The climate science behind wildfires: why are they getting worse?

This is a crisis.

If we were on a plane,
I think the pilot's control panel

would have several alarms going off.

Siberia, Usa, Turkey, Greece,
and Italy and Portugal in recent years.

Huge areas just going up in flames.
Everything just being reduced to ash.

Scene after scene of hillsides ablaze.

Wildfires are in one sense very simple.

It just needs a spark
in dry conditions to set them off.

But in another sense
they're also very complex,

because the extent to which they spread

depends very much on
conditions in the ecosystem.

How much moisture is there
in the ground, in the air?

How long has it been
since there was last rainfall?

What kind of trees there are.

How dense is the biodiversity?

Fires tend to burn faster
when they're in a plantation

and there's just one type of tree.

There isn't much undergrowth from moss

and things like that,
that could absorb water.

You get what scientists are always
describing as tinderbox-like conditions,

where it doesn't
take much to start the fire.

and then once the fire is started,
it spreads very, very quickly.

They can be set off by lighting strikes,
by barbeques, dropped cigarettes,

or by farmers who use fires
to clear land and then lose control.

Wildfires have always existed.

They are natural and they do
play a process in forest management.

But when you've just got plantations
or when everything has been dried out,

wildfires can spread
over enormous distances

very very quickly.

The meshing together

of lots of different plants and mosses,

and animals, and streams,

and all of these things
that create an eco system

are actually very strong and resilient

when they're together.

When you strip that all away,
if you just take out all of the biodiversity,

you're making the forest more vulnerable.

Once a fire has got
ahold of a monoculture,

if it's burnt a stretch of five trees,

the chances are, it can burn 5000 trees

because they're all planted in lines
at roughly the same distance.

Counter-intuitively, there are actually
fewer wildfires than there were in the past

But what is happening is that there is
a different type of wildfire now.

We're seeing fewer fires,
but more intense ones.

Because fires are spreading to areas
where there's more fuel, more trees.

And when trees burn,

obviously much more
carbon is being released.

And they burn
much longer and much harder.