While trying to find information on the second season of The Walking Dead I came across this little snippet on Wikipedia:
On August 31, 2010, Darabont reported that The Walking Dead had been picked up for a second season, with production to begin in February 2011. On November 8, 2010, AMC confirmed that there would be a second season consisting of 13 episodes. He would also like to include some of the "environmental elements" that take place during Volume 2 of Kirkman's book.
Now, maybe my memory is failing me here, but I don't remember there being a lot of focus on environmental issues in the early stages of the books. That may come in later on (I'm only 48 issues in), but if those things came up in Volume 2, I don't remember them. Again, there may have been mention, but environmental issue were not the focal point of the narrative. Just more reason to believe this series cannot save itself.