This episode examines how plants either share environments harmoniously or compete for dominance within them. It looks at the ways in which plants have to fight to survive, using any means available, be it excessive growth, capitalizing on disaster or even courting.
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AnimalsTranscript
01:00But for those plants with much longer lives than ours, such events may be crucial for survival.
01:06And those with beaver lives may only be able to exist at all in the aftermath of such disasters.
02:34The greatest British hurricane of recent times struck on the night of October the 16th,
02:401987.
02:41Ancient woodlands that had stood for centuries were devastated.
02:45For individual trees, like this 250-year-old beech, it was, of course, a catastrophe.
02:52But for other plants, it was an opportunity that they had been waiting for for decades.
03:02The seeds from which these young plants are springing may have come from adults growing in a clearing elsewhere in the wood over a century ago.
03:17Since then, they have lain dormant in the soil.
03:21But now, the light has triggered them into life.
03:26They won't have this clearing to themselves for long, so they grow swiftly.
03:31And the soil, enriched by rotting woodland leaves, feeds them well.
03:36In their second year, they flower.
03:39They're foxgloves.
03:41The seeds from these flowers will not sprout here.
03:45There's no room for them.
03:47They will have to find a new clearing and, in their turn, may have to wait decades for it.
03:58Willow herb competes with the foxgloves for this kind of territory, so it, too, needs to reproduce urgently.
04:05Willow herb competes with his offspring?
04:30The willow herb seeds
04:59Supported by no more than fluff
05:01Will be carried in millions
05:03Far and wide by the wind
05:05After a few years
05:22Other claimants appear
05:24And contest the ownership of the clearing
05:26Young birches
05:28The willow herb
05:32May not be able to stay here
05:33For much longer
05:34A few years later
05:42The willow herb is gone
05:43The birches it seems
05:45Have won
05:46But the soil is now losing its richness
05:49Most of these birches
05:57Started their lives about ten years ago
05:59But there were a lot of them
06:01And competition was intense
06:03So most of them didn't do well at all
06:06This one
06:07Is pretty well dead
06:08This is one of the winners
06:11That has overshadowed the rest
06:13But even this one
06:14Will not be the final holder
06:16Of this territory
06:17That prize will go to a little seedling like this
06:24An oak
06:25Birches on the timescale of a wood
06:33Have short lives
06:34After 40 or 50 years
06:36They begin to succumb to fungus
06:38And disease
06:39Oaks grow more slowly
06:42But more strongly
06:43Eventually
06:45They overtake the ailing birches
06:47And capture the sunshine
06:48The social struggle in the woodland
06:50Is over
06:51At least for the time being
06:53The oaks rule
06:55But as befits ruling monarchs
06:59They have to support
07:00A multitude of lesser mortals
07:02The wide spreading expanses of leaves
07:18All full of starches and sugars
07:20Are rich meadows
07:21In which vast numbers of creatures
07:23Can graze throughout the summer
07:25The oaks protect themselves
07:31To some degree
07:32By generating toxins
07:34In their leaves
07:34But that doesn't deter weevils
07:37Or bush crickets
07:44Sawfly larvae
07:54Munch away
07:55Within the thickness of the leaves
07:56The caterpillar
08:01Of the yellow-tailed moth
08:03The tortrix moth caterpillar
08:08Converts a leaf
08:09Into a tube
08:10Eats it from within
08:11And then uses it
08:13As a shelter
08:14While it changes into an adult
08:15The bagworm caterpillar
08:19Tunnels inside a leaf
08:21But shelters inside
08:22A portable tube
08:23Which it hangs
08:24Beneath the leaf
08:25Which it's currently consuming
08:27The meals the oak provides
08:45For these insects
08:46Then nourish others
08:47When the insects themselves
08:49Become meals for bigger diners
08:51The great tit
08:54With chicks to feed
08:55Will collect at least
08:56300 caterpillars
08:58A day
08:59The banquet only lasts
09:10A few months
09:11As summer gives way to autumn
09:14The oaks drop their leaves
09:17And halt all activities
09:18And so do their lodgers
09:20Within their cocoons
09:22Or hibernating in crevices
09:24As the year turns
09:27Sunshine warms the soil
09:29And plants that spent the winter
09:31As bulbs below ground
09:32Race to make use of the light
09:34Before the oaks
09:35Can regrow their leaves
09:37First are the snowdrops
09:54As spring proceeds
10:02And the sunlight strengthens
10:03Bluebells take over
10:24These glorious carpians
10:41Of uninterrupted blue
10:43Are a British speciality
10:4520,000 years ago
10:49Glaciers advanced
10:51Over most of Britain
10:52Driving many plant species
10:54Southwards in front of them
10:55When at last the ice melted
10:59The English channel
11:00Began to form
11:01And became a barrier
11:02That prevented many plants
11:04From spreading back
11:05From Europe
11:05Into Britain
11:06The bluebell
11:09Was one of the few
11:11That made it
11:12In the woodlands
11:18Of North America
11:19Things are rather different
11:20These lilies
11:22Are growing in the Appalachian mountains
11:24Spring here
11:26Is even richer
11:27Than it is in Britain
11:29Instead of just
11:31Two or three species
11:32Of flower
11:33In a square yard
11:34As you might find
11:34In an English woodland
11:35Here there are a dozen
11:37Or even more
11:38Glaciers once covered
11:44These mountains too
11:45But no arm of the sea
11:47Has ever cut them off
11:48From the rest of the American continent
11:49So when the glaciers melted
11:51Nothing prevented all the spring plants
11:54From returning
11:54From warmer areas
11:56Down south
11:56And here
11:58Instead of the uniform carpet
12:00Created by bluebells
12:01There is one with a rich pattern
12:03Of many colours
12:04Trillium lilies
12:07Trillium lilies
12:07Dutchman's britches
12:12Wild geranium
12:15A member of the lily family
12:27The bellwirt
12:28Blue flocks
12:31But the glories of spring
12:35Do not last long
12:36In April
12:38English oaks
12:39Rebuild their canopy
12:40The bluebell's time
12:42Is over
12:42In their few weeks of activity
12:46They manufactured enough food
12:48Not only to set seed
12:50But below ground
12:51To bud off new bulbs
12:53So next spring
12:55If there's room
12:56They will extend
12:58Their splendid carpet
12:59A young beech
13:02Reinforces the canopy
13:03By adding another lower layer
13:06Shade returns
13:11To the woods
13:12In tropical forests
13:21It's never winter
13:22And the trees are in leaf
13:24Throughout the year
13:25If a plant
13:28Sitting on the ground
13:29Beneath such a permanent canopy
13:30As this
13:31Needs sunshine
13:32It will have to climb
13:33To get it
13:34These youngsters
13:43Search for some kind of ladder
13:46By lashing around
13:47With their whip-like tendrils
13:49Once one of them
13:51Gets a grip
13:52It puts a coil
13:53In the tendril
13:54So shortening it
13:55And pulling itself
13:56Closer to the branch
13:57Up which it might climb
13:58Like a Landesуля
14:00For a long way
14:04If your family
14:05To be with my grandma
14:06Also
14:07Dominic
14:08To be with them
14:09For a long way
14:11Liziz
14:11China
14:11Caribbean
14:12annual
14:13After Chick
14:14On the victory
14:14House
14:14Of hashtags
14:15Who
14:16Is
14:16You
14:16You
14:17I
14:17You
14:18You
14:19You
14:19You
14:20Man
14:20Other plants ascend by twining their main stem around their support.
14:50As a climber gets nearer the canopy and the light, it expands its leaves.
15:16There are no more determined competitors in this upward scramble than the rattans that
15:21live in the forests of Southeast Asia and Tropical Australia.
15:25A mature rattan produces the longest stem of any plant.
15:30One has been measured at 560 feet.
15:33The mature plant doesn't develop leaves on its stem down here on the forest floor.
15:37It only does that up in the canopy.
15:47This luxuriant growth, basking in the full sunshine 200 feet above the ground, is the crown of
15:53the rattan.
15:54And it makes the plant's character quite plain.
15:57It's a kind of palm.
16:00The tendrils with which it climbs are so thin they are easily overlooked.
16:05But snag one of these on your arm and it will rip your clothes and your flesh.
16:12The tendrils are rigid enough to reach up and hook onto the branches of established trees.
16:17They then hold the stouter heavier main stem in position while it grows upwards from the
16:23fearsomely protected bud at its tip.
16:30There is of course an easier way to get up here.
16:33You can float up as a seed.
16:43More plants among these squatters arrived here as seeds stuck to the fur of a monkey or within
16:49the gut of a bird.
16:56Orchids have seeds that are as fine as dust.
16:58So small that they can be lifted by even the faintest breath of air.
17:02As a consequence, even the highest branches of the tallest trees may carry spectacular displays
17:09of breathtaking blooms.
17:15But living up here has its problems.
17:18Water must be collected and stored.
17:21And away from the ground it's difficult to get mineral nutriment.
17:26This orchid deals with those difficulties by wrapping its green roots around the branch
17:30it sits on.
17:32They then intercept rainwater trickling down the bark that carries with it a trace of nourishing
17:37dust.
17:40In some forests at higher altitudes there are almost permanent mists.
17:45And the canopies of all rain forests get intermittent supplies of water from regular storms.
17:55Many plants store water as permanent pools in their centres and have little difficulty in
18:01keeping them topped up.
18:17Orchids may keep water in swollen bulb-like stems.
18:23The ponds in the centre of bromeliads are more than water reservoirs, they are a source
18:28of nourishment.
18:29Tiny animals such as mosquito larvae take up residence in them and their excrement and dead
18:35bodies accumulate at the bottom as a rich sludge.
18:38So the bigger a plant grows, the more food it accumulates.
18:48I'm 200 feet above the ground, suspended in the branches of a Kumpassia tree, which is the tallest
19:03of all the trees in the Southeast Asian forest.
19:06And here beside me is a magnificent basket fern.
19:12As it grew and put out leaves, so it collected moisture.
19:16And as the leaves got bigger, they in turn collected other leaves falling from above.
19:23They decayed to form a rich leaf mould.
19:28As they grew, so more leaves and with them more seeds, so that now there's a fig tree growing
19:35here.
19:36So here you have a complete garden, 200 feet up in the forest, with not part of it touching
19:43the ground in any way.
19:50But some of these squatters can become murderers.
20:00A young fig tree like this may arrive here as a seed carried by a bird.
20:06At first, it grows quite slowly.
20:14As it gains in strength, its roots crawl downwards over its landlord's branches.
20:22Some dangle free, but keep on growing.
20:30Eventually they reach the ground.
20:37Now, supplied with nutrients from the soil, the fig grows really fast.
20:50The rootlets wrapped around the main trunk thicken and fuse into a lattice.
21:05The host tree's fate is now sealed, for it is in the clutches of a strangler fig.
21:14As years pass, the fig thickens its roots, embracing the trunk ever more completely.
21:20Trees grow by increasing their girth.
21:23For the host tree, that is now impossible.
21:26But growth is difficult anyway, because the fig has a huge crown in the canopy that cuts
21:31off sunshine from its host and its roots in the ground are stealing most of the soil's nutrients.
21:42Eventually, the host tree is killed and its trunk rots away, but the fig does not fall.
21:52Its roots now form a hollow cylinder that is quite capable of standing upright by itself.
21:59This strangler is about 300 years old.
22:22In fact, it may be misleading to refer to it as a single tree.
22:25It's probable that 300 years ago there were several young figs up in the canopy.
22:31Now centuries later, their roots have grown down to the ground.
22:35They've got rid of the body of their victim, and they're clinging to one another in this
22:39extraordinary interlace of pillars and buttresses in order to maintain their dominance of this
22:45part of the forest.
22:55Nor are these monsters always satisfied with just one victim.
23:00This 500-year-old, having strangled its first victim and lost its support, topple sideways into
23:08a second, kill that, and then a third, and now its roots are ready to embrace a fourth.
23:14Dead tree trunks are not wasted, and neither are dead leaves when they fall.
23:28Both are food for fungi.
23:31Some leaves are captured even before they reach the ground.
23:35The fungus has constructed a net stretched between the twigs of the undergrowth.
23:43Once they've caught their leaf, the threads put out white filaments.
24:07Fungis produce powerful acid which dissolves the cellulose in the leaves.
24:12Why doesn't it dissolve the fungus too?
24:15Because fungi are not plants.
24:18Their bodies don't contain cellulose.
24:19They're constructed, instead, from a material much more akin to that of which animal horn
24:25and hooves are made.
24:27Fungi are neither plant nor animal.
24:30They belong to a category of life that is all their own.
24:36Nourished by the liquified tissues of leaves, this fungus puts out more threads.
24:43But fungi do require moisture.
24:46They can only live out in the open like this in the moist atmosphere of the rainforest.
24:53In cooler, drier woodlands, they have great difficulty in living out in the open.
24:58Instead, they hide in the ground or within the tissues of the bodies they feast on.
25:04A fungus has no stem, no root, no leaves.
25:11For most of the time, it's nothing more than a tangled tissue of branching threads.
25:18These produce digestive acids, absorb the resulting soup, and then use it to construct more threads
25:24and widen their search for more dead plant tissue.
25:29But cellulose is very low in nitrogen.
25:34To get that, some fungi trap living animals.
25:39The microscopic threads develop tiny lassoes.
25:43These give off a chemical that attracts microscopic worms, nematodes.
25:54One of them nuzzles into the ring, and the fungus suddenly draws its lasso tight.
26:09The worms are killed, and the fungus has its nitrogen.
26:22All this takes place out of sight below ground or within the body of a dead plant.
26:29Only when a fungus is ready to reproduce does it make itself more visible.
26:36In the middle of a deep thing, it's a physician.
26:41It's a good thing for infertile, and it's not an 학師.
26:44Even if it's a body of a man that doesn't have to turn away for the plant.
26:46It's not an argument for a human being.
26:48It's not an accident for a human being.
26:50It's a very simple thing that takes place for the plant,
26:51It's an assistant for a human being.
26:52It's not an accident for a human being.
26:53But it's busy with a human being.
26:58And it's an honest question for one being.
27:01Maybe it's not an ally of the people.
27:03Maybe it's an easy answer for a human being.
27:05It's the end of the day.
27:07It's the end of the day.
27:09From such apparitions as these come spores, the fungal equivalent of seeds.
27:39They are so small that they drift away like smoke.
27:46But the appearance of these spectacular constructions is brief.
27:50As soon as their spores have been shed, sometimes after only a few days, they collapse.
28:01Now they are merely food for maggots.
28:06Although the corpses of plants do not retain their nutriment forever, some of it is consumed
28:11by fungi.
28:12And the remainder, now in soluble form, seeps back into the soil to sustain the next generation.
28:24But it is not always easy for that new generation to get a start.
28:28Here on the northwest coast of America and in British Columbia, fir, spruce and hemlock
28:33grow so densely and tall that very little light filters down to the world below, except when
28:40one of them dies.
28:43This giant tree fell about ten years ago.
28:47The gap it left in the canopy above is still open, but there is still very little light
28:53on the forest floor itself.
28:55These ferns and mosses are so very thick.
28:58But up here, on the fallen trunk, things are very different.
29:04This is the next generation.
29:07Bare bark doesn't hold the moisture.
29:10Thick moss could bury a seedling.
29:13But in moss like this, growing in such a position, a young plant can get all the moisture and the
29:18light that it needs.
29:20It's thread-like roots grow downwards over the surface of the trunk.
29:36Even before they reach the ground, they find plenty of nourishment, from the soil accumulating
29:41around the clumps of moss, and from the bark that is already being broken down by fungi.
29:49Eventually, the roots make contact with the earth, and one after the other, a whole group
30:00of vigorous saplings establish themselves along the trunk.
30:05So eventually, a row of giant trees stands in the forest in a line of almost regimental straightness.
30:14Which is propped up on arching roots that never were beneath ground, but which still hold between
30:21them the rotting remains of the huge trunk that 150 years ago nursed them into life.
30:30Southern Australia, in the rolling mountains outside Melbourne.
30:39It's drier here than in the American Northwest, but there's still enough rain to support tall
30:44forests, and with them, a rich, dense undergrowth.
30:49These ferns are even taller than the ferns in British Columbia.
30:56These are tree ferns, but they're still only understory.
31:10And with them rise one of the tallest of all trees.
31:17And there's inside a rock with the long-finger seeds.
31:19They're always behind the farm.
31:22They're always behind the ground.
31:25They're still taking up on the rocks.
31:27So, you know, it's the whole tree.
31:30And a little near the rock's edge.
31:35They're still building up on the rocks.
31:36And a little near it.
31:39And it's the back of the orchestra that the ground is.
31:42These are called locally mountain ash, but they're no relation of the European ash.
31:54In fact, they're eucalypts, and they stand over 300 feet tall.
32:02They carry their tiny seeds in small capsules, and shed them a few at a time throughout the year.
32:12But in the deep shade, the seeds stand no chance.
32:27Even if they had landed on the fallen trunk of one of the adults,
32:31they would not have been high enough above the ground to be clear of the tree ferns.
32:36The fact is that in mature forests like this, the mountain ash has a severe problem of regeneration.
32:43The solution could not be more dramatic.
32:49It's another of those events that, for human beings, are major catastrophes.
32:55A forest fire.
33:00Oil in the bark and leaves of eucalyptus make them extremely inflammable.
33:05As the flames leap higher, the seed capsules up in the crowns are singed,
33:15and they shed their contents.
33:19The fire grows in strength and becomes a firestorm.
33:23In the wake of such a huge burn, little is left alive.
33:52But safe in the soil, below the worst of the heat, many of the eucalyptus seeds have survived.
34:08In the sunshine, they sprout with extraordinary speed.
34:18Few, if any of their competitors, can match them.
34:22Nourished by the rich dressing of ash,
34:24they grow around the charred logs as thick and as uniform as a crop of wheat.
34:29Within a year or so, they're so tall that no other competitors are able to invade their land.
34:42This stump was burning exactly ten years ago,
34:55and these saplings around me sprouted from seeds that germinated immediately after that fire.
35:15The saplings are growing so close together that their roots interlock,
35:20forming a dense mat into which few other tree seedlings can get a root hold.
35:25This land still belongs to the mountain ash.
35:28As the trees begin to spread their canopies, the less vigorous saplings are thinned out.
35:41Now there is space on the ground for the tree ferns to return.
35:47Only the giant redwoods of California exceed the mountain ash in height,
35:51and that may only be because of the activities of loggers.
35:54Back in the 19th century, one ash was felled here that measured 435 feet.
36:02That's the tallest tree ever known.
36:06The greatest threat to the survival of this forest
36:10is that it should grow for hundreds of years without fire.
36:16Should that happen, then these huge trees will eventually die from sheer old age,
36:23fall, and lie buried among the tree ferns without ever having receded.
36:29The paradox is that this magnificent forest can only survive
36:34if it is first almost destroyed.
36:38Another fire, this time in the west of Australia.
37:00Here the soil is so poor and the climate so dry that tall trees can't grow.
37:09Instead, there's a rich variety of bushy plants.
37:13The grass tree has a shock of long leaves that burn fiercely but quickly.
37:18It is neither a grass nor a tree, but a strange relation of the lilies.
37:22What looks like a woody trunk is a fibrous stem that has a special protection.
37:34The grass tree sheds its leaves each year,
37:37but their bases remain attached to the stem
37:40and produce a thick gum that glues the whole lot together
37:44into a very effective fire guard.
37:46Even if it doesn't save every one, most will survive.
37:52Indeed, every species here has to have the ability
37:54to live through at least a brief fire.
37:57Otherwise, it would quickly lose its place in the community.
38:03It's eight months since the fire,
38:05and the bush has recovered in a most dramatic way.
38:08The fire stimulated the various plants in at least four different ways.
38:13Its sheer heat baked these fruits of the banksias,
38:17opening the windows on the sides
38:18and allowing the seeds to fall to the ground.
38:22The fire also produced great volumes of ethylene gas,
38:26and that triggered the grass tree,
38:29after it had regrown its burnt leaves,
38:32to put up this huge green spike,
38:35which will ultimately carry its flowers.
38:37The smoke of the fire was the stimulus
38:42which caused seeds that had lain dormant in this sand
38:47for the last 20 years or so since the last fire.
38:51It triggered them to produce the annual plants
38:54which are now springing up.
38:56And it was the sudden superabundance of nutrients
38:59produced by the fire in its ash
39:02which allowed the perennial plants like this lovely cat's paw
39:06to cover the whole ground with colour.
39:12Within a few years,
39:15the whole community is fully restored.
39:17The fire was an opportunity for the social struggle to begin again.
39:36Each individual plant had to fight once more for living space,
39:41profiting or suffering from the speed at which it recovered
39:43or its suitability to any slight change in the terrain
39:47that the fire created.
39:49But overall, the character of the bush remains unchanged.
39:59The grasslands of East Africa are not so stable.
40:03Here, fire or its absence can trigger great change.
40:07This fire is advancing quite fast
40:13because the grass is so dry
40:14that as soon as the flames get onto a bunch of leaves,
40:18they're consumed within seconds.
40:20And as long as there's wind behind it,
40:22well then, it will travel.
40:24But in fact,
40:26the line of the fire is very thin.
40:30And if I want to,
40:31it's quite easy to cross it.
40:33Here we go.
40:37The land certainly looks ravaged and destroyed.
40:46But in fact, little damage has been done.
40:49The leaves of these grasses certainly have disappeared.
40:52But the roots are undamaged.
40:57The heat is at its least intense close to the ground.
41:01And this part of the root,
41:02just close to the surface of the earth,
41:05is totally undamaged.
41:07And it's from here that the new growth will come.
41:13And there are many around
41:15to relish the succulent young leaves.
41:20Grasses can survive such cropping
41:22because their leaves readily break at the base when pulled,
41:25leaving the horizontal stems and their buds undamaged.
41:28Plants with vertical stems grow from the top.
41:37If they are cropped, they're likely to be killed.
41:43And if they're pulled,
41:45they come up, roots and all.
41:47So the great herds of Africa, in effect,
41:54weed out the grass's competitors.
41:56And it has vast acres to itself,
41:59which suits the grazers as well as the grass.
42:03But something can upset this happy arrangement,
42:06another of those environmental catastrophes.
42:09This time, it's drought.
42:12The sun turns the soil to dust.
42:16The animals, having eaten the last of the dry stalks,
42:19move away to look for food elsewhere.
42:23The land is left bare.
42:25Scavengers come to clean up the corpses
42:29of those that starve to death.
42:31But they, too, will soon leave.
42:35When the rains at last return,
42:38the grass springs again.
42:40And so do other plants
42:41whose seeds one way or another have landed here.
42:44With no animals to graze them,
42:46acacia seedlings grow into bushes.
42:50And they grow very fast.
42:52Once they're a couple of feet high,
42:54they're tall enough to survive
42:55a quickly moving grass fire.
42:57And their thorns will protect them from most grazers.
43:09By the time they're about ten years old,
43:12their spreading branches
43:13are cutting off most of the light from the ground.
43:16Their thrusting roots
43:17are sucking up most of the moisture.
43:20And the grass has virtually disappeared.
43:24A patch of acacia scrub
43:28has established itself.
43:30And all the trees, significantly,
43:32are of the same age and height.
43:34They all took the same opportunity to sprout.
43:40But this situation isn't permanent either.
43:44Here we go.
43:50Here we go.
43:59Remember,
44:01I've got it.
44:04Remember,
44:05I've got an influence.
44:05So clean the house and land.
44:06Now,
44:07what about the iron?
44:07But I was in a hole.
44:08Let's get out.
44:08What are you going for?
44:09Come on.
44:10No, no, no.
44:10It doesn't take effect.
44:10I recommend you to the earth.
44:11I can't know.
44:11A hungry elephant that fancies a mouthful of acacia leaves
44:28has no problem and no hesitation either
44:31in pushing over the whole tree in order to get it.
44:36Whoa!
44:41Strangely, it's not just acacias that they knock over.
44:46They also push down comifera trees.
44:50They don't even like their leaves and seldom eat them.
44:54So is that just wanton destruction?
44:57Or can they possibly know what the effect of removing the trees will be?
45:11Whether they know it or not, a group of elephant,
45:15once they've taken up residence in an area,
45:18can turn what looked like a promising acacia woodland
45:21back to grass in only four or five years.
45:28The grazers return.
45:30And the elephants, once more, have supplies of their favourite food,
45:35which is grass.
45:37Elephants are, without any doubt, prime factors
45:58in removing thorn scrub from the plain
46:01and allowing grass to spread.
46:04You could argue that, in effect, they are farming the grass,
46:08knocking over trees they don't like
46:10and browsing thorn scrub to destruction.
46:13But you could also argue things the other way round.
46:17You could maintain that it is the grass
46:19which is exploiting the elephants.
46:21By providing them with food, year after year,
46:25the grass remain the dominant plants on the plains.
46:29And if you look at things that way,
46:31well then that is a trick
46:33which other grasses have played on a worldwide scale.
46:37Wheat once grew only around the Mediterranean.
46:42Ten thousand years ago,
46:44its seeds were accepted by a small group of human beings as food.
46:48That food was so much for their liking
46:51that they sowed the plant wherever they settled
46:53and carried it with them as they overran the earth.
46:57So, a few species of grass, by recruiting the aid of animals,
47:04and in particular ourselves, the human animal,
47:07have succeeded in interrupting the ecological cycles
47:11that have operated for millions of years in so many parts of the earth.
47:15They've managed to claim for their own exclusive use
47:19not only wide open plains,
47:22but fertile well-watered lands
47:25that once supported rich communities of animals and plants.
47:29These grasses have solved the social struggle.
47:33They have got rid of their competitors.
47:45They have got rid of the crowds,
47:50and they were alltsåли also to be able to control the causes of.
47:51And we might not end up being able to enjoy other people's lives.
47:53They were soვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვვ