Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated:
1
00:00:37,580 --> 00:00:43,100
The Taklamakan Desert
in northern China,
2
00:00:43,100 --> 00:00:47,380
a constantly shifting landscape
of sand.
3
00:00:50,420 --> 00:00:53,580
Temperatures that swing from -20
4
00:00:53,580 --> 00:00:57,660
to more than
40 degrees centigrade...
5
00:00:59,100 --> 00:01:04,860
..and, most critically,
almost entirely without rain.
6
00:01:12,100 --> 00:01:15,580
Yet, here on the dunes...
7
00:01:21,940 --> 00:01:24,540
{\an8}..a Euphrates poplar tree.
8
00:01:31,860 --> 00:01:34,500
And it's not alone.
9
00:01:35,780 --> 00:01:40,140
Some of these trees have lived
here for 1,000 years.
10
00:01:43,180 --> 00:01:48,300
They have exceptionally long roots
with which to collect water,
11
00:01:48,300 --> 00:01:53,500
and what is more, those roots are
connected to neighbouring trees,
12
00:01:53,500 --> 00:01:56,660
so that if one strikes water,
13
00:01:56,660 --> 00:01:58,260
others can share it.
14
00:02:00,780 --> 00:02:03,460
In every desert across the planet,
15
00:02:03,460 --> 00:02:08,020
plants have found ways
to not only survive,
16
00:02:08,020 --> 00:02:09,900
but flourish.
17
00:02:25,100 --> 00:02:30,580
{\an8}This is the Gran Desierto
of Mexico and the United States.
18
00:02:42,020 --> 00:02:46,700
These dunes may appear
to be totally barren.
19
00:02:46,700 --> 00:02:50,100
In fact, they are full of life.
20
00:02:50,100 --> 00:02:53,100
In the sand beneath my feet
21
00:02:53,100 --> 00:02:56,260
there are seeds
of many different kinds.
22
00:02:56,260 --> 00:03:00,740
In fact, you could say that the dune
itself is one great seed bank,
23
00:03:00,740 --> 00:03:04,740
and when it rains,
it bursts into life.
24
00:03:10,780 --> 00:03:15,700
But rain may come only once
a decade, and even then,
25
00:03:15,700 --> 00:03:19,740
the long-awaited storm
may be very brief.
26
00:03:23,300 --> 00:03:26,940
So seeds must respond immediately.
27
00:03:40,420 --> 00:03:42,300
This is sand verbena.
28
00:03:42,300 --> 00:03:46,740
It can grow from a seed to a
sweetly-scented flowering plant
29
00:03:46,740 --> 00:03:48,580
in just a few weeks.
30
00:03:55,780 --> 00:04:00,140
Primroses and many other plants
soon join the race
31
00:04:00,140 --> 00:04:02,860
to flower before the sand dries.
32
00:04:06,780 --> 00:04:10,780
Desert blooms like this,
however, are rare.
33
00:04:14,180 --> 00:04:18,300
This is the first year for 20 years.
34
00:04:22,540 --> 00:04:25,100
The combination of vibrant colour
35
00:04:25,100 --> 00:04:29,180
and powerful scent
attracts migrating pollinators,
36
00:04:29,180 --> 00:04:32,340
such as these
Painted Lady butterflies,
37
00:04:32,340 --> 00:04:37,900
which fly into the middle of what
were, only recently, barren dunes.
38
00:04:39,740 --> 00:04:42,660
Everything is rushing
to complete their lives
39
00:04:42,660 --> 00:04:44,780
before the moisture has gone.
40
00:04:53,220 --> 00:04:58,660
Such spectacular blooms transform
deserts all around the world.
41
00:05:08,780 --> 00:05:11,620
From the Atacama in South America...
42
00:05:13,340 --> 00:05:16,940
..to the dusty plains
of southern Africa.
43
00:05:35,980 --> 00:05:40,020
Rain in deserts, however,
never lasts long,
44
00:05:40,020 --> 00:05:43,700
and all too soon,
the flowers wither and die.
45
00:05:49,460 --> 00:05:52,980
But not before they've produced
the next generation...
46
00:05:58,220 --> 00:06:02,820
..the seeds that will now wait
in the sand for the next rains.
47
00:06:08,380 --> 00:06:11,300
In the Sonoran Desert
of North America,
48
00:06:11,300 --> 00:06:15,500
the huge saguaro cacti
have a different strategy.
49
00:06:15,500 --> 00:06:18,660
They store water in quantity
50
00:06:18,660 --> 00:06:21,140
and can live to a great age.
51
00:06:22,460 --> 00:06:24,820
But in their early years,
52
00:06:24,820 --> 00:06:27,180
they are extremely vulnerable.
53
00:06:31,100 --> 00:06:35,380
This little saguaro cactus
is about ten-years-old.
54
00:06:35,380 --> 00:06:40,100
When they're really small and
growing out in the open,
55
00:06:40,100 --> 00:06:43,900
there's a real chance that they may
shrivel up and die.
56
00:06:43,900 --> 00:06:46,220
But this one has been lucky.
57
00:06:46,220 --> 00:06:50,820
It's been growing in the shade
of this mesquite tree,
58
00:06:50,820 --> 00:06:54,980
and it's got a very good chance
of surviving to maturity.
59
00:06:56,260 --> 00:07:01,580
The young saguaro is protected
by the mesquite's branches.
60
00:07:01,580 --> 00:07:05,460
They halve the amount of scorching
sunlight reaching the cactus...
61
00:07:07,380 --> 00:07:09,220
..and so, keep it cool.
62
00:07:11,580 --> 00:07:15,620
And the mesquite's extremely
long roots draw up water,
63
00:07:15,620 --> 00:07:19,100
bringing it within reach
of the young saguaro.
64
00:07:23,460 --> 00:07:27,140
So the mesquite
is known as a 'nurse plant',
65
00:07:27,140 --> 00:07:29,540
and a very effective one it is, too.
66
00:07:31,300 --> 00:07:35,300
In fact, this particular mesquite
has already nurtured
67
00:07:35,300 --> 00:07:38,980
seven young saguaros
over the past 30 years.
68
00:07:43,420 --> 00:07:45,660
As a young cactus grows,
69
00:07:45,660 --> 00:07:50,700
it needs the protection of its nurse
plant, not only from the heat,
70
00:07:50,700 --> 00:07:53,980
but from the other hazards
of desert life.
71
00:07:56,860 --> 00:08:00,660
Temperatures can drop
to -10 degrees overnight...
72
00:08:03,620 --> 00:08:06,820
..and very occasionally...
73
00:08:06,820 --> 00:08:08,740
..it even snows.
74
00:08:14,940 --> 00:08:19,340
If the water stored inside a young
cactus should freeze,
75
00:08:19,340 --> 00:08:21,620
the cactus will die.
76
00:08:23,460 --> 00:08:27,940
But the nurse plant traps a blanket
of slightly warmer air around it,
77
00:08:27,940 --> 00:08:30,980
just enough to keep it alive.
78
00:08:33,540 --> 00:08:37,420
Eventually, saguaros outgrow
their nurses,
79
00:08:37,420 --> 00:08:39,020
but by that time,
80
00:08:39,020 --> 00:08:42,700
they are robust enough to face
the elements by themselves.
81
00:08:46,380 --> 00:08:49,140
No matter how old a desert plant
is,
82
00:08:49,140 --> 00:08:52,300
water is always precious,
83
00:08:52,300 --> 00:08:54,620
whether gathered
from melting snow...
84
00:08:59,180 --> 00:09:01,260
..or a shower of rain.
85
00:09:06,580 --> 00:09:10,260
So, cacti have developed
extraordinary adaptations
86
00:09:10,260 --> 00:09:13,020
that enable them
to not only collect water...
87
00:09:14,540 --> 00:09:16,660
..but to retain it.
88
00:09:19,900 --> 00:09:21,380
Instead of leaves,
89
00:09:21,380 --> 00:09:24,900
which would lose precious
moisture through evaporation,
90
00:09:24,900 --> 00:09:26,780
they have spines.
91
00:09:28,300 --> 00:09:31,260
Each spine
has a tiny pad at its base
92
00:09:31,260 --> 00:09:33,540
where the water is absorbed...
93
00:09:35,020 --> 00:09:38,980
..and then stored
in the great swollen trunk.
94
00:09:41,900 --> 00:09:47,580
A large saguaro can
hold 5,000 litres of water
95
00:09:47,580 --> 00:09:52,620
and is able to do so because it
has another special adaptation.
96
00:10:01,580 --> 00:10:06,340
The ridges on its surface
are like the pleats on an accordion.
97
00:10:06,340 --> 00:10:09,140
They allow the saguaro
to change its shape.
98
00:10:10,900 --> 00:10:14,220
After rain has fallen,
the pleats expand
99
00:10:14,220 --> 00:10:17,700
and the saguaro fills
up its water tank.
100
00:10:22,300 --> 00:10:26,100
In the dry times,
it uses its water to grow,
101
00:10:26,100 --> 00:10:30,900
produce flowers and,
eventually, seeds.
102
00:10:33,740 --> 00:10:37,060
Fully-loaded with thousands
of litres of water,
103
00:10:37,060 --> 00:10:41,380
this saguaro won't need to drink
a single drop for another year.
104
00:10:43,860 --> 00:10:47,540
But such valuable stores
of water attract thieves.
105
00:10:49,820 --> 00:10:52,980
Now the spine's function
changes from collecting...
106
00:10:54,660 --> 00:10:56,020
..to guarding.
107
00:10:58,380 --> 00:11:03,100
The spines of some species
are a quarter of a metre long.
108
00:11:09,100 --> 00:11:11,420
Others are needle-like barbs
109
00:11:11,420 --> 00:11:15,900
that grow in clusters and easily
break off in the skin of any animal
110
00:11:15,900 --> 00:11:17,700
that touches them.
111
00:11:19,100 --> 00:11:21,340
But perhaps the most vicious cacti
112
00:11:21,340 --> 00:11:24,660
belong to a group
called the chollas.
113
00:11:25,780 --> 00:11:29,540
This is called a teddy-bear cholla
114
00:11:29,540 --> 00:11:33,340
because of the thick coating
of spines on it.
115
00:11:33,340 --> 00:11:35,940
But don't be deceived by the name,
116
00:11:35,940 --> 00:11:39,780
there is nothing cuddly
about THIS particular teddy bear.
117
00:11:39,780 --> 00:11:43,980
In fact, it's the most dangerous
plant in the desert,
118
00:11:43,980 --> 00:11:47,460
and I wouldn't dream of
putting my hand anywhere near it
119
00:11:47,460 --> 00:11:49,620
without proper protection.
120
00:11:51,700 --> 00:11:53,380
Brush against it...
121
00:11:54,380 --> 00:11:55,660
..this can happen.
122
00:11:55,660 --> 00:11:56,980
Ow!
123
00:11:56,980 --> 00:11:58,900
This can happen,
even with this glove on.
124
00:11:58,900 --> 00:12:01,180
One of them has just gone through,
I can feel it.
125
00:12:01,180 --> 00:12:02,540
It's quite painful!
126
00:12:04,460 --> 00:12:07,940
Look closely at the spine
and you can see very clearly
127
00:12:07,940 --> 00:12:09,460
why they're so dangerous.
128
00:12:10,660 --> 00:12:12,940
Each is like a splinter of glass,
129
00:12:12,940 --> 00:12:14,980
sharp enough to pierce flesh...
130
00:12:16,540 --> 00:12:19,540
..and they're covered
with backward-pointing barbs.
131
00:12:20,980 --> 00:12:25,140
So getting them out, even with a
pair of pliers, is quite hard.
132
00:12:25,140 --> 00:12:28,900
This is not pleasant at all.
133
00:12:28,900 --> 00:12:31,100
It won't come off, or without.
134
00:12:32,460 --> 00:12:33,980
Oh, look at that!
135
00:12:36,700 --> 00:12:41,300
It's hard to imagine a more
aggressive defence than this,
136
00:12:41,300 --> 00:12:45,500
and it makes both the plant and its
buds virtually invulnerable.
137
00:12:56,980 --> 00:13:00,060
Most animals know to keep clear.
138
00:13:03,380 --> 00:13:08,060
Cholla buds grow like tiny barrels
from the top of the adult plant
139
00:13:08,060 --> 00:13:10,780
and then drop off.
140
00:13:19,100 --> 00:13:22,500
If the young cholla
put down roots here,
141
00:13:22,500 --> 00:13:25,900
it would compete with
its parent for water.
142
00:13:28,380 --> 00:13:30,060
Night falls...
143
00:13:31,980 --> 00:13:34,260
..and this one is on the move.
144
00:13:43,900 --> 00:13:48,380
A pack rat. She knows how to deal
with a cholla.
145
00:13:54,260 --> 00:13:57,060
She avoids the spines by gripping
it at the place
146
00:13:57,060 --> 00:13:59,420
where it broke off from its parent.
147
00:14:04,940 --> 00:14:06,940
And she works fast.
148
00:14:10,140 --> 00:14:12,660
There are pack rat hunters here.
149
00:14:21,300 --> 00:14:26,220
She uses the cholla to build a spiny
wall around her nest.
150
00:14:43,180 --> 00:14:45,980
The flesh of the cholla
supplies her with water...
151
00:14:47,620 --> 00:14:52,700
..and the severed spines
further reinforce the defences.
152
00:15:04,300 --> 00:15:06,260
This cholla bud...
153
00:15:07,860 --> 00:15:08,900
..might be next.
154
00:15:12,780 --> 00:15:15,460
But one accidental nudge...
155
00:15:19,900 --> 00:15:22,020
..and it escapes.
156
00:15:48,780 --> 00:15:51,980
The bud starts to put down roots.
157
00:16:00,140 --> 00:16:03,380
So, the cholla,
thanks to the pack rats,
158
00:16:03,380 --> 00:16:05,900
finds new territory
159
00:16:05,900 --> 00:16:08,100
and sets about claiming it.
160
00:16:16,540 --> 00:16:21,660
Few plants deal with the problems
of desert living better than cacti.
161
00:16:23,580 --> 00:16:28,100
There are almost 2,000 different
species of them.
162
00:16:28,100 --> 00:16:31,660
They're spread across the deserts
of the American West,
163
00:16:31,660 --> 00:16:35,940
from Arizona,
all the way to Mexico and beyond.
164
00:16:41,020 --> 00:16:44,940
In South America, the ice-covered
peaks of the Andes
165
00:16:44,940 --> 00:16:46,740
act as a rain barrier...
166
00:16:48,500 --> 00:16:52,940
..beyond which
lies the world's driest desert -
167
00:16:52,940 --> 00:16:54,580
the Atacama.
168
00:17:03,340 --> 00:17:07,580
In the desert world, water thieves
can come in many forms
169
00:17:07,580 --> 00:17:11,660
to exploit even the smallest chink
in a plant's defence.
170
00:17:17,660 --> 00:17:20,820
One of the strangest
travels within the gut
171
00:17:20,820 --> 00:17:23,220
of a fruit-eating mockingbird.
172
00:17:30,140 --> 00:17:34,140
{\an8}These are the seeds
of Tristerix,
173
00:17:34,140 --> 00:17:36,460
a kind of mistletoe.
174
00:17:39,500 --> 00:17:44,900
Their goal is the water
inside this hedgehog cactus.
175
00:17:47,140 --> 00:17:49,500
Using the spines as anchors,
176
00:17:49,500 --> 00:17:52,260
the seeds start to germinate.
177
00:17:55,740 --> 00:17:58,060
Each produces a long probe
178
00:17:58,060 --> 00:18:00,900
with which to try and locate
the cactus' skin.
179
00:18:04,220 --> 00:18:07,020
For most,
that's a stretch too far,
180
00:18:07,020 --> 00:18:09,220
and they perish.
181
00:18:11,460 --> 00:18:16,780
But for this one, the cactus'
surface is within reach.
182
00:18:25,660 --> 00:18:28,500
It clamps onto it
with a special sucker...
183
00:18:32,020 --> 00:18:34,740
..and then waits for darkness.
184
00:18:37,140 --> 00:18:41,460
At night, the cactus opens its pores
in order to respire.
185
00:18:44,180 --> 00:18:46,540
Oxygen goes out,
186
00:18:46,540 --> 00:18:50,300
carbon dioxide goes in,
187
00:18:50,300 --> 00:18:52,220
and so does Tristerix.
188
00:18:57,660 --> 00:19:03,020
Once within, its tissues spread
throughout the body of the cactus,
189
00:19:03,020 --> 00:19:06,860
sustained by the precious store
of water that they find there.
190
00:19:12,580 --> 00:19:14,620
Then, a year later,
191
00:19:14,620 --> 00:19:17,180
it breaks
through the cactus' skin...
192
00:19:23,940 --> 00:19:26,140
..and bursts into flower.
193
00:19:43,500 --> 00:19:46,540
Hummingbirds come to drink
their nectar
194
00:19:46,540 --> 00:19:49,180
and pollinate them as they do so.
195
00:19:59,860 --> 00:20:02,420
And, then, to complete the cycle,
196
00:20:02,420 --> 00:20:07,140
Tristerix produces hundreds
of white, eye-catching seeds,
197
00:20:07,140 --> 00:20:09,660
ready to be carried away by a bird
198
00:20:09,660 --> 00:20:12,420
to invade another cactus.
199
00:20:23,740 --> 00:20:26,540
The Karoo Desert in southern
Africa.
200
00:20:28,780 --> 00:20:31,060
And although it may look bare,
201
00:20:31,060 --> 00:20:35,540
its rocky ground contains an
unrivalled variety of plants that,
202
00:20:35,540 --> 00:20:39,060
one way or another,
store water in their tissues.
203
00:20:41,860 --> 00:20:44,980
They belong to many different
families, but as a group,
204
00:20:44,980 --> 00:20:47,500
they're known as succulents.
205
00:21:05,980 --> 00:21:09,580
Some are small and low
and barely distinguishable
206
00:21:09,580 --> 00:21:11,340
from their surroundings.
207
00:21:13,260 --> 00:21:16,140
These look like little pebbles.
208
00:21:18,060 --> 00:21:20,740
They resemble them so closely
209
00:21:20,740 --> 00:21:24,980
that animals which might be only too
glad to steal their water
210
00:21:24,980 --> 00:21:27,460
just pass them by.
211
00:21:30,500 --> 00:21:34,940
When rain does fall,
they absorb it and quickly expand.
212
00:21:37,300 --> 00:21:40,500
But even this
doesn't spoil their disguise.
213
00:21:40,500 --> 00:21:43,380
They just look like larger pebbles.
214
00:21:44,780 --> 00:21:46,900
Nor are they green.
215
00:21:46,900 --> 00:21:50,180
The cells on their top surface
are transparent
216
00:21:50,180 --> 00:21:52,540
and allow sunlight to pass through.
217
00:21:54,380 --> 00:21:56,540
Deep within and out of sight
218
00:21:56,540 --> 00:22:00,580
are the green cells
where photosynthesis occurs -
219
00:22:00,580 --> 00:22:04,900
the process which uses this light
to make food for the plant.
220
00:22:11,380 --> 00:22:14,260
When the time comes to reproduce,
however,
221
00:22:14,260 --> 00:22:18,620
the stone plant
abandons its disguise.
222
00:22:38,900 --> 00:22:42,140
And now, it blooms.
223
00:22:49,740 --> 00:22:54,060
The flowers open and close
every 24 hours.
224
00:23:02,900 --> 00:23:05,380
So for a few dangerous days,
225
00:23:05,380 --> 00:23:08,100
the plant advertises for pollinators
226
00:23:08,100 --> 00:23:10,940
before returning to life
as a pebble.
227
00:23:25,780 --> 00:23:29,380
Some desert plants
have developed a very different way
228
00:23:29,380 --> 00:23:31,260
of attracting pollinators.
229
00:23:33,060 --> 00:23:36,060
This is a Stapelia.
230
00:23:36,060 --> 00:23:41,540
It produces what is perhaps
the desert's strangest disguise.
231
00:23:41,540 --> 00:23:44,180
It uses water stored in its stems
232
00:23:44,180 --> 00:23:48,140
to grow buds
the size of tennis balls.
233
00:24:07,500 --> 00:24:12,020
The flower, once opened,
is called a desert starfish.
234
00:24:15,060 --> 00:24:18,500
Instead of releasing millions
of loose pollen grains
235
00:24:18,500 --> 00:24:20,460
as most flowers do,
236
00:24:20,460 --> 00:24:25,260
the desert starfish produces them
packed in five tiny sacks.
237
00:24:27,660 --> 00:24:30,140
But if its strategy is successful,
238
00:24:30,140 --> 00:24:34,140
just one of them
will produce hundreds of seeds...
239
00:24:37,940 --> 00:24:40,580
..and this depends on deception.
240
00:24:43,900 --> 00:24:46,140
The flower appears to have hair...
241
00:24:48,060 --> 00:24:50,980
..wrinkly skin...
242
00:24:53,100 --> 00:24:57,300
..and it produces a stench
like the carcass of a dead animal.
243
00:25:11,780 --> 00:25:14,580
And when a carrion fly
investigates...
244
00:25:17,060 --> 00:25:21,340
..the flower tempts a tiny sack
of pollen to its proboscis.
245
00:25:28,660 --> 00:25:33,460
It isn't easy to feed
with such encumbered mouthparts.
246
00:25:35,260 --> 00:25:38,380
But try as it might,
the fly can't get rid of it.
247
00:25:41,700 --> 00:25:44,660
And it's still there when the fly
leaves to try and feed
248
00:25:44,660 --> 00:25:47,260
from another bogus carcass.
249
00:25:52,740 --> 00:25:55,700
This time, however,
when its clamped-up proboscis
250
00:25:55,700 --> 00:25:59,740
slots into the flower,
the pollen sack is released.
251
00:26:06,020 --> 00:26:08,300
With pollination complete,
252
00:26:08,300 --> 00:26:10,660
the fly is no longer needed...
253
00:26:14,540 --> 00:26:16,700
..and just as well.
254
00:26:21,820 --> 00:26:25,780
Some deserts can be so dry
that plants must find techniques
255
00:26:25,780 --> 00:26:30,020
of surviving for long periods
without any water whatsoever.
256
00:26:31,260 --> 00:26:36,100
One of them
is to grow extremely slowly,
257
00:26:36,100 --> 00:26:40,500
and few plants grow more slowly
than this one -
258
00:26:40,500 --> 00:26:42,700
the creosote bush.
259
00:26:43,780 --> 00:26:46,180
It is inactive for most of its life
260
00:26:46,180 --> 00:26:50,340
and only wakes up and grows
for a brief period,
261
00:26:50,340 --> 00:26:53,300
if and when
there is a fall of rain.
262
00:26:56,860 --> 00:27:01,140
I've seen evidence of this
"grow slow" strategy for myself.
263
00:27:02,340 --> 00:27:06,340
40 years ago, I came here
to California's Mojave Desert
264
00:27:06,340 --> 00:27:09,020
to visit one particular plant.
265
00:27:10,260 --> 00:27:12,700
An individual
creosote bush
266
00:27:12,700 --> 00:27:15,740
tends to spread
not by setting seeds
267
00:27:15,740 --> 00:27:17,980
and producing a new generation,
268
00:27:17,980 --> 00:27:22,220
but by sending out new stems
around its base.
269
00:27:22,220 --> 00:27:27,980
This plant started growing between
10,000 and 12,000 years ago.
270
00:27:29,660 --> 00:27:31,940
That was in 1982.
271
00:27:35,100 --> 00:27:40,420
Since then, careful measurement
has shown that it has increased
272
00:27:40,420 --> 00:27:43,980
its size by less than one inch.
273
00:27:46,500 --> 00:27:50,260
Its ability to endure
is truly extraordinary.
274
00:27:54,780 --> 00:27:58,940
So efficient is creosote
at collecting what little rain
275
00:27:58,940 --> 00:28:02,380
falls here, that few other plants
can compete with it.
276
00:28:02,380 --> 00:28:06,820
As a result,
over the last 12,000 years,
277
00:28:06,820 --> 00:28:10,900
it's come to completely
dominate this landscape.
278
00:28:26,700 --> 00:28:31,220
The Chihuahuan Desert
in north Mexico.
279
00:28:31,220 --> 00:28:36,140
Here, one particular plant
plays the waiting game so well
280
00:28:36,140 --> 00:28:39,260
that it spends much of its life
looking dead
281
00:28:39,260 --> 00:28:41,540
and certainly not worth eating.
282
00:28:44,820 --> 00:28:48,660
And it can survive like this
for a decade.
283
00:28:56,300 --> 00:28:59,220
This is the resurrection plant.
284
00:29:02,300 --> 00:29:04,780
It's a kind of moss.
285
00:29:04,780 --> 00:29:09,220
It barely has roots, and it
certainly can't store much water,
286
00:29:09,220 --> 00:29:11,460
but it can travel.
287
00:29:18,020 --> 00:29:20,220
After a particularly long drought...
288
00:29:21,660 --> 00:29:23,620
..it breaks away from its roots...
289
00:29:26,180 --> 00:29:27,340
..and becomes...
290
00:29:28,980 --> 00:29:30,460
..a tumbleweed.
291
00:29:33,220 --> 00:29:35,220
{\an8}Blowing across the desert,
292
00:29:35,220 --> 00:29:38,300
{\an8}it can travel a mile in a week.
293
00:29:41,140 --> 00:29:43,780
With luck, it may find water.
294
00:29:47,020 --> 00:29:49,140
{\an8}THUNDER RUMBLES
295
00:29:51,140 --> 00:29:54,780
{\an8}Just a shower of rain
can bring it back to life.
296
00:29:59,700 --> 00:30:03,620
As its fronds soak up the water,
they unfurl.
297
00:30:17,740 --> 00:30:19,700
In its protected centre,
298
00:30:19,700 --> 00:30:21,700
it still has green cells
299
00:30:21,700 --> 00:30:24,460
which absorb both the water
and sunlight
300
00:30:24,460 --> 00:30:29,700
and rapidly produce the food
it needs to resume its growth.
301
00:30:34,620 --> 00:30:37,620
It will grow for just as long
as there is moisture...
302
00:30:42,420 --> 00:30:44,380
..but when that disappears...
303
00:30:45,980 --> 00:30:48,260
..it closes up once more
304
00:30:48,260 --> 00:30:51,140
and resumes its travels.
305
00:31:00,780 --> 00:31:03,380
Here in the Canyonlands of Utah
306
00:31:03,380 --> 00:31:05,900
lives a plant that has developed
307
00:31:05,900 --> 00:31:08,060
a finely-balanced relationship
308
00:31:08,060 --> 00:31:11,820
with the animals with which
it shares this dramatic desert.
309
00:31:16,780 --> 00:31:19,660
Rain does occasionally fall here
310
00:31:19,660 --> 00:31:23,460
and turns dust into mud.
311
00:31:27,940 --> 00:31:30,380
But that doesn't last long.
312
00:31:32,100 --> 00:31:35,460
A brief window of opportunity opens.
313
00:31:45,180 --> 00:31:47,460
Seeds that have been buried
for years
314
00:31:47,460 --> 00:31:50,540
may now be exposed to light
315
00:31:50,540 --> 00:31:52,980
and come to life.
316
00:32:09,660 --> 00:32:13,020
This is coyote tobacco.
317
00:32:25,780 --> 00:32:29,180
In just a few weeks,
it grows a metre tall
318
00:32:29,180 --> 00:32:31,980
and produces dozens of flowers.
319
00:32:38,460 --> 00:32:41,980
The night air becomes heavy
with their fragrance.
320
00:32:44,060 --> 00:32:46,300
Soon, they attract hawk moths
321
00:32:46,300 --> 00:32:48,260
which sip their nectar,
322
00:32:48,260 --> 00:32:50,540
and in doing so, pollinate them.
323
00:32:52,900 --> 00:32:55,980
But the moths also
lay their eggs on them.
324
00:33:12,340 --> 00:33:15,220
Soon, the caterpillars have hatched
325
00:33:15,220 --> 00:33:16,980
and are munching the leaves.
326
00:33:20,380 --> 00:33:24,900
Their nibbles expose the plant's
sap to the drying air.
327
00:33:27,900 --> 00:33:31,540
But the tobacco plant has a defence.
328
00:33:33,900 --> 00:33:37,460
The leaves under attack
produce nicotine.
329
00:33:41,820 --> 00:33:44,460
This chemical
sedates the caterpillars
330
00:33:44,460 --> 00:33:46,780
and slows them down.
331
00:33:52,260 --> 00:33:55,780
And what is more, it makes them give
off a particular scent...
332
00:33:58,980 --> 00:34:01,300
..one that summons others
333
00:34:01,300 --> 00:34:03,940
to come to the plant's aid.
334
00:34:05,820 --> 00:34:07,580
Big-eyed bugs,
335
00:34:07,580 --> 00:34:10,900
miniature assassins,
only two millimetres long...
336
00:34:12,780 --> 00:34:14,580
..and whiptail lizards.
337
00:34:16,380 --> 00:34:19,860
Big or small, they make
a meal of the caterpillars.
338
00:34:30,380 --> 00:34:32,540
It's certainly effective...
339
00:34:35,340 --> 00:34:38,860
..but there's more to this strategy
than meets the eye.
340
00:34:41,060 --> 00:34:45,980
When the leaf of a tobacco plant
is attacked by a caterpillar,
341
00:34:45,980 --> 00:34:50,660
all the rest of the leaves
prepare to defend themselves.
342
00:34:50,660 --> 00:34:53,740
But how does this leaf know
343
00:34:53,740 --> 00:34:56,980
that that leaf there
is under attack?
344
00:34:56,980 --> 00:35:00,660
Well, scientists here
in the United States
345
00:35:00,660 --> 00:35:04,300
have specially genetically modified
these tobacco plants
346
00:35:04,300 --> 00:35:07,140
so that under special
lighting conditions,
347
00:35:07,140 --> 00:35:11,580
this microscope can show us
exactly what is going on.
348
00:35:14,180 --> 00:35:17,620
I'm going to attack one
of the leaves of this plant
349
00:35:17,620 --> 00:35:21,100
with these tweezers which,
to the plant,
350
00:35:21,100 --> 00:35:23,940
will seem as if it's being nibbled
by a caterpillar.
351
00:35:38,580 --> 00:35:41,340
Signals are being transmitted
along the veins
352
00:35:41,340 --> 00:35:45,180
that link the leaf
to the rest of the plant.
353
00:35:45,180 --> 00:35:48,220
It's rather like
a very simple nervous system.
354
00:35:52,980 --> 00:35:54,900
From that initial injury,
355
00:35:54,900 --> 00:35:58,820
the whole of this little plant is
aware that something has happened.
356
00:36:03,420 --> 00:36:08,020
This signal warns each leaf
of the danger,
357
00:36:08,020 --> 00:36:10,940
so that it is ready
to produce nicotine
358
00:36:10,940 --> 00:36:13,100
the moment it's attacked.
359
00:36:15,860 --> 00:36:17,860
With this defence at the ready,
360
00:36:17,860 --> 00:36:20,540
the tobacco plant
can continue to grow
361
00:36:20,540 --> 00:36:23,420
until eventually, it produces seeds.
362
00:36:36,980 --> 00:36:39,700
It's particularly important
in deserts
363
00:36:39,700 --> 00:36:44,220
for seeds to be distributed as
widely as possible
364
00:36:44,220 --> 00:36:48,300
so that some will have a chance
of reaching moisture.
365
00:36:50,500 --> 00:36:54,540
And deserts have an excellent
agent to help them do that -
366
00:36:56,580 --> 00:36:58,260
the wind.
367
00:37:00,540 --> 00:37:05,340
Many seeds have adaptations
to help them exploit it.
368
00:37:05,340 --> 00:37:10,420
They have shell to protect
the seeds within from abrasion
369
00:37:10,420 --> 00:37:13,620
or wings to help them catch the air.
370
00:37:18,060 --> 00:37:20,420
As the temperature rises
throughout the day,
371
00:37:20,420 --> 00:37:22,660
desert winds increase in strength.
372
00:37:47,060 --> 00:37:48,980
Here in Arizona,
373
00:37:48,980 --> 00:37:54,180
the land is regularly swept by what
is known as a haboob.
374
00:37:54,180 --> 00:37:56,380
It's a giant sandstorm,
375
00:37:56,380 --> 00:38:00,180
but also, in effect, a seed storm.
376
00:38:07,740 --> 00:38:11,780
Countless millions of them
are swept up into the air.
377
00:38:17,700 --> 00:38:21,780
Some seeds can travel
thousands of miles on the wind...
378
00:38:24,780 --> 00:38:29,780
..so that plants may eventually
reach even the most isolated desert.
379
00:38:39,060 --> 00:38:41,820
Some have landed on an island
380
00:38:41,820 --> 00:38:45,260
in the middle of the world's
largest salt flat in Bolivia.
381
00:38:50,820 --> 00:38:56,060
In the Galapagos, they sprout
on fields of recently-erupted lava.
382
00:39:03,420 --> 00:39:08,940
They've even reached one of the most
inhospitable of all sites -
383
00:39:08,940 --> 00:39:12,660
the tiny island of San Pedro Martir,
384
00:39:12,660 --> 00:39:15,220
a scorched, lonely rock
385
00:39:15,220 --> 00:39:17,060
off the coast of Mexico.
386
00:39:21,300 --> 00:39:24,700
This is the home of
the giant cardon,
387
00:39:24,700 --> 00:39:27,540
a species of huge cactus
388
00:39:27,540 --> 00:39:30,100
that can weigh up to 12 tonnes.
389
00:39:38,220 --> 00:39:43,100
They're able to thrive here because
of an extraordinary partnership...
390
00:39:46,300 --> 00:39:50,340
..with brown and blue-footed
boobies.
391
00:39:55,260 --> 00:39:58,060
The cardones here
can become so broad
392
00:39:58,060 --> 00:40:02,300
that they provide cooling
shade for nesting birds.
393
00:40:13,820 --> 00:40:16,660
As the booby chicks get older,
394
00:40:16,660 --> 00:40:19,260
they repay the cardones...
395
00:40:25,060 --> 00:40:26,540
..with their droppings...
396
00:40:28,100 --> 00:40:29,500
..guano -
397
00:40:29,500 --> 00:40:33,740
the digestive remains
of vast shoals of fish.
398
00:40:35,380 --> 00:40:38,900
This guano is of such
strength and quantity
399
00:40:38,900 --> 00:40:42,060
that most plants
would be poisoned by it.
400
00:40:48,460 --> 00:40:51,780
These cardones, however,
have evolved the ability
401
00:40:51,780 --> 00:40:56,500
to tolerate the toxins in the
guano and digest the nutrients.
402
00:40:58,620 --> 00:41:02,420
As a result, the cacti
now grow in a dense forest
403
00:41:02,420 --> 00:41:04,020
over a million strong.
404
00:41:09,500 --> 00:41:12,860
But such relationships
are very finely balanced
405
00:41:12,860 --> 00:41:15,980
and can only too easily
tip into catastrophe...
406
00:41:19,420 --> 00:41:22,420
..as is now happening
in northern Zimbabwe.
407
00:41:26,620 --> 00:41:28,460
For six months of the year,
408
00:41:28,460 --> 00:41:32,700
the savannah here is kept lush
and green by daily rains.
409
00:41:37,980 --> 00:41:39,460
{\an8}ELEPHANTS TRUMPET
410
00:41:41,180 --> 00:41:44,060
{\an8}But when the rainy season is over,
411
00:41:44,060 --> 00:41:46,780
{\an8}it becomes as dry as any desert.
412
00:41:52,180 --> 00:41:57,140
So to survive here, trees must be
able to tolerate both conditions.
413
00:41:59,460 --> 00:42:04,380
And these giants
are adapted to do just that.
414
00:42:04,380 --> 00:42:06,460
They are baobabs.
415
00:42:14,340 --> 00:42:17,900
This one might be over
1,000 years old.
416
00:42:17,900 --> 00:42:21,500
It survives here in part
thanks to its ability
417
00:42:21,500 --> 00:42:24,500
to store thousands
of litres of water
418
00:42:24,500 --> 00:42:27,100
within the spongy wood of its trunk.
419
00:42:30,780 --> 00:42:33,980
But its battered surface is evidence
420
00:42:33,980 --> 00:42:36,820
of a very finely-balanced
relationship.
421
00:42:38,700 --> 00:42:40,620
These huge trees
422
00:42:40,620 --> 00:42:44,580
are a focus for animals
of all kinds.
423
00:42:48,260 --> 00:42:51,900
And they're particularly
important for elephants.
424
00:42:56,420 --> 00:43:00,180
In the wet season,
they eat the baobab's fruit
425
00:43:00,180 --> 00:43:02,660
and disperse the
seeds in their dung.
426
00:43:08,180 --> 00:43:10,580
Now as the dry season begins...
427
00:43:12,180 --> 00:43:15,340
..they migrate
to distant watering holes.
428
00:43:19,660 --> 00:43:22,220
The baobabs have damp inner wood...
429
00:43:23,700 --> 00:43:29,380
..and the elephants use it to
quench their thirst on the journey.
430
00:43:48,020 --> 00:43:51,780
This relationship can only
work because baobabs
431
00:43:51,780 --> 00:43:55,020
have a remarkable
ability to heal themselves.
432
00:44:13,900 --> 00:44:16,900
Between each damaging attack,
433
00:44:16,900 --> 00:44:20,620
they expand their spongy
wood and grow new skin.
434
00:44:25,020 --> 00:44:29,140
And they've done this
time and time again over centuries.
435
00:44:33,820 --> 00:44:38,020
Today, however, it's harder
for the baobabs to recover
436
00:44:38,020 --> 00:44:42,980
as dry seasons become longer
and drier due to climate change.
437
00:44:45,140 --> 00:44:48,980
Not only that, but the elephants
are forced to take ever more wood
438
00:44:48,980 --> 00:44:51,820
from the trees in order to survive.
439
00:44:57,460 --> 00:44:59,220
In some parts of Africa,
440
00:44:59,220 --> 00:45:02,100
many of the largest
and oldest baobabs
441
00:45:02,100 --> 00:45:04,540
have fallen in the last decade.
442
00:45:17,540 --> 00:45:20,740
The loss of a vital species
like the baobab
443
00:45:20,740 --> 00:45:23,780
strikes a blow at all life
in the desert.
444
00:45:28,780 --> 00:45:30,660
In these hostile lands,
445
00:45:30,660 --> 00:45:35,180
few living organisms can survive
without help from others.
446
00:45:40,140 --> 00:45:43,580
You can find an extraordinary
illustration of this
447
00:45:43,580 --> 00:45:46,100
in Arizona's saguaro country.
448
00:45:53,500 --> 00:45:55,860
If you wander off
the beaten track here,
449
00:45:55,860 --> 00:45:59,340
you may be lucky enough
to find one of these.
450
00:45:59,340 --> 00:46:02,100
It might look like an old boot,
451
00:46:02,100 --> 00:46:06,340
but in fact,
it's part of a saguaro cactus.
452
00:46:06,340 --> 00:46:09,620
Almost every saguaro has one.
453
00:46:09,620 --> 00:46:11,220
There's one up there.
454
00:46:15,660 --> 00:46:19,620
It has been produced
indirectly by woodpeckers,
455
00:46:19,620 --> 00:46:23,740
which regularly dig homes for
themselves in the bloated trunks
456
00:46:23,740 --> 00:46:25,460
of the saguaros.
457
00:46:38,660 --> 00:46:40,580
In the next six months,
458
00:46:40,580 --> 00:46:43,460
the cactus heals the wound
459
00:46:43,460 --> 00:46:47,700
and so creates a safe,
cool, and watertight nest hole.
460
00:46:50,500 --> 00:46:53,180
Its tough lining
will persist for years,
461
00:46:53,180 --> 00:46:57,260
even after the cactus itself
has died and rotted away.
462
00:47:01,380 --> 00:47:06,300
A single saguaro may hold several
of these extraordinary homes.
463
00:47:09,140 --> 00:47:15,060
So over its lifetime, it may provide
accommodation for some 3,000 chicks
464
00:47:15,060 --> 00:47:18,140
of several different species.
465
00:47:24,340 --> 00:47:26,980
But in the long term,
the saguaro benefits,
466
00:47:26,980 --> 00:47:29,860
as their lodgers repay the cactus
467
00:47:29,860 --> 00:47:32,820
by pollinating its flowers...
468
00:47:34,260 --> 00:47:36,780
..and dispersing its seeds.
469
00:47:44,260 --> 00:47:46,380
It's relationships like these
470
00:47:46,380 --> 00:47:48,380
that enable life to flourish
471
00:47:48,380 --> 00:47:51,460
in some of the world's
harshest landscapes.
472
00:48:04,980 --> 00:48:06,980
Over millions of years,
473
00:48:06,980 --> 00:48:10,100
plants have become superbly adapted
474
00:48:10,100 --> 00:48:12,340
to hostile desert conditions.
475
00:48:12,340 --> 00:48:15,820
But it's a very
finely-balanced existence
476
00:48:15,820 --> 00:48:18,940
and one that makes them
uniquely vulnerable.
477
00:48:21,500 --> 00:48:25,220
However, our growing understanding
of the complex ways
478
00:48:25,220 --> 00:48:28,860
by which desert animals and plants
rely on one another
479
00:48:28,860 --> 00:48:33,100
is now helping us to understand
how best we can protect them.
480
00:48:37,940 --> 00:48:42,340
90 years ago, a photograph
was taken from this very spot
481
00:48:42,340 --> 00:48:45,660
that shows a population
of saguaro cactus
482
00:48:45,660 --> 00:48:48,620
that was very different
from what it is today.
483
00:48:51,380 --> 00:48:52,820
In the last 50 years,
484
00:48:52,820 --> 00:48:57,220
the population of saguaros
here has greatly diminished,
485
00:48:57,220 --> 00:49:00,780
not because of a direct
assault on the cactus,
486
00:49:00,780 --> 00:49:03,620
but because many of the
shade-giving nurse trees
487
00:49:03,620 --> 00:49:08,460
were harvested for firewood, leaving
young saguaro to die in the sun.
488
00:49:13,620 --> 00:49:16,580
Now that this relationship
is understood
489
00:49:16,580 --> 00:49:18,700
and the nurse trees are protected,
490
00:49:18,700 --> 00:49:23,580
there are already signs
that the saguaro are recovering.
491
00:49:27,020 --> 00:49:32,060
Wherever there's a desert, plants
have evolved to meet its challenge.
492
00:49:33,780 --> 00:49:36,260
But everywhere, they need our help.
493
00:49:38,420 --> 00:49:40,140
As we understand more about them
494
00:49:40,140 --> 00:49:43,140
and their intimate and
complex relationships...
495
00:49:44,660 --> 00:49:49,220
..we will be better able to
protect them and all life
496
00:49:49,220 --> 00:49:53,860
in these beautiful but
increasingly fragile worlds.
497
00:50:08,180 --> 00:50:11,340
The most remote shoot
for the deserts team
498
00:50:11,340 --> 00:50:13,980
is to the island of
San Pedro Martir
499
00:50:13,980 --> 00:50:16,300
in the Sea of Cortez, Mexico.
500
00:50:19,700 --> 00:50:22,100
They are to film the giant cacti
501
00:50:22,100 --> 00:50:24,780
that have found a unique way
to thrive here.
502
00:50:27,580 --> 00:50:31,580
It takes 48 hours
to travel the 260 miles...
503
00:50:32,940 --> 00:50:35,500
..over unpleasantly choppy seas.
504
00:50:41,820 --> 00:50:43,860
{\an8}It's not made some of
us feel very well.
505
00:50:43,860 --> 00:50:46,980
{\an8}I think one of us is quite seasick.
506
00:50:48,460 --> 00:50:50,980
It's nothing but big blue out there,
507
00:50:50,980 --> 00:50:53,620
and the island is
somewhere in that direction.
508
00:50:53,620 --> 00:50:55,100
Can't see it yet.
509
00:50:56,940 --> 00:50:59,100
As they draw close to the island,
510
00:50:59,100 --> 00:51:04,220
there's a spectacular reminder of
how rich life in the sea is here.
511
00:51:04,220 --> 00:51:07,180
Oh, look in front of us!
Look at that for a pod!
512
00:51:08,660 --> 00:51:10,460
Oh! They're everywhere!
513
00:51:16,460 --> 00:51:17,740
Show us the way.
514
00:51:24,700 --> 00:51:28,620
Meeting them here
is desert scientist Ben Wilder.
515
00:51:30,060 --> 00:51:33,100
It's through his research
that the team first heard
516
00:51:33,100 --> 00:51:36,420
about the island's
peculiar residents.
517
00:51:36,420 --> 00:51:39,020
{\an8}I'll never forget
the first time I came
518
00:51:39,020 --> 00:51:41,660
{\an8}to, actually, exactly where
we're standing right now.
519
00:51:41,660 --> 00:51:44,100
{\an8}It was April of 2006,
520
00:51:44,100 --> 00:51:46,660
and saw this view.
521
00:51:46,660 --> 00:51:52,460
And it both settled in my
heart and captivated my mind.
522
00:51:52,460 --> 00:51:57,940
And so that started a process
of trying to understand,
523
00:51:57,940 --> 00:52:00,460
you know, what can produce this?
524
00:52:02,500 --> 00:52:06,340
The secret is in the
relationship between the cactus
525
00:52:06,340 --> 00:52:09,980
and a type of
sea bird called a booby.
526
00:52:12,140 --> 00:52:14,780
{\an8}All the boobies that we need
to film are right up there
527
00:52:14,780 --> 00:52:16,020
{\an8}at the top of the island.
528
00:52:16,020 --> 00:52:18,900
So, it's going to be
a bit of a scramble.
529
00:52:20,540 --> 00:52:24,100
The crew soon discover how
harsh the conditions are here.
530
00:52:25,780 --> 00:52:28,180
I'm pretty tired. It's pretty hot.
531
00:52:28,180 --> 00:52:29,500
It's a great view.
532
00:52:36,460 --> 00:52:37,940
There's very few places on Earth
533
00:52:37,940 --> 00:52:39,820
where you're going to
see this many cactus.
534
00:52:39,820 --> 00:52:43,020
I mean, it's absolutely amazing.
535
00:52:43,020 --> 00:52:45,380
I would say this is the only
place you're going to see this.
536
00:52:45,380 --> 00:52:47,100
Well, there you go, then.
537
00:52:48,940 --> 00:52:52,860
Ben's research is uncovering
the ingenious ways the cacti
538
00:52:52,860 --> 00:52:55,460
have adapted to the conditions here.
539
00:52:56,940 --> 00:52:59,860
The waters just offshore here
are some of the most productive
540
00:52:59,860 --> 00:53:01,420
marine waters in the world.
541
00:53:01,420 --> 00:53:04,420
And so it's kind of an ideal
habitat for sea birds to roost.
542
00:53:04,420 --> 00:53:08,420
But when they do so,
they deposit tonnes of guano.
543
00:53:08,420 --> 00:53:12,460
And so those nutrients, really high
in nitrogen and phosphorus,
544
00:53:12,460 --> 00:53:16,300
actually are toxic
to most plant species.
545
00:53:16,300 --> 00:53:19,500
The cardones thrive because
they're uniquely able
546
00:53:19,500 --> 00:53:24,060
to process the guano and extract
what they need to fuel their growth.
547
00:53:26,780 --> 00:53:29,340
One of the first shots
the crew need to get
548
00:53:29,340 --> 00:53:32,180
is of the boobies
nesting under the cacti.
549
00:53:33,780 --> 00:53:37,380
The lack of predators means
the birds aren't afraid of people.
550
00:53:37,380 --> 00:53:41,860
It should make filming
them up close a bit easier.
551
00:53:41,860 --> 00:53:43,500
That's the theory.
552
00:53:43,500 --> 00:53:46,380
So we've positioned this camera here
to try and get a good perspective
553
00:53:46,380 --> 00:53:48,580
on the chick on the nest.
554
00:53:48,580 --> 00:53:51,460
It's taken quite a
liking to our camera.
555
00:53:51,460 --> 00:53:53,980
Let's hope he doesn't break it.
556
00:53:59,660 --> 00:54:00,820
Bull's-eye.
557
00:54:00,820 --> 00:54:03,500
It's pooed right on
the front of the lens!
558
00:54:03,500 --> 00:54:05,900
It's kind of a shot we need,
but unfortunately,
559
00:54:05,900 --> 00:54:07,780
my camera wasn't rolling
at the time it did it.
560
00:54:07,780 --> 00:54:09,820
So now, I've just got a dirty lens.
561
00:54:12,780 --> 00:54:16,900
After a thorough lens clean,
Ollie eventually gets the shot
562
00:54:16,900 --> 00:54:21,340
to reveal the extraordinary
relationship between bird and plant.
563
00:54:25,420 --> 00:54:27,940
But it's not just the
bird guano that influence
564
00:54:27,940 --> 00:54:29,620
how the cardones grow.
565
00:54:30,700 --> 00:54:34,180
They're way shorter,
they're dwarfed here,
566
00:54:34,180 --> 00:54:35,780
throughout the rest of their range,
567
00:54:35,780 --> 00:54:38,380
they usually get in
upwards of 50-60 feet.
568
00:54:38,380 --> 00:54:42,460
But here, on average,
they're 20-24 feet in height.
569
00:54:42,460 --> 00:54:46,100
They stop growing up,
and they grow out.
570
00:54:47,780 --> 00:54:51,500
Ben's research suggests
that they go wide here
571
00:54:51,500 --> 00:54:54,740
as an adaptation
to the violent winds.
572
00:54:54,740 --> 00:54:57,860
Too tall, and they'd blow over.
573
00:54:57,860 --> 00:55:01,700
A gusting wind isn't
helping the drone crew, either.
574
00:55:01,700 --> 00:55:03,340
{\an8}We really need it
to calm down a bit,
575
00:55:03,340 --> 00:55:05,340
{\an8}otherwise it's
going to be impossible.
576
00:55:11,580 --> 00:55:12,940
{\an8}WIND GUSTS
577
00:55:29,580 --> 00:55:32,980
On the Sonoran mainland, where the
cardon is also found,
578
00:55:32,980 --> 00:55:37,060
you have on average between
50 to 150 plants per hectare.
579
00:55:37,060 --> 00:55:42,860
Here on this island, you have
over 2,500 plants per hectare.
580
00:55:42,860 --> 00:55:46,780
A lull in the wind, and the
team get the chance to reveal
581
00:55:46,780 --> 00:55:49,620
the remarkable density of the cacti,
582
00:55:49,620 --> 00:55:53,820
almost 20 times greater
than anywhere else.
583
00:55:53,820 --> 00:55:56,940
It appears that here
they're doing very well.
584
00:55:58,220 --> 00:56:01,220
But even this island isn't isolated
585
00:56:01,220 --> 00:56:03,660
from the effects
of a changing planet.
586
00:56:04,940 --> 00:56:06,740
Every cactus you see there,
587
00:56:06,740 --> 00:56:10,900
its body is filled with
nutrients from the sea.
588
00:56:10,900 --> 00:56:14,940
Given that we know that the
cardones are linked to the ocean,
589
00:56:14,940 --> 00:56:18,380
what happens in the oceans
affects what happens to the cardon.
590
00:56:18,380 --> 00:56:22,380
So a concern we have right now is
that there's a lot of overfishing,
591
00:56:22,380 --> 00:56:27,100
and we know there are less sea birds
here than there were 20 years ago.
592
00:56:27,100 --> 00:56:31,340
And we have reason to believe
then that will ripple and affect
593
00:56:31,340 --> 00:56:34,660
the nutrients that fuel
the cardones as well.
594
00:56:36,620 --> 00:56:40,220
This finely-balanced relationship
is at risk,
595
00:56:40,220 --> 00:56:42,940
and knowing that
makes leaving the island
596
00:56:42,940 --> 00:56:45,620
particularly thought provoking
for the crew.
597
00:56:47,020 --> 00:56:49,180
The cardones look beautiful.
598
00:56:49,180 --> 00:56:51,380
I've never seen so
many cactus in my life.
599
00:56:51,380 --> 00:56:53,300
It's absolutely amazing.
600
00:56:53,300 --> 00:56:55,940
I'm just hoping that when
we leave this place,
601
00:56:55,940 --> 00:56:59,980
it stays as it is, and things
don't affect it that are negative.
602
00:56:59,980 --> 00:57:03,260
It's an absolutely wonderful thing,
and, yeah, I don't want to go.
603
00:57:03,260 --> 00:57:04,580
I want to stay.
604
00:57:05,900 --> 00:57:10,740
This remote cactus forest is
a reminder of the adaptability
605
00:57:10,740 --> 00:57:15,020
of plants that enables them
to establish green worlds
606
00:57:15,020 --> 00:57:17,300
almost anywhere on Earth.
607
00:57:21,940 --> 00:57:24,700
Next time on The Green Planet...
608
00:57:24,700 --> 00:57:28,060
..our extraordinary relationship
with plants.
609
00:57:30,380 --> 00:57:32,260
From those who eat...
610
00:57:35,620 --> 00:57:37,380
..to those we help...
611
00:57:39,420 --> 00:57:42,180
..plants are our greatest allies.
612
00:57:45,140 --> 00:57:48,620
The Open University
has produced a poster
613
00:57:48,620 --> 00:57:53,140
that explores the vital role
that plants have for our planet.
614
00:57:53,140 --> 00:57:55,460
{\an8}To order your free copy call...
615
00:57:59,500 --> 00:58:01,300
{\an8}Or go to...
616
00:58:05,460 --> 00:58:07,940
{\an8}..and follow the links
to the Open University.
49768
Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.