Matter of perspective -for undocumented trails-thousands km. in Alberta, BC.

[shootingstar]

Thousands of kilometres of undocumented, unmanaged trails found in Alberta and B.C. | CBC News

Not surprising in our area of Canada given the huge wilderness in mountain areas.  Bragg Creek that's mentioned in article is a tiny town/hamlet about 50 km. 1-way from Calgary which we've cycled round trip from downtown. There's probably a very active local mtn. bike group that helps maintain trails. I'm not sure since I don't belong to local mtn. bike groups nor join their chats.

[Razors Edge ★]

Un-managed - probably in an "official" sense, right?  IOW, if folks are actively using them, but not because they are part of a recognized trail network and under some entity's responsibility, then the folks using them probably perform some ad hoc or even organized maintenance like clearing fallen trees.

Undocumented also has two parts - not documented as part of a recognized trail network may not mean it is not documented on countless trail apps.  Garmin or Strava heat maps will certainly start revealing (ie documenting) trail use, and so even trails not on the "official" record will be well documented over the past decade or so.