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00:30This is the Boreal Forest.
00:53The largest forest on earth, 750 billion trees, smothered by snow throughout the winter.
01:18The northernmost boundary of an extraordinary world.
01:25I'm standing at the edge of the Arctic Circle.
01:30To the north of me lies a land dominated for most of the year by snow and ice.
01:373,000 miles to the south, the tropics bathed the year round in warm sunshine.
01:44And in between, a very different world dominated by relentless change.
01:58An endless cycle of four distinct seasons, each with its own challenges.
02:06The short freezing days of winter give way to the urgent awakening of spring.
02:13And the long hot days of summer yield to the cooling of autumn.
02:23Opportunities will be brief.
02:28To survive these extremes, plants have not only got to be hardy and resilient,
02:43but many of them have developed special strategies in order to meet the demands of this seasonal world.
02:51To succeed, they must get their timing just right.
03:01For months now, this world has been asleep.
03:06A change is coming.
03:23Spring is on its way.
03:27Spring is on its way.
03:49In Canada, the forests are starting to stir.
03:55Throughout the winter, the sugar maples here have kept stores of nutrients ready for this moment.
04:06Now, as temperatures start to rise, those nutrients must be brought up from the roots.
04:20Sap is on the rise.
04:25The fuel for new green growth.
04:28The fuel for new green growth.
04:42But just as growth reaches full speed, robbers arrive.
04:48A sap, suckar.
05:05A thief in search... of maple syrup.
05:09A sap sucker, a thief in search of maple syrup.
05:33The tree can tolerate hundreds of wounds.
05:39But if they completely encircle the trunk, the tree will eventually die.
05:57The sap sucker's break-in hasn't gone unnoticed.
06:01Hummingbirds, squirrels, and insects all invade the sap sucker's territory trying to steal a meal.
06:21But unwittingly, they help the tree.
06:33Time spent chasing the competition means less time to drill new holes.
06:40Means less time to drill new holes.
06:43Man 1
06:57Man 1
07:02The tree gets a chance to repair its wounds, and the sap can rise freely again.
07:21So, this year at least, the tree will once more produce its leaves, hundreds of miniature
07:40solar panels that collect energy from the sunlight.
07:48Each leaf is covered by millions of microscopic pores, stomata.
07:58They take in carbon dioxide and release oxygen and water vapour in a process that produces
08:07high energy fuel.
08:12All the trees here can now use that fuel to grow over the coming months.
08:26As spring proceeds, the power of the sun increases.
08:50On riverbanks across Europe, many plants have been lying dormant underground, waiting for
09:03the earth to warm.
09:10And now, a race begins.
09:21Among the first to start are nettles, the sprinters.
09:31Then, only just behind come the brambles.
09:36They're much more aggressive and have backward-pointed hooks with which to scramble over their rivals.
09:46Last to come, the climbers.
09:52Hops and Briony.
10:00They lasso their way towards the light.
10:03They lasso their way towards the light.
10:07Soon, every inch of space and every patch of light has been claimed.
10:32But hidden in the shadows, another plant has been waiting to make its move.
10:55This...
10:56This...
10:59is Dodda.
11:07A hunter...
11:11with an exceptional sense of smell.
11:20Moving swiftly, it searches for its prey.
11:24It detects the scent of a young nettle.
11:27It detects the scent of a young nettle.
11:29It detects the scent of a young nettle.
11:31The Cud 누�dar's lungs
11:32The Cuddar punctures the nettle stem
11:35The Cuddar odda punctures the nettle stem
11:38And sucks out the nutritious sap.
11:42The dodder punctures the nettle stem and sucks out the nutritious sap.
11:59And it doesn't stop at just one victim.
12:05With its energy supply assured, it multiplies.
12:12It's a parasite with an insatiable appetite.
12:42It's a good one here.
12:43Oh, wow.
12:44You're not making sense.
12:45There's no more than a brokerage.
12:47Oh, hey.
12:48I'm saying in a mockery.
12:49It's not good for you.
12:50I'm saying.
12:51I'm getting this one.
12:52I'm saying in a mignon, I'm saying there's no more than a mignon.
12:54I'm saying there's no better than a mignon.
12:55I'll make it a mignon and a mignon.
13:00But, remarkably, its victims can now exploit
13:30the dodder when other springtime enemies appear, caterpillars.
13:53When under attack, a leaf sends out a signal telling the rest of the plant to start building
13:59defenses, foul-tasting toxins that deter the caterpillars.
14:11In an extraordinary twist, the stems of the dodder interconnecting the plants are now being
14:17used as lines of communication to relay these warning signals from plant to plant.
14:23They respond by producing their own protective chemicals.
14:35Eventually, the whole riverbank becomes one huge defensive network.
14:46And the one-time rivals are now better off together.
14:58The first warm days of spring encourage some plants to flower and get ahead of the competition,
15:21creating beautiful displays throughout the seasonal world.
15:28From the spectacular cherry blossoms of Japan, to the goldfield flowers of California.
15:38spring flowering is risky.
15:46If they flower too early, it may not be warm enough for pollinating insects to be active.
15:53But the common daisy gives them every opportunity.
16:01The warmer the flowers are, the more attractive they are.
16:05And they have a remarkable strategy in order to maximize this.
16:11They were closed up tightly throughout the night as a protection against the elements.
16:17Once they feel the warmth and the light of the sun, they spring into action.
16:22It's a behavior called heliotropism.
16:40They turn to keep facing the sun, absorbing as much heat as they can.
16:48This is a thermal camera, and it will tell me the difference between the surrounding temperature
17:14and the temperature in the center of a daisy flower.
17:18The surroundings, 12 degrees.
17:23In the center of a flower, 21.
17:31Pollinators such as bees and wasps prefer the warmed up flowers, because they can get a
17:38share of the heat for themselves.
17:42As a consequence, they can collect more nectar from more flowers, pollinating as they go.
17:51And the daisies, with the help of their pollinators, are able to have a particularly long flowering
17:57season.
18:01Because when the window of opportunity is brief, even more ingenious tactics are necessary.
18:08Here in southwest Australia, summer temperatures can soar to up to 40 degrees Celsius.
18:27Now, for a brief moment in the cooler spring, flowering plants must get busy.
18:46And this hammer orchid, with its strange flower, is doing exactly that.
18:57It needs to attract a pollinator, but has no nectar and doesn't even look like a flower.
19:07Unlike these neighboring huge grass trees, these produce thousands of tiny white flowers, all
19:18dripping with nectar.
19:23But the orchid has a different strategy.
19:33It synchronizes its emergence with the brief mating season of the tinnid wasp.
19:46The flightless female wasp produces pheromones to attract males.
20:01This male detects a scent that seems to be hers, yet flies right on by.
20:21The orchid not only has the same shape and color as a female wasp, but it sits at the
20:27same height as she does.
20:31It even mimics her smell, and the beguiled male attempts to mate with it.
20:55It hammers against the orchid's pollen sacks, and the wasp leaves, doubtless a little shaken, only
21:11to be duped once again.
21:14The pollen on his back now sticks to this different orchid, and the deception has worked.
21:35The orchid's imitation is even more intoxicating, it seems, than the real thing.
21:42Eventually, the male wasps tear of the orchid's enticements.
21:49And now, the wasps, both male and female, find the flowers of the grass trees to feed.
21:56And now, the wasps, both male and female, find the flowers of the grass trees to feed.
22:02And there, at long last, they mate.
22:09And there, at long last, they mate.
22:15And as for the hammer orchid, pollination is complete.
22:34As summer approaches, the need to flower becomes more urgent.
22:59And nowhere more so than here, in South Africa.
23:08This is the Fanebos, part of the Cape Floral Kingdom, a great expanse of open heathlands just
23:16north of the Cape.
23:21Here, there are more different species of plant than anywhere else in the world.
23:27Nearly 9,000, many needing pollinators.
23:35They compete with one another for such help, by flaunting extravagant shapes and vivid colours.
23:45All promising nectar as a sugary reward.
23:53But there is a plant here that avoids this crowded competition.
24:00And the rising temperatures of summer bring just what it needs.
24:15This is the first fire here for 15 years.
24:32Nearly all of the plants are destroyed.
24:51Incinerated.
24:53It might seem from the smoke and the still smouldering embers, that no plant could survive such an inferno.
25:10But just four days after the flames, rising from the ashes, a fire lily.
25:33It has been lying dormant underground for 15 years.
25:45But now, awakened by the smoke, it flowers.
25:50The blooms may be small and unchowy, but that's all they need to be.
26:08In this charred landscape, pollinators such as these sunbirds can spot these little red beacons from great distances.
26:16They're the only source of nectar around.
26:23And the more visitors the flowers attract, the more likely they are to be pollinated.
26:40It's just in time.
27:02Within a few months, the whole landscape is alive once more.
27:10In fact, all these plants need fire to survive.
27:20And as competitors return, the fire lily fades.
27:26It now returns underground and will rest there as a bulb until another fire awakens it.
27:42By the time the long hot days of summer arrive, wildflower meadows are bursting with life.
28:01But autumn is not far away.
28:05So now, pollinated plants must use their remaining energy to produce the next generation.
28:14Seeds.
28:27A dandelion clock contains around 200 seeds.
28:36Each with its own tiny parachute.
28:38Few seeds can fly as far as these.
28:47Some are known to have traveled over 60 miles.
28:51But to travel any distance at all, they need the wind to be just right.
29:10However, before they can get away, there is a risk.
29:13For a risk, voracious hunters live in this meadow.
29:43Tiny harvest mice.
29:47They love dandelion seeds.
29:56But they don't like to share.
29:58Finally, the sun warms the ground.
30:13And a gentle breeze blows in, creating an ideal updraft.
30:28Air flowing between the bristles creates a vortex that lifts the seeds up.
30:43Heading off on a gentle breeze, this seed now starts its travels.
30:58Plants use a variety of different techniques to spread their seeds as far as possible from themselves.
31:24And one of the most remarkable is this one.
31:28It's called Ecbalium.
31:29And it's a relative of the cucumber.
31:32For several weeks now, pressure has been building up inside the pods.
31:37And so now they're as taut as a well-pumped up bicycle tire.
31:41All they need is just a slight nudge.
31:44The further the plant can fire its seeds, the better.
32:06If a seedling germinates close to its parent, the two will have to compete for nutrients and light.
32:19This Himalayan balsam has seed pods that react rather differently, like catapults.
32:26As they dry out, they begin to strain along the precise deposition lines of weakness.
32:34And then just the slightest disturbance, even a single raindrop, is enough to trigger the mechanism.
32:40It's a difficult one.
32:41It's not a good thing.
32:42It's not a good thing.
32:44It's not a good one.
32:48You know how to run it?
32:51It's not a good thing.
32:54You know what?
32:55It's too much to look at the next station.
32:56It's an ordinary place.
32:57And one of the Wواuwen is going to be right away.
33:00We're in an ordinary place.
33:03I've already done it.
33:05But now the light is quiet, it's too much to look at the temperature.
33:07The east coast of South Africa.
33:19Summer here brings scorching temperatures.
33:32This ceratokerium has to get its seeds underground before it gets too hot.
33:40And it has acquired somewhat unlikely allies.
33:50Dung beetles.
33:55They have a particular fondness for antelope droppings.
34:04At this time of the year, these beetles bury the dung and lay their eggs on it.
34:16And the fresher, the better.
34:27Ceratokerium's spindly stems send their seeds flying.
34:37They're the same size, shape, and even smell remarkably like antelope dung.
35:07The beetles simply can't resist them.
35:21The beetles simply can't resist them.
35:33Dung beetles always bury dung balls at the same depth.
35:45And it's one which suits the seeds very well.
35:57So effective is the seeds' deception that the beetles come back for more time and time again.
36:04Most of the ceratokerium's seeds get safely buried.
36:23Exactly where they need to be.
36:30Where they need to be.
36:31As the sun begins to retreat, so autumn arrives.
36:37The cooler, shorter days are the cue for many seasonal florists to prepare for the winter shutdowns.
36:44The trees start to divert their nutrients.
36:51As the trees start to divert their nutrients.
36:53As the sun begins to retreat, so autumn arrives.
36:59The cooler, shorter days are the cue for many seasonal forests
37:04to prepare for the winter shutdown.
37:10The trees start to divert their nutrients back into their roots.
37:17And there, other organisms await them.
37:20Fungi.
37:50Mushrooms are the familiar face of fungi, but they are merely the fruiting bodies.
38:03Some of them only last for a few days.
38:08They are the familiar face of fungi, but they are merely the fruiting bodies.
38:15Some of them only last for a few days.
38:18They are, however, evidence of the giant organism that lies in the soil beneath.
38:25Just a single handful of soil may contain several thousand meters
38:31of their microscopic filaments.
38:33It's only recently that we have discovered the extraordinary role
38:39that these fungi play in a forest like this.
38:43Their filaments plug into the tips of the tree's roots.
38:50And nutrients pass between tree and fungus throughout the year.
38:56Some fungi have the ability to link with not just a single tree,
39:03but with a whole group of trees, so that the entire forest may be linked together
39:10by these microscopic threads, form what you might call a wood-wide web.
39:16Hundreds of trees can be interconnected by these webs.
39:29Scientists call it the mycorrhizal network.
39:33And it might look something like this.
39:46They've discovered that trees not only send nutrients along it,
39:49but chemical and electrical signals,
39:52allowing them to communicate with one another.
39:58But some trees can also be selfish and steal from their rivals.
40:04Or even wage war by sending out toxins that will harm competitors.
40:09It seems, however, that most trees do try to help each other.
40:25They raise the alarm when attacked by leaf-eaters,
40:28giving other trees time to produce defensive chemicals.
40:32Those that are dying may send their food reserves to their neighbors.
40:42And some individuals, known as mother trees,
40:47recognize their own offspring
40:50and will channel resources to them.
40:53So, giving their young the best possible start in life.
41:01As the harshness of winter approaches,
41:24temperate woodlands from Russia to Canada are now in a race to shut down.
41:54The green pigment in the leaves starts to break down,
42:08and nutrients are withdrawn into the branches.
42:11The chemical substances that are left behind then create one of the most spectacular displays of color
42:21in the whole of nature.
42:25The legend.
42:26The chemical substances that are made in the background.
42:27The chemical substances in which are often replaced with the impacts of the plants.
42:28In the ground, you can find the parameters in a regional environment.
42:29A natural environment will be found at the edges of the unconscious nature.
42:30The chemical substances that are made to be remained a sacrifice.
42:31In the ground, you know, in the ground, it's outside the problem.
42:32It has been taken in to the forest,
42:33and it has been taken in to the forest,
42:34this is the �
42:46same thing for the poor.
42:47That's a great way.
42:48This is the process of pain to promote a rollout,
42:49in the climate of the climate.
43:20The first freezing nights of winter bring with them a killer, frost.
43:38Stems, when frozen, rupture, and flowers of ice form in the chilly air.
43:50Stems, when frozen, rupture, and flowers of ice.
44:20For some, winter brings dormancy.
44:27For others, it brings death.
44:32Another cycle of the seasons comes to an end.
44:46Plants all across the seasonal world have developed many different strategies for success.
45:08But they all depend on the seasons changing reliably year after year.
45:15It doesn't matter whether you live for 3,000 years or just a few months.
45:20Everything depends on you getting the timing just right.
45:27But in our changing world, this is becoming a greater challenge every year.
45:34And even the most hardy and resilient of plants are starting to struggle.
45:42These sequoia trees are the giants of the natural world, the largest living thing on the planet.
45:49They can grow to almost 100 meters tall and 11 meters across.
45:56Their bark alone can be over a half a meter thick.
46:03They're also among the oldest, some living to over 3000 years.
46:10And to achieve such age and size, they need very particular living conditions, such as are found here in the Sierra Nevada mountains of California.
46:25Not only do they need energy from the sun, but critically, they also require up to 4,000 liters of water a day.
46:49So they are almost entirely reliant on the seasonal snow melt.
46:54But recent years have brought longer, hotter summers, and their source of water is becoming increasingly unreliable.
47:15Scientists are discovering that even these seemingly indestructible giants are now starting to show signs of vulnerability.
47:23Some are shedding their needles and branches as a way of conserving precious water.
47:33But for others, climate change has already been fatal.
47:48Ten percent of them have been lost in just the last few years.
47:51Ten percent of them have been lost in just the last few years.
47:55A single giant sequoia in its lifetime can produce a hundred million seeds.
48:12These, in my hand from one cone, are more than enough to start a completely new forest.
48:19But they can only do such a thing in a world where the seasons change with some reliability.
48:28Today, our climate is changing, bringing an unprecedented level of unpredictability all across the seasonal world.
48:44The question is, can we curb climate change sufficiently to ensure that the seasons will continue?
48:53Only if we can do that will the future of seasonal plants, including these magnificent trees, be assured.
49:02The
49:26the green planet, it wasn't only the plants that struggled to get their timing right.
49:32The increasing unpredictability of the seasons made it frustratingly difficult for the crew
49:37to be in the right place at the right time.
49:40Whether at the height of summer, we are in the middle of a biblical rainstorm, or a quiet
49:49autumnal afternoon.
49:51This is crazy.
49:52Hurricanes are no joke.
49:53They were always kept on their toes.
49:57That's really scary.
50:00Sometimes very numb ones.
50:05It's been the most snow they've had for 38 years.
50:08And I think this is now our fifth filming trip in a row where the seasons haven't done what
50:15they're predictably meant to do every year.
50:18And these challenges continue in attempting to find and film an elusive plant with a remarkable
50:26survival strategy.
50:28The far lily.
50:30Somewhere out there is a tiny, tiny red plant in all of that.
50:44Travelling to South Africa at the height of summer, the crew witness many extraordinary flowers bursting into bloom.
51:05But if they're there to see a fire lily, they need a fire.
51:15None of the team have filmed wildfire before.
51:18Not something to be underestimated.
51:20In most cases with wildfires is that when they go wrong, they go wrong radically.
51:26And it's very unforgiving.
51:27If you get caught on the wrong side of a fire because you want to get that special shot,
51:31there's a possibility you can get killed.
51:33But that's really what it comes down to.
51:35And after some understandably studious note-taking, it's time to put their training to the test.
51:54The fire's just racing up a gully behind me.
51:57The heat is intense.
51:59You just, you can't even stand to be like five meters far.
52:01It's insane.
52:09This is what any fire lilies here should be waiting for.
52:22Sheepers.
52:24But Feinbos wildfires are starting to become fiercer than in the past.
52:31Something fire chief Reinhard Gildenhuis knows first hand.
52:36Nowadays, we're experiencing more extreme temperature conditions and more extreme wind conditions,
52:42which exacerbates a Feinbos fire.
52:45Feinbos fire in full tilt with a strong wind behind it is an animal that's just running while
52:53It's a very frightening sight if you're standing in front of it.
52:58Guided by the experience of the fire crew, the team are able to safely capture the full fury of the blaze.
53:12It's given me a complete new appreciation for fire.
53:19How intensely it burns and how quickly it roars through this environment.
53:24And the fact that any plants can survive afterwards is just, yeah, it's crazy.
53:36As destructive as it seems, the fire has been part of this ecosystem for millennia.
53:42Fires should refresh and regenerate the landscape.
53:47Worryingly, however, this fine balance between plant and fire is beginning to shift.
53:53More extreme wildfires may spell disaster.
53:58If you disturb the soil in a Feinbos system, you're going to lose a lot of species.
54:03Bigger, hotter fires can burn the soil there and burn out all the seeds.
54:08And for the species that have these really intricate strategies like the fire lily, it really is a difficult game.
54:16Every year is getting hotter and potentially drier.
54:22So it's kind of becoming Russian roulette for a lot of the species here.
54:37In the fire's aftermath, the crew must now try to find a tiny flower.
54:41Tiny flower.
54:44But have any survived the blaze?
54:47It just looks completely dead. The whole valley.
54:56There's nothing for it but to get their hands dirty.
55:01Searching in the ash is a grubby business.
55:04I feel... disgusting.
55:14After scouring this mountainside just days after it burned,
55:20they finally find the first signs of regeneration.
55:27Wow, that's what it's all about. That's the fire lily.
55:30It's like a pop of bright red against all the black.
55:35I mean, that's amazing.
55:37There's another one over there.
55:39And there's another one behind us.
55:42This place hasn't burned for 15 years,
55:45so they've been sat underground waiting for this precise moment for that entire time,
55:50and then within two weeks they're up and they're flowering.
55:52It's incredible.
55:54This time the fire lilies here succeeded in flowering.
55:58But in the 15 years since they last bloomed,
56:01the Earth has experienced 10 of the warmest years on record.
56:06You know, there's huge debates about climate change.
56:10How real is it really? And so on.
56:11We experience it in the fire.
56:15It's more intense, burns easier, burns longer.
56:20In the past we used to have one big fire per season,
56:24and we said, yo, that was a big one.
56:26Now we have five to six big ones per season.
56:30If we don't change our ways, we are going to reach a point where fires are burning with such ferocity
56:35that it will destroy the landscape.
56:41And in recent times, a rapidly changing climate has led to some of the biggest fires in living memory,
56:48not just in South Africa, but around the world.
56:52The next five to ten years are going to be pretty scary to actually see what this has done to the ecosystem.
56:59Let's hope that the next time this fire lily blooms,
57:04it will find a world in which it can still survive.
57:12Next time on the green planet...
57:16Desert worlds.
57:19A landscape of extremes.
57:23Where water equals life.
57:29It only takes a drop.
57:34The Open University has produced a poster that explores the vital role that plants have for our planet.
57:43To order your free copy, call 0300 303 4200
57:49or go to bbc.co.uk forward slash green planet
57:55and follow the links to the Open University.
57:57Find some headspace with David Attenborough's The Green Planet Mindful Mix.
58:02Listen now on BBC Sounds.
58:04Unexpected news means Lucille might need a little headspace of her own here on BBC One.
58:10Call the midwife.
58:12Next.