Hurricane Isaac proved to pack a much bigger punch in terms of water than it did winds. And in the case of nutria, that's a mixed blessing.
The rising storm waters, coupled with the astonishing amount of rainfall, conspired to drown nutria by the thousands. Nutria are an invasive species, highly destructive to the fragile marshland ecosystem, and their numbers are growing every day. So in that sense, the death brought by Isaac is a good thing.
Unfortunately, thousands of dead nutria don't just vanish. They wash up on the beach, where they quickly begin to decompose in the hot late summer sun, as many as 20,000 corpses by some estimates. The beaches of Mississippi are particularly badly hit, with the rotting bodies of nutria lining the wrack line for miles in every direction. It's a serious health hazard, not to mention a disgusting experience for locals. The smell apparently carries well on the ocean breeze. (Yuck!)
Even in death, the nutria are causing a huge problem. State and county clean-up crews are unprepared (both equipment-wise and psychologically) for cleaning up such a huge, putrefying mess. The added flies and bacteria could prove damaging to the local environment.