Well, forests aren’t full of dead animals lying around everywhere, so something has to happen to them when they die.
All of these questions can be answered by knowing how materials are exchanged in cycles within the environment. Not even a magician can make matter disappear – it always has to go somewhere. Matter simply gets exchanged to allow reuse in many ways. The cyclical exchange of certain biological chemicals allow ecosystems to sustain life without the risk of running out of resources.
If matter were not recycled, where would it go once it was used? Think about carbon. All living matter is made with carbon. The amount of carbon present on earth right now is essentially the amount that was present a million years ago and it will be the amount present a million years from now. If organisms just disappeared when they died, they would take their carbon with them. Eventually, all the carbon they contained would be gone, and nothing would be able to grow or develop.
Unfortunately, certain human actions create environmental hazards that tend to disrupt different phases of the cycles and cause harmful effects to all parts of the ecosystem involved with the cycle. Explanations of these different types of hazards can be found in the Properties of Hazards module.
Understanding the effects of disturbing the cycles will make it easier to understand the importance of the cycles. But even at this point, you must realize that the natural exchange cycles are necessary for sustaining ecosystems.