Gutting the forest will greatly increase the risk of landslides.
There’s a detailed article here, with maps showing specific landslide risks on South Ridge and Edgewood.
Here’s a link to a news story “An Eerie Slide in SF,” about an actual slide that took down a house, fortunately unoccupied.
The eucalyptus and blackberry stabilize the hillside. UCSF’s claim that the South Ridge is not steep is not true, as anyone can verify by looking at the “Terrain” option in Google maps. The map below, excerpted from one prepared by State Geologists based on the US Geological Survey shows Mt Sutro as a hazard area for landslides.
We have seen the effects of hillside erosion in the Forest Knolls neighborhood after trees on the hillsides were removed. On a slope on Warren Drive – directly downhill from South Ridge – a blue tarp the size of three houses covered the hillside for a long time before it was stable enough to remove.
Quite apart from actual major landslides, we can expect continual ongoing erosion and rockfalls as are apparent at Twin Peaks, which has similar terrain but no trees.
These landslides could occur up to 6-8 years after the actual cutting, as the roots die and decay and stop binding the soil. An insurance professional pointed out that many insurance policies would not even cover damage to homes caused by such landslides; they would be excluded. (If your home is vulnerable, check the fine print on your policy or ask your agent.)