So if we want to save elephants, that means giving them back some of the space we took from them. It means moving elephants to a different protected area if they outgrow one area. Do people want to save elephants that much? Evidently not.
Terramagne has a couple of solutions. The coolest one is pure Africa: "Cattle grow trees, elephants grow grass." Several connected nations in the heart of elephant territory restored a historic principle in which nomadic herders of cows would follow some distance behind elephant herds. The elephants would tear down trees, allowing grass to rejuvenate and feed domestic herds. Those herds would then graze the grass down to the ground, permitting the tree seedlings to rejuvenate. By the time the elephants made it back around, fresh young trees would be waiting for them. Each species, in diminishing its own resources in the habitat, enhances resources needed by the other species and thus creates a stable loop sustainable over the long term. A bonus is that a nomadic lifestyle is very healthy and active for the people living it, so long as settled bystanders do not molest them. T-Africa resolved this issue by granting the nomads special status as elephant conservationists with citizenship spanning all the countries on the circuit.
Another is an idea that has been tried here, but rarely with enough vigor to work: paying people to conserve wildlife. A prevailing risk is conflict with subsistence, as cited in the Botswana issue. If people are paid more for being good neighbors to wildlife than they could get by killing the wildlife, they will protect it.