Transferable development rights (TDR) allow landowners to transfer the right to develop one parcel of land to a different parcel of land.
A landowner sells development rights and the land is restricted with a permanent conservation easement. A landowner in other locations buys development rights to build at a higher density then normally permitted.
The concept has been around for a long time but has not worked well for the most part.
The paper titled THE TDR SIREN SONG goes into detail.
THE PROBLEMS WITH TRANSFERABLE DEVELOPMENT RIGHTS PROGRAMS AND HOW TO FIX THEM
By Ari D. Bruening Click here for the file 220kb PDF file
There is also a lot of information on the web about TDR. Search transferable development rights.