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David Attenborough:
This is the boreal forest.
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00:01:00,240 --> 00:01:02,640
The largest forest on earth.
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00:01:04,360 --> 00:01:08,160
750 billion trees.
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00:01:10,520 --> 00:01:14,120
Smothered by snow
throughout the winter...
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00:01:19,080 --> 00:01:21,720
This is
the northernmost boundary
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00:01:21,840 --> 00:01:23,920
of an extraordinary world.
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00:01:27,880 --> 00:01:32,200
I'm standing at the edge
of the arctic circle.
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00:01:32,320 --> 00:01:33,920
To the north of me
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00:01:34,040 --> 00:01:36,880
lies a land dominated
for most of the year
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00:01:37,000 --> 00:01:39,200
by snow and ice.
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00:01:39,320 --> 00:01:42,760
3,000 miles to the south,
the tropics,
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00:01:42,880 --> 00:01:46,200
bathed the year round
in warm sunshine.
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00:01:46,320 --> 00:01:50,760
And in between,
a very different world,
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00:01:50,880 --> 00:01:54,040
dominated by relentless change.
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00:01:59,480 --> 00:02:03,760
An endless cycle
of four distinct seasons,
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00:02:03,880 --> 00:02:07,000
each with its own challenges.
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00:02:07,120 --> 00:02:10,440
The short, freezing days
of winter
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00:02:10,560 --> 00:02:14,320
give way to the urgent
awakening of spring.
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00:02:17,280 --> 00:02:20,800
And the long, hot days of summer
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00:02:20,920 --> 00:02:24,200
yield to the cooling of Autumn.
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00:02:28,720 --> 00:02:31,520
Opportunities will be brief.
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00:02:39,080 --> 00:02:41,720
To survive these extremes,
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00:02:41,840 --> 00:02:44,920
plants have not only got to be
Hardy and resilient,
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00:02:45,040 --> 00:02:49,000
but many of them have developed
special strategies
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00:02:49,120 --> 00:02:53,160
in order to meet the demands
of this seasonal world.
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00:02:55,160 --> 00:02:59,640
To succeed, they must
get their timing just right.
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00:03:02,600 --> 00:03:06,720
For months now,
this world has been asleep.
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00:03:06,840 --> 00:03:09,920
But change is coming.
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00:03:25,080 --> 00:03:27,960
Spring is on its way.
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00:03:46,320 --> 00:03:48,640
(Tick/ng)
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00:03:50,680 --> 00:03:55,280
In Canada, the forests
are starting to stir.
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00:03:57,600 --> 00:04:00,480
Throughout the winter,
the sugar maples here
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00:04:00,600 --> 00:04:05,720
have kept stores of nutrients
ready for this moment.
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00:04:05,840 --> 00:04:08,200
(Creaking)
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00:04:08,320 --> 00:04:10,480
Now, as temperatures
start to rise,
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00:04:10,600 --> 00:04:14,880
those nutrients must be
brought up from the roots.
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00:04:15,000 --> 00:04:17,120
(Gurgung)
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00:04:22,640 --> 00:04:25,560
Sap is on the rise.
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00:04:30,440 --> 00:04:33,440
Fuel for new green growth.
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00:04:44,640 --> 00:04:47,200
But just as growth reaches
full speed...
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00:04:48,400 --> 00:04:50,280
Robbers arrive.
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00:04:50,400 --> 00:04:53,240
(Hammering)
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00:04:57,920 --> 00:05:00,720
(Tapping)
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00:05:10,280 --> 00:05:11,960
A sapsucker.
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00:05:13,720 --> 00:05:17,560
A thief in search
of maple syrup.
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00:05:35,080 --> 00:05:38,440
The tree can tolerate
hundreds of wounds.
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00:05:45,320 --> 00:05:48,840
But if they completely encircle
the trunk,
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00:05:48,960 --> 00:05:52,640
the tree will eventually die.
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00:05:59,480 --> 00:06:03,480
The sapsucker's break-in
hasn't gone unnoticed.
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00:06:05,200 --> 00:06:07,360
(Wings vibrate)
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00:06:12,720 --> 00:06:14,760
Hummingbirds,
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00:06:14,880 --> 00:06:16,480
squirrels
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00:06:16,600 --> 00:06:18,920
and insects
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00:06:19,040 --> 00:06:22,200
all invade
the sapsucker's territory,
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00:06:22,320 --> 00:06:24,480
trying to steal a meal.
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00:06:28,880 --> 00:06:31,680
But unwittingly,
they help the tree.
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00:06:34,000 --> 00:06:35,800
(Sapsucker calls)
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Time spent chasing
the competition...
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00:06:41,960 --> 00:06:44,880
Means less time
to drill new holes.
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00:06:53,360 --> 00:06:55,600
(Squawking)
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00:06:59,200 --> 00:07:01,320
(Squeaking)
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00:07:15,080 --> 00:07:19,160
The tree gets a chance
to repair its wounds...
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00:07:20,360 --> 00:07:24,120
And the sap can rise freely
again.
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00:07:30,800 --> 00:07:33,080
So this year at least,
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00:07:33,200 --> 00:07:36,480
the tree will once more
produce its leaves.
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00:07:41,000 --> 00:07:43,400
Hundreds of miniature
solar panels
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that collect energy
from the sunlight.
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00:07:49,520 --> 00:07:54,480
Each leaf is covered by
millions of microscopic pores -
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00:07:54,600 --> 00:07:57,320
stomata.
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00:07:59,480 --> 00:08:02,840
They take in carbon dioxide...
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00:08:04,200 --> 00:08:07,120
And release oxygen
and water vapour
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in a process that produces
high-energy fuel.
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00:08:23,320 --> 00:08:27,000
All the trees here can now
use that fuel to grow
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00:08:27,120 --> 00:08:28,560
over the coming months.
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00:08:48,040 --> 00:08:53,200
As spring proceeds,
the power of the sun increases.
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00:08:56,680 --> 00:08:58,960
On river banks across Europe,
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00:08:59,080 --> 00:09:02,840
many plants have been
lying dormant underground...
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00:09:04,360 --> 00:09:07,200
Waiting for the earth to warm.
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00:09:13,600 --> 00:09:17,120
And now a race begins.
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00:09:23,400 --> 00:09:26,760
Among the first to start
are nettles.
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00:09:26,880 --> 00:09:28,320
The sprinters.
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00:09:34,240 --> 00:09:38,200
Then, only just behind,
come the brambles.
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They're much more aggressive,
and have backward-pointed hooks
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with which to scramble over
their rivals.
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00:09:48,320 --> 00:09:51,680
Last to come, the climbers.
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00:09:54,800 --> 00:09:58,360
Hops and bryony.
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00:10:02,360 --> 00:10:05,800
They lasso their way
towards the light.
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00:10:34,480 --> 00:10:38,520
Soon, every inch of space
and every patch of light
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00:10:38,640 --> 00:10:40,840
has been claimed.
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00:10:43,240 --> 00:10:45,200
But hidden in the shadows,
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00:10:45,320 --> 00:10:49,040
another plant has been
waiting to make its move.
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This...
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Is dodder.
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00:11:09,920 --> 00:11:11,440
A hunter...
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00:11:13,280 --> 00:11:16,040
With an exceptional
sense of smell.
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00:11:22,880 --> 00:11:26,800
Moving swiftly,
it searches for its prey.
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00:11:30,120 --> 00:11:33,080
It detects the scent
of a young nettle.
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00:11:52,400 --> 00:11:54,680
The dodder punctures
the nettle's stem
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00:11:54,800 --> 00:11:57,880
and sucks out
the nutritious sap.
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00:12:02,040 --> 00:12:05,120
And it doesn't stop
at just one victim.
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00:12:08,040 --> 00:12:12,160
With its energy supply assured,
it multiplies.
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00:12:21,840 --> 00:12:23,400
It's a parasite
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with an insatiable appetite.
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00:13:18,360 --> 00:13:20,280
(Birdsong)
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00:13:27,520 --> 00:13:33,280
But remarkably, its victims
can now exploit the dodder...
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00:13:34,560 --> 00:13:38,080
When other springtime
enemies appear.
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00:13:41,840 --> 00:13:44,040
Caterpillars.
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00:13:55,400 --> 00:13:58,880
When under attack,
a leaf sends out a signal
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00:13:59,000 --> 00:14:02,720
telling the rest of the plant
to start building defences...
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00:14:06,080 --> 00:14:09,960
Foul-tasting toxins
that deter the caterpillars.
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00:14:12,400 --> 00:14:15,000
In an extraordinary twist,
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00:14:15,120 --> 00:14:18,440
the stems of the dodder
interconnecting the plants
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00:14:18,560 --> 00:14:21,520
are now being used
as lines of communication
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00:14:21,640 --> 00:14:26,800
to relay these warning signals
from plant to plant.
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00:14:33,280 --> 00:14:37,040
They respond by producing
their own protective chemicals.
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00:14:41,280 --> 00:14:43,360
Eventually, the whole river bank
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becomes one huge
defensive network,
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00:14:47,280 --> 00:14:52,240
and the one-time rivals
are now better off together.
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(Water ripples)
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00:15:13,560 --> 00:15:18,640
The first warm days of spring
encourage some plants to flower
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00:15:18,760 --> 00:15:21,520
and get ahead
of the competition...
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00:15:23,240 --> 00:15:25,080
Creating beautiful displays
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00:15:25,200 --> 00:15:27,560
throughout the seasonal world...
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00:15:30,160 --> 00:15:33,400
From the spectacular
cherry blossoms of Japan...
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00:15:37,160 --> 00:15:40,680
To the Goldfield flowers
of California.
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00:15:45,160 --> 00:15:47,360
But spring flowering is risky.
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00:15:47,480 --> 00:15:50,520
If they flower too early,
it may not be warm enough
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00:15:50,640 --> 00:15:53,320
for pollinating insects
to be active.
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00:15:54,880 --> 00:15:59,040
But the common Daisy
gives them every opportunity.
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00:16:02,880 --> 00:16:06,560
The warmer the flowers are,
the more attractive they are,
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00:16:06,680 --> 00:16:09,280
and they have
a remarkable strategy
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00:16:09,400 --> 00:16:11,760
in order to maximise this.
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00:16:13,040 --> 00:16:16,800
They were closed up tightly
throughout the night
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00:16:16,920 --> 00:16:18,920
as a protection
against the elements.
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00:16:19,040 --> 00:16:22,600
But once they feel the warmth
and the light of the sun,
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00:16:22,720 --> 00:16:24,960
they spring into action.
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00:16:38,840 --> 00:16:42,920
It's a behaviour called
heliotropism.
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00:16:44,400 --> 00:16:48,040
They turn to keep facing
the sun,
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00:16:48,160 --> 00:16:50,760
absorbing as much heat
as they can.
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00:17:07,440 --> 00:17:10,600
This is a thermal camera,
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00:17:10,720 --> 00:17:13,360
and it will tell me
the difference between
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00:17:13,480 --> 00:17:16,240
the surrounding temperature
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00:17:16,360 --> 00:17:20,160
and the temperature in
the centre of a Daisy flower.
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00:17:20,280 --> 00:17:24,640
The surroundings - 12 degrees.
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00:17:24,760 --> 00:17:27,680
In the centre of a flower...
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00:17:28,840 --> 00:17:31,080
21.
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00:17:31,200 --> 00:17:32,600
(Buzzing)
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00:17:32,720 --> 00:17:36,040
Pollinators such as
bees and wasps
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00:17:36,160 --> 00:17:39,080
prefer the warmed-up flowers
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00:17:39,200 --> 00:17:42,200
because they can get a share of
the heat for themselves.
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00:17:43,720 --> 00:17:46,320
As a consequence,
they can collect more nectar
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00:17:46,440 --> 00:17:49,560
from more flowers,
pollinating as they go.
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00:17:53,200 --> 00:17:56,320
And the daisies, with
the help of their pollinators,
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00:17:56,440 --> 00:17:59,680
are able to have a particularly
long flowering season.
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00:18:03,000 --> 00:18:05,600
But when the window
of opportunity is brief,
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00:18:05,720 --> 00:18:08,680
even more ingenious tactics
are necessary.
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00:18:10,120 --> 00:18:11,600
(Birdsong)
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00:18:21,480 --> 00:18:24,760
Here in south-west Australia,
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00:18:24,880 --> 00:18:28,440
summer temperatures can soar to
up to 40 degrees celsius.
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00:18:39,520 --> 00:18:42,520
Now, for a brief moment
in the cooler spring,
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00:18:42,640 --> 00:18:45,640
flowering plants must get busy.
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00:18:50,400 --> 00:18:53,560
And this hammer orchid,
with its strange flower,
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00:18:53,680 --> 00:18:56,080
is doing exactly that.
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00:18:59,280 --> 00:19:01,000
It needs to attract
a pollinator,
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00:19:01,120 --> 00:19:02,520
but has no nectar,
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00:19:02,640 --> 00:19:05,680
and doesn't even
look like a flower...
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00:19:09,080 --> 00:19:12,480
Unlike these neighbouring
huge grass trees.
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00:19:14,440 --> 00:19:16,640
(Buzzing)
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00:19:16,760 --> 00:19:21,360
These produce thousands
of tiny white flowers,
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00:19:21,480 --> 00:19:23,760
all dripping with nectar.
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00:19:29,320 --> 00:19:33,000
But the orchid
has a different strategy.
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00:19:34,760 --> 00:19:37,240
It synchronises its emergence
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00:19:37,360 --> 00:19:41,880
with the brief mating season
of the thynnid wasp.
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00:19:48,360 --> 00:19:52,000
The flightless female wasp
produces pheromones
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00:19:52,120 --> 00:19:54,360
to attract males.
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00:20:01,960 --> 00:20:06,520
This male detects a scent
that seems to be hers...
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00:20:14,680 --> 00:20:17,280
Yet flies right on by.
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00:20:23,440 --> 00:20:26,600
The orchid not only has
the same shape and colour
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00:20:26,720 --> 00:20:28,000
as a female wasp,
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00:20:28,120 --> 00:20:31,040
but it sits at the same height
as she does.
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00:20:33,560 --> 00:20:35,760
It even mimics her smell.
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00:20:37,800 --> 00:20:42,760
And the beguiled male
attempts to mate with it.
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00:20:56,960 --> 00:21:01,080
It hammers against the orchid's
pollen sacs.
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00:21:07,120 --> 00:21:10,560
And the wasp leaves,
doubtless a little shaken...
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00:21:12,800 --> 00:21:15,280
Only to be duped once again.
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00:21:26,040 --> 00:21:27,160
The pollen on his back
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00:21:27,280 --> 00:21:29,640
now sticks to
this different orchid...
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00:21:31,000 --> 00:21:33,600
And the deception has worked.
189
00:21:37,000 --> 00:21:40,520
The orchid's imitation
is even more intoxicating,
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00:21:40,640 --> 00:21:42,200
it seems,
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00:21:42,320 --> 00:21:43,960
than the real thing.
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00:22:04,120 --> 00:22:10,160
Eventually, the male wasps tire
of the orchid's enticements.
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00:22:13,560 --> 00:22:17,000
Now the wasps,
both male and female,
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00:22:17,120 --> 00:22:20,200
find the flowers
of the grass trees to feed.
195
00:22:22,240 --> 00:22:24,320
And there, at long last...
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00:22:26,240 --> 00:22:27,640
They mate.
197
00:22:34,440 --> 00:22:36,680
And as for the hammer orchid...
198
00:22:38,680 --> 00:22:40,800
Pollination is complete.
199
00:22:53,840 --> 00:22:55,760
As summer approaches,
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00:22:55,880 --> 00:22:59,400
the need to flower
becomes more urgent.
201
00:23:00,640 --> 00:23:03,240
And nowhere more so than here...
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00:23:04,760 --> 00:23:06,880
In South Africa.
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00:23:10,400 --> 00:23:14,240
This is the fynbos, part of
the cape floral kingdom,
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00:23:14,360 --> 00:23:17,560
a great expanse
of open heath/ands
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00:23:17,680 --> 00:23:19,400
just north of the cape.
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00:23:22,840 --> 00:23:26,320
Here, there are more
different species of plant
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00:23:26,440 --> 00:23:29,360
than anywhere else
in the world -
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00:23:29,480 --> 00:23:33,080
nearly 9,000 -
many needing pollinators.
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00:23:37,600 --> 00:23:40,000
They compete with one another
for such help
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00:23:40,120 --> 00:23:43,360
by flaunting extravagant shapes
211
00:23:43,480 --> 00:23:45,560
and vivid colours...
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00:23:47,120 --> 00:23:51,720
All promising nectar
as a sugary reward.
213
00:23:54,560 --> 00:23:56,480
But there is a plant here
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00:23:56,600 --> 00:24:00,240
that avoids
this crowded competition.
215
00:24:02,200 --> 00:24:04,200
And the rising temperatures
of summer
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00:24:04,320 --> 00:24:06,720
bring just what it needs.
217
00:24:11,240 --> 00:24:12,880
(Flames crackle)
218
00:24:31,000 --> 00:24:34,720
This is the first fire here
for 15 years.
219
00:24:44,360 --> 00:24:47,600
Nearly all the plants
are destroyed.
220
00:24:53,160 --> 00:24:55,120
Incinerated.
221
00:25:03,080 --> 00:25:05,440
It might seem from the smoke
222
00:25:05,560 --> 00:25:08,560
and the still-smouldering
embers that no plant
223
00:25:08,680 --> 00:25:10,640
could survive such an inferno.
224
00:25:21,240 --> 00:25:24,160
But just four days
after the flames...
225
00:25:25,720 --> 00:25:28,200
Rising from the ashes...
226
00:25:33,160 --> 00:25:35,200
A fire Lily.
227
00:25:42,840 --> 00:25:46,680
It has been lying dormant
underground for 15 years,
228
00:25:46,800 --> 00:25:52,400
but now, awakened by the smoke,
it flowers.
229
00:26:02,200 --> 00:26:05,240
The blooms may be small
and unshowy,
230
00:26:05,360 --> 00:26:08,040
but that's all they need to be.
231
00:26:09,920 --> 00:26:12,000
In this charred landscape,
232
00:26:12,120 --> 00:26:15,080
pollinators such as
these sunbirds
233
00:26:15,200 --> 00:26:18,560
can spot these little red
beacons from great distances.
234
00:26:23,800 --> 00:26:26,720
They're the only source
of nectar around.
235
00:26:36,880 --> 00:26:40,080
And the more visitors
the flowers attract,
236
00:26:40,200 --> 00:26:43,600
the more likely they are
to be pollinated.
237
00:26:46,320 --> 00:26:48,680
(Birds tweet)
238
00:26:56,760 --> 00:26:58,720
It's just in time.
239
00:27:03,880 --> 00:27:09,920
Within a few months, the whole
landscape is alive once more.
240
00:27:12,920 --> 00:27:18,160
In fact, all these plants
need fire to survive.
241
00:27:22,440 --> 00:27:25,040
And as competitors return...
242
00:27:26,560 --> 00:27:28,680
The fire Lily fades.
243
00:27:36,680 --> 00:27:39,320
It now returns underground,
244
00:27:39,440 --> 00:27:44,920
and will rest there as a bulb
until another fire awakens it.
245
00:27:53,400 --> 00:27:55,000
- (Birdsong)
- (Insects buzz)
246
00:27:55,120 --> 00:27:58,320
By the time the long, hot days
of summer arrive,
247
00:27:58,440 --> 00:28:03,320
wildflower meadows
are bursting with life.
248
00:28:05,280 --> 00:28:08,040
But Autumn is not far away.
249
00:28:09,560 --> 00:28:13,840
So now, pollinated plants must
use their remaining energy
250
00:28:13,960 --> 00:28:16,840
to produce the next generation.
251
00:28:29,280 --> 00:28:33,960
A dandelion clock contains
around 200 seeds...
252
00:28:37,920 --> 00:28:40,600
Each with its own
tiny parachute.
253
00:28:46,240 --> 00:28:49,600
Few seeds can
fly as far as these.
254
00:28:49,720 --> 00:28:53,640
Some are known to have
travelled over 60 miles.
255
00:29:00,480 --> 00:29:03,240
But to travel any distance
at all,
256
00:29:03,360 --> 00:29:05,960
they need the wind
to be just right.
257
00:29:11,640 --> 00:29:14,240
However, before
they can get away,
258
00:29:14,360 --> 00:29:16,640
there is a risk.
259
00:29:16,760 --> 00:29:20,240
Voracious hunters
live in this Meadow.
260
00:29:22,040 --> 00:29:23,880
(Sniffs)
261
00:29:44,720 --> 00:29:46,960
Tiny harvest mice.
262
00:29:48,600 --> 00:29:52,280
- They love dandelion seeds.
- (Creaking)
263
00:29:58,440 --> 00:30:00,280
But they don't like to share.
264
00:30:11,920 --> 00:30:15,040
Finally, the sun warms
the ground
265
00:30:15,160 --> 00:30:18,480
and a gentle breeze blows in,
266
00:30:18,600 --> 00:30:22,120
creating an ideal updraught.
267
00:30:24,800 --> 00:30:27,160
(Sniffs)
268
00:30:34,680 --> 00:30:37,280
Air flowing between the bristles
269
00:30:37,400 --> 00:30:40,680
creates a vortex
that lifts the seeds up.
270
00:30:44,640 --> 00:30:47,720
Heading off
on the gentle breeze,
271
00:30:47,840 --> 00:30:51,400
this seed now starts
its travels.
272
00:31:19,440 --> 00:31:22,560
Plants use a variety
of different techniques
273
00:31:22,680 --> 00:31:26,120
to spread their seeds as far
as possible from themselves,
274
00:31:26,240 --> 00:31:29,400
and one of the most
remarkable is this one.
275
00:31:29,520 --> 00:31:34,120
It's called ecballium, and it's
a relative of the cucumber.
276
00:31:34,240 --> 00:31:35,960
For several weeks now,
277
00:31:36,080 --> 00:31:39,400
pressure has been building up
inside the pods,
278
00:31:39,520 --> 00:31:41,320
until now they're as taut
279
00:31:41,440 --> 00:31:44,000
as a well-pumped-up
bicycle tyre.
280
00:31:44,120 --> 00:31:47,080
All they need
is just a slight nudge.
281
00:32:04,400 --> 00:32:07,520
The further the plant can
fire its seeds,
282
00:32:07,640 --> 00:32:09,640
the better.
283
00:32:11,440 --> 00:32:14,680
If a seedling germinates
close to its parent,
284
00:32:14,800 --> 00:32:18,440
the two will have to compete
for nutrients and light.
285
00:32:21,760 --> 00:32:23,600
This himalayan balsam
286
00:32:23,720 --> 00:32:27,160
has seed pods that react
rather differently -
287
00:32:27,280 --> 00:32:29,040
like catapults.
288
00:32:29,160 --> 00:32:32,320
As they dry out,
they begin to strain
289
00:32:32,440 --> 00:32:35,920
along precisely positioned
lines of weakness.
290
00:32:36,040 --> 00:32:38,520
And then just the slightest
disturbance,
291
00:32:38,640 --> 00:32:40,040
even a single raindrop,
292
00:32:40,160 --> 00:32:42,000
is enough to trigger
the mechanism.
293
00:33:02,800 --> 00:33:05,320
(Waves crash)
294
00:33:06,400 --> 00:33:09,280
(Seabirds call)
295
00:33:15,800 --> 00:33:18,640
The east coast of South Africa.
296
00:33:21,600 --> 00:33:24,480
Summer here
brings scorching temperatures.
297
00:33:34,160 --> 00:33:37,040
This ceratocaryum has to
get its seeds underground
298
00:33:37,160 --> 00:33:39,120
before it gets too hot.
299
00:33:41,800 --> 00:33:45,360
And it has acquired
somewhat unlikely allies.
300
00:33:51,160 --> 00:33:53,240
Dung beetles.
301
00:33:56,080 --> 00:34:01,960
They have a particular fondness
for antelope droppings.
302
00:34:05,760 --> 00:34:09,040
At this time of the year,
these beetles Bury the dung
303
00:34:09,160 --> 00:34:10,760
and lay their eggs on it.
304
00:34:16,760 --> 00:34:18,800
And the fresher...
305
00:34:21,800 --> 00:34:23,200
The better.
306
00:34:28,680 --> 00:34:31,840
Ceratocaryum's spindly stems...
307
00:34:33,040 --> 00:34:35,520
Send their seeds flying.
308
00:34:56,000 --> 00:35:00,000
They're the same size, shape,
309
00:35:00,120 --> 00:35:05,600
and even smell remarkably like
antelope dung.
310
00:35:19,880 --> 00:35:23,640
The beetles
simply can't resist them.
311
00:35:42,320 --> 00:35:45,880
Dung beetles always Bury
dung balls at the same depth,
312
00:35:46,000 --> 00:35:49,800
and it's one which suits
the seeds very well.
313
00:35:59,600 --> 00:36:02,880
So effective
is the seeds' deception
314
00:36:03,000 --> 00:36:06,400
that the beetles come back
for more time and time again.
315
00:36:21,880 --> 00:36:26,240
Most of the ceratocaryum's
seeds get safely buried...
316
00:36:28,760 --> 00:36:33,560
Exactly where they need to be.
317
00:36:52,480 --> 00:36:58,480
As the sun begins to retreat,
so Autumn arrives.
318
00:37:01,720 --> 00:37:04,400
The cooler, shorter days
are the cue
319
00:37:04,520 --> 00:37:06,680
for many seasonal forests
320
00:37:06,800 --> 00:37:09,680
to prepare
for the winter shutdown.
321
00:37:12,960 --> 00:37:16,000
The trees start to
divert their nutrients
322
00:37:16,120 --> 00:37:17,840
back into their roots.
323
00:37:19,080 --> 00:37:22,680
And there, other organisms
await them.
324
00:37:29,960 --> 00:37:31,400
Fungi.
325
00:38:10,640 --> 00:38:14,800
Mushrooms are
the familiar face of fungi.
326
00:38:14,920 --> 00:38:17,920
But they are merely
the fruiting bodies.
327
00:38:18,040 --> 00:38:21,080
Some of them only last
for a few days.
328
00:38:21,200 --> 00:38:24,920
They are, however,
evidence of the giant organism
329
00:38:25,040 --> 00:38:27,240
that lies in the soil beneath.
330
00:38:27,360 --> 00:38:29,800
Just a single handful of soil
331
00:38:29,920 --> 00:38:33,240
may contain
several thousand metres
332
00:38:33,360 --> 00:38:36,160
of their microscopic filaments.
333
00:38:36,280 --> 00:38:39,720
It's only recently
that we have discovered
334
00:38:39,840 --> 00:38:43,600
the extraordinary role
that these fungi play
335
00:38:43,720 --> 00:38:45,880
in a forest like this.
336
00:38:48,200 --> 00:38:53,360
Their filaments plug into
the tips of the tree's roots,
337
00:38:53,480 --> 00:38:57,880
and nutrients pass
between tree and fungus
338
00:38:58,000 --> 00:38:59,440
throughout the year.
339
00:39:00,720 --> 00:39:02,960
Some fungi have the ability
340
00:39:03,080 --> 00:39:05,480
to link with
not just a single tree,
341
00:39:05,600 --> 00:39:08,680
but with a whole group of trees,
342
00:39:08,800 --> 00:39:11,320
so that the entire forest
343
00:39:11,440 --> 00:39:14,360
may be linked together
by these microscopic threads
344
00:39:14,480 --> 00:39:18,160
to form what you might call
a wood wide web.
345
00:39:26,200 --> 00:39:29,960
Hundreds of trees can be
interconnected by these webs.
346
00:39:31,480 --> 00:39:34,800
Scientists call it
the mycorrhizal network.
347
00:39:36,640 --> 00:39:39,600
And it might look
something like this.
348
00:39:48,320 --> 00:39:49,960
They've discovered that trees
349
00:39:50,080 --> 00:39:51,920
not only send nutrients
along it,
350
00:39:52,040 --> 00:39:54,840
but chemical
and electrical signals,
351
00:39:54,960 --> 00:39:57,600
allowing them to communicate
with one another.
352
00:40:00,320 --> 00:40:02,840
But some trees
can also be selfish,
353
00:40:02,960 --> 00:40:05,240
and steal from their rivals...
354
00:40:06,440 --> 00:40:08,000
Oi' even wage war,
355
00:40:08,120 --> 00:40:12,800
by sending out toxins
that will harm competitors.
356
00:40:19,200 --> 00:40:21,920
It seems, however,
that most trees
357
00:40:22,040 --> 00:40:23,800
do try to help each other.
358
00:40:27,080 --> 00:40:30,080
They raise the alarm
when attacked by leaf-eaters,
359
00:40:30,200 --> 00:40:34,800
leaving other trees time to
produce defensive chemicals.
360
00:40:39,160 --> 00:40:40,960
Those that are dying
361
00:40:41,080 --> 00:40:43,880
may send their food reserves
to their neighbours.
362
00:40:45,480 --> 00:40:49,480
And some individuals,
known as mother trees,
363
00:40:49,600 --> 00:40:51,960
recognise their own offspring...
364
00:40:53,160 --> 00:40:55,560
And will channel resources
to them...
365
00:40:59,160 --> 00:41:01,240
So giving their young
366
00:41:01,360 --> 00:41:03,760
the best possible start in life.
367
00:41:15,120 --> 00:41:16,440
(Birdsong)
368
00:41:24,200 --> 00:41:27,720
As the harshness of winter
approaches...
369
00:41:29,520 --> 00:41:33,320
Temperate woodlands from Russia
370
00:41:33,440 --> 00:41:35,160
to Canada...
371
00:41:36,360 --> 00:41:40,520
Are now in a race to shut down.
372
00:41:40,640 --> 00:41:42,600
(Tick/ng)
373
00:42:06,520 --> 00:42:10,600
The green pigment in the leaves
starts to break down,
374
00:42:10,720 --> 00:42:14,680
and nutrients are withdrawn
into the branches.
375
00:42:16,920 --> 00:42:19,680
The chemical substances
that are left behind
376
00:42:19,800 --> 00:42:24,080
then create one of the most
spectacular displays of colour
377
00:42:24,200 --> 00:42:26,760
in the whole of nature.
378
00:43:14,240 --> 00:43:15,640
(Tick/ng)
379
00:43:23,400 --> 00:43:26,320
The first freezing nights
of winter
380
00:43:26,440 --> 00:43:28,880
bring with them a killer.
381
00:43:32,160 --> 00:43:33,360
Frost.
382
00:43:33,480 --> 00:43:35,200
(Frost crackles)
383
00:43:39,840 --> 00:43:43,840
Stems, when frozen, rupture...
384
00:43:46,360 --> 00:43:51,640
And flowers of ice form
in the chilly air.
385
00:44:24,120 --> 00:44:27,920
For some,
winter brings dormancy.
386
00:44:29,480 --> 00:44:32,800
For others, it brings death.
387
00:44:43,480 --> 00:44:48,560
Another cycle of the seasons
comes to an end.
388
00:44:50,520 --> 00:44:53,720
(Birdsong)
389
00:45:03,920 --> 00:45:06,520
Plants all across
the seasonal world
390
00:45:06,640 --> 00:45:09,920
have developed many different
strategies for success,
391
00:45:10,040 --> 00:45:15,280
but they all depend on
the seasons changing reliably
392
00:45:15,400 --> 00:45:17,680
year after year.
393
00:45:17,800 --> 00:45:20,960
It doesn't matter whether
you live for 3,000 years
394
00:45:21,080 --> 00:45:23,040
or just a few months,
395
00:45:23,160 --> 00:45:27,640
everything depends on you
getting the timing just right.
396
00:45:31,120 --> 00:45:33,120
But in our changing world,
397
00:45:33,240 --> 00:45:36,920
this is becoming a greater
challenge every year...
398
00:45:39,400 --> 00:45:43,040
And even the most Hardy
and resilient of plants
399
00:45:43,160 --> 00:45:44,800
are starting to struggle.
400
00:45:54,160 --> 00:45:59,880
These sequoia trees are the
giants of the natural world.
401
00:46:00,000 --> 00:46:03,680
The largest living things
on the planet.
402
00:46:03,800 --> 00:46:07,960
They can grow
to almost 100 metres tall
403
00:46:08,080 --> 00:46:09,760
and 11 metres across.
404
00:46:12,480 --> 00:46:15,960
Their bark alone can be
over a half a metre thick.
405
00:46:17,280 --> 00:46:19,840
They're also among the oldest,
406
00:46:19,960 --> 00:46:24,080
some living to over 3,000 years.
407
00:46:24,200 --> 00:46:27,000
And to achieve such age
and size,
408
00:46:27,120 --> 00:46:29,960
they need very particular
living conditions,
409
00:46:30,080 --> 00:46:31,920
such as a farm here
410
00:46:32,040 --> 00:46:35,480
in the Sierra Nevada mountains
of California.
411
00:46:40,400 --> 00:46:44,920
Not only do they need energy
from the sun, but, critically,
412
00:46:45,040 --> 00:46:50,280
they also require up to
4,000 litres of water a day,
413
00:46:50,400 --> 00:46:52,960
so they are
almost entirely reliant
414
00:46:53,080 --> 00:46:55,640
on the seasonal snowmelt.
415
00:47:02,640 --> 00:47:06,360
But recent years have brought
longer, hotter summers,
416
00:47:06,480 --> 00:47:08,160
and their source of water
417
00:47:08,280 --> 00:47:11,120
is becoming increasingly
unreliable.
418
00:47:16,760 --> 00:47:19,800
Scientists are discovering that
419
00:47:19,920 --> 00:47:23,200
even these seemingly
indestructible giants
420
00:47:23,320 --> 00:47:27,720
are now starting to show
signs of vulnerability.
421
00:47:29,440 --> 00:47:32,440
Some are shedding their needles
and branches
422
00:47:32,560 --> 00:47:36,400
as a way of conserving
precious water.
423
00:47:46,280 --> 00:47:51,520
But for others, climate change
has already been fatal.
424
00:47:51,640 --> 00:47:57,080
10% of them have been lost
in just the last few years.
425
00:48:07,440 --> 00:48:11,080
A single giant sequoia
in its lifetime
426
00:48:11,200 --> 00:48:15,720
can produce 100 million seeds.
427
00:48:15,840 --> 00:48:18,600
These in my hand, from one cone,
428
00:48:18,720 --> 00:48:22,360
are more than enough to start
a completely new forest.
429
00:48:25,040 --> 00:48:27,040
But they can only do
such a thing
430
00:48:27,160 --> 00:48:31,680
in a world where the seasons
change with some reliability.
431
00:48:33,720 --> 00:48:36,200
Today, our climate is changing,
432
00:48:36,320 --> 00:48:40,680
bringing an unprecedented level
of unpredictability
433
00:48:40,800 --> 00:48:43,920
all across the seasonal world.
434
00:48:46,280 --> 00:48:51,360
The question is, can we curb
climate change sufficiently
435
00:48:51,480 --> 00:48:55,200
to ensure that the seasons
will continue?
436
00:48:55,320 --> 00:48:57,840
Only if we can do that
437
00:48:57,960 --> 00:49:00,000
will the future
of seasonal plants,
438
00:49:00,120 --> 00:49:03,480
including these magnificent
trees, be assured.
439
00:49:26,400 --> 00:49:29,280
David Attenborough: During
filming the green planet,
440
00:49:29,400 --> 00:49:30,600
it wasn't only the plants
441
00:49:30,720 --> 00:49:32,880
that struggled to get
their timing right.
442
00:49:33,000 --> 00:49:37,720
The increasing unpredictability
of the seasons made it
443
00:49:37,840 --> 00:49:39,960
frustratingly difficult
for the crew
444
00:49:40,080 --> 00:49:42,320
to be in the right place
at the right time.
445
00:49:42,440 --> 00:49:44,640
Whether at the height
of summer...
446
00:49:44,760 --> 00:49:50,040
Alistair: We are in the middle
of a biblical rainstorm.
447
00:49:50,160 --> 00:49:53,080
Or a quiet autumnal afternoon...
448
00:49:53,200 --> 00:49:55,880
Jonny: This is crazy!
Hurricanes are no joke.
449
00:49:56,000 --> 00:49:58,720
They were always
kept on their toes.
450
00:49:59,800 --> 00:50:01,120
Jonny: That's really scary!
451
00:50:01,240 --> 00:50:02,600
Ooh!
452
00:50:03,760 --> 00:50:05,760
Sometimes very numb ones.
453
00:50:07,800 --> 00:50:10,920
It's been the most snow
they've had for 38 years.
454
00:50:11,040 --> 00:50:13,720
And I think this is now
our fifth filming trip
455
00:50:13,840 --> 00:50:17,200
in a row where the seasons
haven't done
456
00:50:17,320 --> 00:50:19,760
what they're predictably
meant to do every year.
457
00:50:21,200 --> 00:50:23,200
And these challenges continue
458
00:50:23,320 --> 00:50:27,200
in attempting to find and film
an elusive plant
459
00:50:27,320 --> 00:50:30,480
with a remarkable
survival strategy -
460
00:50:30,600 --> 00:50:32,560
the fire Lily.
461
00:50:42,440 --> 00:50:45,160
Somewhere out there is a tiny,
tiny red plant...
462
00:50:46,560 --> 00:50:48,880
In all of that.
463
00:50:57,560 --> 00:51:01,680
Travelling to South Africa
at the height of summer...
464
00:51:02,960 --> 00:51:06,920
The crew witnessed
many extraordinary flowers
465
00:51:07,040 --> 00:51:08,240
bursting into bloom.
466
00:51:10,000 --> 00:51:14,920
But if they are to see
a fire Lily, they need a fire.
467
00:51:17,880 --> 00:51:20,560
None of the team
have filmed wildfire before -
468
00:51:20,680 --> 00:51:23,040
not something
to be underestimated.
469
00:51:24,480 --> 00:51:27,080
In most cases with wildfires,
470
00:51:27,200 --> 00:51:29,000
when they go wrong,
they go wrong radically.
471
00:51:29,120 --> 00:51:30,160
And it's very unforgiving.
472
00:51:30,240 --> 00:51:32,000
If you get caught
on the wrong side of a fire
473
00:51:32,040 --> 00:51:34,160
because you want to get
that special shot,
474
00:51:34,280 --> 00:51:35,920
there's a possibility
you can get killed,
475
00:51:36,040 --> 00:51:37,480
that's really
what it comes down to.
476
00:51:37,600 --> 00:51:41,000
And after some understandably
studious note-taking...
477
00:51:42,880 --> 00:51:45,480
It's time to put
their training to the test.
478
00:51:45,600 --> 00:51:47,080
(Horn beeps)
479
00:51:54,240 --> 00:51:56,240
(Fire crackles)
480
00:51:56,360 --> 00:51:59,320
Alistair: The fire's just
racing up a gully behind me.
481
00:51:59,440 --> 00:52:01,000
The heat is intense.
482
00:52:01,120 --> 00:52:02,800
You can't even stand to be,
483
00:52:02,920 --> 00:52:04,720
like, five metres from it.
Ifsinsane.
484
00:52:07,240 --> 00:52:09,440
(Fire whooshes)
485
00:52:11,600 --> 00:52:15,920
This is what any fire lilies
here should be waiting for.
486
00:52:21,880 --> 00:52:24,040
(Wind roars)
487
00:52:25,200 --> 00:52:26,400
Jeepers.
488
00:52:27,680 --> 00:52:30,600
But fynbos wildfires
are starting to become
489
00:52:30,720 --> 00:52:32,560
fiercer than in the past...
490
00:52:34,160 --> 00:52:38,480
Something fire chief reinard
geldenhuys knows first-hand.
491
00:52:38,600 --> 00:52:39,920
Nowadays,
492
00:52:40,040 --> 00:52:42,720
we're experiencing more extreme
temperature conditions
493
00:52:42,840 --> 00:52:45,320
and more extreme
wind conditions,
494
00:52:45,440 --> 00:52:48,160
which exacerbates a fynbos fire.
495
00:52:49,760 --> 00:52:54,480
A fynbos fire in full tilt
with a strong wind behind it
496
00:52:54,600 --> 00:52:56,440
is an animal
that's just running wild.
497
00:52:57,920 --> 00:52:59,080
It's a very frightening sight
498
00:52:59,200 --> 00:53:00,640
if you're standing
in front of it.
499
00:53:06,720 --> 00:53:10,240
Guided by the experience
of the fire crew,
500
00:53:10,360 --> 00:53:12,440
the team are able to
safely capture
501
00:53:12,560 --> 00:53:14,280
the full fury of the Blaze.
502
00:53:18,280 --> 00:53:22,760
It's given me a complete,
new appreciation for fire,
503
00:53:22,880 --> 00:53:24,800
how intensely it burns
504
00:53:24,920 --> 00:53:27,200
and how quickly it roars
through this environment.
505
00:53:28,840 --> 00:53:31,600
And the fact that any plants
can survive afterwards
506
00:53:31,720 --> 00:53:34,480
is just... yeah, it's crazy.
507
00:53:38,240 --> 00:53:39,840
As destructive as it seems,
508
00:53:39,960 --> 00:53:43,440
the fire has been part of
this ecosystem for millennia.
509
00:53:43,560 --> 00:53:47,720
Fires should refresh
and regenerate the landscape.
510
00:53:49,240 --> 00:53:51,960
Worryingly, however,
this fine balance
511
00:53:52,080 --> 00:53:55,480
between plant and fire
is beginning to shift.
512
00:53:56,520 --> 00:54:00,040
More extreme wildfires
may spell disaster.
513
00:54:02,160 --> 00:54:03,960
If you disturb the soil
in a fynbos system,
514
00:54:04,080 --> 00:54:05,640
you're going to lose
a lot of species.
515
00:54:05,760 --> 00:54:09,840
Bigger, hotter fires
can burn the soil layer
516
00:54:09,960 --> 00:54:12,360
and burn out all the seeds.
517
00:54:12,480 --> 00:54:14,080
And for the species that have
518
00:54:14,200 --> 00:54:16,800
these really intricate
strategies, like the fire Lily,
519
00:54:16,920 --> 00:54:19,280
it really is a difficult game.
520
00:54:21,120 --> 00:54:24,280
Every year is getting hotter
and potentially drier,
521
00:54:24,400 --> 00:54:27,200
so it's kind of becoming
Russian roulette
522
00:54:27,320 --> 00:54:29,120
for a lot of the species here.
523
00:54:39,520 --> 00:54:41,360
In the fire's aftermath,
524
00:54:41,480 --> 00:54:44,400
the crew must now try to find
a tiny flower.
525
00:54:46,240 --> 00:54:49,160
But have any survived the Blaze?
526
00:54:49,280 --> 00:54:50,800
It just looks completely dead.
527
00:54:50,920 --> 00:54:52,280
The whole valley.
528
00:54:58,440 --> 00:55:01,920
There's nothing for it
but to get their hands dirty.
529
00:55:03,600 --> 00:55:07,640
Searching in the ash
is a grubby business.
530
00:55:07,760 --> 00:55:09,520
(Sighs)
531
00:55:14,360 --> 00:55:16,000
Disgusting.
532
00:55:17,640 --> 00:55:20,600
After scouring this
mountainside just days
533
00:55:20,720 --> 00:55:22,200
after it burned,
534
00:55:22,320 --> 00:55:26,640
they finally find the first
signs of regeneration.
535
00:55:29,680 --> 00:55:31,880
Wow. That's what it's all about!
536
00:55:32,000 --> 00:55:33,320
That's the fire Lily.
537
00:55:33,440 --> 00:55:37,440
It's like a proper bright red
against all the black.
538
00:55:37,560 --> 00:55:39,160
I mean, that's amazing.
539
00:55:39,280 --> 00:55:40,960
There's another one over there,
540
00:55:41,080 --> 00:55:43,200
and there's another one
behind those.
541
00:55:44,640 --> 00:55:47,200
This place hasn't burned
for 15 years,
542
00:55:47,320 --> 00:55:50,440
so they've been sat underground
waiting for this precise moment
543
00:55:50,560 --> 00:55:52,920
for that entire time,
and then within two weeks,
544
00:55:53,040 --> 00:55:55,800
they're up and they're
flowering. It's incredible.
545
00:55:57,000 --> 00:56:00,720
This time, the fire lilies here
succeeded in flowering,
546
00:56:00,840 --> 00:56:03,840
but in the 15 years
since they last bloomed,
547
00:56:03,960 --> 00:56:08,200
the earth has experienced ten
of the warmest years on record.
548
00:56:09,640 --> 00:56:12,000
You know, there's huge debates
about climate change,
549
00:56:12,120 --> 00:56:14,160
how real is it really,
and so on.
550
00:56:14,280 --> 00:56:15,760
Erm...
551
00:56:15,880 --> 00:56:17,400
We experience it in the fire.
552
00:56:17,520 --> 00:56:21,320
It's more intense, it burns
easier, it burns longer.
553
00:56:22,880 --> 00:56:25,480
In the past, we used to have
one big fire per season,
554
00:56:25,600 --> 00:56:28,480
and we said,
"yo, that was a big one."
555
00:56:28,600 --> 00:56:31,680
Now we have five to six
big ones per season.
556
00:56:33,120 --> 00:56:35,840
If we don't change our ways,
we are going to reach a point
557
00:56:35,960 --> 00:56:38,440
where fires are burning
with such ferocity
558
00:56:38,560 --> 00:56:40,760
that it will destroy
thelandscape.
559
00:56:42,720 --> 00:56:46,440
And in recent times,
a rapidly changing climate
560
00:56:46,560 --> 00:56:49,800
has led to some of the biggest
fires in living memory,
561
00:56:49,920 --> 00:56:54,280
not just in South Africa,
but around the world.
562
00:56:54,400 --> 00:56:57,920
The next five to ten years
are going to be pretty scary
563
00:56:58,040 --> 00:57:01,800
to actually see what this
has done to the ecosystem.
564
00:57:01,920 --> 00:57:06,280
Let's hope that the next time
this fire Lily blooms,
565
00:57:06,400 --> 00:57:09,840
it'll find a world
in which it can still survive.
40572
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