Quite frankly, anyone responsible for envionmental destruction on this scale should be tried on the same basis as war criminals.

Indeed! Even more so, arguably, as environmental damage arguably kills, harms and endangers even more people than war. This would also provide another hammer with which to beat the war criminals given the environmental costs of mobilising enormous armies.
One problem, though: we seem to be pretty rubbish at prosecuting war criminals, except in the few cases where it is politically convenient for the powerful to do so. How else are George and Tony still walking free?