Ok, great idea, but... such a big game and no saving? Unforgivable. Besides, after some time of playing it just got disconnected from NG. I should be awarded for 2 more things: digging 100 km and having 100 plants. With this problem I doubt if anybody will earn the final medals.
As for the gameplay: there is too much running around. There should be some setting for a general control, like for example if plants are at age x to y then they are focusing on z, later evolving or spreading etc. I just can't think of a situation where I would have to manage hundreds of plants/bunnies/humans the way it looks like now.
And one more thing: when plants/sprouts/bunnies are too close to each other it is impossible to examine each one of them.
As for saving: what is the "shape" of the generated world? Is it considered by the game as "unlimited"? You could make it so the world would look like a sphere for the player - if you would go to the left far enough digging you would finally end up where you started. But that would be just a visual effect, because in fact the game world could be actually a square with "teleports" on the borders. And if we got a square then the game could remember the x,y values, remember where a plant or a bunny was located. Though I agree that saving the status of the plants would be more problematic.