Grey squirrels are a native species here in North America (all of the continent) and as such are part of our eco-sysytem. In England however they are what we would call an "invasive" species. Any invasive species will wreak havok on your natural environment. Probably much deeper damage than the complaints I usually read about them supplanting your native Red Squirrel and tearing up your gardens. We have enough invasive species here as well to see the damage: wild pigs, wild horses (oddly wild horses have become almost an icon though because of their association with the west even though they aren't native and their hooves destroy the range) and now exotic species such as pythons and boas. The saddist part is that even if hunting Grey Squirrels becomes popular there, it won't have much effect. They are prolific breeders and will survive any amount of hunting pressure as long there is an adequate food supply (acorn crop). They are an extremely poplular small game animal here, usually being the first game a young boy or girl learns to hunt with his/her Dad. Most states have a harvest limit of anywhere from 8 to 16 squirrels per hunter per day with no season limit (the season varies by state because of differing regional climates but usually lasts most of the Fall and Winter). Multiply that times a few million hunters annually and that's an aweful lot of hunting pressure and yet they continue to thrive. However even if you cain't eliminate them through hunting remember two things: 1) They are delicious! 2) For those of you who have objections to the idea of hunting, ask yourself, "What's crueler & more barbaric? A hunter stalking wild game or a livestock farmer killing animals that trust him?"