Your meadow sounds lovely, trishs! I'd love to see it. However, I do wonder about the term "untouched". I presume what is meant by that is that it had not been ploughed and sown with crops other than meadow plants for many generations. Is that right? Correct me if that is wrong. But the thing is, even the meadow may not be untouched land really. Presumably it would have been forest before human beings started farming there and using that bit of land for pasture. If the meadow needs to be "maintained", then clearly what nature would do to it is different from what we as humans want it to be. So, in my mind, that is not untouched. It is a human-made landscape, not an untouched natural one. Sorry to be picky but I do think it's important to understand exactly what terms mean. If what I suggest is correct (it may not be), the land is not untouched. And if nature 'wants' dog mercury to grow there, and you can't manage to prevent it and can't get help with the old style pastoral maintenance, why not just let nature do what nature does?
I speak as someone who knows full well that if I didn't maintain our garden as a garden, within thirty years, or possibly less, it would have reverted to a forest of birch, ash, holly and sycamore, with brambles galore, honeysuckle, ivy and so on, with perhaps a few glades where deer browsed or where a old tree fell down and opened up a light area until new trees took hold again.
In some ways this is a challenge, but in other ways I find it very encouraging – give nature half a chance and it will get on with Life all by itself and hide human interference very successfully 