Your note about the drug gangs reminds me of the Chernobyl Exclusion Area and how well plants and wildlife are doing there. The "environment" doesn't really care about humans. The environment can do quite well without humans, thank you very much.
Aside from the whole (alleged) "organised crime setting forest fires in the exclusion zone as cover for illegal logging operations" thing [1], which releases plumes of radioactive ash and ends up with contaminated wood in people's furniture and fireplaces.
But yes, when left alone nature does reclaim the lands rather effectively.
