Back in high school I took an environmental disaster/ apocalyptic literature class. Lately I've been really wanting to re-read one of the books, but I cannot remember the title. It was about a man who lived alone with his animals. He had a lion(ess?), a jackal and others. He was basically trying to save the animals from death as the world was slowly dying. Flood being the most prominent means featured in the book. One of the lines is how only the rats are flourishing but even they will die. The man's daughter was an activist who took up residence in the branches of one of the few remaining old growth trees. She was murdered during a thunder storm and her body thrown from the branches.

Does anyone know the title of this book?

Brave New World?? 1984? Could also be "Watership Down".

Can't be Watership Down, that's about bunnies :) Don't think it's Brave New World either, though I can't say for sure, the blurb didn't sound right. It's definitely more obscure than that. I tried Googling 'Apocalyptic fiction', and I found a site that has an extensive book list (other than wiki) but no synopsis, so it wasn't that helpful. You could still look, maybe one title would ring a bell.
http://www.empty-world.com/book_index.html