BBC_The Green Planet_1of5_Tropical Worlds
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00:00The biggest living thing that exists on this planet is a plant, like this giant sequoia
00:17tree in California.
00:22Plants, whether they are enormous, like this one, or microscopic, are the basis of all
00:29life, including ourselves.
00:32We depend upon them for every mouthful of food that we eat and every lungful of air
00:38that we breathe.
00:43Plants flourish in remarkable ways, yet for the most part the secrets of their world have
00:50been hidden from us, until now.
01:01Now we have new groundbreaking technology that enables us to enter their extraordinary
01:07world and see their lives from their perspective.
01:20This series will reveal the extraordinary and dramatic ways in which plants behave.
01:32And we will explore the challenges demanded by the very different landscapes in which
01:37they live.
01:43The tropics, the richest and most competitive place in which to survive.
01:52The bizarre water world, where giants fight ferocious battles and plants eat animals alive.
02:07The deserts, the world of extremes.
02:18Seasonal lands, where survival depends on precision timing.
02:27And everywhere we will explore the critical and intimate relationships between plants
02:34and animals, including ourselves.
02:41Join me in a world that takes you by surprise.
02:54See our planet as never before.
03:03From the plant's perspective.
03:07This is the Green Planet.
03:33I'm in Costa Rica, in the heart of a rainforest, the richest and most dynamic environment on
04:00earth.
04:03Plants only cover a very small proportion of the earth's surface, yet they contain
04:07over half of all known species of animals and plants.
04:15Up here, the forest canopy is bathed by life-giving sunlight.
04:26The branches of the great trees carry rich, flourishing sky gardens, home to countless
04:38different kinds of beautiful plants.
04:44Each species has evolved its own exquisite solution to the challenges of survival.
04:56This forest world may look peaceful, timeless and unchanging, but that is far from the truth.
05:07This is a battlefield.
05:14Throughout this forest, plants are competing ferociously with one another to claim the
05:20light.
05:22The battle is at its fiercest on the forest floor, where only two percent of the sunlight
05:34filters through.
05:37Plants here have to bide their time.
05:45Their opportunity comes when an old tree dies.
05:51When that happens, sunlight floods the forest floor for the first time in perhaps a hundred
06:00years.
06:11The seedling's wait is over.
06:25It must now race skywards and claim a place in the canopy.
06:32But it's not alone.
06:40Rivals are everywhere, each with its own survival strategy.
06:58Some plants, like this monstera, stretch out divided leaves to collect what light they
07:04can.
07:11This vine is groping blindly around with its tendrils.
07:20It attempts to reach the light by hitching a ride.
07:27Its tendrils are highly sensitive to touch.
07:36And a suitable target is in range.
07:46Got it.
08:07The vine tightens its grip and begins to haul itself upwards.
08:17But it's now overtaken by the forest's fastest-growing tree, a young balsa.
08:30Its giant leaves are already 40 centimeters across and are stealing the light from its
08:35rivals below.
08:39But the balsa's battle is not yet won.
08:43Other different vines are lying in wait.
08:58Each is armed with dozens of claw-like hooks.
09:06If just one hook gets a grip, the vine will be able to smother its victim.
09:25But the balsa is defended by a shield of slippery hairs.
09:54The vine's hooks just can't get a hold.
10:01The balsa brushes them aside and continues to rush skywards, leaving the losers in its
10:17shadow to fight among themselves.
10:24This balsa has won its battle for the light, and it's done so in a little over a year.
10:40Most trees would have grown an inch or so in that time, but this one is already 30 feet,
10:46or 10 meters, tall.
10:53Balsas owe their success to the special character of their wood.
10:59If this section of tree trunk came from a hardwood tree, it would be really quite heavy.
11:05But as it is, it's from balsa, and it's really very light, and that's because of its internal
11:13structure.
11:17Under the microscope, balsa wood looks like a honeycomb.
11:23It contains more air than wood, so not only can it grow very fast, but it gets the maximum
11:30height for minimum weight.
11:35But fast growth needs something else, fuel, and lots of it.
11:52That fuel is created in a plant's leaves as they soak up the sun.
12:08It's a process called photosynthesis, a chemical reaction that is the basis of all life on
12:18Earth.
12:25Leaves are covered by thousands of microscopic pores called stomata.
12:32When open, they extract carbon dioxide from the air, and using energy from the sun, combine
12:38it with nutrients to build the plant's tissues.
12:46And, critically for us, the process releases the oxygen that we and all animals need in
12:53order to breathe.
12:57But for plants, there is a downside.
13:09These precious, energy-packed leaves attract predators.
13:15In every shape, size, and agility.
13:36A sloth can only move slowly, but you don't need speed to gather leaves, and it eats nothing
13:45else.
14:05The plants here are under constant attack from all kinds of leaf eaters.
14:12But the most voracious by far is hardly ever seen.
14:17It consumes 50,000 leaves every day.
14:22It's created this great clearing in the forest, and it lives just beneath my feet.
14:37It's called Leucoagaricus.
14:43It's neither animal nor plant.
14:47It's a fungus.
14:51It lives five meters underground, far from the leaves that it devours.
15:01To get them, it employs the best leaf gatherers in the tropics.
15:12Leafcutter ants.
15:19Millions of them provide the fungus with its food, and in return, the fungus cultivates
15:25tiny mushrooms as food for the ants.
15:34The fungus releases chemical signals that tell the worker ants what type of leaf it
15:40wants to eat.
15:44Scouts are sent out with the latest orders.
15:55The ants will travel hundreds of meters to find the right kind.
16:03Today's crop is being taken from a young bixa tree.
16:10Just a few years old and still battling to reach the canopy, it can ill afford to lose
16:14any of its leaves.
16:34Between them, the ants can demolish a large leaf in a matter of minutes.
17:01The sound of cutting attracts more ants.
17:03The leaves are carried back to the underground fungus.
17:12The ants can run at speeds of two meters a minute, and each can carry a load ten times
17:23its own weight.
17:39It's a river of leaves across the jungle floor, part of a vast network that extends for miles
17:48through the forest.
17:59To avoid congestion, worker ants dig trenches around obstacles.
18:16Thousands of pieces are delivered every hour to the waiting fungus.
18:41Fed by such a continuous supply, the fungus grows rapidly, filling the chambers in which
18:55it lives.
18:59So the ants excavate more space.
19:07It seems that the fungus has the upper hand, and the bixa tree will not survive.
19:20But it fights back, using chemical warfare.
19:28The bixa tree floods its leaves with toxins that could kill the distant fungus.
19:38As the ants carry the fragments back, they are themselves poisoning the fungus on the
19:43tree's behalf.
19:50It's a long-distance attack.
20:00As the poison takes effect, the ants sense that their fungus is weakening, and they respond
20:17to its signals by changing to another source of leaves.
20:27So the plant's chemical response forces the ants to constantly switch from tree to tree.
20:40Strike and counter-strike.
20:46That ensures that enough leaves remain uneaten for each tree to recover.
21:08Once a plant becomes adult, it can switch its energies from growth to reproduction.
21:21The tropical forests of the Americas stretch from Mexico to the southern reaches of the
21:26Amazon.
21:28They contain more than a hundred thousand different species of plant, each with its
21:35own particular survival strategy.
21:40One species that has adopted a grow-fast lifestyle flourishes throughout this vast region.
21:51The balsa.
21:54But it has to pay a high price for doing so.
21:58The lightweight wood that enables it to grow at such speed is not strong and is easily
22:04broken.
22:06Few balsas live longer than 20 years.
22:12This one is approaching the end of its brief life, so the time has come for it to reproduce.
22:25It has used a huge amount of energy to produce some of the most extravagant flowers in the
22:31forest in immense numbers.
22:43Each is the size of a human hand.
22:52As night falls, the tree prepares an enticing treat.
23:05This is a kinkajou, a kind of fruit-eating raccoon.
23:15Each flower is filled with huge quantities of exceptionally rich nectar supercharged
23:22with sugar.
23:32Irresistible.
23:43The kinkajous drink so greedily that they get pollen all over their faces.
23:51So as they move from tree to tree, they carry pollen with them.
24:03But the balsa leaves little to chance.
24:08The nectar might appear to have run out, but this is just the first round.
24:14Now the balsa refills its flowers, enticing the kinkajous back to repeat the process seven
24:22times a night.
24:26Pollination is complete, and the kinkajous, they also get well-served with over a hundred
24:37pints of nectar in just a few weeks.
24:44Both plant and animal do well out of this arrangement.
24:51But in the tropical world, that isn't always so.
25:01Borneo.
25:06Here, on the slopes of Mount Kinabalu, live plants that eat animals using pitcher-shaped
25:14leaves full of water.
25:26Insects are attracted by the expectation of nectar, but tumble into the pitcher, where
25:32they're drowned and absorbed.
25:40On the lower slopes of the mountain, a plant grows that has no leaves at all, or even a
25:48stem.
25:51All that can be seen is this, a bud.
26:03It is a parasite.
26:13The rest of its body lies within the tissues of a liana, on which it feeds.
26:24After about five years, the bud finally opens into a monstrous flower.
26:33It now has only a day or so in which to be pollinated before it starts to wither.
26:42These petals are the color of blood.
26:47Their surface is tough and warty.
26:55It appears to have fur, even whiskers and teeth.
27:08At first sight, it might be mistaken for a dead animal.
27:14This is rafflesia, the corpse flower.
27:23A meter across, it's the world's biggest flower.
27:30And this one is a male.
27:35From its center comes the pungent odor of death.
27:47It's a scent that might not appeal to every animal.
27:57But it's very attractive to carrion flies.
28:03They lay their eggs on rotting flesh.
28:19The scent lures the fly deep into the flower in search of meat.
28:30The fly finds nothing.
28:33The rafflesia, however, has the fly exactly where it wants it.
28:42It's stuck pollen to the fly's back.
28:57If this male rafflesia's strategy is to work, the fly carrying its pollen must now visit
29:04a female corpse flower.
29:10Such as this one.
29:19Success.
29:42Once pollinated, plants are able to produce seeds, the next generation.
29:48Once again, there are animals all over the forest that are eager to make a meal of them.
30:09The Malay archipelago, a vast tropical world of a thousand islands.
30:24It's home to giants, the tallest trees in the tropics, many of which live for centuries.
30:38They produce seeds in enormous numbers, but only do so when the time is right.
30:47This individual hasn't produced a single seed for nearly a decade.
30:53But in the last weeks, it has become festooned with more than 10,000 of them.
31:02Each seed has the potential to produce a giant like its parent.
31:15But success will depend on timing.
31:33Seed hunters are gathering.
31:40Bearded pigs.
31:49But these seeds have been produced by a dipterocarp, trees that create the tropical world's largest
31:59seed nursery.
32:07After years of waiting, thousands upon thousands of individual dipterocarps have synchronized
32:14to produce the next generation, all at exactly the same time.
32:36Now, these seeds will face the dangers below together.
33:06By releasing billions of seeds all at the same time, they swamp the pigs and any other
33:33animals with more than they could possibly eat.
33:58And that buys time for some of the seeds to take root and sprout.
34:29The tree's strategy has worked, but a seedling will have to overcome many more dangers over
34:38the years if it, too, is to become a giant.
34:49And there are many ways in a tropical forest by which a tree's life can be ended before
34:54it reaches its prime.
35:01The northernmost tip of Australia.
35:07This is the world's most ancient rainforest.
35:28Tensions between animals and plants have raged here for 180 million years.
35:41So the plants have had time to develop effective defensives.
35:48This is a poison arrow tree, one of the tropical world's most heavily defended plants.
35:58Its trunk is tall and slippery and exudes a poisonous sap.
36:08It appears to be almost invulnerable.
36:17But even so, just as this individual reaches maturity, its life has become endangered.
36:30Each monsoon season, it is invaded from above.
36:41It attracts hundreds of shining starlings.
36:47Its immense, smooth trunk makes its high branches above a safe place to nest.
36:54But over the years, this has created a major problem for the tree.
37:04After feeding, the starlings return to the nest to digest their food, with inevitable
37:10consequences.
37:17Every year, they produce almost a quarter of a ton of droppings.
37:25The toxic chemicals they contain create a dead zone that completely surrounds the tree.
37:38The toxins are absorbed by its roots and travel up through the trunk and into every leaf.
38:01Branch by branch, the tree is slowly dying.
38:09It has become a victim of its own success.
38:14It has been poisoned.
38:24Now a new battle begins.
38:28One to claim the tree's dead body and the vast amount of nutrients that it contains.
38:36It's a battle that is fought throughout the natural world, involving a group of organisms
38:42that we rarely notice.
38:47Here on the floor of a tropical rainforest, it's dark, it's humid, and it's hot.
38:55Natural conditions for fungi.
38:58We normally think of fungi as things like this, mushrooms of one kind or another.
39:04But these are just the fruiting bodies.
39:10They exist, for most of the time, hidden in the leaf litter and the earth as a network
39:16of fine white threads.
39:19The threads of competing fungi envelop their victim's body, releasing enzymes which digest
39:26the tree's tissues and unlock the nutrients within.
39:31There are a million or so different species of fungi in the tropics.
39:39Some feed on dead plants, others eat them alive, and some reveal their existence in
39:48an eerily beautiful way.
40:00In Africa, in the Congo, this is known as chimpanzee fire.
40:11The mysterious bioluminescent glow becomes brighter as the fungus digests the tree.
40:23When fungi have fed sufficiently, they develop their reproductive organs.
40:53Each can produce literally billions of spores, the tiny particles that carry the species'
41:06genetic blueprint.
41:10Each spore, like this, has the potential to kill a tree.
41:23The spores are so light, they can be carried by the slightest air currents.
41:45At least a billion float above every square meter of rainforest.
42:04Recently, it has been discovered that these spores do far more than just bring death and
42:12decay.
42:13They are, in fact, at the very center of the rainforest's life-support system.
42:29High in the humid air, the spores combine with molecules of water.
42:48Gradually, they collect into droplets, which, when they are heavy enough, fall and rain.
43:18Over two and a half meters of rain falls every year in a rainforest.
43:46And in the center of almost every rainfall, there is a fungal spore.
44:11The world's rainforests are the richest and most dynamic environments on Earth, built
44:18on complex connections and relationships.
44:25And these connections, competitive or collaborative, are now becoming increasingly fragile.
44:48When Charles Darwin was exploring the tropical world nearly 200 years ago, he wrote this
44:56in his diary, among the scenes which are deeply impressed on my mind, none exceed in sublimity
45:06the primeval forests undefaced by the hand of man.
45:13He would struggle to find such a place today.
45:22Today, 70% of all the world's rainforest plants grow within a mile of a road or a clearing
45:38that we have cut into the forest.
45:45And this is creating new battlefields in the tropical world.
45:52Alien armies of identical cultivated plants now stand where thousands of different species
45:59once grew.
46:09We have planted vast regiments of crops in order to provide ourselves with food and other
46:16commodities.
46:18And the ancient forest has been reduced to ever fewer isolated fragments.
46:29All, however, is not lost.
46:32The fragments can still be sanctuaries, keeping alive the intimate relationships within them.
46:41Their size is nonetheless critical.
46:53This is the seven-hour flower.
47:08This plant produces its flowers at night.
47:11They open at about six o'clock, and each blossom only lasts that night.
47:18It opens for about seven hours, and then it dies.
47:24But during that time, it provides food for one particular animal, a bat.
47:31And here it is.
47:32During the seven-hour flower's flowering season, Underwood's bat feeds almost exclusively
47:58on its nectar.
48:01It is the plant's primary pollinator.
48:06It might seem that this is a fairly evenly balanced relationship, but not so.
48:16The bat likes this nectar because it's sweet, but it's not very nourishing.
48:23So the bat must visit hundreds of flowers a night, and it pollinates them as it feeds.
48:35But if a patch of forest becomes too small, with too few flowers, the bats will disappear,
48:47and without the bats, the flowers can't reproduce and will soon die out.
48:55The partnership is broken.
49:07Life in the forest depends on countless close relationships, but they are increasingly under
49:13threat as forests become more fragmented.
49:17The solution, of course, is to join these remaining fragments together again.
49:23Thirty years ago, I came to this exact spot.
49:28This land belonged to a scientific research establishment, and it was covered with grass
49:34being grazed by cattle.
49:36The scientists got rid of the cattle and allowed nature to take its course.
49:42Just look at it now.
49:53This new forest has become a bridge that connects several fragments, allowing plants and animals
50:01to both renew old connections and create fresh ones.
50:17Of course, we urgently need to protect what healthy forests still remain.
50:25But looking forward, we must take what may well be our last chance to re-establish the
50:34lost rainforest and help the tropical world to heal itself.
50:45It will take the cooperation of nations around the world, but it is the only way in which
50:52we will be able to preserve the treasures of the tropical rainforest for future generations.
50:58And with it, ultimately protect all life on this, our green planet.
51:23The aim of the Green Planet team was to take the viewer into the world of plants so that
51:29it could be seen from the plant's perspective in a way that had not been possible till now.
51:36That meant developing an entirely new camera system.
51:46This is the Game Changer, a specially designed robot camera that we affectionately call the Trifid.
51:59The Trifid started life in the garage of an American ex-military engineer, Chris Field.
52:05I've seen quite a few of these Planet Earth style documentaries and they always absolutely
52:09blew my mind, especially the Botanic Timelapse really spoke to me.
52:14In his spare time, Chris spent a decade building elaborate motion controlled timelapse camera
52:21rigs and teaching himself how to film plants.
52:25Plants often behave like animals in so many ways and being able to see it through timelapse
52:31is one thing, but using the motion control brings you into that time scale.
52:40We could really see the potential in how we could use this sort of movement to bring
52:44plants alive and film them in the same way that we film animals.
52:50Soon Chris joins the team in a quiet corner of the Devon countryside and the robot army
52:56begins to take shape.
53:00After 40 years of filming timelapse, these rigs opened up a whole new world for us.
53:07So it'll be like hovering around something with a drone or a helicopter but in a timelapse speed.
53:15The holy grail for us is being able to take this technology out into the wild, try and
53:20get the same sorts of dynamic moves in some of the most extreme environments in the world.
53:27So what we needed to do was develop this technology even further.
53:32Six months later, the triffid is born.
53:37And with slight trepidation they hand me the controls.
53:42That makes it go away and this makes it come back and this sends it up.
53:55I think I'd better hand it over to the experts.
54:01Now it's time to put this new member of the team properly through its paces.
54:08The aim here is for Ollie to find a target, aim for it and fly through it as if he is
54:12a tiny fly going through a hole in a leaf.
54:15Easier said than done.
54:17Oops.
54:18Trying to find the target.
54:22Whether the kit's going to stand up to that sort of use and the abuse that we throw at
54:27most pieces of kit has yet to be seen.
54:30From the studio it seems to be working pretty well.
54:33But this is only a dress rehearsal.
54:36It's time for the triffid to face the challenges of the Costa Rican rainforest and leafcutter
54:42ants.
54:43We want to film their journey all the way down the trunk and along this buttress root
54:56and down to their nesting.
54:59The team and the triffid need several days of dry weather, but a storm can hit at any
55:05moment and rain is one thing the triffid does not like.
55:12The conditions that we're working in now are a little bit more challenging than the studio.
55:18All the ground is really bumpy, got loads of plants in the way.
55:23I know we're making a series about plants, but sometimes they're a complete pain in the
55:27neck.
55:30The triffid needs to be programmed to capture images from 7,000 different camera positions
55:37on the ant's trail.
55:40Just one drop of rain on the lens, or a wobble, and the whole process will have to start again.
55:47And I think this is when we're going to find out if our ambition outweighs our ability.
55:56For the crew, the ambition is certainly high.
56:00Fortunately, it's all down to the triffid now.
56:15We've been filming the ants with the triffid for eight days now, and we're on our third
56:20set up.
56:21It's pretty slow going.
56:25While the triffid seems to be handling the pressure well, for the crew, trying to take
56:29a tree's eye view of ants is turning into a bit of a nightmare.
56:36Wake up, film ants, go to sleep.
56:39Dream of ants, wake up, film ants, sleep.
56:42Dream of ants, wake up, film ants, go to sleep, dream of ants.
56:51After two weeks in the jungle, ambition and ability finally come together, for the triffid
56:57at least.
56:59Thousands of individual images creating a single extraordinary time lapse.
57:06One that follows a river of leaves across the jungle floor from a unique perspective.
57:13For the triffid, this was just the beginning.
57:21Take a bow, triffid.
57:30Time on the green planet, the wonder of water worlds, where plants hunt, go on the move,
57:45fight, and create the air we breathe.
57:52The Open University has produced a poster that explores the vital role that plants have
57:59for our planet.
58:00To order your free copy, call 0300 303 4200 or go to bbc.co.uk forward slash green planet
58:12and follow the links to the Open University.
58:19Into those water worlds here next Sunday at seven.
58:22Later tonight, see beauty off world, looking up for the first time in 2022.
58:27The new Sky at Night is across on BBC4 at ten.
58:30Here next, a demanding house guest tests her sister's patience.
58:33The new series of Call the Midwife continues in a tick.