Find them. Bill them.
In California, intentional felling of a tree is subject to treble damages.
And the monetary “value” of a tree is astoundingly high.
Prosecute them. Trespassing. Vandalism. Malicious destruction of property. Even if it’s all misdemeanors, it’s worth it. Slap them down. Others are watching.
And use the chainsaw to make sure the vandals don't pass on their defective genes.
Odd. That is the same place where unborn babies have no value.