Aliveness may be the largest thing the model has under-measured. You could satisfy every other function — efficient, safe, fair, educated, traversable — and still build a dead civilization. Play, beauty, celebration, humor, sport, creativity, festival, delight, and pride in a thing done well do not need to justify themselves through ecological return, and a fully optimized system tends to strangle exactly these.
Why it counts as ecological health
A grandparent laughing with a child produces essentially no measurable project capacity — and yet something living passes through the field, which is not a rounding error but part of the point. It matters especially for the people a scoreboard undervalues: children, elders, the not-currently-productive. So one plain measure of ecological health is simply does participation leave people more alive? — a necessary counterweight to a model that could otherwise optimize its way into joylessness. It is one of the functions a whole living ecology needs, and it is now worked out in full as Aliveness: the right not to be systematically deadened, protected uselessness, the value of process against AI abundance, charismatic capture, and the central guarantee that the system must never become so busy optimizing life that it forgets to leave room for people to actually live it.