ARMAGH City, Banbridge and Craigavon Borough Council has railed against those behind what they called "unauthorised & dangerous".
A number of the unauthorised bike trails, known as ‘wild trails’, have been reported in Gosford Forest Park, the council said.
A council spokesperson said, "Wild trails are not permitted and this type of activity is illegal and dangerous.
"A number of trees have been cut down causing significant damage to the park’s habitat and disrupting wildlife.
"We appeal to users to safely enjoy the existing 32km bike trails and refrain from this hazardous and unauthorised activity.
"Unauthorised trails will be removed and we encourage park users to report any unlawful activity to the Park Management."