How much damage could one invasive species do?

How much damage could one invasive species do?  A lot.  In Florida, introduced Burmese pythons are wiping out some mammalian populations.  How much? A recent study found that "populations of raccoons dropped 99.3 percent, opossums 98.9 percent and bobcats 87.5 percent.  Marsh and cottontail rabbits, as well as foxes, were not seen at all."