All mines are temporary structures. They can remain active for many years, but they will eventually run out of minerals and cease operations. This does not automatically mean that the environment and wildlife will no longer suffer.
Responsible owners would backfill the underground mine. However, not all mine operators would resort to this option because the process can be very expensive. Failure to backfill the mine can lead to a problem called subsidence, which occurs when abandoned mines collapse. This will undo any efforts to reestablish a healthy ecosystem in the area, and often render it useless for many years to come. The problem only increases if contaminants were left on the site, since removing them after a collapse is exceedingly difficult. Ensuring that every abandoned mine is duly filled in and wastes are eliminated will help nature to recover.