Mapping peatland extent and condition in the conterminous United States and Hawaii to inform peatland protection and restoration.

Peatland conservation and restoration are globally important goals because of peatlands' potential to sequester and store carbon for millennia, regulate hydrology, and emit greenhouse gases (GHGs) when degraded. To provide information that can be used to identify possible targets for restoration, we have developed a peatland condition map for the conterminous US and Hawaii using existing GIS-based information. We intersected gSSURGO histosols and histic epipedons (HE) with layers for land use, crops, ditches, roads, and railroads (within 150 m buffers for the last three), land protection classes, and USDA Natural Resources Conservation Service (NRCS) wetland easements. Of the 94,750 km of histosols and 13,533 km of HE analyzed, 7 % (7709 km) were under agricultural use. Of 100,415 km of histosols and HE not in agricultural use, 19 % were within 150 m of ditches, roads, or railroads. Of mapped histosols, 38 % (36,042 km) were legally protected from extractive use, and 635 km were in NRCS wetland easements. Based on IPCC tier 1 emission factors, the greatest reduction of CO-e emissions per unit area and nationally would be from rewetting of peatlands under agriculture. In non-agricultural areas, rewetting peatlands affected by ditching alone is likely more cost-effective than if they are also affected by roads and railroads. Total potential emission reduction associated with rewetting of currently analyzed drained peatlands is estimated at >36.8 Tg CO-e yr. Future gap filling of the map will likely increase this estimate. This map can be used to evaluate potential peatland restoration opportunities at a variety of scales.