0:00:06 > 0:00:10Ten million species live on planet Earth.
0:00:12 > 0:00:13Each one is remarkable.
0:00:15 > 0:00:17But none can survive on its own.
0:00:22 > 0:00:24All life depends upon connections.
0:00:26 > 0:00:29Unexpected, invariably complex,
0:00:29 > 0:00:33beautiful relationships between millions of plants and animals.
0:00:37 > 0:00:40Starting in our jungles.
0:00:42 > 0:00:43Wow!
0:00:43 > 0:00:45It's a different world.
0:00:45 > 0:00:50Why do jungles have more animals and plants than anywhere else?
0:00:51 > 0:00:56And why can't this mighty brazil nut tree survive without an orchid
0:00:56 > 0:00:59and this nimble little rodent?
0:01:00 > 0:01:06Connections like these form the planet's great ecosystems.
0:01:06 > 0:01:09They're vital for all life.
0:01:09 > 0:01:13I want to show you our world as you've never seen it before.
0:01:28 > 0:01:30DISTANT BIRD AND ANIMAL CALLS
0:01:41 > 0:01:43Central America.
0:01:46 > 0:01:51The narrow isthmus of land joining two vast continents.
0:02:07 > 0:02:10This is Pipeline Road in Panama.
0:02:12 > 0:02:16Named because it runs alongside an old pipeline that was put in
0:02:16 > 0:02:18during the Second World War to get oil from the Pacific
0:02:18 > 0:02:20through to the Atlantic Ocean.
0:02:20 > 0:02:25And it cuts through some of the most pristine rainforest in this part
0:02:25 > 0:02:29of Central America, and I have to tell you that amongst birdwatchers,
0:02:29 > 0:02:33this is a hallowed place.
0:02:33 > 0:02:34It's world famous.
0:02:47 > 0:02:48Semiplumbeous hawk.
0:02:51 > 0:02:53Green honeycreeper.
0:03:00 > 0:03:02Blue-crowned motmot.
0:03:05 > 0:03:07Black-tailed trogon.
0:03:11 > 0:03:14I've been out here since first thing this morning,
0:03:14 > 0:03:15that's about five hours,
0:03:15 > 0:03:18and during the course of that time,
0:03:18 > 0:03:22I've seen or heard 75 different species of bird.
0:03:26 > 0:03:29Some of them are quite tricky to identify -
0:03:29 > 0:03:30I've just got glimpses through the trees.
0:03:39 > 0:03:41If I was to stay out here all day
0:03:41 > 0:03:43and work really hard,
0:03:43 > 0:03:48I might see as many as 200 different species.
0:03:52 > 0:03:57During Christmas of 1989, a party from the Audubon Society came here
0:03:57 > 0:04:03and recorded no fewer than 357 different types of birds.
0:04:03 > 0:04:10It was a new world record, set in this area of rainforest in Panama.
0:04:15 > 0:04:17To put that in context,
0:04:17 > 0:04:23the most anyone has ever seen in Britain in a single day is just 143.
0:04:25 > 0:04:27And it's not just birds.
0:04:27 > 0:04:31In this tiny reserve, there are twice as many mammal species
0:04:31 > 0:04:34as there are in the whole of the UK,
0:04:34 > 0:04:39three times more butterflies and 13 times as many frogs.
0:04:49 > 0:04:52Perhaps this astonishing diversity is shown best
0:04:52 > 0:04:55by the richness of these superb birds.
0:04:55 > 0:04:59LOUD VIBRATING
0:05:03 > 0:05:06Hummingbirds are nectar feeders
0:05:06 > 0:05:10so they find these dishes of sugar solution irresistible.
0:05:16 > 0:05:20But it's not just the individuals that are so dazzling,
0:05:20 > 0:05:23it's the sheer variety.
0:05:28 > 0:05:30Blue-chested hummingbird.
0:05:30 > 0:05:32Long-billed hermit.
0:05:32 > 0:05:35Violet sabrewing.
0:05:35 > 0:05:38Black-throated mango.
0:05:38 > 0:05:40And white-necked jacobin.
0:05:41 > 0:05:47There are 59 different species of hummingbird in Panama's jungles.
0:05:54 > 0:05:58The almost bewildering variety of life that you find in rainforests
0:05:58 > 0:06:02is exhibited by almost every animal and plant group that lives there,
0:06:02 > 0:06:06and it's the same in rainforests all over the planet.
0:06:06 > 0:06:09It's the remarkable thing that sets them apart
0:06:09 > 0:06:12from the rest of our terrestrial ecosystem,
0:06:12 > 0:06:17and it's a profound example of what we call biodiversity.
0:06:17 > 0:06:22The number of different living things in a given area at a given time.
0:06:24 > 0:06:26The big question is why?
0:06:26 > 0:06:30And it's a question that's been vexing scientists for decades.
0:06:30 > 0:06:35Why are there so many different living things in the rainforest?
0:06:51 > 0:06:56In Asia, rainforests cover hundreds of islands -
0:06:56 > 0:06:59some small, some vast.
0:06:59 > 0:07:01New Guinea,
0:07:01 > 0:07:04Java, Sumatra.
0:07:04 > 0:07:08Amongst them, some of the remotest places on the planet.
0:07:12 > 0:07:19Across the Indian Ocean, Africa and the rainforests of the Congo Basin.
0:07:25 > 0:07:29Further west still and we reach the Americas,
0:07:29 > 0:07:33home to the Amazon rainforest,
0:07:33 > 0:07:37the largest unbroken expanse of trees in the tropics.
0:07:40 > 0:07:47Together, these jungles form an emerald band that circles our globe.
0:07:50 > 0:07:51CLAP OF THUNDER
0:07:59 > 0:08:02Here on the equator, there are virtually no seasons.
0:08:02 > 0:08:07It's hot and wet all year round.
0:08:10 > 0:08:12Humidity barely drops below 90%...
0:08:16 > 0:08:20..and the sunlight is more intense than anywhere else on the planet,
0:08:20 > 0:08:23day in and day out.
0:08:27 > 0:08:29All of this rain and all of this sun
0:08:29 > 0:08:34results in a phenomenon on a scale unseen anywhere else.
0:08:37 > 0:08:43It's happening here, in these leaves, in all of these billions of leaves.
0:08:43 > 0:08:46And even if you're a really hard-nosed biologist,
0:08:46 > 0:08:48really pragmatic about life,
0:08:48 > 0:08:50it's nothing short of miraculous.
0:08:53 > 0:08:57It's the chemical process of photosynthesis.
0:08:58 > 0:09:02What plants are doing is combining two very abundant ingredients -
0:09:02 > 0:09:06carbon dioxide in the air, and water.
0:09:09 > 0:09:13Two ingredients that are almost impossible to combine.
0:09:13 > 0:09:18If we take carbon dioxide and water and mix them together,
0:09:18 > 0:09:21even under great pressure, all we get is fizzy water.
0:09:26 > 0:09:30On the other hand, when plants mix carbon dioxide and water,
0:09:30 > 0:09:33they get something else.
0:09:35 > 0:09:37They get food.
0:09:40 > 0:09:42They get sugar.
0:09:46 > 0:09:50More of these sugars are produced in a given area of rainforest
0:09:50 > 0:09:52than in any other habitat
0:09:52 > 0:09:57because of the sheer quantities of water and solar energy.
0:09:57 > 0:10:03In fact, the energy captured by rainforests in one year alone
0:10:03 > 0:10:08could power the UK for over a million years.
0:10:08 > 0:10:11All of that energy is turned into food,
0:10:11 > 0:10:14quite literally out of thin air.
0:10:14 > 0:10:17It's a bit like the botanical equivalent
0:10:17 > 0:10:19of turning water into wine.
0:10:36 > 0:10:40Photosynthesis might explain why there's so much life here.
0:10:44 > 0:10:48But it doesn't explain why there are so many different types of life.
0:10:58 > 0:11:02There's one very special animal that I'd like you to meet.
0:11:14 > 0:11:19She's a leafcutter ant, and she's an ant with a challenge.
0:11:24 > 0:11:29You see, her problem is that she can't digest leaves on her own.
0:11:30 > 0:11:33She needs to take them back to her nest.
0:11:43 > 0:11:47But what possible effect could a tiny pest like her
0:11:47 > 0:11:49have on this immense forest?
0:11:55 > 0:11:58There are plenty of plant pests in temperate forests,
0:11:58 > 0:12:01but there's one crucial difference.
0:12:01 > 0:12:04Temperate forests have winters
0:12:04 > 0:12:08and each winter, the cold kills off creatures like the ants
0:12:08 > 0:12:11and they have to rebuild their colonies
0:12:11 > 0:12:14and start from scratch each spring.
0:12:14 > 0:12:16But here in the rainforest, there is no winter
0:12:16 > 0:12:22and as a consequence, the plants here are under almost relentless attack.
0:12:33 > 0:12:37Our ant is just one worker among thousands in a single colony.
0:12:43 > 0:12:47Each ant deposits her leaf fragment deep within the nest.
0:12:47 > 0:12:51There it will be composted and turned into a fungal food
0:12:51 > 0:12:53for the whole colony.
0:13:05 > 0:13:10Added together, the impact of all of these thousands of ants is enormous.
0:13:20 > 0:13:21It's relatively easy to work out
0:13:21 > 0:13:25just how much these ants are harvesting.
0:13:25 > 0:13:27We know there's around 100,000 in every nest,
0:13:27 > 0:13:29and scientists counted
0:13:29 > 0:13:34the number of journeys they made every day carrying pieces of leaf.
0:13:34 > 0:13:37374,200.
0:13:37 > 0:13:39They also measured the leaf area -
0:13:39 > 0:13:44the total being carried each day by the ants - 11 square metres.
0:13:44 > 0:13:47Multiply that up and during the course of a year,
0:13:47 > 0:13:52it adds up to 3,855 square metres
0:13:52 > 0:13:56and that is 20% of the leaf cover
0:13:56 > 0:13:59that's produced here in the area of the forest
0:13:59 > 0:14:02where these little guys are foraging.
0:14:03 > 0:14:07That's one fifth of all of the leaves here
0:14:07 > 0:14:09destroyed by nothing more than ants.
0:14:19 > 0:14:20And that's just the ants.
0:14:23 > 0:14:27Grasshoppers, caterpillars, slugs and snails...
0:14:27 > 0:14:29everything seems to be eating its greens here.
0:14:40 > 0:14:44Wherever you look in the forest, it's almost impossible to find a leaf
0:14:44 > 0:14:46that hasn't been attacked by pests.
0:14:52 > 0:14:55The simple fact that there's no winter
0:14:55 > 0:14:59to kill off these pests is a huge problem for plants.
0:15:07 > 0:15:11So to stand any chance of survival,
0:15:11 > 0:15:14every single plant in the rainforest is armed.
0:15:21 > 0:15:25And many are filled with toxic chemicals which render them inedible.
0:15:37 > 0:15:39All of this has had a profound effect
0:15:39 > 0:15:43on the evolution of the animals that live here.
0:15:45 > 0:15:49Take a closer look at these creatures. What do you notice?
0:15:51 > 0:15:54Many of them are plain weird.
0:15:54 > 0:15:57They're unlike anything else.
0:16:01 > 0:16:06And one of the strangest of all is found here in Latin America.
0:16:11 > 0:16:14Here it is, and what an amazing animal.
0:16:14 > 0:16:17Really charming as well.
0:16:17 > 0:16:19But if we take a closer look at it,
0:16:19 > 0:16:21you can see exactly what I mean by weird.
0:16:26 > 0:16:30This is a female three-toed sloth.
0:16:32 > 0:16:37And she's embarking on a 20-metre vertical climb to find food.
0:16:47 > 0:16:51She is charming, but she's also quite unlike any other animal.
0:17:02 > 0:17:05So why is she so weird?
0:17:09 > 0:17:15Well, it's a direct result of a very peculiar diet.
0:17:21 > 0:17:27You see, she is a very fussy eater.
0:17:27 > 0:17:30Feeding on only one or two trees,
0:17:30 > 0:17:35the leaves of which are tough and full of toxins.
0:17:39 > 0:17:42But her gut has evolved to host bacteria
0:17:42 > 0:17:45which are specially equipped to break down
0:17:45 > 0:17:47these otherwise inedible leaves.
0:17:54 > 0:17:58It's a slow process.
0:17:58 > 0:18:01Digesting this salad can take weeks.
0:18:06 > 0:18:09She gets so little energy from this diet
0:18:09 > 0:18:13that she's forced to keep her movement to a minimum.
0:18:19 > 0:18:22She's almost become part of the forest furniture.
0:18:23 > 0:18:27So much so that other creatures have started to move in.
0:18:34 > 0:18:37She's the ideal home for a colony of sloth moths.
0:18:55 > 0:19:00The way she looks, the way she eats and the way she moves
0:19:00 > 0:19:02are all a result of having to overcome
0:19:02 > 0:19:05heavily defended leaves,
0:19:05 > 0:19:09and THAT is why sloths are so weird -
0:19:09 > 0:19:11they're specialists.
0:19:22 > 0:19:27In order to survive in a rainforest, you need to be a specialist.
0:19:27 > 0:19:30There are no jack of all trades here.
0:19:32 > 0:19:37The battle between plants and animals goes on every day
0:19:37 > 0:19:43and it's this battle that creates the jungle's biodiversity.
0:19:49 > 0:19:52Let me show you what I mean, with one of the most toxic plants of all.
0:19:55 > 0:19:58This a passion flower vine
0:19:58 > 0:20:02and its leaves are laced with a pretty toxic defence.
0:20:02 > 0:20:05Cyanogenic glycoside molecules,
0:20:05 > 0:20:08and when they break down, they form cyanide.
0:20:08 > 0:20:10As you might imagine, it works wonders
0:20:10 > 0:20:14because cyanide is every bit as dangerous to insects
0:20:14 > 0:20:15as it is to us humans.
0:20:15 > 0:20:19Well, that is to the majority of insects, but not all of them.
0:21:11 > 0:21:16These are caterpillars from a species of butterfly called Heliconius doris.
0:21:16 > 0:21:20They have evolved a unique internal body chemistry,
0:21:20 > 0:21:23to do what few other creatures can -
0:21:23 > 0:21:26counteract the plant's deadly cyanide.
0:21:43 > 0:21:48They even incorporate the poison into their own bodies.
0:21:48 > 0:21:51And after metamorphosing into the adult butterfly,
0:21:51 > 0:21:55their bright colours advertise their toxicity.
0:21:55 > 0:21:56Very clever.
0:22:01 > 0:22:04As one of the few animals that can eat these leaves,
0:22:04 > 0:22:09they have this food source pretty much all to themselves.
0:22:09 > 0:22:14But the downside is, they can't eat anything else.
0:22:14 > 0:22:16They are wedded to this vine.
0:22:19 > 0:22:24The adult butterflies will not lay their eggs on anything else.
0:22:26 > 0:22:29But, of course, plants evolve too.
0:22:32 > 0:22:35This is a different species of passion flower vine.
0:22:35 > 0:22:39It grows in exactly the same patch of rainforest as the first.
0:22:39 > 0:22:40And were it to arm itself
0:22:40 > 0:22:44with exactly the same cocktail of cyanide as that first plant
0:22:44 > 0:22:46then clearly it wouldn't be able to protect itself
0:22:46 > 0:22:51from these Heliconius doris caterpillars, so it doesn't do that.
0:22:51 > 0:22:55It's changed very subtly the type of compounds that it's got in the leaves
0:22:55 > 0:22:57that produce the cyanide.
0:22:57 > 0:23:01And as a consequence of that, it's totally toxic
0:23:01 > 0:23:03to this species of caterpillar.
0:23:08 > 0:23:10A victory for the vine, perhaps?
0:23:15 > 0:23:19Except THIS is a never-ending battle.
0:23:58 > 0:24:01Another species of butterfly has evolved.
0:24:03 > 0:24:06One that can cope with the different toxins.
0:24:07 > 0:24:10Introducing Heliconius cydno.
0:24:13 > 0:24:16Its wing patterning is a little different to that of doris.
0:24:18 > 0:24:21But the most important changes are internal.
0:24:23 > 0:24:26Because each of these butterfly species
0:24:26 > 0:24:30has evolved to be able to eat a different type of vine.
0:24:38 > 0:24:42The battle between plant defence and caterpillar attack never stops.
0:24:47 > 0:24:49The result?
0:24:49 > 0:24:55A proliferation of species of both vine and butterfly.
0:24:58 > 0:25:02In fact, each species of plant and tree in the rainforest
0:25:02 > 0:25:06has ended up with its own specialised pests.
0:25:07 > 0:25:11It's become an evolutionary arms race.
0:25:20 > 0:25:24Just as pest pressure is driving the diversity of trees,
0:25:24 > 0:25:30the diversity of trees is driving the diversity of tree pests.
0:25:30 > 0:25:34And it's not just the pests, it's their predators too.
0:25:34 > 0:25:38Animals like this praying mantis are continually evolving
0:25:38 > 0:25:40to try and outwit those pests,
0:25:40 > 0:25:44which, in turn, are continually evolving
0:25:44 > 0:25:46to try and outwit the mantis.
0:25:46 > 0:25:49If conditions in the forest here remain stable,
0:25:49 > 0:25:54and new species have time to evolve, one thing is for certain.
0:25:54 > 0:25:59This rainforest will become a whirlpool of biodiversity.
0:27:03 > 0:27:07Now, it's easy for us to think of biodiversity as a wonderful thing.
0:27:07 > 0:27:11But the pressures that create this biodiversity
0:27:11 > 0:27:15make the rainforest a very dangerous place.
0:27:17 > 0:27:19Especially when it comes to the survival
0:27:19 > 0:27:22of the forest's youngest inhabitants.
0:27:24 > 0:27:28Let's think about it from the plant's point of view.
0:27:39 > 0:27:43I've collected about 15 different types of tree seed here,
0:27:43 > 0:27:47all of which have come from this small patch of forest behind me.
0:27:47 > 0:27:51Now, imagine that each of these seeds represents a tree.
0:27:53 > 0:27:58And imagine that the forest was made up of a single species.
0:27:58 > 0:28:02Like this one, that the locals call prischaco.
0:28:06 > 0:28:09What you'd have is a monoculture.
0:28:15 > 0:28:19But in the pest-infested rainforest, this doesn't happen.
0:28:19 > 0:28:21And here's why.
0:28:23 > 0:28:27You see, imagine you're a seedling trying to germinate and grow here.
0:28:27 > 0:28:29We know that each of these tree species
0:28:29 > 0:28:32has a highly specialised set of herbivores which attack it.
0:28:32 > 0:28:35So this one will be accessible to
0:28:35 > 0:28:38all of the herbivores living on these trees.
0:28:39 > 0:28:41Not a good situation at all.
0:28:41 > 0:28:46But what if you were a different species of tree germinating here?
0:28:46 > 0:28:51Then you wouldn't be susceptible to this particular set of herbivores,
0:28:51 > 0:28:55and that would confer a real advantage to you.
0:28:55 > 0:28:57Then there's a far greater chance
0:28:57 > 0:28:59that it would prosper through to maturity,
0:28:59 > 0:29:01that it would survive. And in fact...
0:29:04 > 0:29:07..if another tree species were to grow here,
0:29:07 > 0:29:09it too would enjoy the same advantages.
0:29:09 > 0:29:13Reduced susceptibility to this type of herbivore attack.
0:29:16 > 0:29:21The strategy spreads like wildfire through the forest.
0:29:21 > 0:29:23What we end up seeing...
0:29:25 > 0:29:28..is a complete mosaic of species.
0:29:33 > 0:29:35A seedling is far more likely to survive
0:29:35 > 0:29:38if it germinates in isolation,
0:29:38 > 0:29:43far away from the parent tree, surrounded by different tree species.
0:29:45 > 0:29:50So how do plants get their precious seeds away to safety,
0:29:50 > 0:29:54away from their set of voracious pests?
0:30:06 > 0:30:10To find the answer, I'm going to the jungles of Borneo.
0:30:15 > 0:30:19Home to some of the largest animals in any rainforest.
0:30:39 > 0:30:45In the Kinabatangan river, a group of pygmy elephants.
0:30:57 > 0:31:01Among the herd is a baby, born only a few weeks ago.
0:31:17 > 0:31:19Nearby, in the Sepilok sanctuary,
0:31:19 > 0:31:23this young orang-utan is just days old.
0:31:27 > 0:31:31They don't know it, but these youngsters are incredibly important.
0:31:33 > 0:31:36Because not only are both species rare,
0:31:36 > 0:31:40but both will play a crucial role in this ecosystem.
0:31:46 > 0:31:47Orang-utans.
0:31:47 > 0:31:51Absolutely extraordinary animals.
0:31:52 > 0:31:56So easy to see why we generate so much affection for them.
0:31:56 > 0:31:59And when you look into their eyes,
0:31:59 > 0:32:02it's like a reflection in a not-so-distant mirror.
0:32:04 > 0:32:06But there is another reason
0:32:06 > 0:32:09why we should value both orang-utans and elephants.
0:32:11 > 0:32:13If you're a tree, seed dispersal
0:32:13 > 0:32:17and germination is a pretty risky business.
0:32:17 > 0:32:19After all, you're covered with pests,
0:32:19 > 0:32:22all of which want to gobble up those seeds
0:32:22 > 0:32:25or snap up any tasty germinating seedling.
0:32:25 > 0:32:30Your only chance is to get your seeds as far away from yourself
0:32:30 > 0:32:32and those pests as possible.
0:32:32 > 0:32:35The question is, how do you do it?
0:32:40 > 0:32:41There's a clue.
0:32:46 > 0:32:49This young orang-utan will grow to be
0:32:49 > 0:32:52the heaviest arboreal animal in the world.
0:32:54 > 0:32:59And this pygmy elephant will grow to be nearly three metres tall.
0:33:02 > 0:33:05By most standards, that's not pygmy.
0:33:19 > 0:33:21They both face the same problem...
0:33:23 > 0:33:25..how to find enough food.
0:33:34 > 0:33:35The solution,
0:33:35 > 0:33:40as the baby is starting to realise, is that they never stop moving.
0:33:55 > 0:33:59She will have to work hard to keep up with the herd.
0:33:59 > 0:34:03You see, these elephants are on the lookout for fruit.
0:34:09 > 0:34:15Overhead, orang-utans search for fruit in the canopy.
0:34:24 > 0:34:27And thanks to their agility, they can reach almost all of it.
0:34:34 > 0:34:36But for the young elephant,
0:34:36 > 0:34:39even low-hanging fruit can be just out of reach.
0:34:49 > 0:34:51Her mother shows her how to get them.
0:35:05 > 0:35:10But what's important here is that this elephant can smell some fruit
0:35:10 > 0:35:13from well over a kilometre away.
0:35:15 > 0:35:16And there are some plant species here
0:35:16 > 0:35:21that have specifically evolved to attract elephants.
0:35:23 > 0:35:26For instance, this jackfruit is so large
0:35:26 > 0:35:29that nothing else can really deal with it.
0:35:35 > 0:35:39His huge gut will take a couple of days to digest that meal,
0:35:39 > 0:35:44by which time he may have travelled over ten kilometres.
0:35:48 > 0:35:51Between them, the orang-utan and the elephant
0:35:51 > 0:35:55disperse thousands of species of fruit.
0:35:59 > 0:36:04Not only will the seeds be supplied with ready-made fertilizer,
0:36:04 > 0:36:08they will germinate safely away from the threat of attack
0:36:08 > 0:36:11from the mother tree's pests.
0:36:28 > 0:36:31Rainforests, more than any other ecosystem,
0:36:31 > 0:36:36rely on animals to spread their seeds over large distances.
0:36:44 > 0:36:48But paradoxically, this has created a nightmare.
0:37:30 > 0:37:36It's not often you get the chance to walk 30 metres up in the treetops.
0:37:40 > 0:37:44This canopy walkway certainly gives a unique perspective
0:37:44 > 0:37:46on the diversity of the rainforest.
0:37:47 > 0:37:50It's been built in Sabah in Borneo.
0:37:50 > 0:37:53Look at this!
0:37:53 > 0:37:54Wow!
0:37:58 > 0:38:04There's no doubt that there is a huge range of species here.
0:38:04 > 0:38:08But the flipside is that in any given area,
0:38:08 > 0:38:11there aren't that many individuals of each of those species.
0:38:16 > 0:38:18This tree is just coming into flower.
0:38:19 > 0:38:25But the thing is, if I look around the forest here,
0:38:25 > 0:38:27I can't see another of these trees.
0:38:29 > 0:38:30No.
0:38:31 > 0:38:34And this is bound to present a challenge
0:38:34 > 0:38:36when it comes to sex, to pollination.
0:38:36 > 0:38:39But it's a challenge that nature has risen to.
0:38:41 > 0:38:43The simple problem is,
0:38:43 > 0:38:46how do you cross-pollinate to fertilize your seeds
0:38:46 > 0:38:48if you're all alone?
0:38:52 > 0:38:57The methods British trees might use won't work here.
0:38:58 > 0:39:01Below the canopy, there's virtually no wind.
0:39:02 > 0:39:06And relying on a general pollinator, such as a honeybee,
0:39:06 > 0:39:09is a bit like posting a letter without an address.
0:39:09 > 0:39:12It might have collected YOUR pollen,
0:39:12 > 0:39:16but it's just as likely to deposit it on the wrong flowers.
0:39:18 > 0:39:22No, what's required in the rainforest is special delivery.
0:39:25 > 0:39:30The nectar in these long flowers is out of the reach of most animals.
0:39:32 > 0:39:35Because these petals have evolved in harmony with
0:39:35 > 0:39:37a very specific pollinator...
0:39:39 > 0:39:40..a sunbird.
0:39:47 > 0:39:51With his long bill, he can reach the nectar deep within the flower.
0:39:52 > 0:39:54And he needs to get this nectar
0:39:54 > 0:39:57because he's evolved to feed on little else.
0:40:12 > 0:40:16And critically, when he's had his fill here,
0:40:16 > 0:40:21he'll have to find another tree with the same type of flowers.
0:40:21 > 0:40:25If you're a tree in a rainforest, this relationship is ideal.
0:40:30 > 0:40:35For plants, specialist pollinators act as a form of insurance policy.
0:40:37 > 0:40:41You see, these animals have evolved to feed on your flowers
0:40:41 > 0:40:43and only your flowers.
0:40:43 > 0:40:44So once they've visited you,
0:40:44 > 0:40:47no matter how far away your nearest neighbour is,
0:40:47 > 0:40:51they'll get there and effect pollination.
0:40:51 > 0:40:53And this is typical.
0:40:53 > 0:40:59Many of the trees and plants out here will have specialist pollinators.
0:40:59 > 0:41:01And because there are thousands of species,
0:41:01 > 0:41:06this in turn means that there are a vast array of these types of animal.
0:41:22 > 0:41:26The final leg of my journey takes me to Amazonian Peru.
0:41:45 > 0:41:49Now we know why jungles are so productive,
0:41:49 > 0:41:50so diverse,
0:41:50 > 0:41:55I want to see how the whole ecosystem fits together.
0:42:15 > 0:42:19There's one series of remarkable relationships
0:42:19 > 0:42:23that even in this distant rainforest involves me and you.
0:42:29 > 0:42:33Now, you may not know what this is.
0:42:33 > 0:42:35But I'm certain you know what this is.
0:42:35 > 0:42:38This is a brazil nut.
0:42:38 > 0:42:40And this is a brazil nut pod.
0:42:40 > 0:42:44So inside here are about 20 of these.
0:42:44 > 0:42:45Come down here.
0:42:47 > 0:42:51Because quite naturally, this has come from a brazil nut tree.
0:42:53 > 0:42:57And here is that tree.
0:42:57 > 0:42:58What a thing!
0:42:58 > 0:42:59It's magnificent.
0:43:18 > 0:43:23Each huge seed pod takes 12 months to grow.
0:43:27 > 0:43:31And this mighty tree owes its entire existence
0:43:31 > 0:43:35to connections that have taken science years to uncover.
0:43:41 > 0:43:48One of the most intricate relationships takes place up there.
0:43:54 > 0:43:55I think I've got it.
0:43:55 > 0:43:58It's difficult to say, it's so high up.
0:44:01 > 0:44:04Now, that is it, that's it.
0:44:05 > 0:44:07Yeah.
0:44:33 > 0:44:38Well, after a bit of a climb, here's the plant that I was looking for,
0:44:38 > 0:44:42and saw from all the way down there on the ground.
0:44:42 > 0:44:44It's an orchid.
0:44:45 > 0:44:48This little orchid is absolutely essential to the brazil nut.
0:44:48 > 0:44:52In fact, if you've ever eaten one yourself,
0:44:52 > 0:44:55then you owe a debt of gratitude to these flowers.
0:44:57 > 0:45:03The story of why the brazil nut needs the orchid is extraordinary.
0:45:03 > 0:45:07It's so wonderful, it's almost beyond belief.
0:45:07 > 0:45:09And through unravelling that story,
0:45:09 > 0:45:12we can understand some astonishing things.
0:45:13 > 0:45:15SAWING
0:45:17 > 0:45:20It starts with those amazing-looking seed pods.
0:45:24 > 0:45:27How on Earth do they get dispersed?
0:45:29 > 0:45:33They're not only very heavy, they're unbelievably tough.
0:45:43 > 0:45:46I want to try a little experiment to find out.
0:45:50 > 0:45:54All I need is some fishing line and some little pink flags.
0:46:01 > 0:46:04I know this might seem a bit odd, but trust me,
0:46:04 > 0:46:06this is cutting-edge ecology.
0:46:16 > 0:46:18It's all primed and ready for action,
0:46:18 > 0:46:21but there are none of the animals around at the moment.
0:46:21 > 0:46:24So I'm going to put this down here,
0:46:24 > 0:46:26wait for them to sniff it out, and be patient.
0:46:35 > 0:46:39Given their size, you might expect something large.
0:46:41 > 0:46:45But the animal that can handle it is actually rather small.
0:46:51 > 0:46:54It's a rodent called an agouti.
0:47:04 > 0:47:06She may look insignificant,
0:47:06 > 0:47:10but her actions have a very significant impact
0:47:10 > 0:47:11on this rainforest.
0:47:16 > 0:47:20She specialises in eating tough seeds and nuts.
0:47:20 > 0:47:23Thanks to her teeth, which work like chisels.
0:47:36 > 0:47:39So this is how they're meant to be opened!
0:47:47 > 0:47:51That nut is packed full of energy and nutrients.
0:47:51 > 0:47:54After all, it contains everything you need
0:47:54 > 0:47:56to start growing a brazil nut tree.
0:48:09 > 0:48:13And what happens next is the bit that I'm really interested in.
0:48:14 > 0:48:17Because there are so many nuts in the pod,
0:48:17 > 0:48:20she can't eat all of them in one go.
0:48:22 > 0:48:24She's saving the rest for later.
0:48:34 > 0:48:38The question is, where is she going to put them?
0:49:07 > 0:49:09And look at that.
0:49:09 > 0:49:13She's even putting every leaf back exactly where she found it.
0:49:27 > 0:49:32Each nut is being carefully carried away to a different hiding place.
0:49:41 > 0:49:46As far as she is concerned, this is the ideal place for a larder.
0:49:51 > 0:49:55And by complete coincidence, as far as the tree is concerned,
0:49:55 > 0:49:59this is the ideal place for its seed to germinate.
0:50:09 > 0:50:12Here is one of our marked nuts.
0:50:12 > 0:50:17And the mother tree is hundreds of metres through there.
0:50:17 > 0:50:22So the tree, a plant, has managed to get a mammal to bury its seeds
0:50:22 > 0:50:26with just as much care as a really good gardener.
0:50:26 > 0:50:29It's one of those magical rainforest relationships.
0:50:36 > 0:50:41And the best thing about it is that she has no idea how important she is.
0:50:45 > 0:50:48The agouti is the only animal
0:50:48 > 0:50:52that can disperse the seeds of the brazil nut tree,
0:50:52 > 0:50:58so the brazil nut tree is completely reliant on the agouti.
0:50:58 > 0:51:02It's a case of what we call species specific dependency.
0:51:02 > 0:51:05Off it goes to bury one of the nuts.
0:51:05 > 0:51:06And you know,
0:51:06 > 0:51:11I can guarantee that every brazil nut that you've ever cracked open
0:51:11 > 0:51:16has come from a tree that was planted by one of these animals.
0:51:17 > 0:51:19That's fantastic.
0:51:19 > 0:51:22You've got to admit, ecology is fantastic.
0:51:34 > 0:51:38It's clear why the brazil nut tree needs an agouti.
0:51:38 > 0:51:42But how does the orchid that I found fit into our story?
0:51:45 > 0:51:50Like many flowers, it uses pollinating insects, bees.
0:51:51 > 0:51:52In fact, these orchids
0:51:52 > 0:51:56use a very special group of bees called Euglossine,
0:51:56 > 0:51:57or orchid bees.
0:52:01 > 0:52:04And more specifically, they have to be males.
0:52:08 > 0:52:11Unlike most bees, which are after nectar,
0:52:11 > 0:52:15this one is after something quite different.
0:52:15 > 0:52:16He's after perfume.
0:52:19 > 0:52:24He collects a waxy secretion by rubbing his legs all over the flower.
0:52:24 > 0:52:28And in doing so, pollinates that flower.
0:52:38 > 0:52:42Collecting this perfume is so important to a male orchid bee
0:52:42 > 0:52:47that it may fly miles all over the forest in search of it.
0:52:49 > 0:52:51The reason that he's collecting scent
0:52:51 > 0:52:55is that the males compete with one another using smell.
0:52:55 > 0:52:57They have a sort of a scent-off.
0:52:57 > 0:52:59The one with the best bouquet of perfumes
0:52:59 > 0:53:02gets the right to mate with the females.
0:53:07 > 0:53:12But what has all of this got to do with our story of brazil nut trees
0:53:12 > 0:53:13and agoutis?
0:53:15 > 0:53:18Only the male orchid bees pollinate the orchids.
0:53:18 > 0:53:21To reduce competition between the sexes,
0:53:21 > 0:53:24the males and females have evolved different niches.
0:53:24 > 0:53:27It's another example of the extreme diversification
0:53:27 > 0:53:29that takes place here in the rainforest.
0:53:29 > 0:53:34So the females pollinate a completely different species.
0:53:34 > 0:53:36A very, very much larger one.
0:53:38 > 0:53:39The one that I'm sat on.
0:53:39 > 0:53:40The brazil nut tree.
0:53:43 > 0:53:47Once a year, the tips of the brazil nut tree branches
0:53:47 > 0:53:50are adorned with large white flowers.
0:53:52 > 0:53:55They attract insects from all over the forest.
0:53:57 > 0:54:01Including the much larger female orchid bees.
0:54:05 > 0:54:09The nectar is hidden beneath a special petal.
0:54:13 > 0:54:15And the female orchid bees
0:54:15 > 0:54:18are one of the few insects that are big enough
0:54:18 > 0:54:21and strong enough to open the flowers.
0:54:24 > 0:54:26This smaller bee, on the other hand,
0:54:26 > 0:54:29simply doesn't have the strength to open it.
0:54:32 > 0:54:33This selective door policy
0:54:33 > 0:54:38is the tree's way of ensuring that it will only be used
0:54:38 > 0:54:44by insects which are guaranteed to visit other brazil nut tree blooms
0:54:44 > 0:54:48and then pollinate them.
0:54:51 > 0:54:56The intricate relationship between the male orchid bee and the flowers
0:54:56 > 0:55:00is the reason that brazil nut trees like this one
0:55:00 > 0:55:05can only grow in intact rainforest ecosystems.
0:55:05 > 0:55:10Now, the brazil nut tree needs the agouti,
0:55:10 > 0:55:13way down there, to disperse the seeds.
0:55:13 > 0:55:19The agouti needs the female orchid bee up here to pollinate the flowers
0:55:19 > 0:55:21so those seeds are produced in the first place.
0:55:21 > 0:55:25The female orchid bee needs the male,
0:55:25 > 0:55:29which in turn needs those orchid flowers.
0:55:29 > 0:55:34That's why the brazil nut needs the orchid.
0:55:34 > 0:55:36You just couldn't make it up, could you?
0:55:43 > 0:55:48This wonderfully complex web of connections has all come about
0:55:48 > 0:55:51due to the sheer biodiversity of rainforests.
0:55:52 > 0:55:54And understanding it
0:55:54 > 0:55:58reveals the natural world in a very different light.
0:56:02 > 0:56:05Animals don't simply live in forests.
0:56:05 > 0:56:07They are the forests.
0:56:08 > 0:56:14And forests without orang-utans and elephants are broken ecosystems.
0:56:16 > 0:56:19We might want to save rainforests for the elephants,
0:56:19 > 0:56:24when, really, we should be saving the elephants for the forest.
0:56:24 > 0:56:29We've been motivated by what an orang-utan looks like.
0:56:29 > 0:56:32We should be motivated by what it does.
0:56:37 > 0:56:42Stretched out around me is the most complex ecosystem on our planet,
0:56:42 > 0:56:46home to millions of different species.
0:56:46 > 0:56:49And whilst there's wonder in the detail of their individual lives,
0:56:49 > 0:56:54nothing competes with the sheer beauty of the bigger picture.
0:56:54 > 0:56:59The dynamic, functional, living, breathing rainforest.
0:56:59 > 0:57:05For me, science is the art of understanding truth and beauty.
0:57:05 > 0:57:08Well, here's the beauty.
0:57:09 > 0:57:11And we've seen just a little of its truth.
0:57:42 > 0:57:43Join me next time,
0:57:43 > 0:57:48when I'll be travelling to some of the world's greatest grasslands.
0:58:15 > 0:58:17From the depths of our forests and rivers,
0:58:17 > 0:58:19to the peaks of our mountains...
0:58:21 > 0:58:24..we're on a mission to prove the UK is wilder than you think.