The original CBI/WWF Protected Areas Database (PAD) was the result of a collaborative effort between the Conservation Biology Institute and the World Wildlife Fund U.S. The database was developed as a geographic information system (GIS) dataset that represents protected areas in the coterminous United States, Alaska, and Canada, and their associated protection levels presented as Gap Analysis Program (GAP) codes.
The second version of the PAD was completed with funding from the Moriah Fund and only includes the coterminous U.S. and Alaska (The PAD for Canada is still the original from WWF Canada). It included additional GAP datasets which became available after the completion of the original PAD. It also contained most of the new National Monuments that were created at the end of the Clinton administration, and significantly more wilderness areas than the original.
The third and fourth versions of the PAD were completed with funding from the U.S. Geological Survey and USDA Forest Inventory and Analysis (FIA) and also only focus on the coterminous U.S. and Alaska (as in the second version).
Version 4 contains additional GAP datasets which became available after the completion of the third version; the new SWReGAP stewardship data for CO, UT, NV, NM, and AZ; nearly all National Wildlife Refuge boundaries from the most current U.S. Fish & Wildlife Service datasets (with exception to Alaska); and a number of wilderness area boundaries. Identified labeling errors and inconsistencies from the previous version have also been corrected.