Let’s have a thought experiment. If Adam, before sin, had tripped and fell on a big sharp rock and cut his head open, would he die? Think about it, the neurological and cranial damage would be tremendous and even if that wasn’t damaged, there is still the risk of infection. What if Adam wanted to enjoy a swim in the river, what if he got a cramp and couldn’t swim anymore and drowned? I hear the objections already, “Well God could alter the physics or perform a miracle,” or, “Adam would have seen that rock or would have known not to swim at that time.” Sure, these are possible, but not plausible. I think those objections won’t work because you have a problem of a theodicy on your hands, why wouldn’t God interfere with Adam sinning? Both were free decisions. Also, you have a problem of noetic sin if you play the cognitive card. Was Adam’s cognitive faculty super human (in comparison to today’s faculty) in that he would have known where all the big and sharp rocks were and would he have known where to step and what to do and when to do it to avoid any harm? I think both objections are too ad hoc and are cases of special pleading.
The issue rests with Romans 5.12.
Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned.
The result of sin is both physical and spiritual death to mankind. Wait, didn’t I just advocate physical death before the fall? Yes, of the natural order. Adam was removed from Eden, which prohibited him from partaking in the fruit of the tree of life. I believe that the tree of life provides the needed substance for overcoming physical death. You’ll notice in Revelation 22 the tree of life returns so we may live eternally. Spiritual death is what separates us from God and is only a consequent of the fall of Adam.
So, did plants die before the fall? Yes. Did animals die before the fall? Yes. Did humans (homo sapiens sapiens) die before the fall? No. Could humans die before the fall? Yes, but only of the natural order previously discussed.