Austin Tree Interventionism

Single Family Residential Properties

The removal of or impact to any tree 60 inches in circumference and larger (measured at 4.5 feet above the ground). Sixty inches in circumference is equivalent to 19 inches in diameter. Trees smaller than 60 inches in circumference are not regulated. Protected size trees that are dead and/or hazardous also require a permit. A Tree Risk Assessment (example form) may be requested to further document the condition of the tree.
Examples of when a tree permit may be needed

Commercial and Non Single Family Development

All trees 8 inches in diameter and larger (25'' circumference) are required to be accurately located on site plans submitted for development review. The trees are depicted on the grading and tree protection plan sheets per the Environmental Criteria standards.
See Critical Root Zone and Tree Preservation Requirements.

Austin Arborist Program

In Austin, TX, property owners are not free to dispose of the trees on their property as they see fit.  This intervenes in their freedom to improve their land according to their own values.  As such, this is an infringement upon private property rights and a truly free market.

My girlfriend and I spent the better part of Saturday afternoon clearing out saplings, young trees, and dead trunks out of my backyard.  We did not pause to consider whether anything I wanted out was greater than 60" around, I simply set a standard ("if it's arm width and alive, it goes!") and we acted.  The dead trees were rotten down to the roots and much larger.  Ditching them removed threats to my neighbors' property, increased the chances of grass taking root, removed insect infestations, and gave me more space to do something with the yard.

But apparently I should have kept a tape measure handy, because I don't really own these trees.

Think this is an idle concern?  Take a look at what happened to this guy in Portland.