Prehistoric monsters consumed lots of trees, if they didn't consume each other. What would the avid environmentalists do if the dinosaurs were still here? There would have been far fewer trees to protect by now.
Dinosaurs would presumably be unimpressed by activists chained to trees they wantonly intended to consume. Also, if the creatures wantonly consumed all of those things, including the trees, chains and activists, there would be no one left to protect the environment.
I discussed this and the traffic implications in my hub about cement dinosaurs.