1. We need to be clear that when God declared His work to be ‘good’, he was speaking from His viewpoint not ours. There was certainly death in the world from the earliest days of biological life, because God gave the plants to the animals for food, and plant death is as much death as animal death. Moreover, there were many, many generations of animal death before humans came on the scene. The dinosaurs had flourished - and then become extinct. We know from their fossils that they suffered from bone disease, just as we do.  We are wrong to assume that there was no death or disease before the Fall.
2. The ‘death’ that entered the world with Adam (Romans 5:12; 1 Corinthians 15:21) was primarily separation from God, the source of that which makes us truly human. Our first parents ‘died’ the day they sinned; they were removed from God’s presence (i.e. evicted from Eden), but they survived for years and had all their children outside Eden. Through Christ’s redeeming death, we are raised to life, "born anew" by being reunited with God.
I found this while preparing for a presentation on Environmental Theology. Worth a read.