[Carry_Okie]

I think they have abandoned the practice, but Earth First! used to put lethal spikes in trees hoping to injure or kill an unsuspecting logger or millworker.

IIRC Earth Liberation Front still does it and they use ceramic spikes (undetectable to a magnetic sensor).

[sasquatch]

A tree-sitter protesting logging in the slopes above Ramsey Creek fell 50 feet from his redwood perch and onto a stump Tuesday night.

If he hit a stump the trees were too tight in the first place! (Still looking for validation of the rumored croak)