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(ANIMALS CALL)
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We live in extraordinary times.
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We are surrounded by more
species of animals and plants
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than there's probably ever existed,
at any one time, in the history of the earth.
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For nearly fifty years,
I've been lucky enough to spend my time
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travelling around the earth
documenting those animals and those plants.
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It's now increasingly apparent
that one species, our own,
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has developed the unique ability
of so altering its surroundings
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that it can destroy whole species,
indeed whole environments.
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How great is the damage
we're actually doing to the world?
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Why is it that what we do
has such a destructive effect?
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How can we change what we do, in order
to ensure that our children and grandchildren
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inherit as wonderful and as varied a world
as we were lucky enough to do?
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I'll be putting those questions to some
of the world's leading scientists,
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in order to discover the very important answers.
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I will be looking for clues all over the world.
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Some can be found on the savannahs of Africa.
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Others are to be sought under the sea.
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We will visit our own past
and consider our future.
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Scientists will talk about
their own most recent research,
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in order to help us understand the truth
about the current state of our planet.
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First, we have to establish the facts
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about the scale of the damage
we have done to the earth so far.
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Forty years ago, our curiosity
about the worlds beyond our planet
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led to one of the most stupendous
achievements in human history.
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(GROUND CONTROL)
We have ignition sequence start.
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Five... four... three... two... one... zero...
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- We have contact...
- Lift off...
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(ATTENBOROUGH) Paradoxically,
sending a rocket towards the moon
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made us aware in a radically new way
of the true nature of the world it left behind.
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For most of human history,
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our world had seemed vast
and its resources infinite.
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But those men in space saw something different.
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(ASTRONAUT) It is a most beautiful sight.
What a view!
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It's absolutely unreal!
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I have never seen... All I can say
is it's spectacular!
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(ATTENBOROUGH) The astronauts' view
made us realise more vividly than ever before
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that the earth is limited
in both its space and its resources.
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From that, it follows that there must also be
a limit on the amount of life our planet can hold.
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Living creatures on this planet have always
had to endure natural catastrophe and change.
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Yet now there is a greater variety of life on earth
than there has ever been.
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So change and damage are not necessarily
destructive to life as a whole,
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and the view from space showed us why.
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It's because such damage,
even when on a scale that seems disastrous
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to those of us in the midst of it,
is usually local in extent.
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We now realise that such change is the spur
which has created life's richness
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by presenting new opportunities and challenges
to which animals and plants have responded.
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Life, in fact, can recover from or adapt to
even very great local damage.
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But today the damage inflicted
by humanity is global
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and it's taking place at a speed
that is without precedent
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in the whole three and a half billion years
of its history.
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To understand the scale
of our impact on the rest of life,
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we have to discover just how great
the diversity of life on earth really is.
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For the past 500 years,
scientists and explorers have travelled the world
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cataloguing its natural wonders.
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We can still see the biggest creature
that has ever lived, the blue whale,
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and the simplest, microscopic bacteria.
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0n land, in the air and under the sea,
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we have discovered
an astonishing variety of life-forms.
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That work is still going on,
giving us an ever better understanding
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of this astonishing variety of life,
this biodiversity.
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So, how many different kinds
of living things are there?
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Biologist Sir Robert May
has made a special study of this question.
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Amazingly, we don't actually know how many
distinct species have been named and recorded.
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For the major groups, like birds and mammals,
the furries and the featheries,
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we really do know that for most groups,
they're on scattered records in different museums,
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not yet coordinated into one big computer base.
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Best guess would be about one and a half million
different plants, animals, fungi, algae...
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This listing and cataloguing of the natural world
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has occupied the lives
of many experts and still does.
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A total as great as one and a half million
species might seem to suggest
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that we have discovered the majority
of life-forms on the planet.
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But that is not so.
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Again and again, new discoveries
suddenly make us aware
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of just how limited our knowledge still is.
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Nowhere demonstrates this better
than the savannah grasslands of East Africa.
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In this environment, as in many others,
it's the big mammals that capture our attention.
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They've become so famous through books,
television programmes and safari holidays,
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that you might well think that they represent
the majority of the animals here.
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The scale of biodiversity
on the African grasslands is a bit deceptive.
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If you go out during the day, you're probably
looking for spectacular animals like elephants.
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You'll also see a few smaller things
like butterflies and beetles and bugs,
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but the overwhelming impression you have,
in terms of sheer mass of life,
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is of herds of just a few kinds of big animals.
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The truth, as research has recently shown,
is quite different.
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For evidence of that, just look in the grass.
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This is a column of driver ants.
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Their ferocity is so great
and their appetite so huge
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that they've given rise to all kinds of legends.
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Stories about human beings or horses
stumbling into their path
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and being stripped to skeletons within minutes
are perhaps a little exaggerated,
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but the appetite of these ants is so huge
that they will attack anything
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that can't get out of their way.
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They prey mainly on other small animals
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and move across the grasslands in columns
that may contain twenty million individuals.
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So many ants need vast quantities of prey,
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so their abundance is living proof
that the savannahs teem with smaller life.
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When scientists recently began
to study these smaller creatures,
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they found that 50% of the insects
they were seeing were new to science.
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Simple calculations suggest
that driver ants alone
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consume more animal matter
per year on the grasslands
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than all the famous big predators put together.
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The reason why it's difficult
to appreciate the full scale
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of biodiversity on the savannahs
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is that many creatures that live here
are both nocturnal and very, very small.
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You get some impression of what they are
if you come out at night with a lamp like this.
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To get an idea of the full range of those creatures,
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you have to use a light of a very special kind,
like this one...
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The bulb that's illuminating this sheet
produces a high proportion of ultraviolet light,
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and many night flying insects
find that absolutely irresistible.
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There are moths... small ones,
big ones, here's a kind of silk moth.
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Beetles... more moths.
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A mantis... a great fat sausage fly.
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An ant lion.
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Lots of tiny little insects,
I can hardly see what they are.
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0h, and mosquitoes!
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Recent work has shown
that there's a far greater variety
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of insect life on the savannahs
than was previously thought.
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There may not be as many species
as are found in the tropical rainforest,
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but in terms of sheer quantity,
the savannahs are their equal.
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It was in the famously rich
rainforests of South America
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that research first revealed
the scale of our ignorance.
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If you walk slowly and look carefully
in a rainforest like this one in Ecuador,
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you can find all kinds of small,
interesting creatures.
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And that's how the first explorers
and naturalists worked.
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It's still possible to find new species that way.
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I picked up this little stick insect from over there.
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In order to discover
whether it's a new species or not,
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I'd have to show it to an expert in stick insects,
and if he couldn't match it exactly,
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then he'll describe it, give it a new name
and I'll have discovered a new species.
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However, I can only search the area from
the ground up to a couple of feet above my head,
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but the trees here grow to over a hundred feet tall.
What might be up there?
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Well, birds and monkeys I know
because I can see them from down here,
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but what else might there be?
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Until very recently,
that was a matter of pure speculation.
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But then professor Terry Erwin
invented a way of finding out.
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He decided that in order to discover what actually
lived high in the canopy of a single tree,
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or even a single branch, he had to use
a machine known as an insecticide fogger.
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This was originally designed for mosquito control,
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but it can be used to sample other insects
equally well.
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(ERWIN) When we first started fogging in Peru,
the results were just absolutely fantastic.
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We never imagined
we were going to get so much.
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(ATTENBOROUGH) The fog,
harmless to anything but insects,
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drifts up into the canopy
and the insects drop down.
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The results of Terry Erwin's early work
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dramatically altered our estimates
of how many different kinds of animals
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there might be on this planet.
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This might seem a rather drastic way
of discovering what lives in the trees.
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However, as well as providing information
that's important for conservation,
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this work has also shown
that insects reproduce so fast here
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that within four months of a tree being fogged
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insects living in it
return to their previous numbers.
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From all of the studies I've made
over these past 25 years,
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and the little bit that we've been able
to analyse in the laboratory,
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it seems like at least 80%
of the species we're getting out of the canopy
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are new species, new to science -
and the reason that's true
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is that the average size, for example of a beetle,
is only three millimetres long.
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And so, just the small stuff hasn't been studied.
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(ATTENBOROUGH) It's not just small things
in rainforests that are still being discovered.
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We're still finding things
even among the primates.
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Among the mammals, our closest relatives,
there are about half a dozen
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new species of primate
that have turned up this decade...
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small marmoset things...
really underlines what we don't know.
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Most of those small primates
were found in the Amazon rainforests.
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Until very recently,
European explorers could only penetrate
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any distance into these vast forests
by travelling up the rivers.
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Now, however, using powerful machinery,
roads have been cut through the forests
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that enable scientists to reach
even the least known areas
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in their search for biological gold - new species.
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It's here that they discovered new marmosets.
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One way of enticing a primate to show itself
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is to play back the calls
of a closely related species.
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This can trick it into thinking
its territory has been invaded by rivals,
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so it may emerge from the forest to investigate.
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In 1992, this technique revealed a new species
of marmoset in this area of southern Brazil.
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Since that discovery,
no one has been back again to look for it,
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and until now it has never been filmed.
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This kind of waiting game can go on for weeks
or months, usually without success.
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- (HIGH-PITCHED SCREECH)
- There it is, the call of a new species.
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This is the black-faced marmoset.
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We have no idea how this animal lives
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or what kind of social interactions
take place in its groups. It has yet to be studied.
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As quickly as they appeared, the black-faced
marmosets melt back again into the forest.
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It's not only on land that the scale
of recent discoveries has amazed scientists.
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The oceans too have been found to contain
a far greater diversity of life
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than was previously thought.
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The sea covers two-thirds of the planet.
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In some parts it's filled
with a huge range of species.
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The famous coral reefs, which occupy
just a tiny fraction of the oceans,
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are probably its best known,
most closely studied habitat.
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Would it be fair to suggest that here at least,
we have discovered most of the inhabitants?
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Sylvia Earle is an expert in marine biology.
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Just as with what we have begun
to understand about rainforests,
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is that there are thousands,
perhaps millions of species
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that have yet to be discovered,
described, even named.
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So it is with coral reef systems
that are enormously complex and diverse,
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but diverse on a scale that exceeds
even that in rainforests.
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(ATTENBOROUGH) If so much remains
to be discovered even about coral reefs,
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which occupy the most shallow
and accessible parts of the sea,
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what about the rest of it?
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The average depth is two and a half miles,
the depth where the Titanic rests.
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The maximum depth is seven miles,
and we're still nibbling around the surface.
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Scuba divers go to a hundred,
a hundred and fifty feet, fifty metres or so.
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We have a few submersibles that can go
down to half the ocean's depth
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and one has been to full ocean depth once,
but most of the ocean remains a mystery.
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(ATTENBOROUGH) What does this tell us
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about the scale of discoveries
still to be made in the sea?
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(EARLE) The greatest area
of discovery has just begun.
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The oceans, less than 5%
have really been looked at.
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Mapping has been done, we know where
the valleys are, the mountains and plains, etc,
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but who lives in the sea?
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What do we really know of how
the natural systems actually function?
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We are just beginning to understand
the magnitude of our ignorance.
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(ATTENBOROUGH) How little we know
has been brought home to us
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by research in the deep ocean,
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where conditions are so severe
that it was once thought
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that no life of any kind could possibly exist.
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In fact, there are great numbers
of creatures in these ocean depths.
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Some recently discovered are so strange
that it can be difficult to see any relationship
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to organisms that live in shallower water.
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Even in the best-known environments,
there are still discoveries to be made.
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00:21:13,727 --> 00:21:16,844
Surprisingly, the greatest
may come from underground.
223
00:21:17,087 --> 00:21:21,205
The topmost layer of land in many places
is of course soil.
224
00:21:20,967 --> 00:21:24,926
This is crucial because, quite simply,
it's what most plants grow on,
225
00:21:25,487 --> 00:21:28,684
and it's vital to us
because we plant our crops in it.
226
00:21:28,847 --> 00:21:32,283
We might think that it's just
dead matter with a few worms in it,
227
00:21:32,207 --> 00:21:35,995
but actually it's full
of the most extraordinary creatures.
228
00:21:36,047 --> 00:21:41,280
Beneath the surface of the soil,
the abundance of life is breathtaking.
229
00:21:41,807 --> 00:21:47,040
In this small patch, there could well be
2,000 different species
230
00:21:47,087 --> 00:21:49,601
and a quarter of a million individuals.
231
00:21:49,487 --> 00:21:54,083
Most of them of course are very small.
Some are microscopic.
232
00:21:54,287 --> 00:21:58,678
But on their own scale,
the drama of their world is just as great
233
00:21:59,087 --> 00:22:04,445
as you can find on the plains of East Africa
or the rainforests of South America.
234
00:22:06,367 --> 00:22:10,645
Here, there are predators and prey,
just a few millimetres long,
235
00:22:10,727 --> 00:22:15,278
with their own complex systems
of attack and defence.
236
00:22:16,487 --> 00:22:20,639
This world lies directly beneath our feet
but we know little more about it
237
00:22:20,807 --> 00:22:23,685
than we do about the deepest
depths of the ocean.
238
00:22:25,647 --> 00:22:30,482
Nematode worms, so small they can only
properly be seen under the microscope,
239
00:22:30,847 --> 00:22:35,602
are armed with piercing weaponry
and protected with elaborate armour.
240
00:22:42,207 --> 00:22:45,244
What is the significance
of all the small forms of life
241
00:22:45,567 --> 00:22:48,684
that are being constantly
discovered these days?
242
00:22:48,927 --> 00:22:53,159
Biologist Edward Wilson
is an expert in biodiversity.
243
00:22:54,207 --> 00:22:57,916
What's important about bugs and weeds
244
00:22:58,047 --> 00:23:03,997
is not just that they have most
of the biodiversity around the world,
245
00:23:04,287 --> 00:23:07,996
but that they are the foundation
of the ecosystem.
246
00:23:08,607 --> 00:23:15,285
If you were to remove all of the biggest animals -
humanity is in the process of doing that -
247
00:23:15,007 --> 00:23:20,320
there would be important changes
in the forests and grasslands
248
00:23:20,567 --> 00:23:25,925
and the other major habitats,
but they would survive, they would go on.
249
00:23:26,007 --> 00:23:32,924
If you remove all of the insects,
probably the entire thing would collapse.
250
00:23:34,247 --> 00:23:37,444
It's the little things that make the world work.
251
00:23:38,087 --> 00:23:40,078
(ATTENBOROUGH) Bacteria are among them.
252
00:23:40,287 --> 00:23:42,755
They're also probably the most abundant,
253
00:23:42,887 --> 00:23:47,039
yet they remain among the least
understood of all forms of life.
254
00:23:48,087 --> 00:23:53,286
If a visitor from another planet were to analyse
all the cells that make up my body,
255
00:23:53,367 --> 00:24:00,000
he or she would come to the conclusion
that I am only 10% human.
256
00:24:00,567 --> 00:24:06,039
That is because 90%
of the living cells in my body are bacteria.
257
00:24:05,847 --> 00:24:10,523
Bacteria are the most numerous
living organisms on earth.
258
00:24:10,647 --> 00:24:13,684
They're also among the smallest.
259
00:24:14,007 --> 00:24:20,765
To understand just how small they are,
let me take a perfectly clean... pin
260
00:24:20,967 --> 00:24:26,280
and put it in this scanning electron microscope.
261
00:24:30,047 --> 00:24:34,279
At low magnifications
the pin seems perfectly clean.
262
00:24:34,847 --> 00:24:39,921
It's only when we zoom in
and magnify it to ten thousand times
263
00:24:39,647 --> 00:24:42,878
that the size of the bacteria becomes clear.
264
00:24:58,967 --> 00:25:03,961
Every living thing on the planet depends
on bacteria, in one way or another.
265
00:25:04,247 --> 00:25:08,479
But we still have no accurate idea
of how many kinds there are.
266
00:25:19,327 --> 00:25:23,286
Recently, extraordinary discoveries
deep below ground
267
00:25:23,647 --> 00:25:28,038
have shown that all our previous
estimates were far too low.
268
00:25:40,927 --> 00:25:47,526
These pumps in California are pulling up oil
from a thousand feet below the surface.
269
00:25:48,127 --> 00:25:52,678
They bring up evidence
that there is life down there as well.
270
00:25:52,567 --> 00:25:55,639
Mostly in the form of bacteria.
271
00:25:55,967 --> 00:25:59,721
Indeed, other evidence suggests that
such microscopic forms of life may exist
272
00:25:59,807 --> 00:26:03,277
two miles, three and a half kilometres
below the surface.
273
00:26:03,207 --> 00:26:08,201
Such bacteria may grow so slowly
that an individual bacterium
274
00:26:08,687 --> 00:26:12,805
may only reproduce once every 500 years.
275
00:26:13,447 --> 00:26:18,646
Among the most extraordinary claims made
for this new and unexpected wealth of life
276
00:26:18,727 --> 00:26:23,357
is that if one
were able to gather it all together
277
00:26:23,367 --> 00:26:29,397
it would weigh more than all forms of life,
animal and plant, that live on the surface.
278
00:26:30,167 --> 00:26:34,126
The discoveries are so new
that we can't yet be sure.
279
00:26:34,487 --> 00:26:40,437
As for how many different kinds of life
there is down there, we simply have no idea.
280
00:26:40,247 --> 00:26:46,482
All of which goes to show we still have a lot
to learn about the planet on which we live.
281
00:26:47,727 --> 00:26:53,359
So what might be the final total
of all the different kinds of living organisms
282
00:26:53,567 --> 00:26:55,797
that presently exist on earth?
283
00:26:56,847 --> 00:27:00,760
(WILSON) Different specialists in the field,
using different methods,
284
00:27:00,687 --> 00:27:04,965
have produced estimates
of the number of species out there.
285
00:27:05,327 --> 00:27:09,400
Plants, animals, bacteria
and other micro-organisms
286
00:27:09,647 --> 00:27:14,641
that fall anywhere from... shall we say...
287
00:27:14,447 --> 00:27:18,725
five million up to as high as 100 million.
288
00:27:20,007 --> 00:27:22,840
(ATTENBOROUGH) Now that we appreciate,
if only roughly,
289
00:27:22,887 --> 00:27:25,117
how great life's diversity really is,
290
00:27:25,287 --> 00:27:30,407
we can begin to judge the scale of threat
it faces from human activities.
291
00:27:31,527 --> 00:27:36,521
The sad truth is that even though we have only
identified a minority of the earth's species,
292
00:27:36,967 --> 00:27:40,562
even some of those we've named
have already become extinct,
293
00:27:40,727 --> 00:27:44,003
some so recently that we
have their images on film,
294
00:27:44,207 --> 00:27:48,405
including the Tasmanian tiger
and the golden toad.
295
00:27:48,287 --> 00:27:54,635
Many more are now so rare that there is real
danger that they too will be lost before long.
296
00:28:01,607 --> 00:28:05,236
To access the rate at which species
are now disappearing,
297
00:28:05,447 --> 00:28:08,883
we need to know a little more
about the ways such losses happen.
298
00:28:09,607 --> 00:28:11,677
What does extinction actually mean?
299
00:28:12,007 --> 00:28:18,526
Nothing could illustrate it more dramatically
than the sad and infamous case of the dodo.
300
00:28:19,407 --> 00:28:26,165
This is a kind of giant, ground-living pigeon
that was discovered by Portuguese sailors
301
00:28:26,247 --> 00:28:30,684
at the beginning of the sixteenth century
living on the island of Mauritius.
302
00:28:30,927 --> 00:28:36,718
They didn't think much of it;
apparently they called it fat and lazy and stupid.
303
00:28:36,687 --> 00:28:41,681
But that didn't stop them clubbing it over the head
in vast numbers and eating its flesh.
304
00:28:42,127 --> 00:28:47,326
And they introduced pigs and monkeys
which ate its eggs.
305
00:28:53,807 --> 00:28:59,359
By the mid-sixteen hundreds, the dodo
was teetering on the brink of extinction.
306
00:29:03,007 --> 00:29:05,646
(ANIMAL CRIES 0UT)
307
00:29:07,087 --> 00:29:08,645
(THWACK)
308
00:29:08,847 --> 00:29:10,838
(GRUNTING)
309
00:29:13,327 --> 00:29:18,117
A few dodos were captured
and shipped back to Europe as curiosities.
310
00:29:18,127 --> 00:29:20,800
Most of them died on the way.
311
00:29:21,167 --> 00:29:26,002
How long the last dodo survived
alone on its island, we don't know.
312
00:29:25,807 --> 00:29:31,564
It could have been hours, days or even years,
but eventually that last one also died.
313
00:29:31,847 --> 00:29:35,806
And at that point the dodo,
as a species, was extinct.
314
00:29:37,527 --> 00:29:40,405
The dodo was particularly prone to extinction
315
00:29:40,407 --> 00:29:44,446
because it lived only on the relatively
small island of Mauritius.
316
00:29:44,727 --> 00:29:48,436
But the process of extinction
becomes more difficult to chart
317
00:29:48,567 --> 00:29:51,798
when a species has a wider distribution.
318
00:30:02,447 --> 00:30:08,795
In May 1980, Mount St Helen's, on the Pacific
northwest coast of the United States, erupted.
319
00:30:10,327 --> 00:30:14,878
A huge area of the landscape
was virtually scoured clean of life.
320
00:30:16,007 --> 00:30:19,317
In the hours after the eruption,
rocks and mudflows
321
00:30:19,847 --> 00:30:23,635
swept almost every living thing
off the mountain slopes.
322
00:30:28,447 --> 00:30:33,760
But within weeks, life began slowly
to return to the devastated landscape.
323
00:30:38,807 --> 00:30:41,116
The scale of damage was astonishing.
324
00:30:41,207 --> 00:30:45,041
Within minutes of the eruption beginning,
a superheated blast of gas,
325
00:30:45,047 --> 00:30:47,038
travelling at 500 miles an hour,
326
00:30:47,447 --> 00:30:51,156
had flattened
250 square miles of virgin forest.
327
00:30:54,087 --> 00:30:59,286
No species was exterminated because none
was restricted solely to Mount St Helen's.
328
00:31:03,127 --> 00:31:08,076
Even though the blanket of ash looked so sterile,
some plants were able to grow in it,
329
00:31:08,487 --> 00:31:12,241
and soon the landscape was repopulated
from the surrounding areas.
330
00:31:12,247 --> 00:31:17,162
Some environmental losses, however,
though they may look less dramatic,
331
00:31:17,367 --> 00:31:19,437
are more permanent.
332
00:31:19,287 --> 00:31:23,724
In recent times, virtually the whole of southern
England was covered by woodland.
333
00:31:24,087 --> 00:31:29,241
A small patch of which survives behind me.
It was home to a great range of species.
334
00:31:29,487 --> 00:31:33,036
Plants, insects, birds, mammals.
335
00:31:33,327 --> 00:31:38,765
Now, however, most of that woodland
has been felled in favour of agriculture.
336
00:31:38,607 --> 00:31:45,319
Fields like these are totally unsuitable
for those woodland species, so they disappeared.
337
00:31:45,887 --> 00:31:48,879
When a species disappears
over a small part of its range,
338
00:31:48,967 --> 00:31:51,083
it's known as a local extinction.
339
00:31:51,807 --> 00:31:57,723
If you have too many local extinctions,
the population level will fall dangerously low,
340
00:31:57,847 --> 00:32:02,523
and then that species
may be on the road to total extinction.
341
00:32:05,527 --> 00:32:09,520
(WILSON) There comes a time
in the life of a species
342
00:32:09,847 --> 00:32:14,398
when... it has been reduced to the point
343
00:32:14,567 --> 00:32:20,244
that it can't be recovered...
even by strenuous efforts.
344
00:32:21,287 --> 00:32:26,520
A lot of species are in that condition
and ecologists call them the living dead.
345
00:32:27,567 --> 00:32:31,116
An animal that nearly became
one of the living dead
346
00:32:31,407 --> 00:32:34,763
still lives near the city
of Rio de Janeiro in Brazil.
347
00:32:34,967 --> 00:32:37,879
In this area, 90% of the forest
348
00:32:38,327 --> 00:32:42,036
that once spread hundreds of miles
along the coast has been lost.
349
00:32:41,887 --> 00:32:44,720
The remains have been
split up into small patches.
350
00:32:48,327 --> 00:32:53,765
One of the most famous inhabitants of this forest
is the beautiful golden lion tamarind.
351
00:32:53,647 --> 00:32:58,437
It was in imminent danger of disappearing
because it had lost most of its home.
352
00:33:00,127 --> 00:33:04,359
At the last moment, a major
captive breeding project was started
353
00:33:04,447 --> 00:33:09,441
and strict controls introduced
to conserve the last remnants of its habitat.
354
00:33:09,647 --> 00:33:13,879
So the species may have been pulled back
from the brink of extinction.
355
00:33:15,327 --> 00:33:21,004
But most living dead species
do not receive this kind of intensive help.
356
00:33:22,287 --> 00:33:25,836
One of the difficulties of measuring
the current rates of extinction
357
00:33:26,247 --> 00:33:29,603
is that animals classed as living dead
may be doomed,
358
00:33:29,647 --> 00:33:33,196
yet they can hang on
in slow decline for many years.
359
00:33:34,367 --> 00:33:39,646
John Lawton is a biologist who specialised
in the study of animal populations.
360
00:33:39,527 --> 00:33:42,678
(LAWTON) Some extinction is instantaneous,
361
00:33:43,087 --> 00:33:46,602
some will happen over a 20-
or 30-year time period,
362
00:33:46,447 --> 00:33:50,406
when the population suddenly
gets hit by a rare, extreme event,
363
00:33:50,767 --> 00:33:53,839
and some may take over
a hundred years to happen
364
00:33:54,127 --> 00:33:58,803
as the last adults of a non-reproducing
species finally dies out.
365
00:33:59,247 --> 00:34:03,479
These estimates of extinction
are bedevilled by the fact
366
00:34:03,567 --> 00:34:07,082
that it's very hard to be sure
that something's really gone.
367
00:34:08,287 --> 00:34:12,599
Several species which were thought for many
years to have been lost have reappeared.
368
00:34:13,087 --> 00:34:15,885
An example occurred recently in Australia.
369
00:34:18,327 --> 00:34:23,242
Brisbane Museum holds the preserved
remains of many Australian mammals,
370
00:34:23,367 --> 00:34:28,600
including three dried skins of a small marsupial
known as the mahogany glider.
371
00:34:28,967 --> 00:34:35,406
They were collected by a clergyman in 1886
at a place called Mount Echu in Queensland.
372
00:34:35,607 --> 00:34:40,397
But they were never recorded again.
Was this animal extinct?
373
00:34:41,087 --> 00:34:43,317
That seemed very likely.
374
00:34:43,167 --> 00:34:48,639
But then, in 1989, some unidentified mammal
skins, collected fifteen years earlier,
375
00:34:48,927 --> 00:34:55,639
were by chance re-examined and one
was recognised as a mahogany glider.
376
00:34:58,247 --> 00:35:02,638
The skins came from Barrett's Lagoon,
near the Queensland town of Tully.
377
00:35:02,807 --> 00:35:08,325
But even as the specimens were being collected,
their environment was being destroyed.
378
00:35:08,487 --> 00:35:12,036
Surely the mahogany glider must now be extinct?
379
00:35:13,047 --> 00:35:17,882
Then this stuffed animal was noticed
in a house near Barrett's Lagoon.
380
00:35:17,807 --> 00:35:21,083
The farmer who had collected it
thought it was a squirrel,
381
00:35:21,287 --> 00:35:24,199
so he had had it mounted with a nut in its hand.
382
00:35:24,407 --> 00:35:29,197
But it was a mahogany glider.
The trail was obviously still warm.
383
00:35:30,407 --> 00:35:37,358
Eventually, on 5th December, 1989,
103 years since it was last recorded,
384
00:35:37,327 --> 00:35:42,117
the mahogany glider was rediscovered
alive at Barrett's Lagoon.
385
00:35:42,527 --> 00:35:49,205
Today, it's been provided with nest boxes
but it remains critically rare.
386
00:35:49,167 --> 00:35:53,604
Although mostly nocturnal,
individuals do appear during the day
387
00:35:53,807 --> 00:35:58,961
and put on a splendid display
of aerobatics, gliding between the trees.
388
00:36:06,207 --> 00:36:09,358
There was great excitement,
and not only among scientists,
389
00:36:09,527 --> 00:36:12,724
that this beautiful creature was still around.
390
00:36:15,847 --> 00:36:18,236
This was a narrow escape,
391
00:36:18,367 --> 00:36:21,245
but is it something about which
we should be greatly concerned?
392
00:36:21,247 --> 00:36:24,205
Haven't such losses always been happening?
393
00:36:26,967 --> 00:36:30,403
Extinction is a natural event.
394
00:36:30,327 --> 00:36:34,684
These drawers and racks
in the Natural History Museum in London
395
00:36:35,127 --> 00:36:39,086
are full of the fossilised remains
of creatures called ammonites.
396
00:36:39,287 --> 00:36:44,156
They first appeared about 250 million years ago.
397
00:36:44,087 --> 00:36:49,161
Over the millennia, some species died out,
other ones appeared.
398
00:36:49,527 --> 00:36:54,760
But 65 million years ago,
all the ammonites disappeared,
399
00:36:54,807 --> 00:37:00,325
and with them went a great number
of other species of animals and plants.
400
00:37:01,047 --> 00:37:06,405
Such mass extinctions have happened
five times in the history of our planet.
401
00:37:06,767 --> 00:37:12,956
The question arises, are we ourselves,
at this moment, on the verge of such an event?
402
00:37:14,967 --> 00:37:19,961
In some groups, such as the birds,
all recent extinctions have been recorded.
403
00:37:20,167 --> 00:37:25,605
So we can estimate the rate at which extinctions
are happening and compare it with the past.
404
00:37:27,207 --> 00:37:32,645
There's absolutely no doubt in my mind
and of all my professional biological colleagues
405
00:37:32,487 --> 00:37:35,365
that the Earth is facing a massive extinction
crisis.
406
00:37:35,847 --> 00:37:39,840
The extinction rate is of crisis proportions.
407
00:37:39,687 --> 00:37:43,885
Perhaps a hundred to a thousand times higher
than before humanity came along.
408
00:37:44,367 --> 00:37:48,997
That's the kind of acceleration in extinction rates,
a hundred- to a thousand-fold,
409
00:37:49,167 --> 00:37:56,039
that characterises the lead-in to the five great
waves of mass extinction in the fossil records.
410
00:37:58,247 --> 00:38:03,879
The last of those five mass extinctions
took place 65 million years ago,
411
00:38:04,087 --> 00:38:06,203
when the dinosaurs disappeared.
412
00:38:06,327 --> 00:38:13,483
Studying that event reveals the scale of loss that
a mass extinction can inflict on life's diversity.
413
00:38:13,527 --> 00:38:17,759
Palaeontologist Peter Ward
has made a study of these events.
414
00:38:19,167 --> 00:38:21,237
What we've got here on a beach in France
415
00:38:21,567 --> 00:38:24,240
is evidence of one of the world's
greatest mass extinctions.
416
00:38:24,447 --> 00:38:28,042
We had a global catastrophe,
and that catastrophe is written in the rocks
417
00:38:27,807 --> 00:38:30,196
with this very thin layer through here.
418
00:38:30,687 --> 00:38:34,919
This is the end of the age of the dinosaurs,
this is the start of the age of mammals,
419
00:38:35,007 --> 00:38:40,001
and that differentiation is deposited
as this very thin band of strata.
420
00:38:40,287 --> 00:38:43,757
In that band of strata
we have evidence of a meteor impact.
421
00:38:43,647 --> 00:38:47,117
We have pieces of Mexico which have
been thrown into space, come down,
422
00:38:47,487 --> 00:38:50,604
deposited on the deep sea bottom in France.
423
00:38:50,847 --> 00:38:54,760
Ancient dinosaur creatures are found
in the strata, right up to this point,
424
00:38:54,687 --> 00:38:57,804
and they suddenly go extinct.
This mass extinction was sudden,
425
00:38:58,127 --> 00:39:02,643
it was catastrophic, it wiped out
over 60 to 70% of all species on earth.
426
00:39:02,927 --> 00:39:05,521
(ATTENBOROUGH)
Can we define such an event?
427
00:39:06,727 --> 00:39:11,562
Mass extinctions are very short intervals of time
when huge numbers of species go extinct.
428
00:39:11,527 --> 00:39:15,520
They are over thousands of years,
maybe tens of thousands of years,
429
00:39:15,887 --> 00:39:20,199
when more than half of the biodiversity
then on earth goes extinct.
430
00:39:20,647 --> 00:39:24,640
(ATTENBOROUGH) Now, due to the spread
of the human species over the earth,
431
00:39:24,967 --> 00:39:27,845
it seems we are on the verge
of an even more dramatic one.
432
00:39:29,327 --> 00:39:34,037
The difference between the last
five great mass extinctions and the sixth,
433
00:39:34,127 --> 00:39:39,565
which some scientists think
we're on the verge of, is one of speed.
434
00:39:39,887 --> 00:39:44,039
Each of the last took place
over many thousands of years.
435
00:39:44,207 --> 00:39:48,917
The next, according to some predictions,
could happen within a hundred.
436
00:39:49,007 --> 00:39:53,558
It will take a great deal of willpower
and economic strength
437
00:39:53,807 --> 00:39:58,562
if we're to significantly reduce
the damage we're doing to biodiversity.
438
00:39:58,607 --> 00:40:02,600
In order to decide whether
that's worthwhile, we must ask,
439
00:40:02,927 --> 00:40:07,000
"Does the disappearance of a species
really matter?"
440
00:40:07,487 --> 00:40:11,002
In a very few cases the species that go extinct...
441
00:40:12,287 --> 00:40:16,200
are likely to prove to be what we call
keystone species.
442
00:40:16,127 --> 00:40:20,166
That is, like the keystone
of an arch but pulled out,
443
00:40:20,447 --> 00:40:25,840
a lot of the remaining structure changes,
and usually not for the good.
444
00:40:26,167 --> 00:40:34,882
It's often extremely difficult to know beforehand
which species will be keystone species.
445
00:40:36,487 --> 00:40:39,479
(ATTENBOROUGH)
Sea otters are a clear example.
446
00:40:42,927 --> 00:40:45,600
They live off the Pacific coast of North America.
447
00:40:45,967 --> 00:40:50,643
In the southern part of their range,
a huge seaweed, the giant kelp,
448
00:40:50,767 --> 00:40:55,204
grows up from the sea floor
and creates a kind of underwater forest.
449
00:40:58,327 --> 00:41:01,637
Many different animals
depend on these kelp forests.
450
00:41:01,687 --> 00:41:04,440
They're the spawning ground for fish.
451
00:41:07,407 --> 00:41:10,956
Seals live here as well,
and many smaller creatures
452
00:41:10,767 --> 00:41:13,679
such as clams, snails and urchins.
453
00:41:21,607 --> 00:41:24,758
Sea otters feed on these clams and urchins.
454
00:41:24,887 --> 00:41:28,402
They bring them to the surface
and open them by smashing them on stones
455
00:41:28,487 --> 00:41:30,762
balanced on their stomachs.
456
00:41:48,087 --> 00:41:53,798
During the eighteenth and nineteenth centuries,
sea otters were intensively hunted for their skins
457
00:41:53,847 --> 00:41:56,725
and exterminated over huge areas.
458
00:41:56,727 --> 00:42:01,118
Their disappearance led to dramatic
changes in the environment.
459
00:42:04,527 --> 00:42:08,236
The sea urchins, with no sea otters
to keep their numbers down,
460
00:42:08,247 --> 00:42:10,283
increased explosively.
461
00:42:15,367 --> 00:42:21,397
Urchins eat kelp, and their vast numbers
soon began to destroy the underwater forests.
462
00:42:27,527 --> 00:42:32,726
As the kelp disappeared, so did
all the animals that depended on it.
463
00:42:35,207 --> 00:42:39,758
What was left was a bare seabed
carpeted with sea urchins.
464
00:42:40,967 --> 00:42:43,959
Species do not exist in isolation.
465
00:42:43,847 --> 00:42:50,320
They're linked to one another in complex ways,
and when those links are cut a crisis may result.
466
00:42:51,087 --> 00:42:53,885
Eventually, hunting the otters was banned.
467
00:42:53,967 --> 00:43:00,315
They spread back into this area from further
afield and the kelp forests slowly recovered.
468
00:43:02,687 --> 00:43:05,485
Clearly many of the species
that are on the verge of extinction,
469
00:43:05,567 --> 00:43:10,004
when they were taken out, their loss is not
going to cause the collapse of an ecosystem.
470
00:43:10,367 --> 00:43:13,200
We should lament their passing
for other reasons.
471
00:43:13,247 --> 00:43:18,401
But there are many that might
cause serious repercussions,
472
00:43:18,527 --> 00:43:22,361
and until we understand the whole process better,
473
00:43:22,367 --> 00:43:27,646
we're rolling the dice, we're taking chances
whenever we let a species go extinct.
474
00:43:28,407 --> 00:43:32,446
So how would the loss of species
and environments affect us?
475
00:43:33,407 --> 00:43:36,080
First of all, if you want to be completely practical,
476
00:43:36,287 --> 00:43:42,726
there is the matter of wild species
being an almost bottomless source
477
00:43:42,527 --> 00:43:48,045
of new antibiotics and other pharmaceuticals,
yet to be discovered and developed.
478
00:43:48,487 --> 00:43:53,800
New crops, new fibres
and other new natural products.
479
00:43:54,247 --> 00:43:59,799
We're just getting underway the whole effort
to make use of biodiversity in this way.
480
00:44:00,567 --> 00:44:04,401
(ATTENBOROUGH) An example of a useful
product from a surprising source
481
00:44:04,767 --> 00:44:07,600
comes from Cape Cod in the United States.
482
00:44:10,487 --> 00:44:13,923
Horseshoe crabs are collected here daily
from the seabed,
483
00:44:14,047 --> 00:44:18,006
for their blood contains a substance
that can save human lives.
484
00:44:27,887 --> 00:44:34,042
The crabs are taken to a laboratory and,
in what looks like a scene from a sci-fi film,
485
00:44:34,127 --> 00:44:39,997
they're restrained in racks and some
of their blue blood is extracted from them.
486
00:44:41,447 --> 00:44:45,520
One of the substances it contains
is used in many parts of the world
487
00:44:45,727 --> 00:44:51,279
to test whether batches of inoculants are healthy
or contaminated with lethal bacteria.
488
00:44:53,367 --> 00:44:55,278
The crabs are then released unharmed
489
00:44:55,287 --> 00:44:59,246
in a part of the sea
that will not be harvested again for a year.
490
00:45:00,727 --> 00:45:05,323
Clearly, many individual wild species
can be of great use to us,
491
00:45:05,607 --> 00:45:09,566
but are there benefits to be gained
from conserving natural environments?
492
00:45:11,247 --> 00:45:17,402
The whole matter of ecosystem services,
an ecosystem like the one we're sitting in here,
493
00:45:17,407 --> 00:45:20,001
is doing a tremendous amount for humanity.
494
00:45:20,287 --> 00:45:26,522
It's creating soil, it's cleansing water,
it's creating the very air we breathe.
495
00:45:26,607 --> 00:45:30,361
The important thing is it's doing it all for free.
496
00:45:31,647 --> 00:45:36,163
(ATTENBOROUGH) Many reasons
for preserving biodiversity are selfish,
497
00:45:36,447 --> 00:45:38,119
to do with our health and comfort.
498
00:45:38,367 --> 00:45:42,679
Is there any other reason for us
to be concerned about the loss of species?
499
00:45:43,087 --> 00:45:47,444
There is a care, an ethical argument,
an argument of stewardship.
500
00:45:47,407 --> 00:45:51,958
An argument of handing on a world
as rich as the one we inherited.
501
00:45:52,207 --> 00:45:57,440
That's an argument we in the First World
have the luxury to consider.
502
00:45:57,487 --> 00:46:01,878
But we'd have a different perspective
if we were struggling to get the next meal.
503
00:46:02,607 --> 00:46:08,523
It is an extraordinary gift that our
generation received as natural heritage,
504
00:46:08,687 --> 00:46:14,239
and to destroy a large part of it
just fundamentally seems wrong,
505
00:46:14,287 --> 00:46:17,597
especially when you think
of what we're doing to future generations.
506
00:46:20,767 --> 00:46:23,156
(ATTENBOROUGH) Scientists have a word
507
00:46:23,287 --> 00:46:26,643
for environments which have lost
a number of their animals and plants -
508
00:46:26,647 --> 00:46:28,638
they call them "impoverished".
509
00:46:28,567 --> 00:46:34,119
Some may have lost almost all their species,
as happened recently on many coral reefs.
510
00:46:37,607 --> 00:46:40,963
Other environments may appear
to be largely intact,
511
00:46:40,847 --> 00:46:44,522
even though many of their original inhabitants
have become critically rare,
512
00:46:45,087 --> 00:46:47,362
or even lost altogether.
513
00:46:47,727 --> 00:46:52,801
Future losses will include many smaller
kinds of life yet to be discovered,
514
00:46:53,247 --> 00:46:56,523
as well as some of the best-known
animals on the planet.
515
00:46:58,527 --> 00:47:04,079
There is a spiritual value, an aesthetic value,
a psychological benefit
516
00:47:04,407 --> 00:47:09,527
for having a large diversity of life on earth;
we should not be removing it.
517
00:47:09,567 --> 00:47:16,439
I believe it could conceivably be possible
that in a few hundred years time
518
00:47:16,287 --> 00:47:22,157
we reduce that dependence and we lived in an
almost wholly science-fictiony, artificial world,
519
00:47:22,527 --> 00:47:25,166
the world of a cult movie, "Blade Runner".
520
00:47:25,407 --> 00:47:29,286
The question you have to ask is,
"Do you want to live in that world?"
521
00:47:32,007 --> 00:47:34,202
(ASTRONAUT)
That is the most beautiful sight.
522
00:47:34,407 --> 00:47:37,843
- What a view!
- It's absolutely unreal.
523
00:47:41,607 --> 00:47:45,600
(ATTENBOROUGH) The view the astronauts
gave us when they looked back at earth
524
00:47:45,447 --> 00:47:48,917
enabled us to see more vividly than ever before
525
00:47:49,367 --> 00:47:54,885
just how limited space is
on this small planet for life.
526
00:47:55,127 --> 00:47:59,962
We now know that we are
seriously damaging biodiversity,
527
00:47:59,927 --> 00:48:04,603
and there's the risk that the world
that we hand on to our next generation
528
00:48:04,727 --> 00:48:09,596
will be less rich, poorer in variety,
than the one we inherited.
529
00:48:10,047 --> 00:48:14,040
Why is it that the activities of our one species,
530
00:48:14,367 --> 00:48:18,679
aimed at no more than living
in reasonable comfort and avoiding hunger,
531
00:48:18,687 --> 00:48:23,158
should cause such devastation
on the rest of the natural world?
532
00:48:23,527 --> 00:48:27,486
That is the question we'll look at
in the next programme.
533
00:48:31,687 --> 00:48:36,681
We will see what the extinction of the dinosaurs
can show us about events today.
534
00:48:38,287 --> 00:48:42,439
A remarkable story from our own past
will provide vital clues.
535
00:48:44,087 --> 00:48:47,762
I'll look for evidence
from the bed of the North Sea.
536
00:48:49,527 --> 00:48:54,123
And we will unravel some surprising stories
from remote islands.