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David Attenborough:
The taklamakan desert
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00:00:35,040 --> 00:00:36,920
in northern China.
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00:00:38,240 --> 00:00:41,240
A constantly shifting
landscape of sand...
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00:00:41,360 --> 00:00:43,960
(Wind whooshes)
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00:00:45,560 --> 00:00:48,800
Temperatures that swing
from minus 20...
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00:00:48,920 --> 00:00:50,400
(Sand rustles)
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00:00:50,520 --> 00:00:52,880
To more than
40 degrees centigrade...
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00:00:54,360 --> 00:00:56,080
And most critically,
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00:00:56,200 --> 00:01:00,240
almost entirely without rain.
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00:01:07,480 --> 00:01:10,240
Yet, here on the dunes...
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00:01:16,960 --> 00:01:19,480
A euphrates poplar tree.
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00:01:26,720 --> 00:01:29,560
And it's not alone.
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00:01:30,960 --> 00:01:35,440
Some of these trees have
lived here for 1,000 years.
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00:01:38,560 --> 00:01:40,920
They have exceptionally
long roots
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00:01:41,040 --> 00:01:43,440
with which to collect water.
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00:01:43,560 --> 00:01:45,280
And what is more,
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00:01:45,400 --> 00:01:48,400
those roots are connected to
neighbouring trees
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00:01:48,520 --> 00:01:50,600
so that if one strikes water...
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00:01:51,920 --> 00:01:53,880
Others can share it.
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00:01:55,800 --> 00:01:58,560
In every desert
across the planet,
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00:01:58,680 --> 00:02:03,160
plants have found ways to
not only survive...
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00:02:03,280 --> 00:02:04,600
But flourish.
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00:02:20,760 --> 00:02:25,880
This is the gran desierto of
Mexico and the United States.
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00:02:37,080 --> 00:02:41,600
These dunes may appear to be
totally barren.
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00:02:41,720 --> 00:02:45,400
In fact, they are full of life.
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00:02:45,520 --> 00:02:48,240
In the sands beneath my feet,
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00:02:48,360 --> 00:02:51,400
there are seeds
of many different kinds.
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00:02:51,520 --> 00:02:54,120
In fact, you could say that
the dune itself
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00:02:54,240 --> 00:02:55,920
is one great seed bank,
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00:02:56,040 --> 00:02:57,680
and when it rains,
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00:02:57,800 --> 00:02:59,880
it bursts into life.
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00:03:00,000 --> 00:03:03,120
(Thunder crashes and rolls)
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00:03:05,960 --> 00:03:09,920
But rain may come
only once a decade,
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00:03:10,040 --> 00:03:14,920
and even then, the long-awaited
storm may be very brief.
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00:03:18,560 --> 00:03:22,160
So seeds must respond
immediately.
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00:03:36,160 --> 00:03:37,440
This is sand verbena.
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00:03:37,560 --> 00:03:41,880
It can grow from a seed to a
sweetly scented flowering plant
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00:03:42,000 --> 00:03:44,640
in just a few weeks.
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00:03:51,080 --> 00:03:53,280
Primroses and many other plants
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00:03:53,400 --> 00:03:58,200
soon join the race to flower
before the sand dries.
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00:04:01,400 --> 00:04:06,000
Desert blooms like this,
however, are rare.
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00:04:08,920 --> 00:04:13,520
This is the first year
for 20 years.
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00:04:18,280 --> 00:04:21,720
The combination of vibrant
colour and powerful scent
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00:04:21,840 --> 00:04:24,560
attracts migrating pollinators,
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00:04:24,680 --> 00:04:27,800
such as these painted lady
butterflies,
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00:04:27,920 --> 00:04:31,920
which fly into the middle
of what were only recently
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00:04:32,040 --> 00:04:33,440
barren dunes.
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00:04:34,520 --> 00:04:37,800
Everything is rushing
to complete their lives
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00:04:37,920 --> 00:04:40,600
before the moisture has gone.
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00:04:48,480 --> 00:04:50,720
Such spectacular blooms
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00:04:50,840 --> 00:04:53,760
transform deserts
all around the world...
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00:05:03,840 --> 00:05:06,760
From the atacama
in South America...
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00:05:08,600 --> 00:05:12,120
To the dusty plains
of Southern Africa.
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00:05:30,760 --> 00:05:34,720
Rain in deserts, however,
never lasts long,
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00:05:34,840 --> 00:05:38,880
and all too soon, the flowers
wither and die.
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00:05:44,440 --> 00:05:48,200
But not before they've produced
the next generation...
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00:05:52,880 --> 00:05:57,960
The seeds that will now wait
in the sand for the next rains.
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00:05:58,080 --> 00:06:01,360
(Sand rustles)
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00:06:03,480 --> 00:06:06,240
In the sonoran desert
of North America,
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00:06:06,360 --> 00:06:08,400
the huge saguaro cacti
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00:06:08,520 --> 00:06:10,240
have a different strategy.
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00:06:10,360 --> 00:06:13,040
They store water in quantity...
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00:06:14,080 --> 00:06:16,320
And can live to a great age.
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00:06:17,720 --> 00:06:19,800
But in their early years,
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00:06:19,920 --> 00:06:22,240
they are extremely vulnerable.
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00:06:26,160 --> 00:06:30,720
This little saguaro cactus
is about ten years old.
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00:06:30,840 --> 00:06:34,960
When they're really small
and growing out in the open,
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00:06:35,080 --> 00:06:38,760
there's a real chance that
they may shrivel up and die.
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00:06:38,880 --> 00:06:41,360
But this one has been lucky.
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00:06:41,480 --> 00:06:45,720
It's been growing in the shade
of this mesquite tree,
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00:06:45,840 --> 00:06:50,240
and it's got a very good chance
of surviving to maturity.
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00:06:51,720 --> 00:06:55,800
The young saguaro is protected
by the mesquite's branches.
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00:06:56,880 --> 00:06:59,320
They halve the amount of
scorching sunlight
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00:06:59,440 --> 00:07:01,000
reaching the cactus...
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00:07:02,240 --> 00:07:04,200
And so keep it cool.
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00:07:06,520 --> 00:07:09,040
And the mesquite's
extremely long roots
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00:07:09,160 --> 00:07:10,680
draw up water,
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00:07:10,800 --> 00:07:14,360
bringing it within reach
of the young saguaro.
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00:07:18,560 --> 00:07:22,400
So the mesquite is known as
a "nurse plant",
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00:07:22,520 --> 00:07:24,840
and a very effective one it is,
too.
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00:07:26,160 --> 00:07:28,520
In fact,
this particular mesquite
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00:07:28,640 --> 00:07:32,320
has already nurtured seven
young saguaros
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00:07:32,440 --> 00:07:34,120
over the past 30 years.
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00:07:38,760 --> 00:07:40,440
As a young cactus grows,
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00:07:40,560 --> 00:07:43,200
it needs the protection
of its nurse plant
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00:07:43,320 --> 00:07:45,640
not only from the heat,
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00:07:45,760 --> 00:07:49,240
but from the other hazards
of desert life.
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00:07:51,480 --> 00:07:56,440
Temperatures can drop to
minus 10 degrees overnight...
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00:07:58,600 --> 00:08:01,160
And very occasionally,
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00:08:01,280 --> 00:08:03,400
it even snows.
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00:08:09,840 --> 00:08:14,400
If the water stored inside
a young cactus should freeze,
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00:08:14,520 --> 00:08:16,440
the cactus will die.
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00:08:18,600 --> 00:08:20,760
But the nurse plant traps
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00:08:20,880 --> 00:08:23,240
a blanket of slightly warmer
air around it,
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00:08:23,360 --> 00:08:26,240
just enough to keep it alive.
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00:08:28,720 --> 00:08:32,240
Eventually, saguaros outgrow
their nurses,
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00:08:32,360 --> 00:08:35,320
but by that time,
they are robust enough
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00:08:35,440 --> 00:08:38,000
to face the elements
by themselves.
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00:08:41,680 --> 00:08:44,440
No matter how old
a desert plant is,
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00:08:44,560 --> 00:08:47,240
water is always precious,
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00:08:47,360 --> 00:08:49,720
whether gathered from
melting snow...
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00:08:49,840 --> 00:08:51,760
(Thunder crashes and rolls)
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00:08:54,480 --> 00:08:56,600
Or a shower of rain.
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00:09:01,880 --> 00:09:05,320
So cacti have developed
extraordinary adaptations
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00:09:05,440 --> 00:09:08,120
that enable them
to not only collect water...
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00:09:09,320 --> 00:09:11,360
But to retain it.
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00:09:15,400 --> 00:09:18,200
Instead of leaves, which would
lose precious moisture
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00:09:18,320 --> 00:09:20,040
through evaporation,
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they have spines.
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00:09:23,360 --> 00:09:26,360
Each spine has a tiny pad
at its base
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00:09:26,480 --> 00:09:28,720
where the water is absorbed...
112
00:09:30,320 --> 00:09:34,440
And then stored in
the great swollen trunk.
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00:09:37,160 --> 00:09:41,920
A large saguaro can hold
5,000 litres of water...
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00:09:43,160 --> 00:09:44,400
And is able to do so
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00:09:44,520 --> 00:09:48,560
because it has another
special adaptation.
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00:09:50,360 --> 00:09:52,280
(Slow creaking)
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The ridges on its surface
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are like the pleats
on an accordion.
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00:10:01,360 --> 00:10:04,360
They allow the saguaro
to change its shape.
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00:10:06,360 --> 00:10:07,960
After rain has fallen,
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00:10:08,080 --> 00:10:10,160
the pleats expand,
122
00:10:10,280 --> 00:10:12,920
and the saguaro
fills up its water tank.
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00:10:17,280 --> 00:10:20,760
In the dry times,
it uses its water
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00:10:20,880 --> 00:10:23,040
to grow, produce flowers,
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00:10:23,160 --> 00:10:26,160
and, eventually, seeds.
126
00:10:28,800 --> 00:10:31,920
Fully loaded with thousands
of litres of water,
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00:10:32,040 --> 00:10:35,120
this saguaro won't need
to drink a single drop
128
00:10:35,240 --> 00:10:37,120
for another year.
129
00:10:38,600 --> 00:10:43,520
But such valuable stores
of water attract thieves.
130
00:10:45,000 --> 00:10:48,720
Now the spines' function
changes from collecting...
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00:10:49,840 --> 00:10:51,280
To guarding.
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00:10:53,720 --> 00:10:57,920
The spines of some species
are a quarter of a metre long.
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00:11:03,720 --> 00:11:06,600
Others are needle-like barbs
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00:11:06,720 --> 00:11:08,960
that grow in clusters,
135
00:11:09,080 --> 00:11:11,320
and easily break off
in the skin of any animal
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00:11:11,440 --> 00:11:12,920
that touches them.
137
00:11:14,280 --> 00:11:16,360
But perhaps
the most vicious cacti
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00:11:16,480 --> 00:11:19,640
belong to a group called
the chollas.
139
00:11:20,880 --> 00:11:24,640
This is called
a Teddy bear cholla
140
00:11:24,760 --> 00:11:28,280
because of the thick coating
of spines on it.
141
00:11:28,400 --> 00:11:30,960
But don't be deceived by
the name.
142
00:11:31,080 --> 00:11:35,000
There is nothing cuddly about
this particular Teddy bear.
143
00:11:35,120 --> 00:11:39,080
In fact, it's the most
dangerous plant in the desert,
144
00:11:39,200 --> 00:11:42,480
and I wouldn't dream of putting
my hand anywhere near it
145
00:11:42,600 --> 00:11:44,840
without proper protection.
146
00:11:47,680 --> 00:11:49,160
Brush against it...
147
00:11:49,280 --> 00:11:51,480
This can happen. Ow!
148
00:11:51,600 --> 00:11:53,840
This can happen.
Even with this glove on,
149
00:11:53,960 --> 00:11:56,360
one of them has just
gone through, I can feel it.
150
00:11:56,480 --> 00:11:58,520
It's quite painful.
151
00:12:00,040 --> 00:12:01,480
Look closely at the spine
152
00:12:01,600 --> 00:12:04,880
and you can see very clearly
why they're so dangerous.
153
00:12:05,000 --> 00:12:08,040
Each is like
a splinter of glass,
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00:12:08,160 --> 00:12:10,160
sharp enough to Pierce flesh.
155
00:12:11,680 --> 00:12:14,280
And they're covered
with backward-pointing barbs.
156
00:12:15,800 --> 00:12:18,600
So getting them out,
even with a pair of pliers,
157
00:12:18,720 --> 00:12:20,280
is quite hard.
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00:12:20,400 --> 00:12:24,040
This is not pleasant at all.
159
00:12:24,160 --> 00:12:26,200
They won't come off without...
160
00:12:27,920 --> 00:12:29,840
Oh, look at that.
161
00:12:31,720 --> 00:12:35,240
It's hard to imagine a more
aggressive defence than this.
162
00:12:35,360 --> 00:12:38,960
And it makes both the plant
and its buds
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00:12:39,080 --> 00:12:40,760
virtually in vulnerable.
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00:12:52,000 --> 00:12:55,240
Most animals know to keep clear.
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00:12:55,360 --> 00:12:57,080
(Sniffs)
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00:12:58,720 --> 00:13:01,240
Cholla buds
grow like tiny barrels
167
00:13:01,360 --> 00:13:04,560
from the top of the adult plant
and then drop off.
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00:13:06,120 --> 00:13:08,000
(Barks)
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00:13:14,520 --> 00:13:18,120
If the young cholla
put down roots here,
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00:13:18,240 --> 00:13:21,160
it would compete
with its parent for water.
171
00:13:23,280 --> 00:13:24,720
(Barking)
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00:13:24,840 --> 00:13:26,200
Night falls...
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00:13:27,440 --> 00:13:29,960
And this one is on the move.
174
00:13:39,760 --> 00:13:41,280
A pack rat.
175
00:13:41,400 --> 00:13:43,960
She knows how to
deal with a cholla.
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00:13:49,400 --> 00:13:52,080
She avoids the spines
by gripping it
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00:13:52,200 --> 00:13:54,800
at the place where it broke off
from its parent.
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00:14:00,200 --> 00:14:02,120
And she works fast.
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00:14:05,040 --> 00:14:07,360
There are pack rat hunters here.
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00:14:16,640 --> 00:14:21,120
She uses the cholla to build
a spiny wall around her nest.
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00:14:37,520 --> 00:14:41,360
The flesh of the cholla
supplies her with water...
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00:14:42,920 --> 00:14:46,920
And the severed spines
further reinforce the defences.
183
00:14:59,800 --> 00:15:01,200
This cholla bud...
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00:15:02,760 --> 00:15:04,120
Might be next.
185
00:15:08,080 --> 00:15:10,680
But one accidental nudge...
186
00:15:15,040 --> 00:15:17,200
And it escapes.
187
00:15:39,560 --> 00:15:41,560
(Spines crackle)
188
00:15:44,200 --> 00:15:46,800
The bud starts
to put down roots...
189
00:15:54,960 --> 00:15:58,200
So the cholla,
thanks to the pack rats,
190
00:15:58,320 --> 00:15:59,920
finds new territory...
191
00:16:01,360 --> 00:16:03,400
And sets about claiming it.
192
00:16:09,240 --> 00:16:11,160
- (Birdsong)
- (Insects buzzing)
193
00:16:11,280 --> 00:16:15,120
Few plants deal with
the problems of desert living
194
00:16:15,240 --> 00:16:16,880
better than cacti.
195
00:16:18,520 --> 00:16:22,400
There are almost 2,000
different species of them.
196
00:16:22,520 --> 00:16:26,960
They're spread across the
deserts of the American west,
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00:16:27,080 --> 00:16:30,760
from Arizona all the way
to Mexico and beyond.
198
00:16:34,960 --> 00:16:36,480
In South America,
199
00:16:36,600 --> 00:16:40,080
the andes catch virtually all
the rain-carrying clouds
200
00:16:40,200 --> 00:16:42,160
that blow in from the pacific...
201
00:16:44,520 --> 00:16:47,240
And that has created
to the east of them
202
00:16:47,360 --> 00:16:49,720
the world's driest desert -
203
00:16:49,840 --> 00:16:51,440
the atacama.
204
00:16:58,240 --> 00:16:59,880
In the desert world,
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00:17:00,000 --> 00:17:02,600
water thieves
can come in many forms,
206
00:17:02,720 --> 00:17:06,720
to exploit even the smallest
chink in a plant's defence.
207
00:17:12,960 --> 00:17:16,160
One of the strangest
travels within the gut
208
00:17:16,280 --> 00:17:18,320
of a fruit-eating mockingbird.
209
00:17:20,240 --> 00:17:23,120
(Burbling call)
210
00:17:25,160 --> 00:17:26,680
These are the seeds...
211
00:17:28,240 --> 00:17:29,760
Of tristerix,
212
00:17:29,880 --> 00:17:31,680
a kind of mistletoe.
213
00:17:34,720 --> 00:17:40,160
Their goal is the water
inside this hedgehog cactus.
214
00:17:41,760 --> 00:17:44,640
Using the spines as anchors,
215
00:17:44,760 --> 00:17:47,720
the seeds start to germinate.
216
00:17:51,000 --> 00:17:52,720
Each produces a long probe
217
00:17:52,840 --> 00:17:56,960
with which to try and locate
the cactus's skin.
218
00:17:58,720 --> 00:18:02,160
For most, that's a stretch
too far
219
00:18:02,280 --> 00:18:03,800
and they perish.
220
00:18:06,560 --> 00:18:08,040
But for this one,
221
00:18:08,160 --> 00:18:11,680
the cactus's surface
is within reach.
222
00:18:20,560 --> 00:18:23,720
It clamps onto it with
a special sucker...
223
00:18:27,120 --> 00:18:30,080
And then waits for darkness.
224
00:18:32,080 --> 00:18:35,600
At night, the cactus
opens its pores
225
00:18:35,720 --> 00:18:36,760
in order to respire.
226
00:18:39,560 --> 00:18:41,800
Oxygen goes out,
227
00:18:41,920 --> 00:18:44,560
carbon dioxide goes in.
228
00:18:45,720 --> 00:18:47,520
And so does tristerix,
229
00:18:52,840 --> 00:18:54,120
Once within,
230
00:18:54,240 --> 00:18:58,720
its tissues spread throughout
the body of the cactus,
231
00:18:58,840 --> 00:19:01,800
sustained by the precious store
of water that they find there.
232
00:19:08,200 --> 00:19:09,720
Then, a year later,
233
00:19:09,840 --> 00:19:12,520
it breaks through
the cactus's skin...
234
00:19:19,200 --> 00:19:22,120
And bursts into flower.
235
00:19:39,080 --> 00:19:41,160
Hummingbirds come to drink
their nectar
236
00:19:41,280 --> 00:19:44,800
and pollinate them
as they do so.
237
00:19:54,560 --> 00:19:57,200
And then, to complete the cycle,
238
00:19:57,320 --> 00:20:02,160
tristerix produces hundreds of
white eye-catching seeds,
239
00:20:02,280 --> 00:20:04,440
ready to be carried away
by a bird
240
00:20:04,560 --> 00:20:07,720
to invade another cactus.
241
00:20:18,640 --> 00:20:22,160
The karoo desert
in Southern Africa.
242
00:20:23,880 --> 00:20:26,000
And although it may look bare,
243
00:20:26,120 --> 00:20:30,040
its rocky ground contains
an unrivalled variety of plants
244
00:20:30,160 --> 00:20:34,360
that, one way or another,
store water in their tissues.
245
00:20:35,920 --> 00:20:39,320
They belong to
many different families,
246
00:20:39,440 --> 00:20:42,720
but as a group,
they're known as succulents.
247
00:21:00,280 --> 00:21:03,640
Some are small and low
248
00:21:03,760 --> 00:21:06,600
and barely distinguishable from
their surroundings.
249
00:21:08,720 --> 00:21:11,160
These look like little pebbles.
250
00:21:13,360 --> 00:21:15,760
They resemble them so closely
251
00:21:15,880 --> 00:21:18,840
that animals which might be
only too glad
252
00:21:18,960 --> 00:21:21,840
to steal their water
just pass them by.
253
00:21:26,000 --> 00:21:28,160
When rain does fall,
they absorb it
254
00:21:28,280 --> 00:21:30,080
and quickly expand.
255
00:21:32,600 --> 00:21:35,400
But even this doesn't spoil
their disguise.
256
00:21:35,520 --> 00:21:38,400
They just look like
larger pebbles.
257
00:21:40,040 --> 00:21:42,080
Nor are they green.
258
00:21:42,200 --> 00:21:45,360
The cells on their top surface
are transparent
259
00:21:45,480 --> 00:21:48,120
and allow sunlight
to pass through.
260
00:21:49,840 --> 00:21:51,680
Deep within, and out of sight,
261
00:21:51,800 --> 00:21:55,640
are the green cells
where photosynthesis occurs -
262
00:21:55,760 --> 00:21:58,000
the process
which uses this light
263
00:21:58,120 --> 00:22:00,000
to make food for the plant.
264
00:22:06,680 --> 00:22:09,360
When the time comes
to reproduce, however,
265
00:22:09,480 --> 00:22:12,640
the stone plant
abandons its disguise.
266
00:22:33,560 --> 00:22:37,040
And now it blooms.
267
00:22:44,840 --> 00:22:49,120
The flowers open and close
every 24 hours.
268
00:22:57,720 --> 00:23:00,880
So, for a few dangerous days,
269
00:23:01,000 --> 00:23:03,200
the plant advertises
for pollinators,
270
00:23:03,320 --> 00:23:06,480
before returning to life
as a pebble.
271
00:23:15,120 --> 00:23:16,560
(Antlers clatter)
272
00:23:20,680 --> 00:23:24,680
Some desert plants have
developed a very different way
273
00:23:24,800 --> 00:23:27,080
of attracting pollinators.
274
00:23:28,240 --> 00:23:30,880
This is stapelia.
275
00:23:31,000 --> 00:23:35,120
It produces what is perhaps the
desert's strangest disguise.
276
00:23:36,600 --> 00:23:40,040
It uses water
stored in its stems
277
00:23:40,160 --> 00:23:42,360
to grow buds
the size of tennis balls.
278
00:23:42,480 --> 00:23:44,000
(Creaking)
279
00:24:02,640 --> 00:24:04,480
The flower, once opened,
280
00:24:04,600 --> 00:24:07,160
is called a desert starfish.
281
00:24:10,160 --> 00:24:13,840
Instead of releasing millions
of loose pollen grains,
282
00:24:13,960 --> 00:24:15,200
as most flowers do,
283
00:24:15,320 --> 00:24:20,360
the desert starfish produces
them packed in five tiny sacs.
284
00:24:22,800 --> 00:24:25,440
But if its strategy
is successful,
285
00:24:25,560 --> 00:24:29,440
just one of them will produce
hundreds of seeds.
286
00:24:33,600 --> 00:24:36,000
And this depends on deception.
287
00:24:38,640 --> 00:24:41,440
The flower
appears to have hair...
288
00:24:43,280 --> 00:24:46,200
Wrinkly skin...
289
00:24:48,080 --> 00:24:50,400
And it produces a stench
290
00:24:50,520 --> 00:24:52,840
like the carcass
of a dead animal.
291
00:24:55,960 --> 00:24:57,480
(Sniffs)
292
00:24:58,560 --> 00:25:00,800
(Flies buzz)
293
00:25:07,080 --> 00:25:09,840
And when a carrion fly
investigates...
294
00:25:12,200 --> 00:25:15,800
The flower clamps a tiny sac
of pollen to its proboscis.
295
00:25:23,960 --> 00:25:29,040
It's not easy to feed with
such encumbered mouth parts.
296
00:25:30,240 --> 00:25:33,720
But try as it might,
the fly can't get rid of it.
297
00:25:35,480 --> 00:25:36,800
(Leaves creak)
298
00:25:36,920 --> 00:25:39,080
And it's still there
when the fly leaves
299
00:25:39,200 --> 00:25:42,080
to try and feed from
another bogus cactus.
300
00:25:45,960 --> 00:25:47,760
(Fly buzzes)
301
00:25:47,880 --> 00:25:50,360
This time, however, when its
clamped-up proboscis
302
00:25:50,480 --> 00:25:54,920
slots into the flower,
the pollen sac is released.
303
00:26:01,480 --> 00:26:03,480
With pollination complete,
304
00:26:03,600 --> 00:26:05,880
the fly is no longer needed.
305
00:26:09,840 --> 00:26:11,600
And just as well!
306
00:26:16,840 --> 00:26:19,360
Some deserts can be so dry
307
00:26:19,480 --> 00:26:22,160
that plants must find
techniques of surviving
308
00:26:22,280 --> 00:26:25,920
for long periods without
any water whatsoever.
309
00:26:26,040 --> 00:26:30,960
One of them is to grow
extremely slowly,
310
00:26:31,080 --> 00:26:35,400
and few plants grow more slowly
than this one -
311
00:26:35,520 --> 00:26:37,920
the creosote bush.
312
00:26:39,040 --> 00:26:41,720
It is inactive
for most of its life
313
00:26:41,840 --> 00:26:44,560
and only wakes up and grows
for a brief period...
314
00:26:45,720 --> 00:26:49,000
If and when
there is a fall of rain.
315
00:26:52,560 --> 00:26:55,160
I've seen evidence
of this grow-slow strategy
316
00:26:55,280 --> 00:26:56,400
for myself.
317
00:26:57,680 --> 00:26:59,000
40 years ago,
318
00:26:59,120 --> 00:27:01,480
I came here to California's
mojave desert
319
00:27:01,600 --> 00:27:03,800
to visit one particular plant.
320
00:27:05,560 --> 00:27:07,720
An individual creosote bush
321
00:27:07,840 --> 00:27:11,320
tends to spread not by
setting seeds
322
00:27:11,440 --> 00:27:13,120
and producing a new generation,
323
00:27:13,240 --> 00:27:17,360
but by sending out new stems
around its base.
324
00:27:17,480 --> 00:27:19,920
This plant started growing
325
00:27:20,040 --> 00:27:23,200
between 10,000 and 12,000
years ago.
326
00:27:25,280 --> 00:27:27,560
That was in 1982.
327
00:27:30,520 --> 00:27:33,800
Since then, careful measurement
has shown
328
00:27:33,920 --> 00:27:39,120
that it has increased its size
by less than one inch.
329
00:27:42,080 --> 00:27:45,600
Its ability to endure
is truly extraordinary.
330
00:27:47,000 --> 00:27:48,680
(Birdsong)
331
00:27:50,040 --> 00:27:52,400
So efficient is creosote
332
00:27:52,520 --> 00:27:55,040
at collecting what little rain
falls here
333
00:27:55,160 --> 00:27:58,000
that few other plants can
compete with it.
334
00:27:58,120 --> 00:28:02,080
As a result,
over the last 12,000 years,
335
00:28:02,200 --> 00:28:05,080
it's come to completely
dominate this landscape.
336
00:28:22,080 --> 00:28:25,320
The chihuahuan desert
in north Mexico.
337
00:28:26,480 --> 00:28:29,320
Here, one particular plant
338
00:28:29,440 --> 00:28:31,400
plays the waiting game so well
339
00:28:31,520 --> 00:28:34,520
that it spends much of its life
looking dead
340
00:28:34,640 --> 00:28:37,040
and certainly not worth eating.
341
00:28:39,920 --> 00:28:43,720
And it can survive like this
for a decade.
342
00:28:51,920 --> 00:28:54,560
This is the resurrection plant.
343
00:28:56,840 --> 00:28:59,160
It's a kind of moss.
344
00:28:59,280 --> 00:29:01,560
It barely has roots
345
00:29:01,680 --> 00:29:04,160
and it certainly can't store
much water.
346
00:29:05,440 --> 00:29:06,920
But it can travel.
347
00:29:08,200 --> 00:29:10,120
(Wind blows)
348
00:29:13,040 --> 00:29:15,400
After a particularly long
drought...
349
00:29:16,600 --> 00:29:18,640
It breaks away from its roots...
350
00:29:21,240 --> 00:29:22,640
And becomes...
351
00:29:24,400 --> 00:29:26,600
A tumbleweed.
352
00:29:28,160 --> 00:29:33,520
Blowing across the desert,
it can travel a mile in a week.
353
00:29:35,960 --> 00:29:38,600
With luck, it may find water.
354
00:29:42,320 --> 00:29:45,200
(Thunder rolls)
355
00:29:46,360 --> 00:29:49,880
Just a shower of rain
can bring it back to life.
356
00:29:55,400 --> 00:29:59,200
As its fronds soak up
the water, they unfurl.
357
00:30:12,240 --> 00:30:16,760
In its protected centre,
it still has green cells,
358
00:30:16,880 --> 00:30:19,680
which absorb both the water
and sunlight,
359
00:30:19,800 --> 00:30:24,480
and rapidly produce the food
it needs to resume its growth.
360
00:30:29,680 --> 00:30:33,000
It will grow for just as long
as there is moisture.
361
00:30:33,120 --> 00:30:34,720
(Leaves crackle)
362
00:30:37,480 --> 00:30:39,480
But when that disappears...
363
00:30:41,120 --> 00:30:43,400
It closes up once more
364
00:30:43,520 --> 00:30:46,080
and resumes its travels.
365
00:30:56,080 --> 00:30:58,040
Here in the canyon lands of Utah
366
00:30:58,160 --> 00:31:00,400
lives a plant that has developed
367
00:31:00,520 --> 00:31:03,360
a finely balanced relationship
368
00:31:03,480 --> 00:31:07,080
with the animals with which
it shares this dramatic desert.
369
00:31:12,160 --> 00:31:15,080
Rain does occasionally fall here
370
00:31:15,200 --> 00:31:18,680
and turns dust into mud.
371
00:31:21,480 --> 00:31:23,280
(Cracking)
372
00:31:23,400 --> 00:31:25,480
But that doesn't last long.
373
00:31:27,200 --> 00:31:30,040
A brief window of opportunity
opens.
374
00:31:39,760 --> 00:31:42,920
Seeds that have been
buried for years
375
00:31:43,040 --> 00:31:44,920
may now be exposed to light...
376
00:31:46,320 --> 00:31:48,280
And come to life.
377
00:32:05,120 --> 00:32:07,360
This is coyote tobacco.
378
00:32:21,040 --> 00:32:24,360
In just a few weeks,
it grows a metre tall
379
00:32:24,480 --> 00:32:27,360
and produces dozens of flowers.
380
00:32:33,480 --> 00:32:37,640
The night air becomes heavy
with their fragrance.
381
00:32:39,680 --> 00:32:41,240
Soon, they attract hawk moths,
382
00:32:41,360 --> 00:32:43,400
which sip their nectar,
383
00:32:43,520 --> 00:32:45,800
and in doing so, pollinate them.
384
00:32:47,840 --> 00:32:51,800
But the moths also
lay their eggs on them.
385
00:33:07,680 --> 00:33:10,440
Soon, their caterpillars
have hatched
386
00:33:10,560 --> 00:33:13,160
and are munching the leaves.
387
00:33:16,000 --> 00:33:18,040
Their nibbles expose
the plant's sap
388
00:33:18,160 --> 00:33:20,120
to the drying air.
389
00:33:23,280 --> 00:33:25,720
But the tobacco plant
has a defence.
390
00:33:28,960 --> 00:33:32,800
The leaves under attack
produce nicotine.
391
00:33:37,240 --> 00:33:39,600
This chemical
sedates the caterpillars
392
00:33:39,720 --> 00:33:41,400
and slows them down.
393
00:33:47,480 --> 00:33:50,960
And what is more, it makes them
give off a particular scent...
394
00:33:54,280 --> 00:33:59,320
One that summons others
to come to the plant's aid.
395
00:34:00,960 --> 00:34:02,760
Big-eyed bugs -
396
00:34:02,880 --> 00:34:06,800
miniature assassins
only 2mm long.
397
00:34:08,080 --> 00:34:09,800
And whiptail lizards.
398
00:34:11,360 --> 00:34:15,080
Big or small, they make
a meal of the caterpillars.
399
00:34:25,960 --> 00:34:27,800
It's certainly effective.
400
00:34:30,320 --> 00:34:33,960
But there's more to this
strategy than meets the eye.
401
00:34:36,040 --> 00:34:38,840
When the leaf of a tobacco plant
402
00:34:38,960 --> 00:34:41,000
is attacked by a caterpillar,
403
00:34:41,120 --> 00:34:45,080
all the rest of the leaves
prepare to defend themselves.
404
00:34:46,240 --> 00:34:49,000
But how does this leaf know that
405
00:34:49,120 --> 00:34:52,120
that leaf there is under attack?
406
00:34:52,240 --> 00:34:56,040
Well, scientists here
in the United States
407
00:34:56,160 --> 00:35:00,040
have specially genetically
modified these tobacco plants
408
00:35:00,160 --> 00:35:02,480
so that under special
lighting conditions,
409
00:35:02,600 --> 00:35:06,920
this microscope can show us
exactly what is going on.
410
00:35:09,040 --> 00:35:12,800
I'm going to attack
one of the leaves of this plant
411
00:35:12,920 --> 00:35:15,760
with these tweezers,
which, to the plant,
412
00:35:15,880 --> 00:35:19,160
will seem as if it's being
nibbled by a caterpillar.
413
00:35:33,680 --> 00:35:36,480
Signals are being transmitted
along the veins
414
00:35:36,600 --> 00:35:39,240
that link the leaf
to the rest of the plant.
415
00:35:40,440 --> 00:35:43,440
It's rather like a very simple
nervous system.
416
00:35:48,400 --> 00:35:51,320
From that initial injury,
the whole of this little plant
417
00:35:51,440 --> 00:35:54,040
is aware that something
had happened.
418
00:35:58,760 --> 00:36:02,000
This signal warns each leaf
of the danger...
419
00:36:03,440 --> 00:36:05,840
So that it is ready
to produce nicotine
420
00:36:05,960 --> 00:36:08,200
the moment it's attacked.
421
00:36:11,160 --> 00:36:14,040
With this defence at the ready,
the tobacco plant
422
00:36:14,160 --> 00:36:18,720
can continue to grow until,
eventually, it produces seeds.
423
00:36:32,520 --> 00:36:34,880
It's particularly important
in deserts
424
00:36:35,000 --> 00:36:39,200
for seeds to be distributed
as widely as possible
425
00:36:39,320 --> 00:36:42,880
so that some will have a chance
of reaching moisture.
426
00:36:46,080 --> 00:36:49,720
And deserts have an excellent
agent to help them do that.
427
00:36:49,840 --> 00:36:52,080
(Wind blows)
428
00:36:52,200 --> 00:36:53,520
The wind.
429
00:36:55,840 --> 00:36:59,640
Many seeds have adaptations
to help them exploit it.
430
00:37:00,880 --> 00:37:03,360
They have shells to protect
the seeds within
431
00:37:03,480 --> 00:37:04,520
from abrasion...
432
00:37:05,880 --> 00:37:09,240
Or wings to help them
catch the air.
433
00:37:12,480 --> 00:37:15,480
As the temperature rises
throughout the day,
434
00:37:15,600 --> 00:37:17,760
desert winds
increase in strength.
435
00:37:42,600 --> 00:37:46,560
Here in Arizona,
the land is regularly swept by
436
00:37:46,680 --> 00:37:49,080
what is known as a haboob.
437
00:37:49,200 --> 00:37:51,640
It's a giant sandstorm,
438
00:37:51,760 --> 00:37:54,920
but also, in effect,
a seed storm.
439
00:38:02,960 --> 00:38:07,080
Countless millions of them
are swept up into the air.
440
00:38:13,280 --> 00:38:14,640
Some seeds can travel
441
00:38:14,760 --> 00:38:17,040
thousands of miles
on the wind...
442
00:38:18,520 --> 00:38:20,040
(Thunder cracks)
443
00:38:20,160 --> 00:38:22,280
So that plants
may eventually reach
444
00:38:22,400 --> 00:38:24,400
even the most isolated desert.
445
00:38:27,520 --> 00:38:29,360
(Thunder rolls)
446
00:38:34,240 --> 00:38:37,080
Some have landed on an island
447
00:38:37,200 --> 00:38:40,720
in the middle of the world's
largest salt flat, in Bolivia.
448
00:38:40,840 --> 00:38:42,800
(Birds call)
449
00:38:46,040 --> 00:38:47,680
In the galapagos,
450
00:38:47,800 --> 00:38:51,560
they sprout on fields
of recently erupted lava.
451
00:38:51,680 --> 00:38:54,160
(Fire crackles)
452
00:38:59,000 --> 00:39:00,280
They've even reached
453
00:39:00,400 --> 00:39:03,680
one of the most inhospitable
of all sites -
454
00:39:03,800 --> 00:39:08,040
the tiny island
of San Pedro martir,
455
00:39:08,160 --> 00:39:12,120
a scorched, lonely rock
off the coast of Mexico.
456
00:39:16,440 --> 00:39:19,840
This is the home
of the giant cardon,
457
00:39:19,960 --> 00:39:25,920
a species of huge cactus that
can weigh up to 12 tonnes.
458
00:39:33,360 --> 00:39:35,160
They're able to thrive here
459
00:39:35,280 --> 00:39:38,480
because of an extraordinary
partnership...
460
00:39:41,400 --> 00:39:45,520
With brown
and blue-footed boobies.
461
00:39:50,560 --> 00:39:53,560
The cardons here
can become so broad
462
00:39:53,680 --> 00:39:57,520
that they provide cooling shade
for nesting birds.
463
00:40:09,120 --> 00:40:15,080
As the booby chicks get older,
they repay the cardons...
464
00:40:20,440 --> 00:40:21,760
With their droppings.
465
00:40:23,200 --> 00:40:24,640
Guano.
466
00:40:24,760 --> 00:40:28,400
The digested remains
of vast shoals of fish.
467
00:40:30,240 --> 00:40:33,840
This guano is of such strength
and quantity
468
00:40:33,960 --> 00:40:37,440
that most plants
would be poisoned by it.
469
00:40:43,760 --> 00:40:47,840
These cardons, however, have
evolved the ability to tolerate
470
00:40:47,960 --> 00:40:52,760
the toxins in the guano
and digest the nutrients.
471
00:40:53,960 --> 00:40:57,320
As a result, the cacti
now grow in a dense forest
472
00:40:57,440 --> 00:40:59,480
over a million strong.
473
00:41:04,640 --> 00:41:08,120
But such relationships
are very finely balanced
474
00:41:08,240 --> 00:41:11,200
and can only too easily
tip into catastrophe...
475
00:41:14,720 --> 00:41:17,520
As is now happening
in northern Zimbabwe.
476
00:41:21,920 --> 00:41:23,440
For six months of the year,
477
00:41:23,560 --> 00:41:27,760
the Savannah here is kept
lush and green by daily rains.
478
00:41:31,800 --> 00:41:34,480
(Animals call)
479
00:41:36,600 --> 00:41:38,560
But when the rainy season
is over,
480
00:41:38,680 --> 00:41:42,000
it becomes as dry as any desert.
481
00:41:46,440 --> 00:41:50,840
So to survive here, trees
must be able to tolerate
482
00:41:50,960 --> 00:41:52,440
both conditions.
483
00:41:54,120 --> 00:41:58,520
And these giants
are adapted to do just that.
484
00:41:59,760 --> 00:42:01,760
They are baobabs.
485
00:42:09,760 --> 00:42:13,160
This one might be
over a thousand years old.
486
00:42:13,280 --> 00:42:16,040
It's survived here
in part thanks to
487
00:42:16,160 --> 00:42:19,360
its ability to store
thousands of litres of water
488
00:42:19,480 --> 00:42:22,080
within the spongy wood
of its trunk.
489
00:42:26,080 --> 00:42:27,760
But its battered surface
490
00:42:27,880 --> 00:42:31,640
is evidence of a very finely
balanced relationship.
491
00:42:33,680 --> 00:42:38,680
These huge trees are a focus
for animals of all kinds.
492
00:42:40,840 --> 00:42:43,120
(Rumbling and snorting)
493
00:42:43,240 --> 00:42:46,000
And they're particularly
important for elephants.
494
00:42:51,320 --> 00:42:55,160
In the wet season,
they eat the baobabs' fruit
495
00:42:55,280 --> 00:42:57,680
and disperse the seeds
in their dung.
496
00:43:03,640 --> 00:43:05,160
Now, as the dry season begins...
497
00:43:05,280 --> 00:43:07,360
(Snorts)
498
00:43:07,480 --> 00:43:10,520
They migrate
to distant watering holes.
499
00:43:14,880 --> 00:43:17,440
The baobabs
have damp inner wood...
500
00:43:19,240 --> 00:43:21,080
And the elephants use it
501
00:43:21,200 --> 00:43:23,360
to quench their thirst
on the journey.
502
00:43:24,800 --> 00:43:28,240
(Elephant trumpets)
503
00:43:37,680 --> 00:43:39,760
(Low rumbling)
504
00:43:43,200 --> 00:43:47,040
This relationship can only work
because baobabs
505
00:43:47,160 --> 00:43:50,960
have a remarkable ability
to heal themselves.
506
00:44:09,040 --> 00:44:11,040
Between each damaging attack,
507
00:44:11,160 --> 00:44:15,800
they expand their spongy wood
and grow new skin.
508
00:44:20,280 --> 00:44:22,760
And they've done this
time and time again,
509
00:44:22,880 --> 00:44:24,240
over centuries.
510
00:44:28,600 --> 00:44:33,040
Today, however, it's harder
for the baobabs to recover,
511
00:44:33,160 --> 00:44:36,280
as dry seasons
become longer and drier
512
00:44:36,400 --> 00:44:38,200
due to climate change.
513
00:44:39,640 --> 00:44:42,720
Not only that,
but the elephants are forced
514
00:44:42,840 --> 00:44:46,840
to take ever more wood from
the trees in order to survive.
515
00:44:52,560 --> 00:44:55,760
In some parts of Africa,
many of the largest
516
00:44:55,880 --> 00:44:59,800
and oldest baobabs
have fallen in the last decade.
517
00:45:13,040 --> 00:45:15,640
The loss of a vital species
like the baobab
518
00:45:15,760 --> 00:45:18,640
strikes a blow
at all life in the desert.
519
00:45:23,840 --> 00:45:28,400
In these hostile lands, few
living organisms can survive
520
00:45:28,520 --> 00:45:31,160
without help from others.
521
00:45:35,600 --> 00:45:38,720
You can find an extraordinary
illustration of this
522
00:45:38,840 --> 00:45:41,480
in Arizona's saguaro country.
523
00:45:48,800 --> 00:45:51,080
If you wander off
the beaten track here,
524
00:45:51,200 --> 00:45:54,040
you may be lucky enough
to find one of these.
525
00:45:54,160 --> 00:45:56,920
It might look like an old boot,
526
00:45:57,040 --> 00:46:01,520
but in fact,
it's part of a saguaro cactus.
527
00:46:01,640 --> 00:46:03,960
Almost every saguaro has one.
528
00:46:04,080 --> 00:46:05,440
There's one up there.
529
00:46:05,560 --> 00:46:07,560
(Birds call)
530
00:46:10,840 --> 00:46:14,480
It has been produced,
indirectly, by woodpeckers,
531
00:46:14,600 --> 00:46:17,720
which regularly dig homes
for themselves
532
00:46:17,840 --> 00:46:20,480
in the bloated trunks
of the saguaros.
533
00:46:33,240 --> 00:46:35,640
In the next six months,
534
00:46:35,760 --> 00:46:38,240
the cactus heals the wound,
535
00:46:38,360 --> 00:46:43,560
and so creates a safe, cool
and watertight nest hole.
536
00:46:45,320 --> 00:46:48,200
It's tough lining
will persist for years,
537
00:46:48,320 --> 00:46:52,360
even after the cactus itself
has died and rotted away.
538
00:46:57,000 --> 00:46:58,640
A single saguaro may hold
539
00:46:58,760 --> 00:47:01,480
several of these
extraordinary homes.
540
00:47:03,680 --> 00:47:06,040
So over its lifetime,
541
00:47:06,160 --> 00:47:08,560
it may provide accommodation
542
00:47:08,680 --> 00:47:11,840
for some 3,000 chicks
of several different species.
543
00:47:11,960 --> 00:47:14,800
(Bird squawks)
544
00:47:19,240 --> 00:47:22,240
But in the long term,
the saguaro benefits,
545
00:47:22,360 --> 00:47:25,040
as their lodgers repay
the cactus
546
00:47:25,160 --> 00:47:28,040
by pollinating its flowers...
547
00:47:29,160 --> 00:47:32,000
And dispersing its seeds.
548
00:47:38,800 --> 00:47:44,000
It's relationships like these
that enable life to flourish
549
00:47:44,120 --> 00:47:47,560
in some of the world's harshest
landscapes.
550
00:48:00,160 --> 00:48:02,080
Over millions of years,
551
00:48:02,200 --> 00:48:05,200
plants have become
superbly adapted
552
00:48:05,320 --> 00:48:07,520
to hostile desert conditions.
553
00:48:07,640 --> 00:48:11,280
But it's a very finely balanced
existence,
554
00:48:11,400 --> 00:48:14,160
and one that makes them
uniquely vulnerable.
555
00:48:16,920 --> 00:48:19,880
However, our growing
understanding
556
00:48:20,000 --> 00:48:22,920
of the complex ways by which
desert animals and plants
557
00:48:23,040 --> 00:48:26,000
rely on one another
is now helping us to understand
558
00:48:26,120 --> 00:48:28,280
how best we can protect them.
559
00:48:33,240 --> 00:48:37,400
90 years ago, a photograph
was taken from this very spot
560
00:48:37,520 --> 00:48:40,520
that shows a population
of saguaro cactus
561
00:48:40,640 --> 00:48:43,680
that was very different
from what it is today.
562
00:48:45,800 --> 00:48:48,120
In the last 50 years,
563
00:48:48,240 --> 00:48:52,360
the population of saguaros here
has greatly diminished -
564
00:48:52,480 --> 00:48:55,360
not because of a direct assault
on the cactus,
565
00:48:55,480 --> 00:48:58,920
but because many of
the shade-giving nurse trees
566
00:48:59,040 --> 00:49:00,880
were harvested for firewood,
567
00:49:01,000 --> 00:49:03,600
leaving young saguaro
to die in the sun.
568
00:49:09,240 --> 00:49:11,680
Now that this relationship
is understood
569
00:49:11,800 --> 00:49:13,840
and the nurse trees
are protected,
570
00:49:13,960 --> 00:49:16,160
there are already signs
571
00:49:16,280 --> 00:49:19,520
that the saguaro are recovering.
572
00:49:21,840 --> 00:49:23,400
Wherever there's a desert,
573
00:49:23,520 --> 00:49:26,320
plants have evolved
to meet its challenge.
574
00:49:29,040 --> 00:49:31,360
But everywhere,
they need our help.
575
00:49:33,440 --> 00:49:35,240
As we understand more about them
576
00:49:35,360 --> 00:49:38,360
and their intimate
and complex relationships...
577
00:49:40,360 --> 00:49:42,800
We will be better able to
protect them,
578
00:49:42,920 --> 00:49:45,720
and all life, in these beautiful
579
00:49:45,840 --> 00:49:49,240
but increasingly fragile worlds.
580
00:50:03,480 --> 00:50:06,360
The most remote shoot
for the deserts team
581
00:50:06,480 --> 00:50:09,120
is to the island
of San Pedro martir
582
00:50:09,240 --> 00:50:11,520
in the sea of Cortez, Mexico.
583
00:50:14,560 --> 00:50:17,240
They are to film the giant cacti
584
00:50:17,360 --> 00:50:19,760
that have found a unique way
to thrive here.
585
00:50:22,920 --> 00:50:26,760
It takes 48 hours to travel
the 260 miles...
586
00:50:27,880 --> 00:50:30,800
Over unpleasantly choppy seas.
587
00:50:37,120 --> 00:50:39,240
It's not made some of us
feel very well.
588
00:50:39,360 --> 00:50:41,280
I think one of us
is quite seasick.
589
00:50:43,600 --> 00:50:46,120
There is nothing
but big blue out there,
590
00:50:46,240 --> 00:50:48,480
and the island is somewhere
in that direction.
591
00:50:48,600 --> 00:50:49,880
Can't see it yet.
592
00:50:52,240 --> 00:50:53,960
As they draw close
to the island,
593
00:50:54,080 --> 00:50:55,520
there's a spectacular reminder
594
00:50:55,640 --> 00:50:58,760
of how rich life in the sea
is here.
595
00:50:58,880 --> 00:51:01,920
Oh, look in front of us,
look at that for a pod!
596
00:51:03,960 --> 00:51:06,640
Oh, they're everywhere.
597
00:51:11,160 --> 00:51:12,840
Show us the way!
598
00:51:12,960 --> 00:51:14,280
(Laughs)
599
00:51:19,720 --> 00:51:24,240
Meeting them here is
desert scientist Ben Wilder.
600
00:51:25,320 --> 00:51:29,280
It's through his research
that the team first heard about
601
00:51:29,400 --> 00:51:31,640
the island's peculiar residents.
602
00:51:31,760 --> 00:51:34,400
I'll never forget
the first time I came to
603
00:51:34,520 --> 00:51:37,160
actually exactly where
we're standing right now.
604
00:51:37,280 --> 00:51:41,400
It was April of 2006,
and saw this view,
605
00:51:41,520 --> 00:51:47,520
and it both settled in my heart
and captivated my mind.
606
00:51:47,640 --> 00:51:53,240
And so that started a process
of trying to understand,
607
00:51:53,360 --> 00:51:55,800
you know, what can produce this?
608
00:51:57,840 --> 00:52:01,240
The secret is in the
relationship between the cactus
609
00:52:01,360 --> 00:52:05,400
and a type of seabird
called a booby.
610
00:52:06,760 --> 00:52:09,120
All the boobies
that we need to film
611
00:52:09,240 --> 00:52:11,840
are right up there
at the top of the island,
612
00:52:11,960 --> 00:52:14,120
so it's going to be
a bit of a scramble.
613
00:52:15,920 --> 00:52:19,920
The crew soon discover how
harsh the conditions are here.
614
00:52:20,040 --> 00:52:23,400
I'm pretty tired.
It's pretty hot.
615
00:52:23,520 --> 00:52:24,920
But it's a great view.
616
00:52:31,760 --> 00:52:34,840
There's very few places on
earth where you're going to see
617
00:52:34,960 --> 00:52:37,520
this many cactus. I mean,
it's absolutely amazing.
618
00:52:37,640 --> 00:52:39,400
I would say this is
the only place
619
00:52:39,520 --> 00:52:41,720
- you're going to see this.
- Well, there you go, then.
620
00:52:44,000 --> 00:52:47,400
Ben's research is uncovering
the ingenious ways
621
00:52:47,520 --> 00:52:50,680
the cacti have adapted
to the conditions here.
622
00:52:51,800 --> 00:52:54,320
The waters just offshore here
are some of the most productive
623
00:52:54,440 --> 00:52:56,520
marine waters in the world,
624
00:52:56,640 --> 00:52:59,960
and so it's kind of an ideal
habitat for seabirds to roost.
625
00:53:00,080 --> 00:53:03,400
But when they do so,
they deposit tonnes of guano,
626
00:53:03,520 --> 00:53:05,400
and so those nutrients,
627
00:53:05,520 --> 00:53:08,120
really high in nitrogen
and phosphorus,
628
00:53:08,240 --> 00:53:11,080
actually are toxic
to most plant species.
629
00:53:11,200 --> 00:53:14,640
The cardons thrive because
they're uniquely able
630
00:53:14,760 --> 00:53:16,000
to process the guano
631
00:53:16,120 --> 00:53:19,280
and extract what they need
to fuel their growth.
632
00:53:21,680 --> 00:53:24,440
One of the first shots
the crew need to get
633
00:53:24,560 --> 00:53:27,840
is of the boobies
nesting under the cacti.
634
00:53:27,960 --> 00:53:29,200
The lack of predators
635
00:53:29,320 --> 00:53:32,440
means the birds aren't afraid
of people.
636
00:53:32,560 --> 00:53:36,440
It should make filming them
up close a bit easier.
637
00:53:36,560 --> 00:53:38,600
That's the theory.
638
00:53:38,720 --> 00:53:41,280
Oli: So we've positioned this
camera here to try and get
639
00:53:41,400 --> 00:53:43,880
a good perspective on the chick
on the nest.
640
00:53:44,000 --> 00:53:46,600
It's taken quite a liking
to our camera.
641
00:53:46,720 --> 00:53:48,720
Let's hope he doesn't break it.
642
00:53:54,160 --> 00:53:55,880
Bull's-eye.
643
00:53:56,000 --> 00:53:57,840
It's pooed right on the front
of the lens.
644
00:53:57,960 --> 00:54:01,000
It's kind of a shot we need,
but, unfortunately,
645
00:54:01,120 --> 00:54:02,960
my camera wasn't rolling
at the time it did it,
646
00:54:03,080 --> 00:54:05,040
so now I've just got
a dirty lens.
647
00:54:08,080 --> 00:54:10,640
After a thorough lens clean,
648
00:54:10,760 --> 00:54:12,040
oli eventually gets the shots
649
00:54:12,160 --> 00:54:14,880
to reveal the extraordinary
relationship
650
00:54:15,000 --> 00:54:16,600
between bird and plant.
651
00:54:19,680 --> 00:54:23,400
But it's not just the bird
guano that influence
652
00:54:23,520 --> 00:54:25,520
how the cardons grow.
653
00:54:25,640 --> 00:54:29,320
They're way shorter,
they're dwarfed here.
654
00:54:29,440 --> 00:54:30,840
Throughout the rest
of their range
655
00:54:30,960 --> 00:54:33,240
they usually get upwards
of 50, 60 feet.
656
00:54:33,360 --> 00:54:37,640
But here, on average,
they're 20, 24 feet in height.
657
00:54:37,760 --> 00:54:41,320
They stop growing up
and they grow out.
658
00:54:43,080 --> 00:54:46,600
Ben's research suggests
that they go wide here
659
00:54:46,720 --> 00:54:50,000
as an adaptation
to the violent winds.
660
00:54:50,120 --> 00:54:52,520
Too tall, and they'd blow over.
661
00:54:52,640 --> 00:54:56,840
A gusting wind isn't helping
the drone crew, either.
662
00:54:56,960 --> 00:54:58,336
We really need it
to calm down a bit,
663
00:54:58,360 --> 00:55:00,000
otherwise it's going to
be impossible.
664
00:55:01,760 --> 00:55:03,080
(Drone whirs)
665
00:55:24,680 --> 00:55:28,560
On the sonoran mainland,
where the cardon is also found,
666
00:55:28,680 --> 00:55:32,200
you have on average between
50 to 150 plants per hectare.
667
00:55:32,320 --> 00:55:38,000
Here, on this island, you have
over 2,500 plants per hectare.
668
00:55:38,120 --> 00:55:41,360
A lull in the wind, and the
team get a chance to reveal
669
00:55:41,480 --> 00:55:44,760
the remarkably density
of the cacti -
670
00:55:44,880 --> 00:55:48,960
almost 20 times greater
than anywhere else.
671
00:55:49,080 --> 00:55:52,880
It appears that, here,
they're doing very well.
672
00:55:53,000 --> 00:55:54,600
But even this island
673
00:55:54,720 --> 00:55:58,440
isn't isolated from the effects
of a changing planet.
674
00:55:59,720 --> 00:56:02,280
Every cactus you see there,
675
00:56:02,400 --> 00:56:05,000
its body is filled with
nutrients from the sea.
676
00:56:06,240 --> 00:56:08,680
Given that we know
that the cardons
677
00:56:08,800 --> 00:56:11,960
are linked to the ocean,
what happens in the oceans
678
00:56:12,080 --> 00:56:14,200
affects what happens
to the cardon.
679
00:56:14,320 --> 00:56:15,600
So a concern we have right now
680
00:56:15,720 --> 00:56:17,480
is that there's
a lot of overfishing,
681
00:56:17,600 --> 00:56:20,480
and we know there are
less seabirds here
682
00:56:20,600 --> 00:56:22,240
than there were 20 years ago,
683
00:56:22,360 --> 00:56:24,720
and we have reason
to believe that
684
00:56:24,840 --> 00:56:26,800
that will ripple and affect
685
00:56:26,920 --> 00:56:29,080
the nutrients that fuel
the cardons as well.
686
00:56:31,320 --> 00:56:34,760
This finely balanced
relationship is at risk,
687
00:56:34,880 --> 00:56:38,040
and knowing that
makes leaving the island
688
00:56:38,160 --> 00:56:40,480
particularly thought-provoking
for the crew.
689
00:56:42,320 --> 00:56:44,960
The cardons look beautiful.
I've never seen
690
00:56:45,080 --> 00:56:48,280
so many cactus in my life.
It's absolutely amazing.
691
00:56:48,400 --> 00:56:50,560
I'm just hoping that
when we leave this place,
692
00:56:50,680 --> 00:56:51,840
it stays as it is,
693
00:56:51,960 --> 00:56:54,400
and things don't affect it
that are negative.
694
00:56:54,520 --> 00:56:57,480
It's an absolutely wonderful
thing, and...
695
00:56:57,600 --> 00:57:00,360
Yeah, and I don't want to go.
I want to stay.
696
00:57:00,480 --> 00:57:04,640
This remote cactus forest
is a reminder
697
00:57:04,760 --> 00:57:06,640
of the adaptability of plants,
698
00:57:06,760 --> 00:57:09,760
that enables them
to establish green worlds
699
00:57:09,880 --> 00:57:12,680
almost anywhere on earth.
50320
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