Back in 2008 the US Army Corps of Engineers (USACE) and the Environmental Protection Agency (EPA) issued the 2008 Compensatory Mitigation Rule governing compensatory mitigation for activities authorized by Corps permits. Each division of USACE has published Regional Compensatory Mitigation and Monitoring Guidelines.
Mitigation banks are restoration and conservation sites that preserve, enhance, or create important ecological functions that may be impacted elsewhere. For example, since 2008 wetland banks can invest in the for-profit creation of new wetlands; developers can purchase credits in the bank to mitigate any impacted wetlands in the same watershed as the proposed development.
There are now over 2000 mitigation banks in the U.S.
USACE runs the RIBITS website, which is their Regulatory in-lieu fee and bank information tracking system.
This map from RIBITS shows the distribution of mitigation banks in the continental U.S. Some USAE districts already have dozens to hundreds of banks in operation, whereas some, such as the Albuquerque USACE district, have none.
This figure, courtesy of Kevin Janni, shows the distribution of mitigation banks and HUC watersheds in Texas for the Fort Worth and Galveston USACE districts. Each bank may only be used to offset development within the same watershed. Due to differing application processes and timelines for different USACE district, some districts have many more banks than others.
Mitigation banks are evaluated based on the quality of the wetlands created, using rapid assessments such as NMRAM.
The 2016 Mitigation Banking Conference will be held in Texas, May 10-13.