Mr Smail said issues regarding a lack of signage could have led to horse riders heading up the wrong tracks, leaving large potholes and damaging jumps and berms.
"It's nothing we can't fix ... and not as bad as damage caused by storms and trees coming down.
"This is not careless vandalism, just some people making some bad decisions - some mountain bikers use the wrong trails as well."
Mr Smail said it cost about $5000 to build 1km of a new trail, but a lot of the work was done by volunteers.
Rotorua district councillor and mountain biking advocate Dave Donaldson said the damage had been done and people needed to realise the forest was for everyone, not one select group.
"There has not been time to signpost all of the new trails. A project is under way to re-sign all of the trails in the forest."
But he said mountain biking trails were not built to take the weight of a horse and its rider so the damage could be significant.
Inflammatory comments left by a small number of angry mountain bikers on Facebook suggested some could take illegal action against horse riders, including the damaging of horse floats.
However, Mr Donaldson and Mr Smail said those comments only made the situation worse.
"Yes, it's disappointing it's happened but we all have to respect each other's rights as forest users.
"We try to work with all forest users ... but it is disappointing to see so much damage after a lot of time and effort had been put into building the trail by club members," Mr Donaldson said.
Redwoods Visitor Centre manager Julianne Wilkinson said she had spoken to two women from Taupo who got lost while riding in the forest recently and admitted causing damage to bike trails.
"They were really lovely, but had never ridden in the forest before.
"From what I can gather they turned on to the wrong trail and ended up on the newly established mountain bike track.
"In retrospect they said they should have come and got a map.
"They were quite upset about the damage they had caused ... I genuinely think they got lost and made some bad decisions on their way out."
She said the forest was a big place and there was room for everyone to enjoy their recreational activities.
"If people do this intentionally, it would be just a few of them.
"Horse riders have just as much right to be in the forest as mountain bikers."
However, Mrs Wilkinson said the majority of complaints she received were regarding mountain bikers using horse, dog or walking trails.
She said it was difficult to help horse riders as they were a lot less organised than mountain bikers and clubs were a lot smaller.
