0:00:07 > 0:00:10My name's Stewart McPherson, I'm an explorer and naturalist.
0:00:12 > 0:00:15I've climbed dozens of unexplored mountains
0:00:15 > 0:00:17and discovered many new species.
0:00:19 > 0:00:22And yet the journey I've always wanted to make
0:00:22 > 0:00:25is to the most remote parts of Britain.
0:00:27 > 0:00:29And I mean remote.
0:00:29 > 0:00:33Not the islands of Scotland or the mountains of Wales,
0:00:33 > 0:00:36but the UK overseas territories.
0:00:36 > 0:00:3814 islands and archipelagos
0:00:38 > 0:00:41scattered all across the seven seas.
0:00:41 > 0:00:43They have seven times the land area of the UK.
0:00:45 > 0:00:46Some are uninhabited
0:00:46 > 0:00:51but 350,000 people live on the others.
0:00:51 > 0:00:55People who have voted to remain part of the United Kingdom.
0:00:55 > 0:00:58I read about these far-flung places when I was a child
0:00:58 > 0:01:00and this was my treasure map.
0:01:00 > 0:01:02Not to hoards of gold and silver,
0:01:02 > 0:01:06but something even more special -
0:01:06 > 0:01:09untold riches of wildlife and unique cultures.
0:01:13 > 0:01:17I wanted to stand on the biggest penguin colonies on the planet.
0:01:29 > 0:01:32I wanted to dive on the world's richest coral reefs.
0:01:40 > 0:01:43And I can do all that without leaving Britain.
0:01:43 > 0:01:48No single person has ever explored all 14 overseas territories
0:01:48 > 0:01:51and that is just too much of a challenge
0:01:51 > 0:01:52for any explorer to resist.
0:01:52 > 0:01:55So, I'm going to follow my childhood treasure map
0:01:55 > 0:01:57right the way across the globe
0:01:57 > 0:02:00to discover the furthest reaches of Britain.
0:02:09 > 0:02:13My first journey will take me right around the world,
0:02:13 > 0:02:15through the tropics and subtropics
0:02:15 > 0:02:17and across three oceans...
0:02:19 > 0:02:21..to visit Pitcairn in the Pacific ocean...
0:02:23 > 0:02:26..the Chagos Archipelago in the Indian Ocean...
0:02:26 > 0:02:30but first, the oldest of all the overseas territories
0:02:30 > 0:02:33in the Atlantic Ocean, Bermuda,
0:02:33 > 0:02:381,000km from the shores of the United States.
0:02:42 > 0:02:44The English found Bermuda by accident
0:02:44 > 0:02:48after a ship trying to cross the Atlantic ran into it...
0:02:48 > 0:02:50literally.
0:02:50 > 0:02:54That vessel was carrying supplies to Jamestown,
0:02:54 > 0:02:57England's first permanent colony in America.
0:02:57 > 0:03:00HORN TOOTS
0:03:00 > 0:03:02The year was 1609,
0:03:02 > 0:03:05just two years after Jamestown was founded.
0:03:08 > 0:03:12The wreck of that ship, the Sea Venture, became famous
0:03:12 > 0:03:15and probably inspired Shakespeare to write The Tempest.
0:03:19 > 0:03:21The shipwreck was a happy accident
0:03:21 > 0:03:23and not just for Shakespeare.
0:03:25 > 0:03:28The British realised the strategic importance of Bermuda
0:03:28 > 0:03:31and built forts to protect it.
0:03:36 > 0:03:38This is the oldest.
0:03:38 > 0:03:39Fort St Catherine.
0:03:41 > 0:03:44A stone fort was built here in 1614
0:03:44 > 0:03:47followed by many others across the island.
0:03:48 > 0:03:52Some of those buildings are still standing.
0:03:52 > 0:03:54The earliest surviving buildings
0:03:54 > 0:03:57built by the English in the New World.
0:04:02 > 0:04:06This small island has been settled for 500 years -
0:04:06 > 0:04:10long enough to be developed from shore to shore.
0:04:13 > 0:04:16Even so, it's a beautiful place...
0:04:18 > 0:04:20..with its history visible on every street.
0:04:25 > 0:04:28I've always wanted to come to Bermuda,
0:04:28 > 0:04:30but not for its human history.
0:04:30 > 0:04:33It's natural history is just as fascinating.
0:04:36 > 0:04:39The British weren't the first to come here.
0:04:39 > 0:04:41The islands were discovered by the Spanish.
0:04:41 > 0:04:43By Juan de Bermudez,
0:04:43 > 0:04:47just a few years after Columbus first arrived in the New World.
0:04:49 > 0:04:51But the Spanish didn't stay.
0:04:54 > 0:04:56As they dropped anchor offshore
0:04:56 > 0:04:58and the sun began to set,
0:04:58 > 0:05:02the air was filled with terrifying, unearthly noises.
0:05:06 > 0:05:09The Spanish were convinced of the islands of Bermudez
0:05:09 > 0:05:12were the abode of devils
0:05:12 > 0:05:13and they never came back.
0:05:18 > 0:05:22When the British settled here, over 100 years later,
0:05:22 > 0:05:25they realised that there were no devils here,
0:05:25 > 0:05:28just a huge colony of sea birds.
0:05:28 > 0:05:30They named them cahows,
0:05:30 > 0:05:32imitating their strange cries,
0:05:32 > 0:05:35and instead of being afraid of them,
0:05:35 > 0:05:37the British simply ate them,
0:05:37 > 0:05:40every last one...
0:05:40 > 0:05:44aided by rats and hogs that roamed the island
0:05:44 > 0:05:46since the Spanish first anchored here.
0:05:49 > 0:05:53Bermuda was the only place where these birds nested.
0:05:55 > 0:05:59And by the 1630s, the cahow was declared extinct.
0:06:01 > 0:06:03Then, in 1951,
0:06:03 > 0:06:05something amazing happened.
0:06:08 > 0:06:12A few pairs of cahows were found on a group of tiny, rocky islets
0:06:12 > 0:06:14off the main island.
0:06:16 > 0:06:19No-one had seen this bird for more than 300 years.
0:06:21 > 0:06:24It was like finding a living, breathing dodo.
0:06:28 > 0:06:32But their tiny, rocky homes were exposed to high seas
0:06:32 > 0:06:34and Atlantic hurricanes.
0:06:34 > 0:06:37They needed somewhere more secure to nest.
0:06:39 > 0:06:41'I'm travelling out with Jeremy Medeiros
0:06:41 > 0:06:44'to a place I read about as a child.'
0:06:47 > 0:06:49This is Nonsuch Island
0:06:49 > 0:06:52and it's been cleared of rats and cats.
0:06:52 > 0:06:55It's now the Nonsuch Living Museum.
0:06:57 > 0:07:00But it still lacked Bermuda's charismatic devil bird...
0:07:02 > 0:07:05..partly because of a problem from another bird...
0:07:06 > 0:07:08..the tropicbird.
0:07:09 > 0:07:11These are also a protected species...
0:07:13 > 0:07:16..but they evict cahows from their burrows and they even kill them.
0:07:20 > 0:07:25How could tropicbirds and cahows be persuaded to live as neighbours?
0:07:31 > 0:07:32This is the answer.
0:07:34 > 0:07:36Luxury apartments for the tropicbirds.
0:07:38 > 0:07:41Tropicbirds love these artificial burrows,
0:07:41 > 0:07:43which also makes it easier
0:07:43 > 0:07:47to monitor the progress of this important population.
0:07:50 > 0:07:55OK, here's one of the artificial tropicbird nests
0:07:55 > 0:07:57that I've been monitoring for...
0:07:57 > 0:07:59'Now, with less competition for nest sites,
0:07:59 > 0:08:03'an ambitious plan to reintroduce cahows could begin.'
0:08:06 > 0:08:12Starting in 2004, cahows were moved from their tiny islets to Nonsuch.
0:08:13 > 0:08:15When they're fully grown,
0:08:15 > 0:08:17the parents abandon the chicks
0:08:17 > 0:08:21so that hunger drives them to fly out to sea to find their own food.
0:08:24 > 0:08:29If they're moved to a new burrow on Nonsuch before they fledge,
0:08:29 > 0:08:32it was hoped that they'd return to their new home when they matured.
0:08:36 > 0:08:38It seems to have worked
0:08:38 > 0:08:41and cahows are now returning to Nonsuch to breed.
0:08:51 > 0:08:53This huge, ungainly-looking chick
0:08:53 > 0:08:55will soon fledge
0:08:55 > 0:08:58to soar far and wide over the Atlantic.
0:08:58 > 0:09:01And yet, when it's ready to breed,
0:09:01 > 0:09:05it can still find this tiny pinprick of land in the vast Atlantic.
0:09:12 > 0:09:14Across the UK overseas territories,
0:09:14 > 0:09:17I'm going to find many such stories
0:09:17 > 0:09:20of battles to save rare and strange species
0:09:20 > 0:09:23living on tiny islands.
0:09:24 > 0:09:27Such small, isolated islands - like Bermuda -
0:09:27 > 0:09:30have been too easily damaged by development
0:09:30 > 0:09:34and by the introduction of alien plants and animals,
0:09:34 > 0:09:38and many of the territories face another threat.
0:09:39 > 0:09:44I can find the evidence of this by going deep underground
0:09:44 > 0:09:48into the limestone foundations of Bermuda,
0:09:48 > 0:09:51where there are spectacular caves.
0:09:58 > 0:10:01This is Fantasy Cave,
0:10:01 > 0:10:03decorated with amazing displays
0:10:03 > 0:10:05of stalagmites and stalactites.
0:10:07 > 0:10:10These formations take thousands of years to form
0:10:10 > 0:10:14as rainwater filters through the porous limestone
0:10:14 > 0:10:16and deposits calcium carbonate...
0:10:16 > 0:10:18drip by single drip.
0:10:19 > 0:10:23But these formations only form in air.
0:10:26 > 0:10:31Here, in Fantasy Cave, many of these structures are underwater.
0:10:33 > 0:10:36The cave records a history of sea level change
0:10:36 > 0:10:38from the end of the last ice age.
0:10:40 > 0:10:45When the ice melted, sea level rose by more than 100 metres,
0:10:45 > 0:10:48flooding many of the caves.
0:10:51 > 0:10:54These caves offer irrefutable evidence of sea level change,
0:10:54 > 0:10:57but there's even more evidence just offshore.
0:11:08 > 0:11:11Now under ten metres of water,
0:11:11 > 0:11:13these are the roots of trees
0:11:13 > 0:11:15that once grew on dry land.
0:11:20 > 0:11:23Wind back the clock to a time when these trees were still growing
0:11:23 > 0:11:26and we'd see a very different world.
0:11:29 > 0:11:34After the ice age, rising sea levels created many of the small islands
0:11:34 > 0:11:38that now make up the UK Overseas Territories.
0:11:38 > 0:11:41It also isolated them from other landmasses,
0:11:41 > 0:11:44allowing their unique species to evolve.
0:11:51 > 0:11:56But these species are now threatened by a new rise in sea level -
0:11:56 > 0:11:58this time, caused by us.
0:12:00 > 0:12:04As climate change warms the planet, so sea levels rise.
0:12:09 > 0:12:12Sea level change is still a major threat today -
0:12:12 > 0:12:15especially on flat, low-lying islands such as these.
0:12:15 > 0:12:18Normally, if the water level would rise,
0:12:18 > 0:12:21these mangrove forests would retreat inland to higher ground.
0:12:21 > 0:12:25But the problem today is that there's nowhere for them to go.
0:12:25 > 0:12:28Some of the islands of the UK Overseas Territories
0:12:28 > 0:12:31are so low-lying that the predicted rise in sea level
0:12:31 > 0:12:33over the next few hundred years
0:12:33 > 0:12:35will have a huge impact on them.
0:12:38 > 0:12:41That's certainly true of where I'm going next -
0:12:41 > 0:12:45half a world away, the British Indian Ocean Territory.
0:12:47 > 0:12:50It's made up of the Chagos Archipelago,
0:12:50 > 0:12:52a series of coral atolls
0:12:52 > 0:12:57that lie more than 600km to the south of the Maldives.
0:12:58 > 0:13:00These atolls are so remote,
0:13:00 > 0:13:02my journey to the British Indian Ocean Territory
0:13:02 > 0:13:06will have to start in the Maldives...
0:13:06 > 0:13:08in Male, the island's capital.
0:13:20 > 0:13:23I can't imagine anywhere more different
0:13:23 > 0:13:26from the unspoiled tropical islands I'm trying to reach.
0:13:27 > 0:13:31Crammed with people, cars, bikes, scooters -
0:13:31 > 0:13:35this is urban chaos at its most extreme.
0:13:36 > 0:13:39HORN BLARES
0:13:39 > 0:13:42So, this whole island is one massive concrete jungle,
0:13:42 > 0:13:47but there's not one square metre of forest or natural vegetation
0:13:47 > 0:13:49and no wildlife here at all.
0:13:53 > 0:13:55I'm only here to catch a boat,
0:13:55 > 0:13:57but that took me nearly a week to organise.
0:14:01 > 0:14:02And we're off.
0:14:02 > 0:14:05Not bad. We're still checking out.
0:14:06 > 0:14:08I can't believe we're actually going now.
0:14:10 > 0:14:14It's taken me three years of planning just to reach this stage.
0:14:14 > 0:14:18Getting permission to travel to the Chagos Archipelago
0:14:18 > 0:14:20is nearly impossible.
0:14:20 > 0:14:23But now, I'm just two boat trips away.
0:14:26 > 0:14:28Nice to meet you, my name is Stu.
0:14:31 > 0:14:34Chagos really is one of the hardest places on the planet
0:14:34 > 0:14:36to get to.
0:14:36 > 0:14:39We've charted this dhoni, this Maldivian dhow,
0:14:39 > 0:14:42and we're going to sail in her down south from Male
0:14:42 > 0:14:44right the way down to Gan,
0:14:44 > 0:14:46the island at the southernmost part of the Maldives.
0:14:46 > 0:14:50From there, hopefully a charter boat has been arranged to meet us.
0:14:50 > 0:14:53HORN BLARES
0:14:53 > 0:14:55Well, that was the plan -
0:14:55 > 0:14:58but we were still sitting on the boat until after sunset.
0:14:58 > 0:15:00Yay! We're finally off.
0:15:00 > 0:15:02We had to wait a few more hours.
0:15:02 > 0:15:06The captain didn't actually show up. We had to wait for someone else.
0:15:06 > 0:15:08But now, as you can see,
0:15:08 > 0:15:11we're casting off and, after three years,
0:15:11 > 0:15:13on our way to Chagos.
0:15:13 > 0:15:15Bye-bye.
0:15:15 > 0:15:17Bye-bye. See you later.
0:15:23 > 0:15:25It's such a relief to escape Male.
0:15:29 > 0:15:31It'll take three days to get to Gan -
0:15:31 > 0:15:35with nothing much to do, but enjoy the ride and soak up the sun.
0:15:46 > 0:15:48The only boat I could find to take us
0:15:48 > 0:15:51from Gan to the Chagos Archipelago
0:15:51 > 0:15:54was based in South Africa - but if the plan worked,
0:15:54 > 0:15:57they'll already be in Gan waiting for us.
0:15:57 > 0:16:00These guys have travelled for seven weeks,
0:16:00 > 0:16:02halfway across the globe.
0:16:02 > 0:16:04It's almost like Dr Livingstone meeting them here.
0:16:04 > 0:16:06Jeremy, I presume.
0:16:07 > 0:16:11- It's good to see you again. - It's so good to see you both.
0:16:11 > 0:16:16There's hardly enough room for all of our film kit and dive equipment,
0:16:16 > 0:16:18let alone us.
0:16:21 > 0:16:25It's going to be very cosy in here over the next few weeks.
0:16:32 > 0:16:35But now we start the final part of the journey.
0:16:37 > 0:16:40Almost right away, we're joined by a school of dolphins.
0:16:45 > 0:16:46Oh, man.
0:16:48 > 0:16:51An excuse to take the dinghy out and race with them.
0:16:53 > 0:16:55I'm not sure who's enjoying it most.
0:17:04 > 0:17:09At last, our first glimpse of the British Indian Ocean Territory.
0:17:12 > 0:17:15Coming here is one of my life ambitions
0:17:15 > 0:17:19and I know it's going to live up to everything I imagined.
0:17:21 > 0:17:25This is simply one of the most beautiful places
0:17:25 > 0:17:28I have ever had the privilege of going to.
0:17:28 > 0:17:30The water is just crystal clear,
0:17:30 > 0:17:34the reefs come right up onto the beaches
0:17:34 > 0:17:36and, well, the landscape speaks for itself.
0:17:36 > 0:17:38It's just stunning.
0:17:38 > 0:17:42Who would have thought this is a British Territory?
0:17:44 > 0:17:48The Chagos Archipelago is made of seven huge coral atolls,
0:17:48 > 0:17:51each, the tip of an extinct volcano.
0:17:53 > 0:17:55The summit of each volcano
0:17:55 > 0:17:57reaches to just below the surface
0:17:57 > 0:17:59where it's colonised by coral.
0:18:03 > 0:18:05Each atoll is a roughly circular coral reef,
0:18:05 > 0:18:08which sometimes breaks the surface
0:18:08 > 0:18:11to create a ring of islands enclosing a sheltered lagoon.
0:18:14 > 0:18:18The reefs and islands of this archipelago are vast.
0:18:18 > 0:18:21They cover an area twice the size of the UK.
0:18:23 > 0:18:26In 2010, this was declared a marine reserve.
0:18:27 > 0:18:33This is the biggest, fully-protected marine reserve on earth.
0:18:37 > 0:18:40These reefs and islands are largely unexplored.
0:18:42 > 0:18:45One island doesn't even have a name.
0:18:47 > 0:18:50Where else in the world can you travel
0:18:50 > 0:18:53and find an island that hasn't even been named yet?
0:18:53 > 0:18:56This has surely got to be one of the last in the Indian Ocean,
0:18:56 > 0:18:58or maybe even on the whole planet.
0:19:06 > 0:19:08It truly isn't an exaggeration
0:19:08 > 0:19:11to say that Chagos is one of the least explored
0:19:11 > 0:19:14and least known places on the entire planet.
0:19:14 > 0:19:16I mean, just look at these charts.
0:19:16 > 0:19:19This is where we're going, the Northern Atolls.
0:19:19 > 0:19:21And all across this chart,
0:19:21 > 0:19:23look, it says, "Unsurveyed",
0:19:23 > 0:19:25"Unsurveyed", "Unsurveyed".
0:19:25 > 0:19:28So, where else can you see that in the world?
0:19:29 > 0:19:31The charts aren't very helpful,
0:19:31 > 0:19:33so we'll have to go very carefully.
0:19:33 > 0:19:37There are massive reefs and rocks just below the surface.
0:19:41 > 0:19:42We're slowly picking our way
0:19:42 > 0:19:45towards the largest atoll,
0:19:45 > 0:19:46the Great Chagos Bank.
0:19:49 > 0:19:52This is the largest coral atoll on the planet...
0:19:54 > 0:19:57..and I'm really keen to see what lives down there.
0:19:58 > 0:20:00OXYGEN HISSES
0:20:00 > 0:20:04This place is a world record breaker for all sorts of reasons.
0:20:04 > 0:20:09I'm about to dive onto the most pristine coral reef on earth.
0:20:18 > 0:20:21There's up to six times more fish on this reef
0:20:21 > 0:20:23than any other in the Indian Ocean -
0:20:23 > 0:20:25perhaps even the whole world.
0:20:31 > 0:20:34The diversity of life down here is breathtaking...
0:20:35 > 0:20:38..and no-one has ever filmed here before.
0:20:53 > 0:20:56It's very likely we are the first people ever
0:20:56 > 0:20:59to have dived on this site.
0:20:59 > 0:21:04It's an enormous area, completely unexplored reefs.
0:21:04 > 0:21:06No-one really knows what's down here.
0:21:08 > 0:21:10We know more about the surface of the moon
0:21:10 > 0:21:13than we do about these coral systems.
0:21:16 > 0:21:19There are dozens of different types of coral growing here
0:21:19 > 0:21:22and they completely cover the seabed.
0:21:22 > 0:21:25Staghorn corals...
0:21:25 > 0:21:27table corals...
0:21:31 > 0:21:33..and pillar corals.
0:21:37 > 0:21:40And it's not just the diversity of the corals,
0:21:40 > 0:21:42but their sheer size.
0:21:45 > 0:21:47Diving on these reefs,
0:21:47 > 0:21:52it's amazing to see the size of some of these coral growths.
0:21:52 > 0:21:55This is a Porites coral
0:21:55 > 0:21:57and this one clearly represents
0:21:57 > 0:22:00hundreds and hundreds of years of growth.
0:22:00 > 0:22:03This demonstrates that the reefs here are healthy
0:22:03 > 0:22:07and have remained stable for a very long time
0:22:07 > 0:22:09and continue to do so today.
0:22:14 > 0:22:16All the corals grow in different ways,
0:22:16 > 0:22:18building up a complex structure -
0:22:18 > 0:22:21providing homes for different fish.
0:22:31 > 0:22:32This city of coral,
0:22:32 > 0:22:34with its varied living space,
0:22:34 > 0:22:37is one reason for the diversity of fish down here.
0:22:41 > 0:22:45Table coral provides a roof over the head of an oriental sweetlips...
0:22:47 > 0:22:51..and shelter for an emperor angelfish.
0:22:54 > 0:22:58Schools of green chromis rarely venture far from the staghorn coral.
0:23:02 > 0:23:05At the slightest hint of danger,
0:23:05 > 0:23:08they disappear into the branching arms.
0:23:15 > 0:23:19These reefs fringe the summit of a huge extinct volcano
0:23:19 > 0:23:21and, while I've got air left,
0:23:21 > 0:23:24I'm going to the edge of the reef
0:23:24 > 0:23:26where the volcano's slopes plunge into the depths.
0:23:31 > 0:23:33This is the drop-off of the reef.
0:23:33 > 0:23:36It falls away for hundreds of metres.
0:23:36 > 0:23:39No-one has ever been down there...
0:23:41 > 0:23:43..and we have absolutely no idea
0:23:43 > 0:23:46what lives down in the darkness.
0:23:48 > 0:23:53The years of planning to get here seemed endless,
0:23:53 > 0:23:55but every day of that time was worth it.
0:23:58 > 0:24:01Those are the most incredible reefs I've ever seen.
0:24:01 > 0:24:03It's stunning down there.
0:24:07 > 0:24:11And the scattered islands should be just as interesting.
0:24:13 > 0:24:15They're fringed by coconut palms,
0:24:15 > 0:24:18which are well adapted to life on remote islands.
0:24:20 > 0:24:24Coconuts are huge seeds that can float on the ocean
0:24:24 > 0:24:25for a very long time.
0:24:27 > 0:24:31They're borne by winds and currents for great distances...
0:24:33 > 0:24:37..and a lucky few will wash up on one of these coral sand beaches.
0:24:43 > 0:24:47The flesh and milk of the coconut provides the plant with food
0:24:47 > 0:24:49as it grows in the sterile sand.
0:24:51 > 0:24:54But that same food is valuable to us.
0:24:55 > 0:24:58Coconuts are big business
0:24:58 > 0:25:01and these palms have been taken to tropical islands
0:25:01 > 0:25:03right around the world.
0:25:05 > 0:25:08In the past, they were also planted on this island.
0:25:10 > 0:25:13As well as fringing the beach, their natural habitat,
0:25:13 > 0:25:17they now grow in the island's interior as well.
0:25:20 > 0:25:23The people who managed this coconut plantation
0:25:23 > 0:25:25were resettled in the late 1960s
0:25:25 > 0:25:27and the plantations abandoned.
0:25:29 > 0:25:33Nature has been left to itself for nearly half a century,
0:25:33 > 0:25:36which is one reason why the reefs are so rich.
0:25:38 > 0:25:41But these plantations aren't the only legacy
0:25:41 > 0:25:43of the island's settlement.
0:25:44 > 0:25:46Rats.
0:25:46 > 0:25:49They still thrive on the islands that used to be inhabited.
0:25:49 > 0:25:51Rats eat seabird chicks,
0:25:51 > 0:25:55so there aren't many seabirds on rat-infested islands.
0:26:00 > 0:26:03But some native creatures do survive -
0:26:03 > 0:26:05land hermit crabs.
0:26:08 > 0:26:10The reefs offshore are so diverse,
0:26:10 > 0:26:14all shapes and sizes of empty shells are washed up -
0:26:14 > 0:26:16homes for the crabs.
0:26:16 > 0:26:18Some extravagant...
0:26:19 > 0:26:21..and some just plain homely.
0:26:23 > 0:26:26And the crabs are everywhere,
0:26:26 > 0:26:29feeding on scraps of carrion or fallen fruits.
0:26:31 > 0:26:35But there is one crab that rules supreme on these islands.
0:26:35 > 0:26:38It's called the coconut crab
0:26:38 > 0:26:42and it's the biggest land arthropod that exists on the planet today.
0:26:42 > 0:26:44And it's actually as big as arthropods can get
0:26:44 > 0:26:47in the current atmosphere and the current oxygen levels.
0:26:47 > 0:26:52They're mostly nocturnal, but if we have a look around here,
0:26:52 > 0:26:53we might just find one.
0:27:02 > 0:27:03Ah.
0:27:03 > 0:27:05This...
0:27:05 > 0:27:07This is a coconut crab nest.
0:27:07 > 0:27:10If you look down here, you can see very clearly,
0:27:10 > 0:27:13the crab's burrowed down into the ground
0:27:13 > 0:27:16and this is where he would have lived - down in this hollow.
0:27:16 > 0:27:18There's no-one at home here now,
0:27:18 > 0:27:21but this is a good sign, so we'll keep looking.
0:27:35 > 0:27:37Ah, here we go.
0:27:39 > 0:27:42Yep, I can see claws peeking out.
0:27:42 > 0:27:46OK, this obviously isn't a natural nest.
0:27:46 > 0:27:48There's a crab under here,
0:27:48 > 0:27:50under a sheet of metal -
0:27:50 > 0:27:52but, opportunistically, he's just found this
0:27:52 > 0:27:54and thought it's obviously made a good nest.
0:27:54 > 0:27:57So, let's delicately lift it up and have a look.
0:28:00 > 0:28:02Wow!
0:28:02 > 0:28:04What a whopper!
0:28:04 > 0:28:05Hello, crab.
0:28:07 > 0:28:10Oh! God, that's a big one!
0:28:10 > 0:28:12Look at this specimen.
0:28:12 > 0:28:14This is enormous!
0:28:14 > 0:28:16What a beauty. Look at those claws.
0:28:16 > 0:28:18Wow!
0:28:19 > 0:28:22Let's gently...
0:28:23 > 0:28:24Oh!
0:28:24 > 0:28:26..gently try and pick him up.
0:28:26 > 0:28:28Wow, look at this guy.
0:28:28 > 0:28:30This...
0:28:30 > 0:28:32Oh!
0:28:32 > 0:28:35This is pretty much a full-size coconut crab.
0:28:35 > 0:28:38They can get up to a 90cm leg span to leg span.
0:28:38 > 0:28:42But this one, I'd say, is getting on for that size.
0:28:42 > 0:28:45They can reportedly weigh up to 4kg
0:28:45 > 0:28:48and this one would be a good three, I suppose.
0:28:48 > 0:28:51So, this is near for the maximum for this species.
0:28:51 > 0:28:54And you can easily see why they've become so rare.
0:28:54 > 0:28:56Just with a piece of wood, you could kill them
0:28:56 > 0:28:59and people have killed them for hundreds of years.
0:28:59 > 0:29:01And as a consequence, it's been wiped out
0:29:01 > 0:29:04from many of the islands from the Indo-Pacific.
0:29:04 > 0:29:08But here, at least, on the Chagos Archipelago, this species is safe,
0:29:08 > 0:29:11and here is one of the last places in the world
0:29:11 > 0:29:15where you get these really large, full-sized, adult specimens.
0:29:15 > 0:29:17What an absolute beauty.
0:29:17 > 0:29:19Let's put him back in his home.
0:29:22 > 0:29:24There we go.
0:29:24 > 0:29:28Coconut crabs are relatives of land hermits.
0:29:28 > 0:29:32And when they're young, they also use old shells for protection.
0:29:35 > 0:29:38But they grow so big, an adult wouldn't find a big enough shell.
0:29:40 > 0:29:43But by then, they don't need one.
0:29:43 > 0:29:45They have their own tough body armour
0:29:45 > 0:29:48and claws that can do a lot of damage.
0:29:50 > 0:29:53Adults and young both love coconuts -
0:29:53 > 0:29:56so they thrive in these abandoned plantations.
0:29:57 > 0:30:01The youngsters need to find coconuts already broken open,
0:30:01 > 0:30:04but adults can use their powerful claws
0:30:04 > 0:30:07to rip through the tough outer shell.
0:30:10 > 0:30:12And once they've broken into a coconut,
0:30:12 > 0:30:14those big powerful claws
0:30:14 > 0:30:16become precision instruments.
0:30:23 > 0:30:25They're also very good at climbing.
0:30:30 > 0:30:33They scale the tallest coconut trees...
0:30:37 > 0:30:39..and when they reach the top,
0:30:39 > 0:30:41they use their versatile claws
0:30:41 > 0:30:43to cut down more coconuts.
0:30:46 > 0:30:49These islands do seem to belong to crabs.
0:30:51 > 0:30:54Land hermits venture out onto the beach
0:30:54 > 0:30:56to see what the tide has brought them.
0:30:58 > 0:31:00But they're soon put in their place.
0:31:02 > 0:31:06These coral sand beaches really belong to ghost crabs.
0:31:15 > 0:31:20These idyllic beaches are built from tiny fragments of coral skeleton...
0:31:21 > 0:31:24..but how it gets here is an interesting story.
0:31:29 > 0:31:33Much of it is generated by one particular group of reef fishes.
0:31:36 > 0:31:37Parrotfish.
0:31:39 > 0:31:42Many different species live on this reef,
0:31:42 > 0:31:44but all have powerful jaws,
0:31:44 > 0:31:47armed with a razor-sharp beaks
0:31:47 > 0:31:50which they use to bite off chunks of coral.
0:31:56 > 0:31:59Underwater, the reef is really noisy...
0:32:00 > 0:32:03..and most of the rasps and clicks
0:32:03 > 0:32:06come from untold numbers of parrotfish eating the reef.
0:32:16 > 0:32:19They digest the living, fleshy parts of the coral,
0:32:19 > 0:32:22but every mouthful is mostly just the chalky skeleton
0:32:22 > 0:32:24of the coral polyp -
0:32:24 > 0:32:26not very nutritious.
0:32:29 > 0:32:32So, the parrotfish have a simple solution.
0:32:32 > 0:32:35They just excrete the inedible bits as coral sand
0:32:35 > 0:32:37in unbelievable quantities.
0:32:40 > 0:32:44Sometimes, curtains of fine sand
0:32:44 > 0:32:46hang in the clear water.
0:32:53 > 0:32:55It builds up on the floor of the reef
0:32:55 > 0:32:57and, eventually, is washed ashore.
0:32:59 > 0:33:03So, next time you're relaxing on a white, tropical beach -
0:33:03 > 0:33:05remember where the sand's come from.
0:33:08 > 0:33:12Some of the species here are found nowhere else
0:33:12 > 0:33:14but the reefs of the Chagos Archipelago.
0:33:17 > 0:33:19Like Chagos anemonefish.
0:33:19 > 0:33:23They live amongst the tentacles of these huge anemones,
0:33:23 > 0:33:25somehow immune to their stings.
0:33:26 > 0:33:29This keeps them safe from most predators
0:33:29 > 0:33:32and the anemone makes use of the fish excretions.
0:33:35 > 0:33:39This anemone also shelters a porcelain crab.
0:33:40 > 0:33:42When it's sure it's safe,
0:33:42 > 0:33:45it comes out to filter particles from the water
0:33:45 > 0:33:48with legs modified into sieves.
0:33:51 > 0:33:55The Chagos anemonefish is just one unique species here.
0:33:55 > 0:34:00Less than 1% of these reefs have been explored by scientists.
0:34:01 > 0:34:04There must be hundreds of other new species here,
0:34:04 > 0:34:06all living their own lives,
0:34:06 > 0:34:08completely unknown to us.
0:34:12 > 0:34:15Although the reefs here are totally unspoilt,
0:34:15 > 0:34:17the islands I've visited so far
0:34:17 > 0:34:20have been touched by humanity.
0:34:20 > 0:34:22But now, we're sailing towards
0:34:22 > 0:34:25a really remote part of the archipelago,
0:34:25 > 0:34:29to a group of islands as untouched as the coral reefs.
0:34:30 > 0:34:32For any explorer or naturalist,
0:34:32 > 0:34:35this is the ultimate experience.
0:34:36 > 0:34:39We don't reach the island until nightfall,
0:34:39 > 0:34:43so I'll have to wait until morning before I can explore.
0:34:54 > 0:34:57At first sight, this island doesn't look very different
0:34:57 > 0:34:59from the islands I've already visited.
0:35:02 > 0:35:05Coconut palms growing at the top of the beach.
0:35:08 > 0:35:10But step through the coconuts...
0:35:10 > 0:35:12and there's a whole new world.
0:35:14 > 0:35:17A native forest of hardwood trees and ferns.
0:35:18 > 0:35:21How on earth did they get to such a remote place?
0:35:22 > 0:35:26Some of these trees have big floating seeds, like coconuts.
0:35:26 > 0:35:29Others, have seeds that stick to birds.
0:35:29 > 0:35:32And these hardwood forests are full of birds,
0:35:32 > 0:35:35like fairy terns.
0:35:36 > 0:35:39Some seabirds nest high in trees,
0:35:39 > 0:35:43but there's nowhere secure to build a nest on a coconut palm,
0:35:43 > 0:35:45so these huge seabird colonies
0:35:45 > 0:35:48depend on the hardwood trees for their nest sites.
0:35:50 > 0:35:54But there's another reason why there are so many birds here.
0:35:54 > 0:35:57This is an island that's never had rats on it.
0:35:57 > 0:36:01The birds are able to nest on the bushes
0:36:01 > 0:36:03or directly on the ground.
0:36:03 > 0:36:07And just look at the difference. It's deafening.
0:36:07 > 0:36:09The air is full of birds.
0:36:14 > 0:36:15Red-footed boobies...
0:36:26 > 0:36:28..and sooty terns.
0:36:28 > 0:36:30They nest on the ground,
0:36:30 > 0:36:34so can only live in such numbers where there are no rats.
0:36:45 > 0:36:48Visiting the British Indian Ocean Territory
0:36:48 > 0:36:50has been a real privilege,
0:36:50 > 0:36:52and discovering its natural treasures
0:36:52 > 0:36:54has been a unique experience.
0:36:57 > 0:37:00The Chagos Islands feel incredibly remote...
0:37:01 > 0:37:04..but that's nothing to where I'm going next -
0:37:04 > 0:37:09into the centre of the biggest ocean of them all, the Pacific.
0:37:12 > 0:37:15The British Territory of the Pitcairn Islands seems lost
0:37:15 > 0:37:17in the vastness of this ocean.
0:37:18 > 0:37:21And it's another very difficult territory to reach.
0:37:21 > 0:37:25I have to start in Mangareva, in French Polynesia,
0:37:25 > 0:37:29and, from here, the journey to Pitcairn will take three days.
0:37:31 > 0:37:32Getting to Pitcairn Island,
0:37:32 > 0:37:36one of the most remote inhabited islands on the planet, isn't easy.
0:37:36 > 0:37:38This vessel behind me is the MV Claymore II.
0:37:38 > 0:37:41She's the official supply vessel that supports the islands,
0:37:41 > 0:37:44and she's the only vessel in the world
0:37:44 > 0:37:46that visits the islands on a regular basis,
0:37:46 > 0:37:48and she calls just four times a year.
0:37:48 > 0:37:51I've been lucky to secure passage on her
0:37:51 > 0:37:54and she leaves in about an hour, so I'd better get on board.
0:37:55 > 0:37:57HE CLICKS TONGUE Hello. Hello.
0:38:01 > 0:38:03Even on a modern cargo vessel,
0:38:03 > 0:38:06the scale of this ocean is daunting.
0:38:08 > 0:38:11For those first explorers, at the mercy of the wind and the weather,
0:38:11 > 0:38:14it must have been overwhelming and disheartening.
0:38:16 > 0:38:19And sometimes, it was all just too much.
0:38:19 > 0:38:22In 1789, the Bounty sailed these waters
0:38:22 > 0:38:25to collect breadfruit plants from Tahiti
0:38:25 > 0:38:28and to take them to the West Indies to feed slaves.
0:38:29 > 0:38:32They spent five months in Tahiti
0:38:32 > 0:38:35and loaded up 1,000 or so breadfruit plants.
0:38:35 > 0:38:39But as they sailed west, many of the crew mutinied,
0:38:39 > 0:38:42casting Captain Bligh and his followers
0:38:42 > 0:38:44adrift in an open boat.
0:38:48 > 0:38:50The crew sailed the Bounty into the Pacific
0:38:50 > 0:38:54looking for somewhere no-one could find them.
0:38:56 > 0:39:00Their leader, Fletcher Christian, knew just the place.
0:39:03 > 0:39:06The tiny island of Pitcairn
0:39:06 > 0:39:09was the perfect place to hide from the harsh justice
0:39:09 > 0:39:11of the Royal Navy.
0:39:12 > 0:39:16It's easy to find today, but in the 18th century,
0:39:16 > 0:39:19it was misplaced on the Admiralty charts,
0:39:19 > 0:39:23so the Navy could only find the mutineers by chance.
0:39:28 > 0:39:30This was to be their new home.
0:39:31 > 0:39:34'I was fascinated by the story as a child
0:39:34 > 0:39:36'and now I can hardly believe
0:39:36 > 0:39:40'I've finally arrived at the mutineer's remote hiding place.'
0:39:43 > 0:39:47The Pitcairn islanders come out to meet the Claymore
0:39:47 > 0:39:48and pick up vital supplies.
0:39:50 > 0:39:52HORN BLARES
0:39:54 > 0:39:56So I can hitch a ride to shore.
0:40:08 > 0:40:10'First, I check in with the authorities.
0:40:10 > 0:40:14'Then, I pick up the island's standard form of transport.'
0:40:17 > 0:40:21The island is roughly 4km long and this is the only way to get around.
0:40:25 > 0:40:27And it doesn't take long to feel at home.
0:40:32 > 0:40:34I'm heading to the island's museum
0:40:34 > 0:40:37to see what remains of the infamous Bounty.
0:40:37 > 0:40:41But on the way, I can't resist popping into the only shop -
0:40:41 > 0:40:45a great place to find out more about life on Pitcairn.
0:40:46 > 0:40:48So, this is the Pitcairn shop.
0:40:48 > 0:40:51It's supplied just four times a year -
0:40:51 > 0:40:53when the Claymore, the ship, comes in.
0:40:53 > 0:40:55It's got everything you'd find in a normal supermarket.
0:40:55 > 0:40:57I can't believe how full it is.
0:40:57 > 0:40:58Oh, my God.
0:40:58 > 0:41:02My wife searched everywhere for a yoghurt maker.
0:41:02 > 0:41:05In London and when we went to Sydney.
0:41:05 > 0:41:08Every shop she found, she looked for this and couldn't find one.
0:41:08 > 0:41:11And now you come to Pitcairn Island and find a yoghurt maker.
0:41:11 > 0:41:14That's absolutely unbelievable, so there you go.
0:41:14 > 0:41:17At the end of the world, one of the best shops in the world.
0:41:20 > 0:41:22Now, back to where I was going -
0:41:22 > 0:41:24to find the museum.
0:41:27 > 0:41:31It turns out to be a treasure trove of artefacts from the Bounty.
0:41:32 > 0:41:34The ship's anchor.
0:41:35 > 0:41:37Even the ship's Bible.
0:41:39 > 0:41:42And this is the actual bell from the Bounty.
0:41:42 > 0:41:46And by ringing it, we can actually hear what the ship sounded like.
0:41:48 > 0:41:52BELL TOLLS But what happened to the Bounty herself?
0:41:52 > 0:41:55The ship that brought the mutineers here.
0:41:55 > 0:41:58To find out, I'll have to venture offshore.
0:42:02 > 0:42:05The water around Pitcairn is teeming with fish.
0:42:10 > 0:42:12It's tempting to stop and study the fish,
0:42:12 > 0:42:15but I'm here to find a ship.
0:42:19 > 0:42:23There are several spectacular wrecks down here,
0:42:23 > 0:42:26but my guide knows exactly what he's looking for.
0:42:28 > 0:42:31This is all that is left of the Bounty -
0:42:31 > 0:42:33ballast stones from her hold.
0:42:34 > 0:42:36They don't look like much,
0:42:36 > 0:42:40but to touch these last remnants of such a famous ship
0:42:40 > 0:42:43really brings history alive.
0:42:51 > 0:42:54Now, it's time to head back to the surface.
0:42:54 > 0:42:56It's Bounty Day on Pitcairn
0:42:56 > 0:42:58and I don't want to miss the celebrations.
0:43:02 > 0:43:04Once they'd arrived at Pitcairn,
0:43:04 > 0:43:08the mutineers knew that a large sailing ship, anchored offshore,
0:43:08 > 0:43:12could be seen by any Navy vessel passing by.
0:43:12 > 0:43:16So they set fire to the Bounty and scuttled her.
0:43:19 > 0:43:22And every year, the islanders commemorate the event
0:43:22 > 0:43:26by building a model of the ship out of old boxes and bits of wood,
0:43:26 > 0:43:28and setting fire to it.
0:43:46 > 0:43:50It's a great excuse for all the islanders to get together,
0:43:50 > 0:43:53and it's a great chance for me to meet everyone...
0:43:54 > 0:43:57..because the story of the mutiny on the Bounty
0:43:57 > 0:43:59is more than just history here.
0:44:02 > 0:44:06CAMERA SHUTTER CLICKS All of these people are direct descendants
0:44:06 > 0:44:07of the mutineers.
0:44:09 > 0:44:12I'm Jackie Christian, I'm a seventh-generation descendant
0:44:12 > 0:44:15from Fletcher Christian and Maimiti.
0:44:15 > 0:44:17I'm Sean Christian, eighth-generation
0:44:17 > 0:44:18from Fletcher Christian.
0:44:18 > 0:44:21Why do you think the mutiny happened? Who was to blame?
0:44:21 > 0:44:24Well, I think it was a combination of things -
0:44:24 > 0:44:26but being on Tahiti for much longer than expected
0:44:26 > 0:44:29and then going back to the discipline on ship,
0:44:29 > 0:44:32it was hard work and they missed all the fun and free time
0:44:32 > 0:44:35and wine, women and song in Tahiti.
0:44:35 > 0:44:38And I guess the harsh treatment aboard the Bounty
0:44:38 > 0:44:41and no-one will tolerate the leadership that William Bligh...
0:44:41 > 0:44:45And how he treated his crew and so, I guess that led...
0:44:45 > 0:44:48- like, a big part of the mutiny on the Bounty.- Yeah.
0:44:52 > 0:44:57I've been invited to the Bounty Day party - a cook-out, Pitcairn-style.
0:44:59 > 0:45:02But first, we have to collect the food up here.
0:45:04 > 0:45:06So, I'm wondering what's on the menu.
0:45:06 > 0:45:09Perhaps it's some local bird.
0:45:17 > 0:45:20No. This is a first for me.
0:45:20 > 0:45:22Somewhere you have to shoot the plants.
0:45:22 > 0:45:25That's a tiny target. That's an awesome shot.
0:45:25 > 0:45:27These are breadfruits,
0:45:27 > 0:45:30probably descended from those on the Bounty
0:45:30 > 0:45:32that never made it to the West Indies.
0:45:32 > 0:45:35Now, everyone lends a hand
0:45:35 > 0:45:37to prepare a gigantic feast.
0:45:39 > 0:45:42Their style of cooking is Polynesian.
0:45:42 > 0:45:44When the mutineers left Tahiti,
0:45:44 > 0:45:47they brought with them Polynesian men and women.
0:45:47 > 0:45:51When they got here, Pitcairn was uninhabited -
0:45:51 > 0:45:53but, in the distant past,
0:45:53 > 0:45:56native Polynesians had lived on this island.
0:46:01 > 0:46:03This type of cooking takes a while
0:46:03 > 0:46:06so, while I'm waiting, I'll find out more
0:46:06 > 0:46:08about the original inhabitants of Pitcairn.
0:46:15 > 0:46:17The island had been discovered
0:46:17 > 0:46:19long before the Bounty mutineers landed here,
0:46:19 > 0:46:22and the evidence for that is just over here.
0:46:26 > 0:46:30These strange markings are evidence of early Polynesians
0:46:30 > 0:46:33but, as of yet, no-one's been able to decipher them
0:46:33 > 0:46:36and we have no idea what they mean.
0:46:41 > 0:46:44When you were down there, did you see much of this?
0:46:44 > 0:46:48'Reynalda Warren has been painting these symbols for many years...'
0:46:48 > 0:46:49They're just so huge.
0:46:49 > 0:46:52'..but even she's not sure what they mean.'
0:46:52 > 0:46:55What do you think they meant? What do you think they signified?
0:46:55 > 0:46:57I always called that thing...
0:46:57 > 0:47:00Course, that one's a little bit out of perspective there, but...
0:47:00 > 0:47:02- ..the pie. - Maybe this wheel could be...
0:47:02 > 0:47:05'The only people who could answer those questions
0:47:05 > 0:47:07'seem to have vanished from Pitcairn
0:47:07 > 0:47:12'some time in the 14th century, long before the Bounty arrived.'
0:47:14 > 0:47:17If the meaning of the symbols has been lost in history,
0:47:17 > 0:47:20Polynesian cooking techniques certainly haven't.
0:47:22 > 0:47:24Dinner is ready.
0:47:30 > 0:47:32I'll try a bit of breadfruit.
0:47:32 > 0:47:35- Richard, breadfruit? - I'll have a breadfruit with this.
0:47:35 > 0:47:37Oh, lovely.
0:47:37 > 0:47:39'There are only 47 people on the island.
0:47:39 > 0:47:42'I'm not exactly sure who's going to eat all this.'
0:47:46 > 0:47:50So, this is some of the breadfruit that came off the Bounty,
0:47:50 > 0:47:53that's been growing here on Pitcairn for 200 years.
0:47:55 > 0:47:57Mm.
0:47:57 > 0:47:58It tastes like, um...
0:47:58 > 0:48:02Like a sweet potato, like a starchy potato. It's beautiful.
0:48:06 > 0:48:10At first, it seemed that the mutineers had arrived in paradise...
0:48:11 > 0:48:14..but nothing could be further from the truth.
0:48:15 > 0:48:17Confined to a small island,
0:48:17 > 0:48:19tensions began to rise
0:48:19 > 0:48:22between the mutineers and the Polynesians -
0:48:22 > 0:48:24and amongst the mutineers themselves.
0:48:26 > 0:48:28They still worried about being found
0:48:28 > 0:48:31and executed by the Royal Navy,
0:48:31 > 0:48:36and so kept a constant lookout from this cave high in the cliffs.
0:48:39 > 0:48:42But soon, tensions turned to violence
0:48:42 > 0:48:46and Polynesians and mutineers alike were murdering each other.
0:48:53 > 0:48:57Fletcher Christian retreated up to these massive caves
0:48:57 > 0:48:59to live in isolation.
0:48:59 > 0:49:02But within just three years of the Bounty landing in Pitcairn,
0:49:02 > 0:49:03Christian had been murdered
0:49:03 > 0:49:06along with all but two of the other mutineers.
0:49:07 > 0:49:11One reason such brutal violence erupted on Pitcairn
0:49:11 > 0:49:14was the size of the island.
0:49:14 > 0:49:16It didn't take long for the mutineers
0:49:16 > 0:49:20to eat their way through most of the island's resources.
0:49:23 > 0:49:27These tiny islands are incredibly fragile
0:49:27 > 0:49:31and Pitcairn is still suffering from the impact of those early settlers.
0:49:33 > 0:49:37Even these spectacular banyan trees are not native here.
0:49:38 > 0:49:40Neither are these shrubs.
0:49:42 > 0:49:46All these alien species outcompete native ones
0:49:46 > 0:49:48and push them into extinction.
0:49:51 > 0:49:53But some parts of the island
0:49:53 > 0:49:55have been completely stripped of vegetation.
0:49:56 > 0:50:00Now, just barren slopes of dry sand.
0:50:04 > 0:50:06These are the culprits.
0:50:06 > 0:50:08GOATS BLEAT Goats.
0:50:08 > 0:50:11Some of them could even be descended
0:50:11 > 0:50:14from the animals brought here on the Bounty.
0:50:16 > 0:50:19Many of the Pacific Islands were so fragile and tiny,
0:50:19 > 0:50:23it was even a problem for the original Polynesian inhabitants.
0:50:26 > 0:50:30Not every island contained everything needed to survive.
0:50:32 > 0:50:36The Polynesians' answer was to open up trade networks
0:50:36 > 0:50:38across the vastness of the Pacific.
0:50:40 > 0:50:44The length of these journeys was amazing.
0:50:44 > 0:50:47The one I'm about to make would be like, for them,
0:50:47 > 0:50:48popping round to the local shop.
0:50:50 > 0:50:52I'm setting off to Henderson Island,
0:50:52 > 0:50:54nearly 200km away.
0:51:01 > 0:51:03It's a very big ocean
0:51:03 > 0:51:05and a very small boat...
0:51:05 > 0:51:08but the Polynesians often made this journey
0:51:08 > 0:51:10in far more flimsy boats than this.
0:51:12 > 0:51:17The Polynesians were the greatest navigators the world has ever seen.
0:51:17 > 0:51:19At a time when the European explorers
0:51:19 > 0:51:22were just skirting round the edges of the continents,
0:51:22 > 0:51:25and they were afraid of falling off the edges of the maps,
0:51:25 > 0:51:28Polynesians were travelling thousands of kilometres
0:51:28 > 0:51:30between the Ocean islands of the Pacific.
0:51:30 > 0:51:32They didn't have any charts
0:51:32 > 0:51:34or any technology as we understand them today -
0:51:34 > 0:51:37they used the stars to navigate.
0:51:37 > 0:51:40The clouds, the reflection of the land onto the clouds
0:51:40 > 0:51:42and also other signs, such as the birds,
0:51:42 > 0:51:45which they could follow to their destinations.
0:51:46 > 0:51:48We view the oceans as barriers,
0:51:48 > 0:51:51they saw them as means of communication,
0:51:51 > 0:51:55as highways to communicate between these ocean islands.
0:51:55 > 0:51:57Just imagine their journeys.
0:51:57 > 0:52:00I mean, this journey today is just one day,
0:52:00 > 0:52:03but their ones could take weeks or even months
0:52:03 > 0:52:05to travel across the island systems.
0:52:05 > 0:52:09Henderson was once inhabited by Polynesians
0:52:09 > 0:52:11but, as on Pitcairn,
0:52:11 > 0:52:14they vanished before Europeans discovered the island.
0:52:14 > 0:52:17It's been uninhabited for about 400 years.
0:52:17 > 0:52:21So, I'm hoping that I'll get a glimpse
0:52:21 > 0:52:23of what Pacific islands once were like.
0:52:27 > 0:52:29This is Henderson Island.
0:52:29 > 0:52:31It's virtually the last example
0:52:31 > 0:52:33of a raised coral island in the Pacific,
0:52:33 > 0:52:36with an entirely pristine and intact ecosystem.
0:52:36 > 0:52:40It's about as remote as you can get on the surface of the planet.
0:52:41 > 0:52:46Henderson's forests shelter birds found nowhere else on earth
0:52:46 > 0:52:48but this tiny speck of land.
0:52:49 > 0:52:53The Henderson fruit dove and the Henderson lorikeet
0:52:53 > 0:52:55are tiny species of parrot.
0:52:58 > 0:53:00It's also home to seabirds,
0:53:00 > 0:53:03like fairy terns and masked boobies.
0:53:03 > 0:53:06Both of these occur right around the tropics.
0:53:08 > 0:53:11But this seabird, the Henderson petrel,
0:53:11 > 0:53:14only nests on this one single island -
0:53:14 > 0:53:17at least, as far as we know.
0:53:17 > 0:53:19Many of the more remote Pacific islands
0:53:19 > 0:53:21are almost impossible to reach.
0:53:25 > 0:53:30Henderson's forest is impenetrable in places - at least, for me.
0:53:30 > 0:53:32It's no problem for these land hermit crabs,
0:53:32 > 0:53:35built like miniature tanks.
0:53:37 > 0:53:38Henderson is larger than Pitcairn
0:53:38 > 0:53:40and there was abundant food here.
0:53:40 > 0:53:44The flightless land birds would have been easy prey for the Polynesians
0:53:44 > 0:53:47and these land hermit crabs, that live all over the ground,
0:53:47 > 0:53:49would also have been easy pickings.
0:53:49 > 0:53:52And, of course, the reefs that surround the island teem with fish.
0:53:52 > 0:53:55About 20 major habitation sites have been found
0:53:55 > 0:53:57mainly in the cliffs that surround the island.
0:53:57 > 0:54:00That indicates that a population of about 100 Polynesians
0:54:00 > 0:54:02could have once lived here.
0:54:02 > 0:54:05But all of the settlements faced one major problem -
0:54:05 > 0:54:07the island is made out of coral
0:54:07 > 0:54:11and this means there was none of the hard, volcanic stone
0:54:11 > 0:54:14that the Polynesians needed in order to make the tools to survive.
0:54:16 > 0:54:20But Henderson Island Polynesians solved that problem
0:54:20 > 0:54:22by trading with Pitcairn Island,
0:54:22 > 0:54:27and the evidence for that success story is inside this cave.
0:54:27 > 0:54:30This is one of the caves where the Polynesians lived.
0:54:30 > 0:54:34They're thought to have inhabited the island for up to 900 years -
0:54:34 > 0:54:36all the way from the eighth century,
0:54:36 > 0:54:38right the way to as late as the 17th.
0:54:38 > 0:54:40Let's go inside and see what it's like.
0:54:42 > 0:54:44Oh, God. It's a bit of a squeeze.
0:54:46 > 0:54:48The presence of the Polynesians can actually still be seen
0:54:48 > 0:54:50inside this cave.
0:54:50 > 0:54:52If you just look down at the ground,
0:54:52 > 0:54:54you can see layers of ash
0:54:54 > 0:54:57where they used to burn... make fires inside the cave
0:54:57 > 0:55:00and outside, there are big heaps, big middens, of discarded shells.
0:55:00 > 0:55:03Well, actually there's lots of oyster shells
0:55:03 > 0:55:05just littered around inside this cave.
0:55:05 > 0:55:08That could be coincidence, they could have washed in,
0:55:08 > 0:55:11but I don't think so. I also, just a minute ago, found this tool.
0:55:11 > 0:55:13And if you look at it, it fits perfectly into your hand,
0:55:13 > 0:55:16and this edge here is cut razor sharp,
0:55:16 > 0:55:19so this looks like it's been worked by the Polynesians.
0:55:19 > 0:55:22But the most compelling evidence is that, in this very cave,
0:55:22 > 0:55:24many stone tools have been found -
0:55:24 > 0:55:27some of which are made out of volcanic stones
0:55:27 > 0:55:30that are known to have originated from Pitcairn Island
0:55:30 > 0:55:32and other islands hundreds of kilometres away.
0:55:32 > 0:55:34Now, what that proves is that
0:55:34 > 0:55:37there was an immense trading network between the islands.
0:55:37 > 0:55:40It's easy to imagine that the Polynesians, here on Henderson,
0:55:40 > 0:55:43could have traded turtle eggs and bird meat,
0:55:43 > 0:55:47particularly things like bird feathers that were highly valued,
0:55:47 > 0:55:50for these volcanic stones that were then brought across
0:55:50 > 0:55:52on these vast, inter-island canoes.
0:55:53 > 0:55:56The waters surrounding Henderson were also harvested
0:55:56 > 0:55:59but, like the island itself,
0:55:59 > 0:56:02these reefs have had a few hundred years to recover.
0:56:04 > 0:56:06Now, they're breathtaking.
0:56:09 > 0:56:11Colours and diversity to make your head spin.
0:56:15 > 0:56:19A longnose butterflyfish, with mouth parts like tweezers.
0:56:28 > 0:56:32The diversity of fish rivals the Chagos Archipelago.
0:56:45 > 0:56:49The ocean here looks like it's never been affected by humanity...
0:56:49 > 0:56:51but the truth is more sobering.
0:56:54 > 0:56:58This land hermit crab has found itself a plastic shell.
0:56:58 > 0:57:02It's certainly one that won't wear out, but that's the problem.
0:57:02 > 0:57:05Plastic is virtually indestructible.
0:57:07 > 0:57:10The whole beach is littered with plastic.
0:57:10 > 0:57:14We're 4,500 kilometres from the nearest major landmass
0:57:14 > 0:57:17and hundreds of kilometres from any other island,
0:57:17 > 0:57:19and there's bits of plastic boxes,
0:57:19 > 0:57:21toys,
0:57:21 > 0:57:24I don't know what that is, and some foam.
0:57:24 > 0:57:27Basically, everything that floats can be washed ashore
0:57:27 > 0:57:30after years at sea and just accumulates along these beaches,
0:57:30 > 0:57:32polluting an otherwise pristine island.
0:57:35 > 0:57:39Plastic now pollutes all of the world's oceans...
0:57:39 > 0:57:42and, as it breaks up into smaller pieces,
0:57:42 > 0:57:44it's eaten by marine creatures.
0:57:45 > 0:57:49Even on islands as remote as Henderson and Chagos,
0:57:49 > 0:57:53many of these birds will have plastic in their stomachs.
0:57:55 > 0:58:00But Henderson and Chagos also show how resilient nature can be,
0:58:00 > 0:58:01if given the chance.
0:58:01 > 0:58:05This is a rare glimpse at the state of the world
0:58:05 > 0:58:07before the impact of man,
0:58:07 > 0:58:10and a benchmark by which to measure our impacts
0:58:10 > 0:58:12across the rest of the world.
0:58:12 > 0:58:16The sad thing is that all of the world's reefs should be like this,
0:58:16 > 0:58:18with an intact ecosystem.
0:58:18 > 0:58:21But it offers hope because, if we act now
0:58:21 > 0:58:24and conserve the world's reefs, they can recover,
0:58:24 > 0:58:27and one day they might look like this once again.