In Austin you need a permit to cut down large trees. The city requires a justification for trees 19-24" and may require mitigation by the property owner (planting new growth). The criteria for removal get more stringent for trees larger than 24" and public hearings are called for anything larger than 30". It is really only a problem for commercial developments since public pressure can prevent them getting the permits. The maximum fine is only $2000 so some developers just see it as a cost of doing business if they get caught.