I think in defense of the land owners, they'd be more likely to welcome walkers onto their land to access public land if the fly tipping situation was brought under control. I'm not saying walkers do it, but wherever you have free access then you often get fly tipping. Mainland Dartmoor is not as bad, but bridle paths and lanes are a nightmare. Both my Dad and the neighbouring farm have had issues for years. We've had a full sized caravan dumped (whilst on fire), cars, washing machines, asbestos, roof tiles. Dad has to maintain the bridle path out of his own pocket so that a few people a year can walk down it, and a multiple fly tippers per year ruin it for everyone.