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I think it was Nova on PBS that did an episode on studying weather systems created by fires, focusing on fires on the US Pacific coast.
We haven't had rain in a hilarious amount of time for the PNW, and getting more heat warnings. We're used to summers with a fairly consistent ~20° and some rain here and there. What we've been getting since mid-June is 26°+ (outside of the crazy week of over 40°). In some cases, people are literally needing to water the rainforest.
> The fire creates the storm, and then the storm creates lightning, which can cause more fires

> That runaway feedback is the dangerous part.

This is the second year I've heard the term pyrocumulus/pyrocumulonimbus so prominently in relation to the Sierras in California. If this happens more frequently, we might lose a lot of forest. It seems like that would accelerate the effects of climate change... which would also amplify the frequency of these events.

Yes, this is what will happen in many areas.
Would we really lose them? My understanding is that, after a fire, a forest experiences very rich growth, especially of plants that don't grow much under the shade of old trees, which are good food and cover for many animals.
Right, but it takes ages for forests to grow, and that period is plenty time for CO2 emissions to run-away from us.
There is a small but growing movement towards controlled burns of forests and such because not burning for long enough creates conditions that make wildfires even bigger and harder to stop. If you can rotate between enough zones over time the burned area can regrow fully. It has been said that part of the reason wildfires get so bad now is because we do not let them partake in their normal cycle of burning down occasionally.
I'll lead with: yes, these fires are devastating.

Ironically, if topsoil isn't sterilised or washed away, and both can and do happen with the mega fires we've been seeing, fresh growth after a wildfire can be stunningly quick.

A mature forest is self-limited by the existing mature growth --- juvenile trees simply cannot get sufficient light. If mature growth is cleared, the juveniles grow quickly.

It's still a slow process, and we're talking about ~30--50 years for a redwood to hit 100' or so (coast redwoods can grow to over 380' / 115m, giant sequoia are more massive but not quite so tall --- 286' / 87m.

As carbon sinks, redwood, doug fir, ponderosa, and other trees common to the western coastal ranges, Sierra, and Cascades are not insignificant, but probably pale compared to bogs, swamps, wetlands, mangroves, and tropical rainforests. Thats' a general sense, though I don't have solid numbers at hand.

Burning down the Sierra, Cascades, and Rockies isn't going to do us any favours. But it's still relatively modest. I'd be more concerned about tundra / permafrost melting and release, bog fires, wetlands loss, and rainforest.

Unfortunately we'll likely see all of that as well.

Well, I learned a lot today!

Thanks for the free education :)

These current fires are much more destructive because of a combination of the extreme conditions, a dense under story from fire suppression and lots of standing dead wood from beetle kill etc.

So ideally for a forest you would have small fires come through regularly and clean up the under brush but leave a fair number of large mature trees standing leading to open fire resistant mature forest.

With these large super destructive fires that wipe out everything you get slower reseeding which can let invasives weeds take hold. And you get dense stands of young trees and brush which are less fire resistant than mature forests.

Partial solutions include controlled burns in the wet season and thinning where you shoot to leave the large mature trees but reduce fuels. (This isn't always commercially viable though developing wood products that can be made from small trees or even brush harvested during thinning is an interesting area.)

> With these large super destructive fires that wipe out everything you get slower reseeding which can let invasives weeds take hold. And you get dense stands of young trees and brush which are less fire resistant than mature forests.

If you're real unlucky an above average wet season after a super destructive fire will cause untold amounts of topsoil erosion and damage, impacting the follow on reseeding even more.

Oh yeah, full on mud slides are quite common after a fire.
Are current fires actually much more destructive? https://cwfis.cfs.nrcan.gc.ca/data/charts/NFD_NFDB_compariso... seems to suggest that the average year is getting worse but really big outliers are getting rarer. https://www.google.com/amp/s/globalnews.ca/news/8045796/cana... suggests we have a higher number than normal but below average in total area burnt.
In California they absolutely are. Canada has wild land that have been undergoing a natural burn cycle. In the US, fires have been put out, leading to 150 years of built up fuel
You are correct that there have always been really bad years (that chart doesn't go back very far but look up the great burn of 1910). However total size is effected by us getting better at fighting them.

What has changed is that the fires burn hotter and so fully destroy vegetation and even seeds with intense heat which makes it much harder for the forests to regrow in the way they typically would in a "fire adapted ecosystem": https://www.cpr.org/2020/09/01/colorado-wildfires-forests-re...

Beetle kill seems to be a problem on to a few places.
Is the increase in beetle kill related to the suppression/reduction in small scale cooler fires? Would be interesting to understand.

In Australia it is only now becoming widely understood that stopping of the indigenous peoples burning of the bush has lead to an increase not only of large destructive bushfires but also a changing of the nature of the plants growing in an area. We are seeing more weeds and certainly more fire prone species which is leading in turn to an increase in the flammable fuel load. With the widespread 2020 bushfires causing so much destruction there has been an increase in appetite for looking at other options for land management, including trying to tap the fading knowledge of the indigenous elders on there traditional practice.

Biggest factor with beetle kill spreading north is the lack of hard freezes in early fall.

Denser forests are more prone to it though, they'll thin impacted forest to try and keep as many trees as they can.

Yes, that would be the case in normal conditions. Not if huge swaths of the forest are destroyed annually.
> Would we really lose them?

Yes, at least without human intervention. The stress concept in ecology predicts more biodiversity at minor events, but much less at large-scale global events. A pinch of disturbance is good for the life beings. This levels of disturbance at the same time in the North and in Brazil are not good.

There was much much more fire in the past. California is a terrible example if you want to show natural / historic rates of fire. I'm sure native american's burned huge quantities for lots of reasons as well?
If you want to make statements like this on HN, please back them up with sources.
The paper cited below estimates that 1.8M hectares burned annually in California before 1800 (over 4M acres). [1] That's about how much burned in 2020. [2]

[1] https://nature.berkeley.edu/stephenslab/wp-content/uploads/2...

[2] https://en.wikipedia.org/wiki/2020_California_wildfires

Edit: clarity

I'm wondering what type of fires these were. There is a vast difference between a forest crown wild fire, and a cooler one that mostly works burning undergrowth and leaf litter. Still fires, still covering the same amount of ground, one can destroy the forest and anything else in the vicinity, the other can help plants germinate and seeds the forest for the next period of growth.
They were low intensity fires. Many areas burned every 3 years on average before 1850. These same areas haven't experienced a fire since 1900
You only get high intensity fires if you have too LITTLE fire, not too much. If you have annual burning it's not going to be high intensity.

That said, even high intensity fires have pretty impressive recovery. Do you want to give me a high intensity fire from 5+ years ago? I can then show you the recovery if you want.

Someone already linked to the paper - but the eyewitness statements give a good example of just the extent and regularity of fires:

An eye-witness account of smoke in northern California forests (C.H. Merriam 1898, quoted in Morford, 1993) reported ‘‘Of the hundreds of persons who visit the Pacific slope in California every summer to see the mountains, few see more than the immediate foreground and a haze of smoke which even the strongest glass is unable to penetrate.’’ C.H. Merriam traveled extensively in California and was Chief, Division of Biological Survey for the US.

I've seen estimates of everything burned every 5 years which I found credible.

Or this on use by native americans

“Fire was a constant companion, a kind of universal catalyst and technology,” says Stephen Pyne, an emeritus professor at Arizona State University, author and fire historian.

Yosemite itself was routinely burned to clear underbrush, open pasture lands, provide nutrient-rich forage for deer, and to support the growth of woodland food crops to feed and sustain what was once a large and thriving indigenous population.

https://www.history.com/news/native-american-wildfires

A lot of the hot takes about the amount of fire we have no ignore the real issue - too little fire in landscapes that historically were shaped (and need) fire. And no - fire does not destroy nature - though I've seen some Instagram posts of folks rushing into burned areas to get clicks and good shots. Seriously - come back in 1-2 years and be amazed in many cases.

Fire was 101 land management "technology" and indigenous populations used it over literally thousands of years to improve their environment.

Burning forests will increase the CO₂ level, but since there is no "local global warming", the effect is diluted over the whole planet, and I'd be very surprised if the feedback effect is at all significant.
Except that is not happening only in the NW. From Australia to Siberia to the Amazon forest, you see the same pattern.
> since there is no "local global warming"

There is, though. Climate change has different impacts depending on where you are. Some areas are rising in temperature much much faster than others. The arctic is a good example of 'local global warming'.

> I'd be very surprised if the feedback effect is at all significant

Prepare to be surprised. Even if there are 1000 factors each of them only contributing .1% to the total, it is still the case that each one of the 1000 factors is significant.

You're right that some areas are impacted more by climate change, but that's not correlated with the areas that emit more CO2. In other words: local emissions don't determine local warming.
I really don't think that's true, or at least, it's not as clear-cut as you are asserting. There is at least healthy debate about the issue and it is definitely not a closed case of "local emissions don't determine local warming". As far as I can tell, local emissions do relate to increased local warming. Here's a source https://www.scientificamerican.com/article/can-carbon-dioxid...
This made me go back and read about cloud seeding. I'm surprised at how controversial its efficacy is.

It seems it would be simple to set up in a lab conditions that would be favorable for a cloud seeding mission in the real world (conditions where the air is moist but not precipitating). Insert the silver iodide and see how much of the water in the air condenses. Multiply it out to see how much silver iodide you would need to substantially increase rain. Test in different conditions to see the operating window for cloud seeding is.

It should be noted that the benefit of cloud seeding is not necessarily increasing total rainfall in a region, but controlling where that rainfall occurs.

You don't need silver iodide & suchlike. You can build a simple catapult & fire drones into the cloud. The drone delivers an electric charge to the cloud. This dislodges the water which falls down as rain. This is already routine[1]

[1] https://www.bbc.com/news/technology-56428984

Undoubtedly more of these positive feedback loops will identify themselves going into the future.

It was only a few years back the melting of the tundra was identified as 'accelerating effect' of climate change, as that thawing permafrost releases its methane into the atmosphere.

> which would also amplify the frequency of these events.

At least until the fuel is gone. If we don't overcome forest management practices like fire suppression, the ecosystem will simply turn over to something less vulnerable to fire. To your point it won't be the existing species like Doug Fir, Live Oak, or Jeffrey Pine.

> we might lose a lot of forest.

Not a lot, all.

The ecosystem is changing towards the desert side. Forests need a minimum amount of water to sustain them. Could be replaced by arid forests, made to burn. But the humid forests will disappear or became relict. Is happening in California since several years ago.

>which would also amplify the frequency of these events.

Fire needs three things. One of them is fuel. The west coast has an abundance of fuel because for generations we have prevented fires from removing it. If we stop doing that or the fires are too overwhelming to manage the fuel will go away and the problem will solve itself. It will just be way more fiery because you're compressing say 100yr worth of fuel consumption into say a decade.

It is worth adding http://purpleair.com/ who produce the low cost sensors that contribute to at least the first map. They have their own map (with 80 second update intervals) and you can buy a sensor for ~$250... it is a cool product because its a super practical design (housing is a pvc pipe cap) focused on delivering an accurate sensor on the cheap.

We love ours because you can watch it and see in real time when the air quality improves for a brief period.

I found Windy absolutely indispensable during the 2019/2020 Australian wildfire season. I cycle to work and I would check Windy for pockets of clean air blowing in from the coast from the North which from me is the desert, hence no fires.

There was a point where southern, eastern and western winds all blew smoke from one major fire or another. We have air quality testing sites in various parts of the state to reference, but at a certain point you needed to forecast on a national level in order to not get caught in one smoke cloud or another.

The photos in CBC's article really do a terrible job of conveying the scale and terrifying beauty of pyrocumulus clouds. On June 29th, I watched a pyrocumulus cloud [0] from the Sparks Lake fire [0] about 20-25 km from where I was. It reached over the horizon shaped like a "thunderhead" or a mushroom cloud. I was in awe. One could see the shadow that it cast in the sky; the darkness gave an impression of the cloud being dense with ash. The scale of it was huge, even though the fire was just 2 days old at that point.

[0] : https://i.imgur.com/C5bwGeQ.jpg

[1] : http://bcfireinfo.for.gov.bc.ca/hprScripts/WildfireNews/OneF...

That's amazing, thank you. It helps to put things to scale - I've tracked that fire on maps and in smoke forecasts, but this makes it 'real' in a more interesting and like you mention, oddly terrifying but beautiful way.
Beautiful, and yet incredibly terrifying.
I've been a volunteer firefighter in Australia for 25 years, my father and his father were.. the understanding that wildfires do this is old, I remember my grandfather talking about big wildfires in his day creating their own weather.

I've been noticing in the media over the last ~5 years this narrative that climate change is causing this 'horrifying new phenomena' .. no. sorry. (PS: not a climate change skeptic, totally agree with the science, just not the media in this instance)

Climate change does not create the concept of a hurricane or wildfire, nor any other physical phenomenon. Nobody has said that.

What it does is induce extreme phenomena more often and in more locations.

Edit: by nobody I mean scientists and knowledgeable people. TV talking heads misunderstand and misrepresent everything all the time, so undoubtedly they’ll have done the same with Climate Change.

Unfortunately the talking heads are what most people listen to. When they get it wrong, it allows the general public to claim the science is getting it wrong.
Is there geological record on how stable these forests have been over the last few thousand years? I can't help but wonder if we're watching the west coast of north america shift to a more desert like climate through the PNW/BC/Sierra regions.

Presumably if the burns are large enough, and the following wet season dry enough this process could occur over the course of only a few years.

Canada is a big place. Wildfires on the coast is kind of rare, but in the boreal forest its so common that there are literally species of trees whose seeds need the heat of a forest fire to germinate.
Isn't this well known already? Don't small volcano eruptions create their own localized weather systems over the crater as well?
I'm so glad I moved out of NorCal (Butte County). The West, SW, PNW, Canada and Siberia are desertifying.
I wish I could accuse you of being sensationalist.
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This would be kind of cool if it wasn’t happening on a planet i live on… such a horrific feedback loop
Small note about the title: I've seen such title about “creating their own weather systems” recently in the news about different forest fire, as if it were something really special. It's not that special, every forest fire becoming big enough will do the same and it occurs quite frequently (at least on a global scale). This phenomenon is called a [Firestorm](https://en.wikipedia.org/wiki/Firestorm)