[jodrellblank]

"the only known mass extinction of insects.[9][10]" - one event that serious in 6 billion years and the planet wasn't destroyed, is your cite for how it's fragile? I'd expect tool-using humans to prepare better, survive more, and recover sooner than the creatures described there, wouldn't you?

"Cod: Over 35,000 fishermen and plant workers from over 400 coastal communities became unemployed.[..] federal government intervened, [..] income assistance [..] retraining of workers [..] Newfoundland has since experienced a dramatic environmental, industrial, economic, and social restructuring, including considerable emigration,[18] but also increased economic diversification, an increased emphasis on education, and the emergence of a thriving invertebrates fishing industry"

and the present status 20 years later is "recovering" up to possibly 10% of earlier levels - nothing like the million years to recover of the previous link.

Change happened, people adjusted to it in many ways. That sounds resilient, not fragile.

[YZF]

Us tool wielding humans are gonna get wiped out just like those insects. Whenever the forces of nature hit us our tool wielding seems to matter very little.

My point re: the fishery collapse is that all the tool yielding people didn't forsee the collapse and when it happened were unable to deal with it effectively. You're not gonna have 20 years to figure stuff out if climate changes dramatically, ecosystems collapse or some feedback loop kicks in. The scale/force/power of these changes is well above our current ability to engineer and our illusion of power is going to disappear very quickly once our society and infrastructure disappear. The romantic notion of 50 people in a bunker surviving and continuing the human race while the oceans turn into acid .. not gonna happen.

[jodrellblank]

Fragile generally means something like you drop a glass on the floor from 30cm and it completely shatters. If you drop a mug on the floor from 2 meters and the handle breaks off but it still works, it's not fragile. If you hit it with a meteor and it breaks, it's not fragile.

Whenever the forces of nature hit us our tool wielding seems to matter very little.

55,000 people were displaced or evacuated in California just now, with a current death toll of <100. They didn't just move all at the same time by luck and on foot; vehicles, radio, TV, fire tracking helicopters and satellites all helped keep 50,000+ people alive in the face of a natural force. We reinforce buildings against earthquakes, we build tornado shelters, the Svalbard Global Seed vault, Dutch land reclamation dykes and countless flood defences around the world, earthquake and tsunami early warning systems, storm tracking weather satellites, and every building with lightning conductors since the 1700s.

With the spread of humans around the world, even huge events like the "imminent" Pacific North West USA Cascadia zone earthquake wouldn't affect most people. Something would have to kill 50% of humans just to take the world population down to 1972 levels. 75% of people is still higher world population than it was in 1900.

What's left? Anything which affects the globe. Climate change, which is currently being talked about in a "2C in 100 years" way which is a lot more than 20 years, and ... supervolcano emissions or massive solar flares or meteor impact. And a handwavy "if some feedback loop kicks in and the oceans acidify".

The romantic notion of 50 people in a bunker surviving and continuing the human race while the oceans turn into acid .. not gonna happen.

What about whole countries putting acid rain covers over their crops and water purifiers? One project in Israel desalinates 150,000,000 cubic meters of seawater every year, providing for 1.5 million people.

If we can plan for a colony on Mars, anything that happens to Earth it will still be hundreds of times more habitable than Mars, even if that means everyone who remains living inside some kind of habitats.

[YZF]

No colony on Mars yet... A colony on Mars relies on Earth. 2c in 100 years isn't the problem. The problem are the low probability events. Animals can run out of the forest during a fire, I don't really see that the humans did significantly better. We didn't stop an entire town from burning down, we didn't have enough of an advance warning, death toll may be well beyond 100, we don't even know how many people perished in the fire.

It is simply foolish to be pushing on this system for no good reason. I don't want to roll a d100 dice where if it comes out 1 we all die. That's a terrible gamble. Sure 90 out of 100 would only be a hotter world with more storms and fires and vast stretches of land disappearing under the oceans.