How much wooded land should be cleared around a new home site?
In California, if you build in the "wildland interface", wildfire risk drives the clearance requirement of 100'. The following quote is from the CalFire web page:


  Protecting a building from wildfire takes a two-pronged approach: Remove flammable materials from around the building;
  Construct the building of fire resistant material.
  The law requires that homeowners do fuel modification to 100 feet (or the property line) around their buildings to create a defensible space for firefighters and to protect their homes from wildfires.