While this post: Course correction for Easter Island discussed potential measures to avoid the collapse of the Rapa Nui culture due to contact with the West, I'm planning to open the scope up now to discuss a competing theory that the collapse was mostly attributed to over-planting/over-hunting. I've learned much from comments and answers to the first post but course correcting for ecocide will entail an entirely different solution space.
If, as Diamond's hypothesis suggests, the Rapa Nui's resource consumption verged on "ecocide" then we will need to introduce some form of stabilizers to ensure that a certain threshold of trees/fauna are left unmolested. The trick is arriving at a scientific (guess)estimate of what that might be. Still, I'd like to keep this question fairly high-level and not split hairs over the mind-bending mechanics of lumber felled per capita and so forth. Technically, the data is out there to see how austere they'd have to be, but I'd just as soon abstract away the effort-prohibitive dimensions of the question where it makes sense to do so; don't need to bog answerers down with that too much.
Instead of austerity, another possible avenue for this question could be through some kind of technological progress. This way they could solve their collapse through productivity gains. Perhaps this time the oracle bones / vision of the Rapa Nui mystic result in a revelation of a new type of land management technique.
What type of land management technique that is consistent with Rapa Nui tool-making proficiency could plausibly lift the productivity of the culture without outstripping the carrying capacity of the island? Ideally, please include heuristics for max carrying capacity (when they know when to start de-risking / dialing back). Bear in mind, these would only be naked-eye heuristics as there are no satellite imagery or soil chemistry kits available to this culture.
- Rapa Nui population stable
- Forest stable in long run
- Fauna diversity / population stable
Note: I'd also allow for a combination of austerity and productivity improvements.