Dear Physics Forums community, This question has been bothering me for a few days, and I must apologize for the ambiguity of it. I'll try to explain it a little bit. I am not asking when the Sun will expand or the Earth cool down via radiative processes. So what I asked myself was: if you treat all organisms on a planet as a single system, how well does it perform "in the long run"? How fast the biosphere is depleting planet's natural resources? How efficiently all sorts of life are being recycled? If you exclude extintion events caused by asteroid impacts or radiation butsts, how the total biomass vs. time function can look like? I do realize that these questions aren't very clear, but I don't really expect definite answers. I don't have a good biology background, so it's hard for me to put it all together.