I tend to think that anything that increases the standard of living and health of people in the third world probably does reduce some forms of existential risk, by reducing the risk of war, and reducing the number of people who would consider extreme forms of terrorism involving weapons of mass destruction, including those that may create a possible existential risk like genetically engineered bioweapons. People who see their health improving and their standard of living rising are much less likely to resort to such extreme measures.
Terrorists don't tend to be very poor.
I think the contribution that lessening poverty would make to dealing with existential risk is that there are presumably some very talented people (or potentially talented people who will only become so if they get enough food when young) who are blocked by poverty from doing the work to reduce existential risk.
My recent posts Robustness of Cost-Effectiveness and Effective Philanthropy and Earning to Give vs. Altruistic Career Choice Revisited concern optimal philanthropy, and I’ll be writing more posts about optimal philanthropy in the near future.
My use of examples from prosaic domains such as global health has given rise to some confusion, because some members of the Less Wrong community believe that existential risk reduction is by far the best target for optimal philanthropy, and also believe that effective philanthropy in the context of global health is very disanalogous to effective philanthropy in the context of x-risk reduction. For example, Eliezer wrote
I believe that studying the issues surrounding philanthropic opportunities in areas such as global health is in fact helpful for better understanding how to assess x-risk reduction opportunities. My reasons for thinking this don’t fit into a few sentences, and fully understanding them requires understanding some of my thoughts about more prosaic domains. So I’ll respond to Eliezer’s comment at a later date.
For now, I’ll just remark:
Note: I formerly worked as a research analyst at GiveWell. All views expressed are my own.