At home, I bag it, pop it in a pedal-bin that we keep outside lined with a carrier bag and then take it to the local dog-poo bin once or twice a week. The waste from these bins is incinerated (as it is considered the same as medical waste) not landfilled
As for leaving poo in public spaces, the Forestry Commission has been promoting a "stick and flick" technique on their land for a couple of years for environmental reasons, and I am sure if it was damaging to their land they would not be asking dog owners to leave poo on their land - dog poo is no worse than fox poo, badger poo or even hedgehog poo; they are all carnivores too
Lets be honest, dogs don't "belong" anywhere - so neither does their poo; we have domesticated them in the same way as we have cows, sheep and horses - and all of those animals have been pooing in the countryside for generations......
As long as the poo is removed from the trafficked areas, then I agree with the Forestry Commission, the most environmentally friendly method is to allow it to degrade, not use plastics and fuel to dispose of it