Why some trees evolved to live underground (2014) | Hacker News Reader

Why some trees evolved to live underground (2014)

bbc.com

61 pointshyperpallium6 comments

Short answer: wildfires.

Long answer: During an atmospheric CO2 minimum, grasses developed a more efficient photosynthesis pathway, which gave them a competitive advantage in recolonizing burnt-out areas. Savannah grasslands were thus able to use fire as a weapon against forests, taking some land territory from the fringes of the elder biome every summer. The primarily subsurface trees were just one of several adaptations to the frequent wildfires in the savannah.

This article may be of interest to those who advocate the intentional use of fire as a tool for sound land management practice. By preventing or extinguishing naturally occurring wildfires, humans may be interfering with an ecological phenomenon that had already existed for millions of years before Homo sapiens, perhaps with some unexpected negative consequences.

On fire suppression and fire management, the core problem is this: large forest fires aren't natural in Europe, and Europe is where the science of forestry developed. Fire has no legitimate place in French or German forestry; but needs to have a large place in its American counterpart.

(I don't know if East Asia is a natural-wildfire zone or not; but it sounds like Africa, or at least East Africa, certainly is.)

Some North American species require forest fires to reseed[1]. This has some implications, for instance, with the logging industry - on the west coast, much more effort goes into replanting after a cut, compared to the east coast, where the species are not fire-dependent to release their seeds.

[1] https://en.wikipedia.org/wiki/Serotiny#Fire-mediated_serotin...

This is a good point, though I think the human side of things is a clear reason why these wildfires are extinguished. Even in some of the most rural places you can imagine, there will be at least some sign of humanity, like say, someone's house or business premises or some other necessary element (even a hut or cabin in a national park). People tend not to want these things burnt to a crisp.

What made sense for those millions of years simply makes less sense now people are likely living or working with said land.

It is a philosophical choice as to whether humans should change nature by eliminating the wildfires or adapt to it by constructing buildings that can survive frequent fires (or be quickly replaced in their wake).

Clearly, the trees in the article, not having the power to stop the fires, adapted to live mostly underground.

Humans could do the same, building the houses underground. Or coat exteriors with fire-resistant coverings, as the corky-barked trees do. Or build on tall stilts, like redwoods, such that a typical grass fire cannot spread upwards to a burnable canopy. Or build only on permanent firebreaks, such as by making broad concrete pads part of the foundations or putting big paved rings around settlements. Or use movable homes that can get out of the way when a fire comes through and return after it passes.

Is it justified for humanity to remove fire from every biome--even those that need it--just because one species finds it to be inconvenient? Maybe. The debate hasn't been settled either way, and I can think of valid arguments supporting both sides.

It would seem that for something like earthquakes, we have opted to adopt stricter building standards, rather than attempting to prevent the disaster. But that may only be because it costs less to do it that way. Fireproofed homes sound rather expensive, and it seems likely that hiring even a legion of firefighters to protect most of the burnable ones might be cheaper.

The article didn't explain more about Geoxyles so I did some research to see how they could photosynthesize adequately. It's funny that all the photographs online are of the above-ground fragments of the tree, sort of like icebergs. In any case to a human it looks like a deeply interconnected set of shrubs with a shared root system; these things must grow relatively slowly as they don't have much of an area (proportionately to most plants) to expose to the sun and air. But otherwise they are unremarkable trees, which I find remarkable!

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