I just planted a forest, and used the clip to camera function. But with the sun coming in from the side, you can clearly see by the lack of shadows under the trees that the forest ends just off camera to the right.
Can the clip to camera function be made to take into account that shadows need to be included, even if the trees that cast them are off-camera?
Easiest thing to do is not use the clip to camera, I'd say. If you place your population such that most instances will be in front of the camera, the extra trees behind it won't take up much memory or populating time.
If you just need a few shadows, you can also edit and place a few behind camera.