Comment by hadlock | Hacker News Reader

Comment by hadlock | Hacker News Reader

I'm curious, with such giant swathes of forest being burnt off annually, and large contiguous chunks being burnt up, leaving only smaller contiguous areas;

1) given the average size of a megafire, how many more megafires can happen (assuming regrowth to current fuel levels takes 50 years)

2) what is the largest megafire that could still happen, given the forested area unburnt for at least 50 years

The chronicle has a map somewhere that lists all the wildfires that have happened in the last 30-40 years, at a casual glance it is looking like any forest areas that haven't burnt yet, are getting increasingly smaller. According to the USDA california has about 101 million acres of forest[1], and the august complex (2020) alone burnt 1 million acres, almost 1%, dixie fire was also almost 1%. The next 18 largest fires burnt another 5% (4.7%) [2]. Since 2001 We've burnt up 22% of all the forests in california [3]

7% in ~12 years seems like a lot, but it takes a long time to grow that much fuel, also the space in between those burnt spaces is going to be increasingly smaller and smaller, or at least so it would seem.

[1] https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsm8_037652.h...

[2] https://www.fire.ca.gov/media/4jandlhh/top20_acres.pdf

[3] https://en.wikipedia.org/wiki/List_of_California_wildfires#A...

I think it's a false assumption that when something burns in a high severity fire, it returns to a healthy state afterwards. Historically, natural fire was low severity because it was high frequency, burning through once a decade (or even more frequently). This left large trees and soil intact, and so dense regrowth was limited, since there was still shade.

With high severity fire, two things can happen. Trees can be totally wiped out (called a stand-replacing fire) which causes extremely dense, brushy regrowth (prone to another high severity fire). Or in really bad conditions, the soil can be damage so no regrowth happens, causing strange moonscape-like forests that are completely dead. This affects watersheds, causes mudslides, etc. Neither is good.

If we could burn large swaths of landscape with low severity fire, that would be a huge step in the right direction but is extremely difficult. We are treating only a small fraction of the acreage in that manner.

Note: This varies from landscape to landscape but is directionally correct. For example, in some climates, stand-replacing fires are healthy and normal. But in most climates, bad.

I was in the Colorado Springs area following a very bad fire about a decade ago, a fire hot enough to scorch the soil and cause issues with regrowth later.

This was followed by a very wet fall, causing massive amounts of runoff, erosion, and mudslides, blocking culverts and drainages, flooding roads, etc. It started with a fire, but the damage and follow on effects continued long after it was extinguished.

I suggest you read this. It's the seminal work on the subject. https://megafirebook.com/

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