B1 Intermediate US 62 Folder Collection
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(gentle music)
- [Instructor] What are
some of the global threats

so biodiversity?
First, I want to emphasize
that virtually everything

we do locally has global consequences.
When we talk about something
like a greenhouse gas

or a pollutant, that's
something we produce locally

from our car or from
other things that make up

so many of our day to
day human activities.

But in the grand scale of things,
even these local activities and impacts
can have global effects.
Greenhouse gases aren't
just carbon dioxide,

they also include water vapor, methane,
ozone and nitrous oxide
but for this tutorial,

we want to focus on the major effects
of carbon dioxide which
chemists refer to as CO2.

Increases in the amount of carbon dioxide
in the atmosphere mostly come through
the burning of fossil fuels.
Fossil fuels contain huge amounts
of carbon and when they're burned,
they not only release heat energy
but they also release carbon dioxide
although it's the energy,
the heat that we want,

carbon dioxide is a side
product of the burning.

That's why atmospheric CO2 is increasing.
Why are so many people
concerned about that

in terms of global change?
The answer means we
need to say a few words

about the greenhouse effect
and how that actually works.

Light rays from the sun
arrive in our atmosphere

as shorter wavelength radiation.
This light energy hits
the surface of the earth.

Some of it is reflected back in the form
of slightly longer wavelength radiation
and it's this longer wavelength radiation
that falls into what is
known as the infrared area

of the spectrum.
Infrared is the same as heat, basically.
So when light hits the
surface of the earth,

it's changed into heat energy.
That heat energy is, to a certain extent,
absorbed and some of it's
reflected back up into space

but greenhouse gases actually have a kind
of snacking preference
for longer wave radiation

like infrared energy.
This keeps the heat energy
close to the earth's surface

instead of allowing it
to go out into space.

The more greenhouse gas you have, the more
the heat builds up.
It's no coincidence that this is called
the greenhouse effect.
It works almost exactly like
a gardener's greenhouse.

A greenhouse is made of panes of glass
and all that nice sunlight
goes through the glass.

It strikes the plants,
the soil, the stuff inside

the greenhouse but much of
it becomes infrared light

or heat held within your
greenhouse and bouncing around

through the air inside to
make things nice and warm.

To a certain extent,
like our little plants

in the greenhouse, earth's
organisms benefit from

the greenhouse effect.
Life on earth would
probably be quite different

or perhaps not exist at
all if we didn't have

some greenhouse effect.
The problem is that now
we've increased the rate

at which greenhouse gases
are being introduced

to the atmosphere and therefore the rate
at which warming occurs.
Even gardeners have to
regulate the flow of light

into a greenhouse to
keep it from overheating

and cooking their veggies
before they even get picked

off the plant.
So there's your problem.
It's not so much that
CO2 buildup is happening,

it's happened before in
the history of the earth.

Scientists even see cycles to these things
but it's the current
rate at which CO2 content

is changing that's the
running theme behind all

of the problems that we're seeing today.
Life just can't keep up.
Here's a graph that
demonstrates CO2 content

in our atmosphere over time.
What I like about this
particular one is we go

from about 400 thousand
years ago to the present.

We've got these hundred
thousand year intervals

and a series of
interesting drops and peaks

and drops and peaks and
then coming to the present,

it kind of goes off the charts so much
that we've gotta magnify
that part of the graph

to see it better.
In here, in the industrial
age, we're experiencing

this greatly enhanced period
of carbon dioxide production

through the activities of humans.
There are agencies out there
that are very concerned

with this problem.
One of them is the Intergovernmental Panel
on Climate Change or IPCC.
According to the most
conservative IPCC estimates,

the global temperature on earth,
and this is an average temperature
over the whole planet by the way,
is going to rise 1.1
to 2.9 degrees celsius

during this century.
That's two to 5.2 degrees fahrenheit.
Modeling or estimating
what will happen is tricky

which is why we have
these suggestive ranges

instead of precise single figures.
But what we can say is that
in the worst case scenario

models, we're talking 2.4
to over six degrees celsius

and that's a whopping 4.3
to 11.5 degrees fahrenheit.

Imagine the repercussions.
If I think about going to my thermostat
and just suddenly overnight
dialing it up 10 degrees,

not only are my electric and
gas bills gonna go through

the roof but it gets beyond cozy
when it's over 80 degrees in my house.
It's not really my optimum temperature.
For one thing, the ice
in my drink's gonna melt

a heck of a lot faster which
is equally unfortunately

one of the major problems
for the earth as well.

We're talking of course
about global sea level rise.

It's really the continental ice masses
that should be giving us the
greatest cause for concern.

It's fairly simple,
melting of ice on places

like Greenland and high
mountains, for example,

will result in more water
going into the ocean.

The frozen elephant in
the room is Antarctica

because almost all of the
ice there is on the continent

which means that when it
melts, it will add enormously

to the amount of water in the ocean.
Even partial melting of
Greenland and Antarctica together

could result in four to six
meters or about 13 to 20 feet

more water in the ocean worldwide.
But it could take several
hundred years for that.

People are looking at
this very, very carefully

because if you think about
20 feet, that's enough

that entire countries like the
Maldives which exist largely

as low lying atolls in the Indian Ocean
would disappear underwater.
Almost any low lying area,
the Netherlands, aka Holland,

for example, or New Orleans, would face
serious additional flooding threats
and then you add to that
things like hurricane

and typhoon storm surges and
it's an enormous problem.

What does this mean for
biodiversity though?

Well, in the first
place, you're gonna lose

these low lying places and
therefore their habitats

and the species living in them.
Some of these habitats are home to rare
and endangered species.
Apart from the actual change in sea level,
what really is a major
problem for biodiversity

is the warming itself.
Again, remember that
every species has its own

optimal habitat and tolerance ranges
and that includes all
the things that go along

with living in the right
temperature regime.

The IPCC estimates that a
four degree celsius increase,

just over seven degrees
fahrenheit is gonna result

in major extinction due to the inability
of organisms to adapt to the changes.
It's this rate thing again.
Organisms can't move to
cooler areas fast enough

or adapt fast enough.
Sure, some migratory animals
can change their patterns

of migration a bit but
what about the organisms

that can't change, what about
the ones that can't move?

Entire forests come to mind,
think of mountain ranges.

Forests will move further
up the mountainsides

completely altering or
displacing entire ecosystems

as they go and we've got
really interesting examples

from some of our own
investigators here at the academy,

please like Dave Kavanaugh
who studies endemic beetles

specialized to live in the
icy areas high on mountains.

These colder places are disappearing.
The beetles are moving to
higher and higher elevations

but pretty soon, they're
going to run out of mountain.

Even marine ecosystems are not immune.
A two degree celsius
increase in the ocean,

about 3 1/2 degrees fahrenheit
doesn't sound like that much

but it's a lot because we're
talking about a huge amount

of extra heat over the
entire huge size of the ocean

and we've been talking
about an average number.

Some places are going
to be warmer than that.

Some are going to be cooler
but an overall two degree

celsius increase is enough to result
in major coral reef die offs.
Reefs just can't respond to
these rapid temperature changes

fast enough nor move to other places.
Even assuming that other
suitable habitat was available.

Those are some of the
effects of global warming

but we also need to talk about
the chemistry of adding CO2

to the world's ecosystem.
There's some early evidence
that shows all the regions

of the world are gonna be
affected one way or another

just by the simple addition
of CO2 even if you don't talk

about the global warming consequences.
Studies indicate that
plant life tends to react

to an increase in CO2 by
building more of themselves

through that amazing
process of photosynthesis.

The amount of carbon
dioxide that plants use

and turn into organic
molecules for their own use

is what we're talking
about in fancy terminology

like sequestration and carbon fixation.
It's just plants saying,
"Oh, hey, there's more carbon

"dioxide, I can make more of myself."
That sounds on the face
of it like a good thing.

How bad could more plants actually be?
In fact, sequestration and
fixation are likely reasons

that we haven't already had
truly runaway global warming.

But there's a limit.
There's an upper level to
how much plants can collect,

use or sequester carbon and thereby reduce
surrounding carbon dioxide levels.
That's because CO2 is
not usually the chemical

that runs out first as plants
build more of themselves.

It's kind of like saying well
you know I could put lots

and lots of oil in my car and
it seems to be running fine.

Without remembering to add
some gas every now and then,

you're gonna run out of gas
and your car eventually stops

even though you have lots of oil.
Biodiversity in that sense
could actually decrease

as the carbon dioxide levels increase
because you've got unequal
abilities among plant species

to sequester or absorb all
this new carbon dioxide.

As that happens, biodiversity
or species' richness

can drop because plants more
sensitive to the limitations

of other necessary chemicals will die.
Forests, marine fighter plankton
and their surrounding ecosystems
become less functional

as species die off and
therefore less effective

in sequestering carbon dioxide
causing a kind of feedback loop
in which global climate change actually
gets worse and worse as
the unused CO2 builds up.

Think of that next time
you hear a car go by.

Even something that local
can go global in a way

that has huge effects
really worth thinking about.

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How does climate change affect biodiversity?

62 Folder Collection
陳劭理 published on October 6, 2018
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