Cotton‐Barratt, O., Daniel, M. and Sandberg, A. (2020), 'Defence in Depth Against Human Extinction: Prevention, Response, Resilience, and Why They All Matter'. Glob Policy. doi:10.1111/1758-5899.12786


We look at classifying extinction risks in three different ways, which affect how we can intervene to reduce risk. First, how does it start causing damage? Second, how does it reach the scale of a global catastrophe? Third, how does it reach everyone? In all of these three phases there is a defence layer that blocks most risks: First, we can prevent catastrophes from occurring. Second, we can respond to catastrophes before they reach a global scale. Third, humanity is resilient against extinction even in the face of global catastrophes. The largest probability of extinction is posed when all of these defences are weak, that is, by risks we are unlikely to prevent, unlikely to successfully respond to, and unlikely to be resilient against. We find that it’s usually best to invest significantly into strengthening all three defence layers. We also suggest ways to do so tailored to the classes of risk we identify. Lastly, we discuss the importance of underlying risk factors – events or structural conditions that may weaken the defence layers even without posing a risk of immediate extinction themselves.




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This is excellent. Very well done.

It crossed my mind to ponder on whether much can be said about where different categories* of risk prevention are under-resourced. For example it maybe that the globe spends enough resources on preventing natural risks as we have seen them in the past so understand them. It maybe that militarisation of states means that we are prepared for malicious risk. It maybe that we under-prepare for large risks as they have less small scale analogues.

Not sure how useful following that kind of thinking is but it could potentially help with prioritisation. Would be interested to hear if the authors have though through this.

*(The authors break down risks into different categories: Natural Risk / Accident Risk / Malicious Risk / Latent Risk / Commons Risk, and Leverage Risk / Cascading Risk / Large Risk, and capability risk / habitat risk / ubiquity risk / vector risk / agency risk).

Thank you for sharing your reaction!

Would be interested to hear if the authors have though through this.

I haven't, but it's possible that my coauthors have. I generally agree that it might be worthwhile to think along the lines you suggested.

I heartily agree-I've been saying for years that response and resilience are neglected in the X risk/GCR community relative to prevention.

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