Discount rates affect so many decisions, I wonder how each rate is chosen in each discipline. In particular the contrast between ecologists and investors. 

The FIRE (Financial Independence, Retire Early) movement adheres to the 4% rule, where you can retire if you have saved enough money that 4% of the total is enough to live off for a year. The logic is that withdrawing 4% of the total each year will be replenished by investment returns. This accounts for inflation too; I believe the estimate is an average return of 7% and an average inflation rate of 3%, leaving the 4% withdrawal rate to indefinitely retire on. Their discount rate is nominally 7% and in real terms 4%.

Contrastingly, ecologists have a different approach to discounting. Firstly there are some ecologists who believe a 0% discount rate is appropriate for ecological systems to ensure intergenerational equity (costs in the future must be fully accounted for today). I don’t see this as appropriate, as ecological systems replenish themselves and have their own form of safe withdrawal rates. However it is clear that ecological systems cannot maintain a 7% nominal discount rate as that would reduce future costs that are far away in time too much. Some impacts of climate change have already been locked in to affect humans for thousands of years, and any discount rate applied will nullify the costs past a few hundred years. It is suggested that natural resources should have 1-3% discounting applied which is lower than the FIRE movement. 

Stock returns have happily averaged 7% or more in the 100 years of reliably measured time (post WW2), I suggest however that this return and therefore discount rate of productivity is not tied to sustainable economic activity. I therefore suggest that the next 100 years of stock returns will align more closely to discount rates ecologists are using, as the companies creating productivity will be increasingly bound by sustainability requirements.

FIRE followers beware: your safe withdrawal rate is based on past data and may not reflect the coming century of returns.