Being both a hiker and a biker, I'll say this cautiously. And remember things in Oz are a bit different. hikers generally do the damage. Alot do not practice minumulistic camping. They leave behind rubbish, bath/wash dishes in streams, feed animals etc. and so on, which overall does more damage than bikers leaving tyre marks. Bikers cover terrain in one day what hikers take 2-5 days on.

In our National parks we have very strict rules. No dogs and cats, but fortunately (mostly) no horses Horsey people have no argument that their activity does not damage the land. No native Australian animals are hard hoofed, and you can see the way landscapes are damaged by cows and horses, as the land prior to 200 years ago, supported no hard hoofed beasts.