Thread by @ErinEARoss

This is a good question with a longish answer. But the short answer is no.

The long answer (thread) Forest management practices (which have nothing to do with 'raking forests') have absolutely contributed to the size and intensity of wildfires over the last 100 or so years.

https://twitter.com/MJT36165368/status/1305047597690822659

Basically, for a long time, if there was a fire you did one thing: put the fire out, ASAP.

But fire is a natural part of forest ecosystems, so that lead to fuel buildup, which increased the intensity of fires.

What a healthy forest looks like depends on the ecoysystem.

In healthy ponderosa forest, for example, is open and park-like. Regular fires clear the underbrush, downed limbs, and young trees. You can walk through these forests with outstretched arms without touching a tree.

There will be stands of denser, younger trees where old trees fell, opening up the ground to light and growth. They'll thin with time.

An unhealthy ponderosa forest is nothing *but* dense stands of young trees and brush.

In a healthy ponderosa forest, fire rips across the understory. But ponderosas are adapted for fire, so very few trees actually catch.

In an unhealthy forest, with lots of brush to fuel flames and smaller trees to reach the fire up towards the canopy, the whole forest can burn

In Oregon, most ponderosa forests are on the east side of the Cascade mountain range. Historically, they would have many small, brief fires. Now, because of decades of fire suppression, they have frequent massive fires.

So... should we clean the forest floor?

No.

Should we log all the trees?

Not that, either.

You can't just rake a forest. Forest ecosystems are more than trees and bushes. Insects, mammals, birds and plants rely on fire to exist. Some types of plant seeds won't even germinate without fire.

If we just "raked the forest", we'd wreck the forest. So instead we use controlled burning. When fire danger is low, crews go into the woods and light small fires, reducing fuel and simulating the fires that would have burned in the past.

But some forests -- particularly ones that were logged or over-suppressed - are full of dense small trees and large trees. They're not safe to controlled burn, and it wouldn't reduce the fuel. So humans need to do even more.

Unfortunately, you can't just go thin trees. That leaves all that fuel sitting on the ground. Some studies have found that forests that were thinned but not burned had *worse* fires than those with no thinning at all.

The thinned trees helped wind carry the fires.

So, you need a combination of thinning and controlled burning in these ponderosa forests. We have to undo some damage before we can return fire to the landscape.

It's really cool to go out with thinning/burning crews. They work hard to recreate natural ecosystems.

A fire boss will say that a certain proportion of an area should be burned, certain areas should be thinned by X percent, others should be thinned by more.

They want a variety of tree ages and densities.

To see well-managed forest in Oregon, check Highway 20 west of Sisters.

We know this helps suppress forest fires. The last time a fire burned near Sisters, it was caught when it reached forest that had been controlled burned the previous year.

But!! There is a MAJOR BACKLOG in controlled burning across the West. We've done the thinning (which the timber industry loves) but an OPB report found we are WAY behind on burning.

opb.org/news/article/w…

Research has shown that IF areas that were supposed to be thinned and burned WERE burned, some Western fires would have slowed:

reuters.com/article/us-usa…

So... does this mean all these increasingly bad wildfires are BECAUSE we aren't burning or thinning enough? Can we blame the size of fires on forest management instead of climate change?

NOPE

We have managed forests poorly for almost 100 years. During that time, we have also changed the climate. But we've also started trying to correct of the damage we've done to forests.

In the last decade, wildfire severity and frequency has skyrocketed.

axios.com/fires-rage-wit…

The math just isn't quite right unless you factor in climate change.

Here's the thing: it doesn't matter how much fuel you have if that fuel isn't *dry*. Ever tried to start a fire with wet logs? It doesn't work.

Climate change is making fire seasons longer, dryer, and hotter. More of the fuel on the ground is capable of burning. So while poor forest management absolutely CONTRIBUTES to the severity of fires, it doesn't work without climate change.

You can't blame the last ten years of fires on "failure to rake forest."

So, where does that leave us with these fires in Oregon?

So far, I've been talking about ponderosa forests. But that's not where (most) of these fires were burning. Many were burning in mixed forests of Douglas Fir, Sitka Spruce, cedar, and other less fire-tolerant trees.

Normally, these areas don't burn. A healthy old-growth forest on the West side of the Cascades is complex: there are multiple forest stories. The top is Douglas fir, old growth trees towering over the floor and dappling sun.

When an old tree falls, a chance for new growth occurs

Unlike Ponderosa forests, where the branches are high above the ground and out of the fires' ways, these forests have multiple stories. Some high and low branches of Douglas Fir. Vine maple and cedar grow below, stretching towards the canopy.

There's a thick, dense layer of underbrush. Rhododendron bushes growing out of decaying logs extend limbs skyward, dense thickets of sword fern, huckleberry, and salmonberry are everywhere. And beneath it all, a layer of sorrel - a clover-like plant.

It's a rainforest. Lots of layers. Lots of life.

Lots of fuel.

Normally, fires don't reach this part of the forest. They start from lightning strikes near the Cascade's high peaks. And because heat rises, they usually either burn further up the mountains, or along them: rarely down into the rainforest below.

Similarly, there used to be frequent fires at the bottom of the Willamette Valley beneath the mountain range. These were usually set by indigenous groups that had been living on the landscape since the ice age. It created vast, open oak savannahs, home to plants and wildlife.

Fires in these mixed oak/grasslands would burn fast, but not hot. And though they'd burn *up*, they wouldn't be hot enough to light that part of the forest.

It's not that fires never happened in the dense rainforest: it did. We have a dry season. But it happened rarely.

Remember: East side burns every dozen years or so, historically. Sometimes more often.

The west side burns rarely. Because of this, controlled burns on the west side are *much less common*.

When fires did happen, they were either small fires that left the old-growth overstory intact, and eventually lead to a two-story forest. Or, in dry years, they could be massive fires that crowned the tops of trees.

To get an idea of how much *normal* fire varies in the West, there are some regions that, as far as researchers can tell by aging carbon remnants in the soil, haven't burned in 6K years.

Others burn every few hundreds, or every hundred. Or, in ponderosa, every handful.

This is all to say that fire management isn't one-size-fits all. I can't tell you whether fire suppression worsened fires on the west side of the Cascades - we'd have to get pretty small-scale on the microecosystem there.

What I *can* say is that forest management practices made them worse. Why?

Douglas Fir is fairly fire-intolerant. But in old growth forests, other, hardier species eventually replace some doug fir.

That also means there's more *space* between each tree of a given species.

That's a big deal because dead wood burns fast. And if you have a lot of the same tree in one place, it's more vulnerable to disease and pests.

On the west side of the Cascades, much of the forest is second-growth.

In fact, it's really not accurate to call it "forest" at all. It's better to think of it as a monocultural farm field -- all one species -- where instead of corn, the only thing growing is douglas fir trees.

Usually in straight lines, closer together, all the same age.

See where I'm going here?

Younger trees are less fire tolerant. These stands are less disease tolerant. They lack the heartier species and big, natural firebreaks that occur in old-growth forests. It's a weakened ecosystem.

So -- that brings us back to these fires. They're still burning, so there's a lot to be answered about the impact forest management practices had on those fires. BUT!

Here is what we do know:

Some of these fires were started by lightning strikes at high altitudes. They'd been burning laterally along the fire line, or up in elevation, and sometimes spotting downhill. But they were manageable.

Then, we had a major wind event.

That wind event came from the east. That's super uncommon for this part of Oregon. And the winds were FAST.

They pushed those already-burning fires downhill, into rarely-burned land that was fuel-filled, regardless of whether it was old growth or second growth.

The high winds also downed powerlines in lower elevations, where much of the forest is heavily logged.

We also know that we had unseasonably warm temperatures and low humidity. We know that weather like that is made increasingly common by climate change.

So there was a LOT of fuel, and, critically, that fuel was DRY.

With the wind to push embers *miles* ahead of the fire line, they were unstoppable.

Because climate change is also lengthening fire seasons, that increases the likelihood that rare wind events will fuel something like this. More time with dry fuel = a larger window to have fires.

Basically, ecosystems are complex. Way more complex than I can describe in a Twitter thread. And fire plays a role in ALL of them.

Forest management is important, but nothing humans do matters -- AT ALL -- if we do not take drastic measures to curb climate change.