> Most are unlikely to emit toxic or greenhouse gasses but they're nevertheless still dangerous because they're often very deep vertical shafts that a person could stumble across and fall in.

That's a problem in Germany as well [1] - particularly in NRW, where most of Germany's mining activity is concentrated for centuries. About two or three times a week an old shaft collapses somewhere in Germany, leading to sinkholes - there's tens of thousands old mine shafts in the country and information on a lot of the legal ones got lost in one of the two world wars, and on top of these come quite the lot of illegal operations. Usually the damage is in some remote area, some forest or whatnot, but in some rare cases, entire buildings vanish or have to be condemned.

[1] https://www.stern.de/gesellschaft/bergbauschaeden--zehntause...