in recent years, a lot of western forests have burned

in large and destructive wildfires.

If you're like me --

this western landscape is actually why my family and I live here.

And as a scientist and a father,

I've become deeply concerned about what we're leaving behind

for our kids, and now my five grandkids.

In the US, an area that's larger than the state of Oregon has burned

in just the last 10 years,

and tens of thousands of homes have been destroyed.

Acres burned and homes destroyed have steadily increased

over the last three decades,

and individual fires that are bigger than 100,000 acres --

they're actually on the rise.

These are what we call "megafires."

Megafires are the result of the way we've managed this western landscape

over the last 150 years

in a steadily warming climate.

Much of the destruction that we are currently seeing

could actually have been avoided.

I've spent my entire career studying these western landscapes,

and the science is pretty clear:

if we don't change a few of our fire-management habits,

we're going to lose many more of our beloved forests.

Some won't recover in our lifetime

or my kids' lifetime.

It's time we confront some tough truths about wildfires,

and come to understand that we need to learn to better live with them

and change how they come to our forests,

our homes

and our communities.

So why is this happening?

Well, that's what I want to talk to you about today.

You see this forest?

Isn't it beautiful?

Well, the forests that we see today

look nothing like the forests of 100 or 150 years ago.

Thankfully, panoramic photos were taken in the 1930s

from thousands of western mountaintop lookouts,

and they show a fair approximation

of the forest that we inherited.

The best word to describe these forests of old is "patchy."

The historical forest landscape was this constantly evolving patchwork

of open and closed canopy forests of all ages,

and there was so much evidence of fire.

And most fires were pretty small by today's standards.

And it's important to understand that this landscape was open,

with meadows and open canopy forests,

and it was the grasses of the meadows

and in the grassy understories of the open forest

that many of the wildfires were carried.

There were other forces at work, too, shaping this historical patchwork:

for example, topography, whether a place faces north or south

or it's on a ridge top or in a valley bottom;

elevation, how far up the mountain it is;

and weather, whether a place gets a lot of snow and rain,

sunlight and warmth.

These things all worked together

to shape the way the forest grew.

And the way the forest grew shaped the way fire behaved

on the landscape.

There was crosstalk between the patterns and the processes.

You can see the new dry forest.

Trees were open grown and fairly far apart.

Fires were frequent here, and when they occurred,

they weren't that severe,

while further up the mountain,

in the moist and the cold forests,

trees were more densely grown and fires were less frequent,

but when they occurred, they were quite a bit more severe.

These different forest types, the environments that they grew in

and fire severity -- they all worked together

to shape this historical patchwork.

And there was so much power

in this patchwork.

It provided a natural mechanism

to resist the spread of future fires across the landscape.

Once a patch of forest burned,

it helped to prevent the flow of fire across the landscape.

A way to think about it is,

the burned patches helped the rest of the forest

to be forest.

Let's add humans to the mix.

For 10,000 years, Native Americans lived on this landscape,

and they intentionally burned it -- a lot.

They used fire to burn meadows and to thin certain forests

so they could grow more food.

They used fire to increase graze

for the deer and the elk and the bison that they hunted.

And most importantly, they figured out

if they burned in the spring and the fall,

they could avoid the out-of-control fires of summer.

European settlement -- it occurred much later, in the mid-1800s,

and by the 1880s, livestock grazing was in high gear.

I mean, if you think about it, the cattle and the sheep ate the grasses

which had been the conveyer belt for the historical fires,

and this prevented once-frequent fires from thinning out trees

and burning up dead wood.

Later came roads and railroads, and they acted as potent firebreaks,

interrupting further the flow of fire across this landscape.

And then something happened which caused a sudden pivot

in our society.

In 1910, we had a huge wildfire.

It was the size of the state of Connecticut.

We called it "the Big Burn."

It stretched from eastern Washington to western Montana,

and it burned, in a few days, three million acres,

devoured several towns, and it killed 87 people.

Most of them were firefighters.

Because of the Big Burn, wildfire became public enemy number one,

and this would shape the way that we would think about wildfire

in our society

for the next hundred years.

Thereafter, the Forest Service, just five years young at the time,

was tasked with the responsibility of putting out all wildfires

on 193 million acres of public lands,

and they took this responsibility

very seriously.

They developed this unequaled ability to put fires out,

and they put out 95 to 98 percent

of all fires every single year in the US.

And from this point on, it was now fire suppression

and not wildfires

that would become a prime shaper of our forests.

After World War II, timber harvesting got going in the west,

and the logging removed the large and the old trees.

These were survivors of centuries of wildfires.

And the forest filled in.

Thin-barked, fire-sensitive small trees filled in the gaps,

and our forests became dense, with trees so layered and close together

that they were touching each other.

So fires were unintentionally blocked by roads and railroads,

the cattle and sheep ate the grass,

then along comes fire suppression and logging, removing the big trees,

and you know what happened?

All these factors worked together

to allow the forest to fill in,

creating what I call the current epidemic of trees.

(Laughter)

Go figure.

(Laughter)

More trees than the landscape can support.

So when you compare what forests looked like 100 years ago and today,

the change is actually remarkable.

Notice how the patchwork has filled in.

Dry south slopes --

they're now covered with trees.

A patchwork that was once sculptured by mostly small

and sort of medium-sized fires

has filled in.

Do you see the blanket of trees?

After just 150 years,

we have a dense carpet of forest.

But there's more.

Because trees are growing so close together,

and because tree species, tree sizes and ages

are so similar across large areas,

fires not only move easily from acre to acre,

but now, so do diseases and insect outbreaks,

which are killing or reducing the vitality

of really large sections of forest now.

And after a century without fire,

dead branches and downed trees on the forest floor,

they're at powder-keg levels.

What's more, our summers are getting hotter

and they're getting drier

and they're getting windier.

And the fire season is now 40 to 80 days longer each year.

Because of this, climatologists are predicting

that the area burned since 2000

will double or triple

in the next three decades.

And we're building houses in the middle of this.

Two recently published studies tell us

that more than 60 percent of all new housing starts are being built

in this flammable and dangerous mess.

So when we do get a fire,

large areas can literally go up in smoke.

How do you feel now

about the forest image

that I first showed you?

It scares the heck out of me.

So what do we do?

We need to restore the power of the patchwork.

We need to put the right kind of fire

back into the system again.

It's how we can resize the severity of many of our future fires.

And the silver lining is that we have tools

and we have know-how to do this.

Let's look at some of the tools.

We can use prescribed burning to intentionally thin out trees

and burn up dead fuels.

We do this to systematically reduce them and keep them reduced.

And what is that going to do?

It's going to create already-burned patches on the landscape

that will resist the flow of future fires.

We can combine mechanical thinning with some of these treatments

where it's appropriate to do so,

and capture some commercial value

and perhaps underwrite some of these treatments,

especially around urban areas.

And the best news of all is that prescribed burning produces

so much less smoke than wildfires do.

It's not even close.

But there's a hitch:

prescribed burning smoke is currently regulated under air quality rules

as an avoidable nuisance.

But wildfire smoke?

It simply gets a pass.

Makes sense, doesn't it? (Laughs)

So you know what happens?

We do far too little prescribed burning,

and we continually eat smoke in the summers

from megafires.

We all need to work together to get this changed.

And finally, there's managed wildfires.

Instead of putting all the fires out,

we need to put some of them back to work

thinning forests and reducing dead fuels.

We can herd them around the landscape

when it's appropriate to do so

to help restore the power of the patchwork.

And as you've probably figured out by now,

this is actually a social problem.

It's got ecological and climate explanations,

but it's a social problem, and it will take us humans to solve it.

Public support for these tools is poor.

Prescribed burning and managed wildfires are not well-supported.

We actually all simply want fires to magically go away

and take that pesky smoke with them, don't we?

But there is no future without lots of fire and lots of smoke.

That option is actually not on the table.

Until we, the owners of public lands, make it our high priority

to do something about the current situation,

we're going to experience continued losses to megafires.

So it's up to us.

We can spread this message to our lawmakers,

folks who can help us manage our fires

and our forests.

If we're unsuccessful,

where will you go to play

when your favorite places are burned black?

Where will you go

to breathe deep

and slow?

Thank you.

(Applause)