That's right! It's been chemical warfare between flora and fauna ever since a fauna first took a fancy to a cob of corn or decided to munch on a bit of hemlock.
Plants use everything from carcinogens to hallucinogens to kill off the flora. They use weaponry such as vicious spikes. They use barbs to hook their seeds into the poor beasts which then cart the seeds for many miles. Some have gone to the extent of hunting. Flies for example die like flies in venus and other fly traps - drowning in the plant's digestive juices.
Plants have found all sorts of pharmacological attack points on those who dare to eat them.
It's not just benign pollution either. It's vicious, malevolent, attack pollution, torture, poisoning and drowning.
I say kill off the lot and just keep lettuce, broccoli, potatoes, rice, sweet corn and such civilized vegetation. Even those could undergo some genetic engineering to improve them.
Mqurice