,040 turning the beaches red. 271 00:34:06,960 --> 00:34:11,800 Like their parents, they also need moisture in the air to breathe. 272 00:34:14,320 --> 00:34:16,680 So before the rains move on, 273 00:34:16,680 --> 00:34:22,320 the young crabs must undertake their own epic journey into the forest, 274 00:34:22,320 --> 00:34:26,120 where they'll wait out the next few months of dry. 275 00:34:46,280 --> 00:34:48,520 The Christmas Island crab - 276 00:34:48,520 --> 00:34:52,920 entirely reliant on the return of the monsoon. 277 00:35:03,680 --> 00:35:09,840 The annual rhythms of the weather shape life across our planet. 278 00:35:12,240 --> 00:35:14,400 In some parts of the world, 279 00:35:14,400 --> 00:35:18,840 seasonal cycles of wet and dry can bring dramatic change. 280 00:35:21,320 --> 00:35:24,240 And there are few places where this is more apparent 281 00:35:24,240 --> 00:35:26,520 than southern Africa. 282 00:35:33,560 --> 00:35:35,920 The Zambezi River. 283 00:35:37,400 --> 00:35:43,880 It flows across six countries and drains half a million square miles. 284 00:35:57,920 --> 00:36:00,440 At the peak of the wet season, 285 00:36:00,440 --> 00:36:07,080 5,000 tonnes of water cascade over Victoria Falls every second. 286 00:36:09,560 --> 00:36:13,000 And yet, each year when the rains stop, 287 00:36:13,000 --> 00:36:16,280 these falls run dry. 288 00:36:23,920 --> 00:36:28,000 It's almost as if someone turns off the tap. 289 00:36:33,080 --> 00:36:34,560 May... 290 00:36:37,960 --> 00:36:39,560 ..December. 291 00:36:42,760 --> 00:36:44,480 Wet season... 292 00:36:48,000 --> 00:36:49,800 ..dry season. 293 00:36:52,600 --> 00:36:56,520 It's happened like this for thousands of years. 294 00:37:02,520 --> 00:37:07,600 But there are signs that the weather here is changing. 295 00:37:07,600 --> 00:37:12,440 In recent years, the volume of water flowing over Victoria Falls 296 00:37:12,440 --> 00:37:14,960 has dropped by half. 297 00:37:19,120 --> 00:37:22,520 A concern for animals that have come to rely on 298 00:37:22,520 --> 00:37:26,200 the natural rhythms of wet and dry. 299 00:37:39,160 --> 00:37:45,040 Zambia's Luangwa River is a major tributary of the Zambezi. 300 00:37:46,800 --> 00:37:50,000 Every year, as the dry season takes hold, 301 00:37:50,000 --> 00:37:53,120 it dwindles into pools. 302 00:37:56,480 --> 00:38:00,080 Accommodation starts to get tight for the locals. 303 00:38:00,080 --> 00:38:01,960 HIPPO SNORTS 304 00:38:03,920 --> 00:38:09,040 With no other water around, the river becomes a magnet for visitors. 305 00:38:14,880 --> 00:38:19,600 Millions of red-billed quelea flock to the water's edge. 306 00:38:23,800 --> 00:38:27,640 These seed eaters need to drink every day... 307 00:38:46,680 --> 00:38:49,360 ...and Nile crocodiles know it. 308 00:38:50,800 --> 00:38:53,200 They may not have eaten for six months. 309 00:38:54,360 --> 00:38:59,320 For them, the dry season is the start of the good times. 310 00:39:08,840 --> 00:39:13,720 And they are not the only ones to depend on this time of year. 311 00:39:18,880 --> 00:39:22,680 Carmine bee-eaters have flown hundreds of miles 312 00:39:22,680 --> 00:39:24,960 from the rainforests of the Congo... 313 00:39:26,600 --> 00:39:29,880 ...arriving at the peak of the dry season, 314 00:39:29,880 --> 00:39:34,800 when steep sandbanks are exposed by the falling water. 315 00:39:41,200 --> 00:39:43,840 They're a perfect place to nest, 316 00:39:43,840 --> 00:39:46,760 out of reach of predators from above. 317 00:39:56,080 --> 00:40:01,600 Bee-eater burrows can extend for two metres into the soft river sand. 318 00:40:03,080 --> 00:40:05,880 Already home to 6,000 nests, 319 00:40:05,880 --> 00:40:10,600 real estate at Bee-eater Towers is in high demand. 320 00:40:14,520 --> 00:40:18,440 But it pays not to build too close to the neighbours. 321 00:40:28,920 --> 00:40:34,000 As more birds arrive, competition for the best nesting sites heats up. 322 00:40:44,960 --> 00:40:47,000 It's thirsty work. 323 00:40:57,760 --> 00:41:01,640 In the sudden commotion, they're vulnerable from below... 324 00:41:03,720 --> 00:41:05,280 ...and above. 325 00:41:09,240 --> 00:41:11,880 African fish eagles. 326 00:41:20,240 --> 00:41:23,200 They are permanent residents here. 327 00:41:23,200 --> 00:41:27,160 But at this time of the year, they don't just eat fish. 328 00:41:32,080 --> 00:41:35,680 The safest place to be is inside a burrow. 329 00:41:37,360 --> 00:41:43,040 But an eagle fly-by sends shock waves of panic through the colony. 330 00:41:55,920 --> 00:42:00,880 The eagles' strategy is to pin their prey against the river bank. 331 00:42:04,840 --> 00:42:07,600 With the colony in disarray, 332 00:42:07,600 --> 00:42:10,040 the predators have the advantage. 333 00:42:50,160 --> 00:42:54,560 These fish eagles also choose to breed in the dry season, 334 00:42:54,560 --> 00:42:58,800 because they need the bee-eaters as food for their chicks. 335 00:43:06,040 --> 00:43:11,080 But this year's dry season shows no sign of letting up. 336 00:43:18,680 --> 00:43:22,040 Parts of the river are now bone-dry, 337 00:43:22,040 --> 00:43:25,840 forcing huge male hippos from their home. 338 00:43:36,280 --> 00:43:38,400 With nowhere left to turn, 339 00:43:38,400 --> 00:43:41,920 they must converge on the few remaining patches of water... 340 00:43:41,920 --> 00:43:43,840 HIPPO GRUNTS 341 00:43:43,840 --> 00:43:46,560 ..but these are already occupied. 342 00:43:59,400 --> 00:44:03,080 The resident bull here can't tolerate another big male 343 00:44:03,080 --> 00:44:05,600 in his shrinking pool. 344 00:44:08,040 --> 00:44:09,960 HIPPO BELLOWS 345 00:44:36,040 --> 00:44:38,960 The newcomer is banished. 346 00:44:50,000 --> 00:44:53,080 Still the sun bakes the land... 347 00:44:56,200 --> 00:44:59,320 ...with devastating consequences. 348 00:45:31,240 --> 00:45:34,320 Hundreds of nests are wiped out. 349 00:45:42,520 --> 00:45:46,640 Southern Africa has experienced dry seasons 350 00:45:46,640 --> 00:45:48,840 for thousands of years. 351 00:45:50,440 --> 00:45:53,400 But this is something different. 352 00:45:58,360 --> 00:46:04,000 Record high temperatures and the lowest rainfall in nearly 40 years 353 00:46:04,000 --> 00:46:09,240 have thrown parts of Africa into one of the worst droughts in a century. 354 00:46:16,560 --> 00:46:18,400 THUNDER CRASHES 355 00:46:24,920 --> 00:46:30,400 Across the planet, our once stable climate is changing. 356 00:46:35,240 --> 00:46:37,440 Weather is less reliable... 357 00:46:39,840 --> 00:46:43,080 ...and is getting more extreme. 358 00:46:46,760 --> 00:46:49,640 Wildfires are becoming more frequent. 359 00:47:05,360 --> 00:47:08,040 Droughts are more intense. 360 00:47:18,960 --> 00:47:23,040 And storms are more ferocious. 361 00:47:27,200 --> 00:47:32,440 All this from a recent rise in global temperatures 362 00:47:32,440 --> 00:47:35,360 of just a single degree Celsius. 363 00:47:37,040 --> 00:47:40,400 Yet if climate change continues unchecked, 364 00:47:40,400 --> 00:47:46,560 we may see a rise of almost five degrees by the end of the century. 365 00:47:48,400 --> 00:47:53,000 We can only imagine what this will do to our weather. 366 00:48:11,680 --> 00:48:15,120 There are a few things more daunting for the wildlife film crew 367 00:48:15,120 --> 00:48:20,120 than the prospect of finding a very rare animal in a vast area. 368 00:48:24,120 --> 00:48:28,120 But that is the mission in Mongolia's Gobi Desert - 369 00:48:28,120 --> 00:48:31,640 to film an animal numbering less than 500 370 00:48:31,640 --> 00:48:35,480 in a wilderness of half a million square miles. 371 00:48:41,280 --> 00:48:44,480 We're all loaded up. We got 40 cases of gear, we got nine vehicles. 372 00:48:44,480 --> 00:48:46,880 We're off, we're heading to the Gobi. 373 00:48:50,240 --> 00:48:52,720 DAVID ATTENBOROUGH: From the capital, Ulaanbaatar, 374 00:48:52,720 --> 00:48:55,720 it'll take the team five days to cross Mongolia 375 00:48:55,720 --> 00:48:58,120 in the depths of winter - 376 00:48:58,120 --> 00:49:02,040 travelling in a convoy of large camping trucks, 377 00:49:02,040 --> 00:49:04,160 home for the next five weeks. 378 00:49:22,000 --> 00:49:27,920 1,000 miles later, the convoy reaches the Gobi and makes camp. 379 00:49:32,040 --> 00:49:35,120 Well, we have woken up on our first morning, 380 00:49:35,120 --> 00:49:38,080 and it's about an hour-and-a-half before sunrise, 381 00:49:38,080 --> 00:49:42,800 and rather foolishly we let the fire go out last night, so it's... 382 00:49:42,800 --> 00:49:44,920 ..a cool minus 20 in here. 383 00:49:44,920 --> 00:49:48,560 Everything's frozen solid - toothpaste, hot sauce for breakfast, 384 00:49:48,560 --> 00:49:50,680 even the AP's pee bottle... 385 00:49:50,680 --> 00:49:52,480 ..so that's nice. 386 00:49:55,000 --> 00:49:58,600 Finding a scarce animal in an area the size of Belgium 387 00:49:58,600 --> 00:50:01,480 is clearly no small task... 388 00:50:01,480 --> 00:50:04,400 GARBLED RADIO CONVERSATION 389 00:50:04,400 --> 00:50:08,400 ...but impossible without the help of local researchers. 390 00:50:10,120 --> 00:50:14,480 Each day, the team scour thousands of square miles. 391 00:50:14,480 --> 00:50:17,000 It's a huge area, and there's only 450 camels, 392 00:50:17,000 --> 00:50:20,360 so it really is a bit like a needle in a haystack. 393 00:50:21,600 --> 00:50:24,840 A truly enormous haystack. 394 00:50:29,040 --> 00:50:31,120 450 camels... 395 00:50:29,040 --> 00:50:31,120 ADIYA LAUGHS 396 00:50:31,120 --> 00:50:32,720 ...28,000 square miles. 397 00:50:32,720 --> 00:50:34,720 Easy, yeah? Yeah. 398 00:50:34,720 --> 00:50:37,720 And when scanning the horizon for camels, 399 00:50:37,720 --> 00:50:39,760 mistakes are all too easy. 400 00:50:39,760 --> 00:50:41,240 Another bush. 401 00:50:42,320 --> 00:50:44,600 A bush. Sorry. 402 00:50:46,040 --> 00:50:48,960 Sometimes there's not even a bush to look at. 403 00:50:48,960 --> 00:50:50,520 See anything? Nothing. 404 00:50:51,800 --> 00:50:53,800 Another hill climbed. 405 00:50:53,800 --> 00:50:55,640 Another trail followed. 406 00:50:55,640 --> 00:50:57,840 Another dead end. 407 00:50:57,840 --> 00:51:00,680 Thankfully, the experts remain positive. 408 00:51:00,680 --> 00:51:02,520 I hope you can see them soon. 409 00:51:02,520 --> 00:51:04,160 Yeah, yeah. Please. 410 00:51:06,960 --> 00:51:08,840 Two weeks since leaving the UK. 411 00:51:08,840 --> 00:51:11,280 I'm just hoping that we haven't... 412 00:51:11,280 --> 00:51:13,160 ...been slightly overambitious on this one. 413 00:51:13,160 --> 00:51:16,200 Getting slightly worried it might actually be impossible. 414 00:51:18,000 --> 00:51:19,680 ED SIGHS 415 00:51:21,560 --> 00:51:23,400 Hmm... Good support there, thanks. 416 00:51:24,760 --> 00:51:28,720 Eventually, the team spot their first camel... 417 00:51:28,720 --> 00:51:31,640 ..but, unfortunately, it spotted them first. 418 00:51:33,040 --> 00:51:35,040 Very far away. 419 00:51:35,040 --> 00:51:38,320 Poaching has made the surviving camels very nervous, 420 00:51:38,320 --> 00:51:42,280 and once they start running they can keep going for miles. 421 00:51:44,520 --> 00:51:46,760 WIND HOWLS 422 00:51:46,760 --> 00:51:49,200 And when the winter winds kick off, 423 00:51:49,200 --> 00:51:52,080 all signs of camel vanish. 424 00:51:52,080 --> 00:51:54,640 So, for about the past 24 hours, we've been experiencing 425 00:51:54,640 --> 00:51:57,520 the Gobi winds. It's been gusting up to 70mph hour all night, 426 00:51:57,520 --> 00:51:59,840 and the temps have probably been down to almost -50 427 00:51:59,840 --> 00:52:03,040 with the wind-chill. We just have to hunker down, we can't film in this. 428 00:52:07,160 --> 00:52:11,440 When the gale eases, the search reveals new hope. 429 00:52:12,760 --> 00:52:14,840 We got a load of fresh camel tracks here. 430 00:52:16,320 --> 00:52:19,560 And all tracks head one way - 431 00:52:19,560 --> 00:52:24,120 towards the even more remote mountainous southern Gobi. 432 00:52:28,160 --> 00:52:31,840 The team must decide if they should follow. 433 00:52:31,840 --> 00:52:35,600 Do you think that landscape is likely to be better for us? 434 00:52:35,600 --> 00:52:38,560 More camels and closer encounters or...? 435 00:52:38,560 --> 00:52:40,560 What's your gut telling you? 436 00:52:42,760 --> 00:52:44,960 Because of the wintertime, 437 00:52:44,960 --> 00:52:47,600 we need to see some snow... Mm. 438 00:52:47,600 --> 00:52:48,760 ...to see camels. 439 00:52:50,200 --> 00:52:54,760 To survive in this waterless desert, the camels depend on finding snow. 440 00:52:56,520 --> 00:52:58,720 So, with none in sight, 441 00:52:58,720 --> 00:53:03,160 the team decide to try their luck in the icy mountains to the south. 442 00:53:07,640 --> 00:53:09,520 Sure enough, there's snow - 443 00:53:09,520 --> 00:53:11,240 and lots of it. 444 00:53:14,600 --> 00:53:18,840 But the larger camping trucks struggle in the mountainous terrain, 445 00:53:18,840 --> 00:53:22,000 and the team are forced to go on without them, 446 00:53:22,000 --> 00:53:27,120 leaving them somewhat more exposed to the winter conditions. 447 00:53:27,120 --> 00:53:29,440 It's been down to -25 over the last week. 448 00:53:29,440 --> 00:53:32,920 So very thin canvas tents will be a whole new experience 449 00:53:32,920 --> 00:53:35,480 in the Gobi Desert for us. 450 00:53:35,480 --> 00:53:39,000 I'm wearing, currently, two pairs of trousers, thermals, 451 00:53:39,000 --> 00:53:42,880 thermals on top, two pairs of jumpers, three coats, two hats... 452 00:53:42,880 --> 00:53:45,480 So I THINK I should be all right. 453 00:53:45,480 --> 00:53:46,600 HE EXHALES 454 00:53:48,920 --> 00:53:50,480 TOBY: You all right, Eddie? 455 00:53:50,480 --> 00:53:52,200 Oh, I'm terrific, yeah. 456 00:53:52,200 --> 00:53:54,560 HE LAUGHS 457 00:53:52,200 --> 00:53:54,560 Really terrific! 458 00:53:54,560 --> 00:53:57,200 HE SIGHS CONTENTEDLY 459 00:53:54,560 --> 00:53:57,200 I'm all cosy. 460 00:53:58,640 --> 00:54:00,120 I'm not. I'm cold. 461 00:54:00,120 --> 00:54:01,560 Really cold! 462 00:54:05,800 --> 00:54:11,240 As Adiya predicted, with snow come camels. 463 00:54:11,240 --> 00:54:14,080 The signs are everywhere. 464 00:54:17,360 --> 00:54:19,080 But having travelled so far, 465 00:54:19,080 --> 00:54:22,200 they can't risk anything ruining this chance. 466 00:54:22,200 --> 00:54:25,760 HUSHED: Camels don't seem to like the cars so... 467 00:54:25,760 --> 00:54:27,240 ...now we walk. 468 00:54:29,320 --> 00:54:31,640 We've been walking for about five miles now, 469 00:54:31,640 --> 00:54:33,960 and hiking across this landscape, 470 00:54:33,960 --> 00:54:37,600 it really does give you a new-found respect for the camels. 471 00:54:43,120 --> 00:54:46,320 We've seen some camels way out on the plain here, 472 00:54:46,320 --> 00:54:50,800 but in order not to scare them, John's going to head out on his own. 473 00:55:03,520 --> 00:55:06,520 Yeah, yeah, I can see him. He's, um... 474 00:55:06,520 --> 00:55:08,120 ADIYA: Going to south? 475 00:55:08,120 --> 00:55:11,480 Yeah, he's going to the south, he's just this side of the ridge. 476 00:55:18,160 --> 00:55:20,120 The camels come to John. 477 00:55:20,120 --> 00:55:22,120 They are? The camels are coming to John? 478 00:55:22,120 --> 00:55:23,600 Yes! Really? 479 00:55:28,080 --> 00:55:31,360 JOHN OVER RADIO: Maybe grab the bags and come down to where I am now 480 00:55:31,360 --> 00:55:35,040 by these bushes, and we'll see if we can't slip down into the oasis. 481 00:55:40,320 --> 00:55:43,520 HUSHED: This is just amazing. It's hard fought... 482 00:55:43,520 --> 00:55:46,240 ..but the reward is so worth it. 483 00:55:46,240 --> 00:55:49,720 Because right now we're about 100 metres away... 484 00:55:51,000 --> 00:55:56,080 ...from some of the rarest and hardiest mammals on the planet. 485 00:55:58,640 --> 00:56:00,160 What a privilege. 486 00:56:02,360 --> 00:56:06,320 The team film behaviour very few people have seen. 487 00:56:07,760 --> 00:56:12,200 Rare images of one of the world's most endangered creatures. 488 00:56:13,720 --> 00:56:17,040 Once widespread across Central Asia, 489 00:56:17,040 --> 00:56:21,760 this uninhabited desert is the wild camels' final home. 490 00:56:23,680 --> 00:56:28,320 Were it not for Adiya's team, it might have disappeared altogether, 491 00:56:28,320 --> 00:56:33,360 but because of their work we may yet save this icon of the Gobi. 492 00:56:38,720 --> 00:56:41,040 Next time... 493 00:56:41,040 --> 00:56:42,480 ..oceans. 494 00:56:45,120 --> 00:56:49,200 All marine life depends on the continuous movement of water. 495 00:56:51,120 --> 00:56:54,400 Our oceans are linked by powerful tides... 496 00:56:56,240 --> 00:56:58,040 ..and where there are currents, 497 00:56:58,040 --> 00:56:59,760 there is life. 498 00:57:03,960 --> 00:57:07,000 The Open University has produced a free poster 499 00:57:07,000 --> 00:57:09,400 exploring our perfect planet. 500 00:57:09,400 --> 00:57:14,440 To order, please call 0300 303 0901. 501 00:57:14,440 --> 00:57:19,320 Or go to bbc.co.uk/perfectplanet 502 00:57:19,320 --> 00:57:22,560 and follow the links to the Open University.