Saw this on a ride the other day...
Shame on you, hippie for f**cking up UCSC's sign!
Anyway, as a mountain biker, I'm not ashamed. I practice sustainable recreation and I know that the forest is a resilient ecosystem. Besides, the upper campus is hardly a wilderness area. The winter runoff from the roads and the parking lots are funneled into the creeks and cause more erosion in a good storm than thousands of bikes over several decades.
Debating about the impact on the forest becomes moot when UCSC implements their Long-Range Development Plan. The supreme irony is that the forest surrounding this gate will be completely developed with student housing and academic buildings by 2020 according to the UCSC plan (see Figure 20 p. 66). Most of this forest (and the trails) will be gone. Pipedream, Ridge Trail, Rock and Roll, Garden of Weeden, Geoff's trail, Swamp trail, Mr. Twisty, RV Park will be a memory.
Heed the words of Jim Morrison: "I wanna have my kicks before the whole sh**house goes up in flames". Get it while you can but be nice out there. Ride slow, say hello and smile like you love the forest. Because you do. You're a mountain biker.