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00:00:56,620 --> 00:00:59,740
This is the boreal forest...
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00:01:04,820 --> 00:01:07,380
..the largest forest on Earth.
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00:01:09,100 --> 00:01:12,740
750 billion trees...
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00:01:15,500 --> 00:01:18,860
..smothered by snow throughout
the winter.
5
00:01:23,940 --> 00:01:28,780
This is the northernmost boundary
of an extraordinary world.
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00:01:32,500 --> 00:01:37,140
I'm standing at the edge
of the Arctic Circle.
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00:01:37,140 --> 00:01:41,700
To the north of me lies a land
dominated for most of the year
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00:01:41,700 --> 00:01:43,860
by snow and ice.
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00:01:43,860 --> 00:01:47,620
3,000 miles to the south -
the tropics,
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00:01:47,620 --> 00:01:51,660
bathed the year round
in warm sunshine.
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00:01:51,660 --> 00:01:55,300
And in between,
a very different world,
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00:01:55,300 --> 00:01:58,780
dominated by relentless change.
13
00:02:04,660 --> 00:02:08,660
An endless cycle
of four distinct seasons,
14
00:02:08,660 --> 00:02:11,020
each with its own challenges.
15
00:02:12,620 --> 00:02:15,260
The short, freezing days of winter
16
00:02:15,260 --> 00:02:19,220
give way to the urgent awakening
of spring.
17
00:02:22,060 --> 00:02:25,620
And the long, hot days of summer
18
00:02:25,620 --> 00:02:28,780
yield to the cooling of autumn.
19
00:02:33,340 --> 00:02:36,180
Opportunities will be brief.
20
00:02:43,660 --> 00:02:45,700
To survive these extremes,
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00:02:45,700 --> 00:02:49,940
plants have not only got to be
hardy and resilient,
22
00:02:49,940 --> 00:02:53,420
but many of them have developed
special strategies
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00:02:53,420 --> 00:02:57,740
in order to meet the demands
of this seasonal world.
24
00:02:59,900 --> 00:03:04,180
To succeed, they must get
their timing just right.
25
00:03:07,220 --> 00:03:10,860
For months now,
this world has been asleep.
26
00:03:12,100 --> 00:03:14,460
But change is coming.
27
00:03:29,820 --> 00:03:32,740
Spring is on its way.
28
00:03:55,780 --> 00:03:59,980
In Canada, the forests are
starting to stir.
29
00:04:02,180 --> 00:04:05,620
Throughout the winter,
the sugar maples here
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00:04:05,620 --> 00:04:09,980
have kept stores of nutrients
ready for this moment.
31
00:04:12,820 --> 00:04:16,100
Now, as temperatures start to rise,
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00:04:16,100 --> 00:04:19,660
those nutrients must be brought
up from the roots.
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00:04:27,180 --> 00:04:29,660
Sap is on the rise.
34
00:04:35,180 --> 00:04:37,980
Fuel for new green growth.
35
00:04:49,180 --> 00:04:51,780
But just as growth reaches
full speed...
36
00:04:53,340 --> 00:04:55,380
..robbers arrive.
37
00:05:15,260 --> 00:05:17,860
A sap sucker.
38
00:05:17,860 --> 00:05:22,140
A thief in search of maple syrup.
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00:05:39,820 --> 00:05:42,780
The tree can tolerate
hundreds of wounds.
40
00:05:50,140 --> 00:05:53,940
But if they completely encircle
the trunk,
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00:05:53,940 --> 00:05:57,180
the tree will eventually die.
42
00:06:04,420 --> 00:06:08,300
The sap sucker's break-in
hasn't gone unnoticed.
43
00:06:17,420 --> 00:06:23,820
Hummingbirds, squirrels and insects
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00:06:23,820 --> 00:06:27,140
all invade the sap sucker's
territory,
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00:06:27,140 --> 00:06:29,180
trying to steal a meal.
46
00:06:33,380 --> 00:06:36,380
But unwittingly, they help the tree.
47
00:06:42,300 --> 00:06:44,860
Time spent chasing the
competition...
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00:06:46,580 --> 00:06:49,940
..means less time to drill
new holes.
49
00:07:19,700 --> 00:07:23,580
The tree gets a chance to repair
its wounds.
50
00:07:25,780 --> 00:07:28,700
And the sap can rise freely again.
51
00:07:36,060 --> 00:07:41,180
So this year, at least, the tree
will once more produce its leaves.
52
00:07:45,780 --> 00:07:48,500
Hundreds of miniature solar panels
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00:07:48,500 --> 00:07:50,860
that collect energy from
the sunlight.
54
00:07:54,340 --> 00:07:58,700
Each leaf is covered by millions
of microscopic pores.
55
00:07:59,860 --> 00:08:01,700
Stomata.
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00:08:04,460 --> 00:08:07,340
They take in carbon dioxide...
57
00:08:08,980 --> 00:08:11,900
..and release oxygen and
water vapour
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00:08:11,900 --> 00:08:15,580
in a process that produces
high-energy fuel.
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00:08:27,980 --> 00:08:31,060
All the trees here can now use
that fuel
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00:08:31,060 --> 00:08:33,500
to grow over the coming months.
61
00:08:52,780 --> 00:08:57,860
As spring proceeds,
the power of the sun increases.
62
00:09:01,540 --> 00:09:03,740
On river banks across Europe,
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00:09:03,740 --> 00:09:09,140
many plants have been lying dormant
underground,
64
00:09:09,140 --> 00:09:11,820
waiting for the earth to warm.
65
00:09:18,300 --> 00:09:20,900
And now a race begins.
66
00:09:28,140 --> 00:09:32,980
Among the first to start
are nettles - the sprinters.
67
00:09:38,620 --> 00:09:42,580
Then, only just behind,
come the brambles.
68
00:09:43,900 --> 00:09:47,500
They're much more aggressive
and have backward-pointed hooks
69
00:09:47,500 --> 00:09:50,460
with which to scramble
over their rivals.
70
00:09:53,220 --> 00:09:56,260
Last to come - the climbers.
71
00:09:59,540 --> 00:10:01,860
Hops...
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00:10:01,860 --> 00:10:03,900
..and bryony.
73
00:10:07,540 --> 00:10:10,580
They lasso their way
towards the light.
74
00:10:39,700 --> 00:10:44,540
Soon, every inch of space and every
patch of light has been claimed.
75
00:10:48,020 --> 00:10:49,820
But hidden in the shadows,
76
00:10:49,820 --> 00:10:53,700
another plant has been waiting
to make its move.
77
00:11:03,180 --> 00:11:06,260
This...
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00:11:06,260 --> 00:11:08,300
..is dodder.
79
00:11:14,460 --> 00:11:16,500
A hunter...
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00:11:18,140 --> 00:11:20,660
..with an exceptional
sense of smell.
81
00:11:27,820 --> 00:11:31,300
Moving swiftly, it searches
for its prey.
82
00:11:34,660 --> 00:11:37,500
It detects the scent of
a young nettle.
83
00:11:56,780 --> 00:12:00,260
The dodder punctures the nettle's
stem
84
00:12:00,260 --> 00:12:02,780
and sucks out the nutritious sap.
85
00:12:06,620 --> 00:12:09,460
And it doesn't stop at just
one victim.
86
00:12:12,700 --> 00:12:15,460
With its energy supply assured,
87
00:12:15,460 --> 00:12:17,500
it multiplies.
88
00:12:26,420 --> 00:12:30,100
It's a parasite with an insatiable
appetite.
89
00:13:32,300 --> 00:13:37,940
But remarkably, its victims can now
exploit the dodder...
90
00:13:40,020 --> 00:13:42,820
..when other springtime enemies
appear.
91
00:13:46,820 --> 00:13:48,860
Caterpillars.
92
00:14:00,060 --> 00:14:03,700
When under attack, a leaf sends out
a signal
93
00:14:03,700 --> 00:14:07,460
telling the rest of the plant
to start building defences...
94
00:14:10,380 --> 00:14:14,340
..foul-tasting toxins that deter
the caterpillars.
95
00:14:17,380 --> 00:14:19,780
In an extraordinary twist,
96
00:14:19,780 --> 00:14:23,060
the stems of the dodder
interconnecting the plants
97
00:14:23,060 --> 00:14:26,780
are now being used as
lines of communication
98
00:14:26,780 --> 00:14:31,340
to relay these warning signals
from plant to plant.
99
00:14:37,780 --> 00:14:41,940
They respond by producing
their own protective chemicals.
100
00:14:45,940 --> 00:14:51,220
Eventually, the whole river bank
becomes one huge defensive network.
101
00:14:52,740 --> 00:14:56,700
And the one-time rivals
are now better off together.
102
00:15:18,300 --> 00:15:23,780
The first warm days of spring
encourage some plants to flower
103
00:15:23,780 --> 00:15:26,180
and get ahead of the competition...
104
00:15:27,740 --> 00:15:32,380
..creating beautiful displays
throughout the seasonal world.
105
00:15:35,060 --> 00:15:38,380
From the spectacular
cherry blossoms of Japan...
106
00:15:41,620 --> 00:15:45,460
..to the goldfield flowers
of California.
107
00:15:49,700 --> 00:15:52,420
But spring flowering is risky.
108
00:15:52,420 --> 00:15:55,260
If they flower too early, it may not
be warm enough
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00:15:55,260 --> 00:15:57,700
for pollinating insects
to be active.
110
00:15:59,620 --> 00:16:03,740
But the common daisy gives
them every opportunity.
111
00:16:07,580 --> 00:16:11,500
The warmer the flowers are,
the more attractive they are -
112
00:16:11,500 --> 00:16:15,980
and they have a remarkable strategy
in order to maximise this.
113
00:16:17,900 --> 00:16:21,460
They were closed up tightly
throughout the night
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00:16:21,460 --> 00:16:23,820
as a protection against the
elements.
115
00:16:23,820 --> 00:16:27,500
But once they feel the warmth and
the light of the sun,
116
00:16:27,500 --> 00:16:29,540
they spring into action.
117
00:16:43,940 --> 00:16:46,700
It's a behaviour called
heliotropism.
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00:16:48,660 --> 00:16:52,580
They turn to keep facing the sun,
119
00:16:52,580 --> 00:16:55,340
absorbing as much heat as they can.
120
00:17:12,100 --> 00:17:15,620
This is a thermal camera,
121
00:17:15,620 --> 00:17:21,060
and it will tell me the difference
between the surrounding temperature
122
00:17:21,060 --> 00:17:25,180
and the temperature in the centre
of a daisy flower.
123
00:17:25,180 --> 00:17:28,500
The surroundings - 12 degrees.
124
00:17:30,180 --> 00:17:32,300
In the centre of a flower...
125
00:17:38,100 --> 00:17:43,620
Pollinators such as bees and wasps
prefer the warmed-up flowers
126
00:17:43,620 --> 00:17:46,540
because they can get a share
of the heat for themselves.
127
00:17:48,420 --> 00:17:52,580
As a consequence, they can collect
more nectar from more flowers,
128
00:17:52,580 --> 00:17:54,620
pollinating as they go.
129
00:17:57,580 --> 00:18:00,940
And the daisies, with the help
of their pollinators,
130
00:18:00,940 --> 00:18:04,260
are able to have a particularly
long flowering season.
131
00:18:07,420 --> 00:18:10,660
But when the window of opportunity
is brief,
132
00:18:10,660 --> 00:18:13,340
even more ingenious tactics
are necessary.
133
00:18:26,820 --> 00:18:29,340
Here in south-western Australia,
134
00:18:29,340 --> 00:18:33,380
summer temperatures can soar
to up to 40 degrees Celsius.
135
00:18:44,140 --> 00:18:47,340
Now, for a brief moment
in the cooler spring,
136
00:18:47,340 --> 00:18:49,540
flowering plants must get busy.
137
00:18:54,980 --> 00:18:58,540
And this hammer orchid,
with its strange flower,
138
00:18:58,540 --> 00:19:00,580
is doing exactly that.
139
00:19:04,100 --> 00:19:06,660
It needs to attract a pollinator,
140
00:19:06,660 --> 00:19:10,100
but has no nectar and doesn't even
look like a flower.
141
00:19:13,500 --> 00:19:16,660
Unlike these neighbouring
huge grass trees.
142
00:19:21,780 --> 00:19:24,780
These produce thousands
of tiny white flowers,
143
00:19:24,780 --> 00:19:26,820
all dripping with nectar.
144
00:19:34,260 --> 00:19:37,140
But the orchid has a different
strategy.
145
00:19:39,460 --> 00:19:45,060
It synchronises its emergence
with the brief mating season
146
00:19:45,060 --> 00:19:47,540
of the thynnid wasp.
147
00:19:53,020 --> 00:19:58,940
The flightless female wasp produces
pheromones to attract males.
148
00:20:07,340 --> 00:20:11,100
This male detects a scent
that seems to be hers...
149
00:20:19,180 --> 00:20:21,860
..yet flies right on by.
150
00:20:28,300 --> 00:20:33,140
The orchid not only has the same
shape and colour as a female wasp,
151
00:20:33,140 --> 00:20:35,820
but it sits at the same height
as she does.
152
00:20:37,780 --> 00:20:39,820
It even mimics her smell.
153
00:20:42,060 --> 00:20:46,380
And the beguiled male attempts
to mate with it.
154
00:21:02,340 --> 00:21:05,660
He hammers against the orchid's
pollen sacks.
155
00:21:11,020 --> 00:21:14,700
And the wasp leaves,
doubtless a little shaken...
156
00:21:17,780 --> 00:21:19,940
..only to be duped once again.
157
00:21:30,580 --> 00:21:33,940
The pollen on his back now sticks
to this different orchid.
158
00:21:35,580 --> 00:21:38,100
And the deception has worked.
159
00:21:41,500 --> 00:21:46,940
The orchid's imitation is even
more intoxicating, it seems,
160
00:21:46,940 --> 00:21:48,980
than the real thing.
161
00:22:09,380 --> 00:22:13,860
Eventually, the male wasps tire
of the orchid's enticements.
162
00:22:17,900 --> 00:22:21,540
{\an8}And now, the wasps,
both male and female,
163
00:22:21,540 --> 00:22:24,700
{\an8}find the flowers of the grass trees
to feed.
164
00:22:26,940 --> 00:22:28,980
And there, at long last...
165
00:22:31,340 --> 00:22:33,380
..they mate.
166
00:22:39,380 --> 00:22:41,420
And as for the hammer orchid?
167
00:22:43,180 --> 00:22:45,380
Pollination is complete.
168
00:22:58,220 --> 00:23:03,620
As summer approaches, the need to
flower becomes more urgent.
169
00:23:05,140 --> 00:23:11,340
And nowhere more so than here
in South Africa.
170
00:23:15,180 --> 00:23:19,900
This is the fynbos,
part of the Cape floral kingdom,
171
00:23:19,900 --> 00:23:24,220
a great expanse of open heathlands
just north of the cape.
172
00:23:27,620 --> 00:23:30,460
Here there are more different
species of plant
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00:23:30,460 --> 00:23:32,500
than anywhere else in the world.
174
00:23:34,060 --> 00:23:37,820
Nearly 9,000,
many needing pollinators.
175
00:23:42,300 --> 00:23:45,020
They compete with one another
for such help
176
00:23:45,020 --> 00:23:49,820
by flaunting extravagant shapes
and vivid colours.
177
00:23:51,780 --> 00:23:55,620
All promising nectar as a
sugary reward.
178
00:23:59,620 --> 00:24:04,180
But there is a plant here that
avoids this crowded competition.
179
00:24:06,700 --> 00:24:11,500
And the rising temperatures
of summer bring just what it needs.
180
00:24:35,700 --> 00:24:39,340
This is the first fire here
for 15 years.
181
00:24:49,620 --> 00:24:52,220
Nearly all the plants are destroyed.
182
00:24:57,660 --> 00:24:59,700
Incinerated.
183
00:25:08,460 --> 00:25:12,020
It might seem from the smoke
and the still-smouldering embers
184
00:25:12,020 --> 00:25:15,180
that no plant could survive
such an inferno.
185
00:25:25,740 --> 00:25:28,820
But just four days after
the flames...
186
00:25:30,540 --> 00:25:32,580
..rising from the ashes...
187
00:25:37,900 --> 00:25:39,940
..a fire lily.
188
00:25:47,340 --> 00:25:52,140
It has been lying dormant
underground for 15 years,
189
00:25:52,140 --> 00:25:56,780
but now, awakened by the smoke,
it flowers.
190
00:26:06,900 --> 00:26:11,820
{\an8}The blooms may be small and unshowy,
but that's all they need to be.
191
00:26:15,020 --> 00:26:19,420
In this charred landscape,
pollinators, such as these sunbirds,
192
00:26:19,420 --> 00:26:23,380
can spot these little red beacons
from great distances.
193
00:26:28,300 --> 00:26:31,420
They're the only source of nectar
around.
194
00:26:42,340 --> 00:26:44,780
And the more visitors the flowers
attract,
195
00:26:44,780 --> 00:26:47,580
the more likely they are to be
pollinated.
196
00:27:01,300 --> 00:27:03,340
It's just in time.
197
00:27:08,780 --> 00:27:14,420
Within a few months, the whole
landscape is alive once more.
198
00:27:17,980 --> 00:27:22,100
In fact, all these plants need fire
to survive.
199
00:27:27,380 --> 00:27:31,180
And as competitors return,
200
00:27:31,180 --> 00:27:33,220
the fire lily fades.
201
00:27:41,500 --> 00:27:44,060
It now returns underground
202
00:27:44,060 --> 00:27:49,100
and will rest there as a bulb
until another fire awakens it.
203
00:27:59,500 --> 00:28:03,740
By the time the long, hot days
of summer arrive,
204
00:28:03,740 --> 00:28:07,900
wild flower meadows are bursting
with life.
205
00:28:10,140 --> 00:28:12,660
But autumn is not far away.
206
00:28:14,540 --> 00:28:19,140
So now pollinated plants must
use their remaining energy
207
00:28:19,140 --> 00:28:21,660
to produce the next generation.
208
00:28:23,740 --> 00:28:25,780
Seeds.
209
00:28:33,620 --> 00:28:37,900
A dandelion clock
contains around 200 seeds...
210
00:28:42,980 --> 00:28:45,380
..each with its own tiny parachute.
211
00:28:51,460 --> 00:28:54,220
Few seeds can fly as far as these.
212
00:28:54,220 --> 00:28:57,860
Some are known to have travelled
over 60 miles.
213
00:29:05,300 --> 00:29:10,380
But to travel any distance at all,
they need the wind to be just right.
214
00:29:16,700 --> 00:29:20,340
However, before they can get away,
there is a risk.
215
00:29:21,460 --> 00:29:24,540
Voracious hunters live in
this meadow.
216
00:29:49,580 --> 00:29:51,620
Tiny harvest mice.
217
00:29:53,500 --> 00:29:55,900
They love dandelion seeds.
218
00:30:02,940 --> 00:30:04,980
But they don't like to share.
219
00:30:16,260 --> 00:30:20,380
Finally, the sun warms the ground
220
00:30:20,380 --> 00:30:23,380
and a gentle breeze blows in,
221
00:30:23,380 --> 00:30:26,180
creating an ideal updraught.
222
00:30:39,660 --> 00:30:43,260
Air flowing between the bristles
creates a vortex
223
00:30:43,260 --> 00:30:45,300
that lifts the seeds up.
224
00:30:49,820 --> 00:30:55,940
Heading off on a gentle breeze,
this seed now starts its travels.
225
00:31:24,100 --> 00:31:27,220
Plants use a variety of different
techniques
226
00:31:27,220 --> 00:31:31,180
to spread their seeds as far as
possible from themselves.
227
00:31:31,180 --> 00:31:34,300
And one of the most remarkable
is this one.
228
00:31:34,300 --> 00:31:39,060
It's called ecballium,
and it's a relative of the cucumber.
229
00:31:39,060 --> 00:31:43,580
For several weeks now, pressure has
been building up inside the pods.
230
00:31:43,580 --> 00:31:48,340
Until now, they're as taut as a
well-pumped-up bicycle tyre.
231
00:31:48,340 --> 00:31:51,620
All they need is just a slight
nudge.
232
00:32:09,460 --> 00:32:14,220
The further the plant can fire
its seeds, the better.
233
00:32:15,900 --> 00:32:19,180
If a seedling germinates close to
its parent,
234
00:32:19,180 --> 00:32:22,940
the two will have to compete for
nutrients and light.
235
00:32:26,380 --> 00:32:32,020
This Himalayan balsam has seed pods
that react rather differently,
236
00:32:32,020 --> 00:32:34,140
like catapults.
237
00:32:34,140 --> 00:32:38,340
As they dry out, they begin to
strain along precisely positioned
238
00:32:38,340 --> 00:32:40,380
lines of weakness.
239
00:32:40,380 --> 00:32:42,940
And then, just the slightest
disturbance,
240
00:32:42,940 --> 00:32:47,140
even a single raindrop, is enough
to trigger the mechanism.
241
00:33:20,420 --> 00:33:23,140
The east coast of South Africa.
242
00:33:26,100 --> 00:33:29,060
Summer here brings scorching
temperatures.
243
00:33:38,860 --> 00:33:42,300
This Ceratocaryum has to get
its seeds underground
244
00:33:42,300 --> 00:33:44,340
before it gets too hot.
245
00:33:46,700 --> 00:33:49,980
And it has acquired somewhat
unlikely allies.
246
00:33:56,420 --> 00:33:58,460
Dung beetles.
247
00:34:01,580 --> 00:34:06,540
They have a particular fondness
for antelope droppings.
248
00:34:10,460 --> 00:34:13,860
At this time of the year,
these beetles bury the dung
249
00:34:13,860 --> 00:34:15,900
and lay their eggs on it.
250
00:34:22,420 --> 00:34:24,460
And the fresher...
251
00:34:26,700 --> 00:34:28,740
..the better.
252
00:34:33,620 --> 00:34:39,460
Ceratocaryum's spindly stems
send their seeds flying.
253
00:35:01,260 --> 00:35:04,620
They're the same size, shape
254
00:35:04,620 --> 00:35:07,780
and even smell remarkably like...
255
00:35:09,100 --> 00:35:11,140
..antelope dung.
256
00:35:24,620 --> 00:35:28,060
The beetles simply can't
resist them.
257
00:35:46,940 --> 00:35:51,220
Dung beetles always bury
dung balls at the same depth.
258
00:35:51,220 --> 00:35:54,380
And it's one which suits the seeds
very well.
259
00:36:04,140 --> 00:36:07,020
So effective is the seed's deception
260
00:36:07,020 --> 00:36:10,980
that the beetles come back for more
time and time again.
261
00:36:26,700 --> 00:36:31,260
Most of the Ceratocaryum seeds
get safely buried...
262
00:36:34,700 --> 00:36:38,140
..exactly where they need to be.
263
00:36:57,580 --> 00:37:03,020
As the sun begins to retreat,
so autumn arrives.
264
00:37:06,260 --> 00:37:11,540
The cooler, shorter days are the cue
for many seasonal forests
265
00:37:11,540 --> 00:37:14,180
to prepare for the winter shutdown.
266
00:37:17,740 --> 00:37:22,340
The trees start to divert their
nutrients back into their roots.
267
00:37:24,100 --> 00:37:27,220
And there, other organisms
await them.
268
00:37:34,700 --> 00:37:36,740
Fungi.
269
00:38:15,460 --> 00:38:19,980
Mushrooms are the familiar face
of fungi,
270
00:38:19,980 --> 00:38:22,620
but they are merely the fruiting
bodies.
271
00:38:22,620 --> 00:38:26,060
Some of them only last
for a few days.
272
00:38:26,060 --> 00:38:30,100
They are, however, evidence
of the giant organism
273
00:38:30,100 --> 00:38:32,660
that lies in the soil beneath.
274
00:38:32,660 --> 00:38:37,940
Just a single handful of soil may
contain several thousand metres
275
00:38:37,940 --> 00:38:41,140
of their microscopic filaments.
276
00:38:41,140 --> 00:38:46,300
It's only recently that we have
discovered the extraordinary role
277
00:38:46,300 --> 00:38:49,860
that these fungi play in a forest
like this.
278
00:38:52,900 --> 00:38:58,420
Their filaments plug into the tips
of the tree's roots
279
00:38:58,420 --> 00:39:03,260
and nutrients pass between tree
and fungus throughout the year.
280
00:39:05,340 --> 00:39:10,260
Some fungi have the ability to link
with not just a single tree,
281
00:39:10,260 --> 00:39:13,340
but with a whole group of trees,
282
00:39:13,340 --> 00:39:16,740
so that the entire forest may be
linked together
283
00:39:16,740 --> 00:39:19,020
by these microscopic threads,
284
00:39:19,020 --> 00:39:22,500
to form what you might call
a wood-wide web.
285
00:39:31,020 --> 00:39:34,940
Hundreds of trees can be
interconnected by these webs.
286
00:39:36,020 --> 00:39:39,580
Scientists call it
the mycorrhizal network.
287
00:39:41,540 --> 00:39:44,020
And it might look something
like this.
288
00:39:52,980 --> 00:39:56,460
They've discovered that trees
not only send nutrients along it
289
00:39:56,460 --> 00:40:00,100
but chemical and electrical signals,
290
00:40:00,100 --> 00:40:02,980
allowing them to communicate
with one another.
291
00:40:05,060 --> 00:40:09,860
But some trees can also be selfish
and steal from their rivals.
292
00:40:10,980 --> 00:40:16,620
Or even wage war by sending out
toxins that will harm competitors.
293
00:40:24,220 --> 00:40:28,620
It seems, however, that most trees
do try to help each other.
294
00:40:31,620 --> 00:40:35,020
They raise the alarm when attacked
by leaf-eaters,
295
00:40:35,020 --> 00:40:39,100
leaving other trees time to produce
defensive chemicals.
296
00:40:44,060 --> 00:40:48,260
Those that are dying may send their
food reserves to their neighbours.
297
00:40:50,060 --> 00:40:54,220
And some individuals
known as mother trees
298
00:40:54,220 --> 00:40:57,580
recognise their own offspring,
299
00:40:57,580 --> 00:41:00,140
and will channel resources to
them...
300
00:41:04,300 --> 00:41:08,620
..so giving their young the best
possible start in life.
301
00:41:29,060 --> 00:41:32,300
As the harshness of winter
approaches...
302
00:41:34,340 --> 00:41:41,340
..temperate woodlands from
Russia to Canada
303
00:41:41,340 --> 00:41:45,180
are now in a race to shut down.
304
00:42:11,420 --> 00:42:15,620
The green pigment in the leaves
starts to break down
305
00:42:15,620 --> 00:42:19,060
and nutrients are withdrawn
into the branches.
306
00:42:21,460 --> 00:42:24,220
The chemical substances
that are left behind
307
00:42:24,220 --> 00:42:29,260
then create one of the most
spectacular displays of colour
308
00:42:29,260 --> 00:42:31,340
in the whole of nature.
309
00:43:28,380 --> 00:43:33,660
The first freezing nights of winter
bring with them a killer.
310
00:43:36,820 --> 00:43:38,860
Frost.
311
00:43:44,460 --> 00:43:48,460
Stems, when frozen, rupture.
312
00:43:51,420 --> 00:43:55,540
And flowers of ice
form in the chilly air.
313
00:44:29,060 --> 00:44:32,460
For some, winter brings dormancy.
314
00:44:34,580 --> 00:44:37,540
For others, it brings death.
315
00:44:48,300 --> 00:44:51,620
Another cycle of the seasons
316
00:44:51,620 --> 00:44:53,660
comes to an end.
317
00:45:08,500 --> 00:45:11,340
Plants all across the seasonal world
318
00:45:11,340 --> 00:45:15,580
have developed many different
strategies for success.
319
00:45:15,580 --> 00:45:22,620
But they all depend on the seasons
changing reliably year after year.
320
00:45:22,620 --> 00:45:25,380
It doesn't matter whether you live
for 3,000 years
321
00:45:25,380 --> 00:45:27,980
or just a few months,
322
00:45:27,980 --> 00:45:32,140
everything depends on you getting
the timing just right.
323
00:45:35,820 --> 00:45:38,060
But in our changing world,
324
00:45:38,060 --> 00:45:41,500
this is becoming a greater challenge
every year.
325
00:45:44,260 --> 00:45:48,060
And even the most hardy
and resilient of plants
326
00:45:48,060 --> 00:45:50,100
are starting to struggle.
327
00:45:59,540 --> 00:46:05,100
These sequoia trees are the giants
of the natural world,
328
00:46:05,100 --> 00:46:08,980
the largest living thing
on the planet.
329
00:46:08,980 --> 00:46:12,300
They can grow to almost
100 metres tall
330
00:46:12,300 --> 00:46:14,340
and 11 metres across.
331
00:46:17,100 --> 00:46:20,700
Their bark alone can be over a
half-a-metre thick.
332
00:46:21,820 --> 00:46:28,620
They're also among the oldest,
some living to over 3,000 years.
333
00:46:28,620 --> 00:46:31,580
And to achieve such age and size,
334
00:46:31,580 --> 00:46:34,780
they need very particular living
conditions,
335
00:46:34,780 --> 00:46:38,500
such as are found here in the
Sierra Nevada mountains
336
00:46:38,500 --> 00:46:40,540
of California.
337
00:46:45,460 --> 00:46:48,140
Not only do they need energy
from the sun but,
338
00:46:48,140 --> 00:46:55,540
critically, they also require
up to 4,000 litres of water a day.
339
00:46:55,540 --> 00:47:00,220
So they are almost entirely reliant
on the seasonal snowmelt.
340
00:47:06,980 --> 00:47:10,740
But recent years have brought
longer, hotter summers
341
00:47:10,740 --> 00:47:15,220
and their source of water
is becoming increasingly unreliable.
342
00:47:21,900 --> 00:47:23,940
Scientists are discovering
343
00:47:23,940 --> 00:47:27,660
that even these seemingly
indestructible giants
344
00:47:27,660 --> 00:47:31,540
are now starting to show
signs of vulnerability.
345
00:47:34,340 --> 00:47:37,580
Some are shedding their needles
and branches
346
00:47:37,580 --> 00:47:40,300
as a way of conserving
precious water.
347
00:47:51,220 --> 00:47:55,100
But for others, climate change
has already been fatal.
348
00:47:57,220 --> 00:48:01,340
10% of them have been lost
in just the last few years.
349
00:48:12,300 --> 00:48:16,020
A single giant sequoia
in its lifetime
350
00:48:16,020 --> 00:48:20,340
can produce 100 million seeds.
351
00:48:20,340 --> 00:48:23,220
These, in my hand, from one cone,
352
00:48:23,220 --> 00:48:26,940
are more than enough
to start a completely new forest.
353
00:48:29,540 --> 00:48:34,340
But they can only do such a thing
in a world where the seasons change
354
00:48:34,340 --> 00:48:36,380
with some reliability.
355
00:48:38,660 --> 00:48:43,660
Today, our climate is changing,
bringing an unprecedented level
356
00:48:43,660 --> 00:48:48,740
of unpredictability
all across the seasonal world.
357
00:48:51,060 --> 00:48:56,260
The question is, can we curb
climate change sufficiently
358
00:48:56,260 --> 00:49:00,300
to ensure that the seasons will
continue?
359
00:49:00,300 --> 00:49:04,220
Only if we can do that will the
future of seasonal plants,
360
00:49:04,220 --> 00:49:08,580
including these magnificent trees,
be assured.
361
00:49:32,020 --> 00:49:34,220
During filming The Green Planet,
362
00:49:34,220 --> 00:49:38,420
it wasn't only the plants that
struggled to get their timing right.
363
00:49:38,420 --> 00:49:41,580
The increasing unpredictability
of the seasons
364
00:49:41,580 --> 00:49:43,980
made it frustratingly difficult
for the crew
365
00:49:43,980 --> 00:49:46,660
to be in the right place
at the right time.
366
00:49:47,780 --> 00:49:49,820
Whether the height of summer...
367
00:49:49,820 --> 00:49:54,660
We are in the middle of a biblical
rainstorm.
368
00:49:54,660 --> 00:49:57,660
..or a quiet autumnal afternoon...
369
00:49:57,660 --> 00:50:00,980
This is crazy.
Hurricanes are no joke.
370
00:50:00,980 --> 00:50:03,300
..they were always kept
on their toes.
371
00:50:04,300 --> 00:50:07,100
That's really scary. Ooh!
372
00:50:08,740 --> 00:50:10,780
Sometimes very numb ones.
373
00:50:12,900 --> 00:50:15,980
It's been the most snow they've had
for 38 years,
374
00:50:15,980 --> 00:50:19,820
{\an8}and I think this is now our
fifth filming trip in a row
375
00:50:19,820 --> 00:50:23,460
{\an8}where the seasons haven't done
what they're predictably meant to do
376
00:50:23,460 --> 00:50:25,780
{\an8}every year.
377
00:50:25,780 --> 00:50:29,780
And these challenges continue
in attempting to find and film
378
00:50:29,780 --> 00:50:34,180
an elusive plant with a remarkable
survival strategy.
379
00:50:35,900 --> 00:50:37,940
The fire lily.
380
00:50:47,100 --> 00:50:51,100
Somewhere out there is a tiny, tiny
red plant...
381
00:50:51,100 --> 00:50:53,140
..in all of that.
382
00:51:02,980 --> 00:51:05,580
Travelling to South Africa
at the height of summer...
383
00:51:08,260 --> 00:51:10,820
..the crew witnessed many
extraordinary flowers
384
00:51:10,820 --> 00:51:12,860
bursting into bloom.
385
00:51:15,060 --> 00:51:19,180
But if they are to see
a fire lily, they need a fire.
386
00:51:22,380 --> 00:51:25,500
None of the team have filmed
wildfire before -
387
00:51:25,500 --> 00:51:27,660
not something to be underestimated.
388
00:51:29,140 --> 00:51:32,420
In most cases, with wildfires,
is that, when they go wrong,
389
00:51:32,420 --> 00:51:34,620
they go wrong radically,
and it's very unforgiving.
390
00:51:34,620 --> 00:51:36,940
If you get caught on the wrong side
of a fire
391
00:51:36,940 --> 00:51:38,820
because you want to get
that special shot,
392
00:51:38,820 --> 00:51:40,740
there's a possibility you can get
killed.
393
00:51:40,740 --> 00:51:42,460
That's really what it comes down to.
394
00:51:42,460 --> 00:51:45,580
And after some understandably
studious note-taking...
395
00:51:47,340 --> 00:51:50,140
..it's time to put their training
to the test.
396
00:52:00,860 --> 00:52:04,260
The fire's just racing up a gully
behind me.
397
00:52:04,260 --> 00:52:07,740
The heat is intense. You just...
You can't even stand to be, like,
398
00:52:07,740 --> 00:52:09,780
five metres from it. It's insane.
399
00:52:12,860 --> 00:52:14,900
Whoa!
400
00:52:16,180 --> 00:52:20,500
This is what any fire lilies here
should be waiting for.
401
00:52:29,580 --> 00:52:31,620
Jeepers.
402
00:52:32,940 --> 00:52:37,220
But fynbos wildfires are starting
to become fiercer than in the past.
403
00:52:38,620 --> 00:52:41,540
Something fire chief Reinard Geldenhuys
404
00:52:41,540 --> 00:52:43,780
knows first-hand.
405
00:52:43,780 --> 00:52:47,260
Nowadays, we're experiencing
more extreme temperature conditions
406
00:52:47,260 --> 00:52:49,300
and more extreme wind conditions,
407
00:52:49,300 --> 00:52:52,740
which exacerbates a fynbos fire.
408
00:52:54,740 --> 00:52:58,460
Fynbos fire in full tilt,
with a strong wind behind it,
409
00:52:58,460 --> 00:53:01,100
is an animal that's just
running wild.
410
00:53:02,420 --> 00:53:05,340
It's a very frightening sight
if you're standing in front of it.
411
00:53:11,660 --> 00:53:15,100
Guided by the experience of the
fire crew,
412
00:53:15,100 --> 00:53:19,380
the team are able to safely capture
the full fury of the blaze.
413
00:53:22,940 --> 00:53:27,740
It's given me a complete new
appreciation for fire.
414
00:53:27,740 --> 00:53:30,620
How intensely it burns
and how quickly it roars
415
00:53:30,620 --> 00:53:32,660
through this environment.
416
00:53:33,700 --> 00:53:37,020
And the fact that any plants
can survive afterwards
417
00:53:37,020 --> 00:53:39,060
is just... Yeah, it's crazy.
418
00:53:42,700 --> 00:53:44,780
As destructive as it seems,
419
00:53:44,780 --> 00:53:48,060
the fire has been part of this
ecosystem for millennia.
420
00:53:49,140 --> 00:53:52,380
Fires should refresh and regenerate
the landscape.
421
00:53:53,900 --> 00:53:58,380
Worryingly, however, this fine
balance between plant and fire
422
00:53:58,380 --> 00:54:01,060
is beginning to shift.
423
00:54:01,060 --> 00:54:04,780
More extreme wildfires may
spell disaster.
424
00:54:06,620 --> 00:54:08,820
If you disturb the soil in a
fynbos system,
425
00:54:08,820 --> 00:54:11,100
you're going to lose
a lot of species.
426
00:54:11,100 --> 00:54:14,300
Bigger, hotter fires can burn
the soil there
427
00:54:14,300 --> 00:54:16,340
and burn out all the seeds.
428
00:54:17,380 --> 00:54:20,420
And for the species that have these
really intricate strategies,
429
00:54:20,420 --> 00:54:23,860
like the fire lily,
it really is a difficult game.
430
00:54:25,620 --> 00:54:29,060
Every year is getting hotter
and potentially drier.
431
00:54:29,060 --> 00:54:31,940
So it's kind of becoming
Russian roulette
432
00:54:31,940 --> 00:54:33,980
for a lot of the species here.
433
00:54:43,940 --> 00:54:45,980
In the fire's aftermath,
434
00:54:45,980 --> 00:54:48,700
the crew must now try to find
a tiny flower...
435
00:54:50,820 --> 00:54:53,780
..but have any survived the blaze?
436
00:54:53,780 --> 00:54:56,580
It just looks completely dead,
the whole valley.
437
00:55:02,900 --> 00:55:06,060
There's nothing for it
but to get their hands dirty.
438
00:55:08,420 --> 00:55:11,460
Searching in the ash is a grubby
business.
439
00:55:17,620 --> 00:55:19,660
I feel...
440
00:55:19,660 --> 00:55:22,020
..disgusting.
441
00:55:22,020 --> 00:55:26,380
After scouring this mountainside
just days after it burned...
442
00:55:27,580 --> 00:55:31,380
..they finally find the
first signs of regeneration.
443
00:55:34,700 --> 00:55:38,300
Wow. That's what it's all about.
That's the fire lily.
444
00:55:38,300 --> 00:55:41,540
It's like a pop of bright red
against all the black.
445
00:55:42,740 --> 00:55:45,700
I mean, that's amazing.
There's another one over there,
446
00:55:45,700 --> 00:55:47,740
and there's another one behind us.
447
00:55:49,100 --> 00:55:51,580
This place hasn't burned for
15 years,
448
00:55:51,580 --> 00:55:55,340
so they've been sat underground
waiting for this precise moment
449
00:55:55,340 --> 00:55:57,500
for that entire time.
And then, within two weeks,
450
00:55:57,500 --> 00:56:00,340
they're up and they're flowering.
It's incredible.
451
00:56:01,660 --> 00:56:05,260
{\an8}This time, the fire lilies here
succeeded in flowering.
452
00:56:05,260 --> 00:56:08,340
{\an8}But in the 15 years since they
last bloomed,
453
00:56:08,340 --> 00:56:12,820
{\an8}the Earth has experienced
ten of the warmest years on record.
454
00:56:14,340 --> 00:56:16,740
You know, there's huge debates
about climate change -
455
00:56:16,740 --> 00:56:19,020
how real is it, really, and so on.
456
00:56:19,020 --> 00:56:22,660
Erm, we experience it in the fire.
457
00:56:22,660 --> 00:56:25,980
It's more intense, burns easier,
burns longer.
458
00:56:27,620 --> 00:56:30,900
In the past, we used to have one big
fire per season,
459
00:56:30,900 --> 00:56:33,140
and we said,
"Ja, that was a big one."
460
00:56:33,140 --> 00:56:36,220
Now we have five to six big ones
per season.
461
00:56:37,740 --> 00:56:41,140
If we don't change our ways,
we are going to reach a point where
462
00:56:41,140 --> 00:56:45,340
fires are burning with such ferocity
that it will destroy the landscape.
463
00:56:47,820 --> 00:56:51,260
And in recent times, a
rapidly changing climate
464
00:56:51,260 --> 00:56:54,340
has led to some of the biggest fires
in living memory -
465
00:56:54,340 --> 00:56:57,820
not just in South Africa,
but around the world.
466
00:56:59,100 --> 00:57:02,940
The next five to ten years
are going to be pretty scary
467
00:57:02,940 --> 00:57:06,020
to actually see what this has done
to the ecosystem.
468
00:57:07,180 --> 00:57:10,740
Let's hope that the next time
this fire lily blooms,
469
00:57:10,740 --> 00:57:14,060
it will find a world in which it
can still survive.
470
00:57:19,020 --> 00:57:21,060
Next time on The Green Planet...
471
00:57:22,660 --> 00:57:24,700
..desert worlds.
472
00:57:26,260 --> 00:57:28,340
A landscape of extremes...
473
00:57:30,060 --> 00:57:32,260
..where water equals life.
474
00:57:36,460 --> 00:57:38,500
It only takes a drop.
475
00:57:41,780 --> 00:57:45,220
The Open University has produced
a poster
476
00:57:45,220 --> 00:57:49,820
that explores the vital role
that plants have for our planet.
477
00:57:49,820 --> 00:57:52,940
To order your free copy, call...
478
00:57:56,100 --> 00:57:58,140
..or go to...
479
00:58:01,860 --> 00:58:04,700
..and follow the links to the
Open University.
37497
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