It's fairly widely accepted that dog/walker/dog walker has the greater impact on flora and fauna. Bikers are transient, won't stop, in and out in a flash, will stick within the trail. A dog will invariably extend 5-10m or more either side of the trail, foraging, chasing anything that moves, criss crossing, dumping and laying their scent.
Hmm? Not trying to steer this into a dog thread but not really convinced.
Again the differentiation between a dog under control and not, dogs on leads don't tend to be able to chase anything that moves. The behaviour you describe of dogs is fairly similar to Foxes, Badgers, Rabbits, Sheep, Cows and Essex Mountain Lions.
I have also seen bikers extending either side of the trail (way more than 10m depending on how vague the route is, chasing other bikers and disturbing wildlife, criss crossing, not seen anyone taking a dump yet but it does happen and on a longish ride there is plenty of bushes and walls marked by the riders
I applaud the scottish methods but also look at them with caution, some paths are not suitable for walkers or riders and should either be closed or repaired.