> So you want to make them more rare so that people have a strong incentive to harvest from the wild?
No. I think them being illegal to posses is working to reduce field collection. This strategy is used for many other endangered plants (such as orchids) and seems to work. If people want to use psychoactives, then "magic" mushroom and morning glory seeds (or Hawaiian wood rose seeds) have a much lower impact on the environment and people should be steered towards those options by making them legal (most already are; carrot) and coming down on anyone who illegally collects Lophophora with a prison sentence (stick).
> You should look at the history of Chestnut blight in the US.
First of all, the species is not extinct. In fact, if you live in Silicon Valley, there is a chestnut orchard with some American chestnut trees just a short drive away in the Santa Cruz Mountains. There are many other populations and ongoing work to try and breed resistant trees.
Second, trees were cut down to create a biological equivalent of a fire break. The idea was, if there was a gap of 10-20 miles in front of the advancing disease front where trees were removed, then it might be possible to contain the disease. In hindsight, this might seem like a overly drastic measure, especially since it ended up only delaying the spread and not stopping it completely, but based on what was known about the disease at the time, and the huge importance of the American chestnut as an economic resource, it was a risk people were willing to take.
> Proactive regulation is not always the best move.
Yes, but sometimes it actually is the best move. I believe it is in this case.