- 2 months ago
Category
📺
TVTranscript
00:00Nuestro planeta es el más grande puzzle de vivienda en el universo.
00:05Un colección de mundos dentro de mundos.
00:09Cada uno un ecosistema de un ecosistema de vida.
00:17Pero cómo funcionan?
00:20El intercambio web de relaciones y la influencia de las fuerzas naturales
00:26makes each micro-world complex and unique.
00:33So, to discover their secrets, we need to explore them one by one.
00:40Untangle their interlocking pieces.
00:43And ultimately reveal the vital piece.
00:47The key to life itself.
00:50Hidden deep within each of nature's micro-worlds.
00:56The Amazon.
01:05The largest rainforest on Earth.
01:10Feeding the mightiest river in the world.
01:13It drains over 40% of South America.
01:23And holds a fifth of the entire world's river water.
01:27Up to 12 metres of rain falls in parts of the Amazon every year.
01:35But what makes the Amazon even more incredible is the life within it.
01:47For sheer diversity of species, it's unparalleled.
01:52It's estimated to be home to up to 3 million species.
01:57Over 500 kinds of mammal.
02:0130% of the world's bird species.
02:04And it's plants produce 20% of the world's oxygen.
02:12The Amazon river even holds more kinds of fish than the whole of the Atlantic Ocean.
02:18A complex ecosystem with infinite connections and relationships.
02:28But as we shall discover, as in all our micro-worlds, there's one piece that this entire system relies on to survive.
02:36And without it, the rainforest would look like this.
02:47Areas that have been slashed and burned for agriculture fail rapidly.
02:52And before long, the land cannot even support crops.
02:56All our micro-worlds rely on nutrients.
03:00They're the building blocks of life.
03:02Phosphorus, potassium and calcium.
03:05Vital elements that plants need to grow.
03:09But these nutrients are not a stable part of any ecosystem.
03:14Here, they're either locked up and unobtainable in living tissue.
03:18Or washed out by the incessant rain.
03:22And it's so poor in available nutrients that scientists refer to the Amazon as a wet desert.
03:35The endless rain affects the trees, plants and soils.
03:43And are constantly washing the building blocks of life away.
03:48Life here is actually surprisingly hard.
03:51So how in such a nutrient-poor micro-world is there so much diversity and life?
03:58The answer is that in nature, adversity leads to adaptation.
04:11Animals and plants have carved out incredible niches and formed vital relationships.
04:17Not just to survive, but to thrive here.
04:21But is there one that holds the key to all this success?
04:26Understanding the Amazon, the most complex ecosystem on Earth,
04:37is one of the greatest challenges that ecologists have ever faced.
04:43Our only chance is by unpicking its web of connections
04:46until we can hopefully discover how the Amazon is able to support such diversity
04:51on such slim pickings.
04:57The Amazon is so massive and so intricate
05:00that we're really going to have to delve deep
05:02and get under this micro-world skin
05:04to search for the pivotal piece.
05:11So in our investigation, we need to start small
05:15and focus on the details first.
05:21Like all micro-worlds, the Amazon is a showcase of natural selection.
05:30The inhabitants have evolved over time
05:32to exploit every niche, every opportunity
05:35that exists within its world.
05:41But what makes the Amazon special
05:43is the vast number of relationships that are developed.
05:46Particularly compelling is the interaction between flowers
05:54and one of the most beautiful groups of birds on the planet.
05:58Hummingbirds.
06:04Like bees, they're attracted to flowers
06:06for their energy-rich nectar.
06:08But in a world where every nutrient has to be locked up safely,
06:16the flowers can't give their valuable resources away
06:19unless they get something in return.
06:25The plants need to be pollinated.
06:29So as the birds feed,
06:31they get their heads sprinkled with pollen.
06:33But this only works
06:38if the hummingbird delivers the pollen
06:40to another flower of the same species.
06:43And that's the clever bit.
06:46Over thousands of years,
06:47the flowers and the birds have evolved together
06:50so that only the species of bird
06:54with the right-shaped beak
06:55can get nectar from their species of flower.
06:58The birds are guaranteed food
07:03and the plant guarantees it gets pollinated.
07:11Relationships like this are born out of necessity,
07:14but they might not hold the key
07:15to how this world works.
07:21The pivotal piece in many microworlds is a constant,
07:25something that doesn't change much,
07:27so the rest of the world can keep up.
07:30So to find the key in this complicated world,
07:33first we need to find this constant.
07:39And there's one thing you can rely on in a rainforest.
07:43Rain.
07:49Massive quantities of rain fall on the Amazon.
07:52An average downpour can dump two and a half centimetres of water
07:57on the forest every hour.
08:03This rain usually comes from water
08:05evaporated from the sea.
08:08However, the Amazon is so immense,
08:11it literally makes its own rain.
08:1370% of the rain that falls
08:16has evaporated from the trees themselves.
08:23And this constant rain has had a direct effect
08:26on the shapes of things in the forest.
08:31Plants have developed leaves with gutters
08:34and spouts to get rid of as much water as possible,
08:38because a leaf that doesn't dry off
08:39will end up rotting alive.
08:44Life can't survive without water,
08:47so the rain's an essential part of this system.
08:49But as we've seen,
08:52all the good it does
08:53is balance by the damage it causes.
08:57Literally washing away the rainforest itself.
09:04So if the rain's effect
09:05is to carry the forest away,
09:07what happens to it after this?
09:13Well, it ends up being transported
09:15by the most obvious force in our microworld,
09:18the Amazon River.
09:32It's a huge destructive force.
09:37Each year, it removes an enormous
09:39one billion tons of sediment and mud
09:41from the forest basin
09:42on its march to the sea.
09:48During the course of this program,
09:50it would have dumped the equivalent
09:51of 150,000 Olympic-sized swimming pools
09:55into the ocean.
09:58But the river is not as constant
10:00as you might think.
10:03It's so powerful
10:05that it scours deep channels
10:06barging its way through the forest,
10:09constantly changing course
10:11on its way to the Atlantic.
10:15But as destructive as it seems,
10:17it also creates opportunities for life.
10:23As the river loops through the forest,
10:26these meanders become very curved
10:28until eventually the neck of the meander
10:30touches the opposite side,
10:33cutting off a big loop
10:35from the main river.
10:40In creating these pools
10:41known as oxbow lakes,
10:43the river creates a slightly different habitat
10:46to be exploited.
10:51These isolated bodies of water
10:53are the ideal space
10:54for one of the river's top predators,
10:57the two-meter-long giant otter.
10:59The lakes are full of fish
11:03and the waters are calm,
11:05so the otters use them
11:06to rear their young
11:07away from the powerful main river.
11:11So in a micro-world
11:12where every available space
11:13is to be exploited,
11:15the otters have turned
11:16this dead-end feature of the river
11:18to their advantage.
11:23The river is actually
11:24a dynamic element
11:25in this environment.
11:27It's not the key to its existence,
11:29but its destructive nature
11:32does open up
11:33a lot of opportunities to life.
11:37Some of the sediment
11:39the river picks up
11:40gets dumped again,
11:41forming large banks.
11:46The minute space becomes available,
11:49something is there to exploit it.
11:51Thousands of giant river turtles
11:53use these banks
11:54to make their nests.
11:59So many come here
12:01that each wave
12:02digs up the nests
12:03laid moments before.
12:05And in a world
12:06short on nutrients,
12:07this bounty
12:08is not missed for long.
12:13At every turn,
12:14another opportunity
12:15is created
12:16and the black vultures
12:17are ready to jump in
12:19and make the most of it.
12:20Like their sea-dwelling cousins,
12:25these turtles
12:26have a strategy
12:27that involves
12:27producing so many eggs
12:29that they can afford
12:30to lose some casualties
12:31along the way.
12:33But in this
12:34ever-changing world,
12:36the turtles
12:36might have to look
12:37for a new nesting site
12:38next year.
12:39So the river
12:44is dependent
12:44on the rains.
12:46Both are prominent players
12:47in the Amazon's ecosystem.
12:49But they both
12:50play a role
12:51in removing
12:51the most vital piece
12:53of this puzzle,
12:54the nutrients.
12:57So how does
12:58the forest
12:58keep hold
12:59of enough
12:59of the good stuff
13:00to stay alive?
13:01In the Amazon,
13:0999% of the nutrients
13:11are locked up
13:12in living tissues.
13:14So when any of this
13:16becomes available,
13:17it's pounced upon.
13:19Nothing goes to waste.
13:22Trees,
13:23leaves,
13:23dung,
13:24and dead bodies
13:24are recycled
13:25almost immediately.
13:31The recycling team
13:33are an ungainly
13:34rabble of floor dwellers
13:35that lurk and skulk
13:37in the dark,
13:38damp recesses
13:39of the forest.
13:42Like this giant
13:44meter-long earthworm,
13:46they methodically
13:47race against the rains
13:48to reclaim
13:49as many nutrients
13:50as possible.
13:56Even so,
13:57commodities are scarce.
14:00Phosphorus,
14:00potassium,
14:01and calcium,
14:03essential elements
14:03for life,
14:05are hard to find,
14:06and because of the rain
14:07can be gone
14:08in a heartbeat.
14:12But the recycling teams
14:14are good.
14:15So good that sometimes
14:16things get recycled
14:17before they're even dead.
14:24Spores of the cordyceps fungus
14:26float through the air
14:27and find their way
14:29inside an insect host.
14:31The fungus attacks them
14:33from inside their bodies,
14:35killing them
14:36and consuming them
14:37from within.
14:40The fruiting body
14:41then erupts
14:42out of the dead insect
14:44and releases its spores
14:45to float through the air
14:46and infect other
14:48unfortunate individuals.
14:51But even here,
14:52there's a dark interdependency.
14:54Each strain of cordyceps fungus
14:58only infects
14:59its own particular species
15:00of insect.
15:11These recyclers
15:12play a vital role,
15:13keeping what little nutrients
15:15there are
15:15moving around the ecosystem.
15:17But this is certainly
15:20not enough
15:21to have created
15:22this forest of giants
15:23in the first place.
15:28So where would the trees
15:30normally get their nutrients from?
15:32Here, trees can grow
15:38to over 50 metres tall.
15:40There's enough light
15:41and water in the Amazon
15:42to fuel rapid growth.
15:44But it's not enough.
15:49These giants,
15:50like everything here,
15:51need those nutrients
15:52to grow to these
15:54incredible sizes.
15:58Trees usually get
15:59all the nutrients
16:00they need from the soil.
16:02But what's different
16:03in this micro-world
16:04is that these are
16:05some of the poorest soils
16:06on the planet.
16:10Only 1% of the nutrients
16:12in this ecosystem
16:13are found in the soil,
16:15compared to 50%
16:16in temperate forests.
16:18So the Amazon trees
16:19are really up against it.
16:24Only the top 50 centimetres
16:26has any nutritional value.
16:28Below this,
16:29there's only clay
16:30that's no use to plants.
16:36So in response,
16:37the trees send their roots
16:39not down,
16:40but out through
16:41as much of the fertile topsoil
16:42as they can.
16:47The only problem with this
16:49is that it makes them
16:50pretty unstable.
16:56One way around this
16:58is to create huge buttress roots
17:00that help stabilise them.
17:01And they need a good foundation
17:06because they're competing
17:07with the other trees
17:08for the other vital resource here.
17:11Sunlight.
17:13The trees are so successful
17:14at exploiting sunlight
17:16that the forest floor
17:17is in constant shade.
17:19Only 2% of sunlight
17:21penetrates this canopy.
17:23So how does a young plant
17:25that's just starting out
17:26get established here?
17:32Cheese plant seedlings
17:34have a strange solution
17:35to this problem.
17:40Instead of heading for light,
17:42they search for darkness.
17:43The shadows created
17:50by a buttress root
17:51of a big tree.
17:58Once there
17:59and using the tree
18:00for support,
18:02they can race upwards
18:03towards the light.
18:04The cheese plant
18:10pours its energy resources
18:12into thin, rapid growth
18:14rather than strong stems
18:16and leans on the tree
18:18for a helping hand.
18:19This gives it an advantage
18:21in a world
18:22where nutrients are limited.
18:31Other plants
18:32don't even bother
18:33to start at the bottom.
18:38Bromeliads
18:38grow high up
18:39in the branches of trees
18:40and so start life
18:42closer to the light.
18:50They have ponds
18:52in their centres
18:52that fill with up to
18:548 litres of rainwater,
18:57offering a water source
18:5830 metres above the ground.
19:03And where there are ponds,
19:10there are usually frogs.
19:12One of the most poisonous creatures
19:14on earth
19:15relies upon the Bromeliads
19:17for their rooftop pools.
19:19This poison arrow frog
19:22carries its tadpole,
19:24hatched from an egg
19:24laid on a leaf
19:25to a pool
19:27in a Bromeliad heart.
19:30Here, the tadpole
19:31has its own private pool
19:33tended by its parents.
19:35So the frogs
19:38rely on the Bromeliad
19:39for a home
19:40but give the plant
19:41nutrients
19:42in the form of faeces
19:43and leftover food.
19:45And the Bromeliad
19:46relies upon the tree
19:47to keep it near the sunlight.
19:49The treetops
19:53are where it's really at.
19:56So successful
19:58are these high-rise communities
19:59that researchers
20:00discovered a single tree
20:02in the Amazon
20:02to be home
20:03to nearly 2,000
20:05species of insect
20:06and spider.
20:07Only 100 of these
20:08were already known to science.
20:10With such limited resources
20:15and so many mouths to feed,
20:18once the plants
20:19have secured nutrients,
20:20they have to keep hold of them.
20:26Many Amazon plants
20:28use poisons
20:28to protect their leaves
20:30from the hungry vegetarians.
20:32But again,
20:34nature finds a way.
20:38The piping guan
20:40only eats the tender
20:41new tips
20:42that hold the least poison.
20:45Most leaf eaters
20:46eat some
20:47then move on
20:48before they get
20:49too large a dose
20:50from any given tree.
20:53The white-faced
20:54Saki monkey, however,
20:55has evolved
20:56a highly specialised
20:57digestive system
20:58that can cope
20:59with virtually any toxin
21:01found in the rainforest.
21:06And there's another primate here,
21:08one of the smallest
21:09in the world,
21:10that's found
21:10a different way
21:11around the tree's
21:12poisonous defences.
21:17Pygmy marmosets
21:19are omnivorous,
21:20eating both plants
21:21and insects.
21:23But their favourite food
21:24is tree gum,
21:26produced by the trees
21:27when their trunks
21:28are damaged.
21:29The marmosets
21:30have learnt
21:30to keep this food supply
21:31going by reopening
21:33previous wounds
21:34on the tree.
21:34and they've evolved
21:36special teeth
21:37to do so.
21:42These tiny monkeys,
21:44which could fit inside
21:45a teacup,
21:46have learnt how to exploit
21:47a particular food source
21:48at the tree's expense.
21:50rather than fighting back,
22:00some plants
22:01have developed
22:01relationships
22:02with animals
22:02that benefit
22:03both parties.
22:04they grow tasty,
22:08energy-rich fruit.
22:1244 different species
22:13of bird and monkey
22:14can feed on a single tree.
22:16And the benefit
22:19for the tree
22:20is that contained
22:22inside the fruit
22:23are seeds
22:24that cannot be digested.
22:27So as the vegetarians
22:28move off
22:29through the forest,
22:30what's gone in
22:31has to come out.
22:34And the minute
22:35it hits the floor,
22:36in come the forest
22:37street cleaners.
22:41Dung beetles
22:42detect the bounty
22:43immediately.
22:46The males meticulously
22:47ball it up
22:48and roll it away
22:49with their hind legs.
22:52However,
22:53it is a lot easier
22:54to steal someone else's
22:56than to make your own.
22:58And the bigger the ball,
23:00the better the chances
23:01of attracting a female.
23:04Once he's clear,
23:05the beetle rolls
23:06his ball away,
23:07burying it in a safe place
23:09so that the female
23:10can lay her eggs inside.
23:12And the tree's seed
23:14is planted
23:14with its own source
23:16of fertiliser.
23:20So in this relationship,
23:22the trees are connected
23:23to both the fruit eaters
23:24and the recycling team.
23:26And they all benefit.
23:33There's one species
23:34of plant that's taken
23:35this one stage further
23:37and developed
23:38a much more direct
23:39and surprising relationship
23:41to get ahead.
23:42This might appear
23:46to be a natural
23:46forest clearing,
23:48but in fact,
23:49it's inhabited
23:50by only one species
23:51of plant.
23:54One species of plant
23:56and thousands of ants.
23:58In this bizarre relationship,
24:04the plant has enlisted
24:05the ants' help
24:05in a very surprising way.
24:10The ants inject
24:11formic acid
24:12directly into the leaves
24:13and stems
24:14of any other plants
24:15that try and grow
24:16in the clearing,
24:17killing off all
24:18but their host plant.
24:25And the ants
24:26don't stop there.
24:29They also provide protection.
24:33They attack any animals
24:34that try and feed
24:35on the plant's leaves.
24:36Even giants,
24:41many thousands
24:42of times their size,
24:43are not immune
24:44to a bit of ankle biting.
24:51This is a great service
24:53if you're a plant
24:53in this competitive environment.
24:56But what do the ants
24:57get in return?
24:59The plant has small openings
25:01and swellings
25:02along its branches.
25:04These tiny cavities
25:05provide the ants
25:06with a home,
25:08protecting them
25:09from predators
25:10and giving them
25:11a safe place
25:12to rear their young.
25:15It's a collaboration
25:16developed over millennia
25:18and another example
25:19of how to survive
25:20out here
25:21by building
25:22a successful relationship.
25:26And it's one
25:27of these relationships
25:28that holds the key
25:29to the success
25:30of this entire ecosystem.
25:34But it's not colorful
25:35or obvious.
25:36and happens
25:37completely out of sight.
25:47Within the soil,
25:49the trees hide
25:49a symbiotic relationship
25:51with a fascinating fungus.
25:53The fungus are attached
25:56to their roots
25:57and absorb the available nutrients
25:59far faster than the trees
26:01because they have
26:01a huge surface area.
26:04They efficiently take elements
26:06like phosphorus,
26:07potassium and calcium
26:08out of the soil
26:09and into the tree
26:11before the rain gets a chance
26:13to wash it all away.
26:14But this relationship
26:16is mutually beneficial.
26:18Both parties benefit.
26:21In return,
26:22the tree supplies
26:23the fungus
26:24with sugars
26:25and starches
26:26that it can't
26:26obtain itself.
26:29One could not survive
26:31without the other
26:32and the rainforest
26:33as we know it
26:34would not exist.
26:35The delicacy
26:40of this relationship
26:41and the importance
26:42it has
26:43on this microworld
26:44is clearly demonstrated
26:46where the rainforest
26:47has been cut down
26:48for agriculture.
26:49The rain quickly washes away
26:55the little goodness
26:56held in the soil
26:57and the sun
26:58bakes the ground solid.
27:02With no trees
27:03to shade the ground
27:04or to provide
27:05essential sugars
27:06the fungus in the soil
27:08dies out
27:08leaving the soil
27:10barren
27:10untenable
27:12for trees
27:12to recolonise.
27:15Without this partnership
27:16there would be
27:17no rainforest
27:18and so many species
27:20rely on this ecosystem.
27:27The Amazon rainforest
27:29is a complex web
27:30of interconnectivity
27:32where many organisms
27:34rely on the others
27:36to survive.
27:36The more diverse
27:49the microworld
27:50the more robust
27:51it is to change.
27:54But as we've discovered
27:56even our biggest
27:57and most diverse ecosystem
27:59relies on a fragile balance
28:01between the environment
28:03and the species
28:04that live within it.
28:07And without one
28:08surprising alliance
28:10between a tree
28:11and a fungus
28:11life in our microworld
28:14would not exist at all.
28:19But it does
28:21and it has created
28:22one of the most incredible
28:24and intricate microworlds
28:26on our planet.
28:27Helping the baby cheetah
28:37with the poorly poor
28:38tomorrow
28:39spend an hour
28:39with the big cats
28:41about the house
28:41on BBC 2
28:42at 8.
28:44Here on BBC 4 next
28:45astonishing designs
28:47and mastery
28:48of metalwork
28:49the blacksmith's tale
28:50in just a moment.
28:51Thank you very much.
Comments