What happened to all the animal waste products, which were the result of eating all that plant fiber? Did it just lay around? Or did it decay back into the soil, so the plants could use it? If it decayed, doesn't that imply that decay would be part of the cycle? And if it didn't decay, how would the plants use it?
Excellent point; How do you know that conditions were the same before the curse as they are now? Are compounds breaking down different than compounds decaying. Could it be the difference between rust, and a catalyst?