Bit late to this but…
1. I don’t see ho riding on footpath disturbs nesting birds, worries sheep or causes localised flooding.
2. I can see how riding across the moors can do those things but the key is to not ride across the moors during nesting season (NT would be well advised to put signs up to warn all visitors of this), avoid sheep (the big white fluffy things are hard to miss) and only stick to proper trails when it’s wet and muddy to stop erosion (goes for all users, especially big groups of walkers and horse riders).
3. I think it’s time that a lot of footpaths were re-assessed and a lot turned into bridleways. Footpaths and bridleways are now mainly used for leisure, not for people walking to work down to the mines or for crossing the moors on their horse taking an important message for the King or whatever.
4. Put up signs during nesting seasons to warn people. Dogs and kids do waaaaay more harm than someone cycling down a man-made or natural trail.
5. A lot of farmers will move their sheep away from rights of way on the lead up to lambing and not put newborn sheep out in a field with a right of way, if they can avoid it. It would also be advised to put a sign up insisting that all dogs are kept on a lead across any land that they use for livestock and tbh I would put bins out for dog mess if it helps stop people leaving it. Which reminds me, we have some signs about the health risks to livestock of dog poo.