Martens are Rural Only in the Squirrel Wars

A Belfast University study has shown that the resurgent Pine marten is unlikely to be the saviour of the UK's native Red squirrel (https://www.theguardian.com/environment/2020/jun/15/hopes-dashed-that-resurgent-pine-martens-can-save-uks-red-squirrel). The Reds have been seriously threatened by the alien Grey squirrel (introduced from Canada in Victorian times) which is larger and out-competes it. The Greys also carry squirrel pox, which is deadly only to the Reds. So Reds only survive in the UK in a few protected locations. Pine martens seem to be adept at catching and eating Grey squirrels, whereas the Reds appear to be better at avoiding this familiar native predator. All so good, so far. The trouble is that the Grey squirrels are well-established in urban areas throughout the UK but the Pine martens are strictly rural. So, even if these predators 'wolfed' many of the Greys in rural areas, squirrels from urban areas would rapidly repopulate those locations. Putting it another way, it appears be impossible to achieve a balance involving just Red squirrels and Pine martens anywhere in the UK, without human culling of the Greys in adjacent towns and cities.