Hawaii is unique among the United States because of its tropical climate, geographic isolation, high rates of species endemism, and discontinuous landmass. The goal of this report is to provide robust baseline estimates of carbon storage and flux across the Hawaiian Islands based on the best available data and to then use this baseline data as input to predict how carbon cycling and storage may respond to projected future changes in climate, land use, land cover, and disturbance. Major components of the assessment include a new high-resolution land-cover map for the State of Hawaiiprojected future shifts in climatic zones owing to global warming; baseline estimates of carbon emissions from wildfire; comprehensive statewide estimates of current ecosystem carbon stocks in soils, live biomass, and detritus; comprehensive statewide estimates of current carbon fluxes from gross primary production (GPP) and ecosystem respiration (Re); current and projected future stream,and groundwater carbon fluxes to nearshore waters; and, statewide estimates of current and projected future net ecosystem carbon balance based on projected changes in climate, wildfire, land use, and land cover. Forest Service scientists found that total terrestrial carbon (TgC) amounted to 258 TgC, of which 71 percent was soil organic carbon, 24 percent was live above and below ground biomass, and 5 percent was litter and downed woody debris. Hawaii Island, the largest island in the Hawaiian archipelago, accounted for 58 percent of the total carbon storage. Between 2003 and 2014, gross primary production across the seven islands averaged 20.2 TgC/yr, with Hawaii Island accounting for 55 percent of this flux.. Terrestrial ecosystems of the seven main Hawaiian Islands sequestered an average of 0.34 TgC/yr during the baseline period, which was approximately 4 percent of statewide terrestrialnet primary productivity.. During the projected future period (2012–2061), the State of Hawaii was projected to remain a net carbon sink in 2061, primarily because of carbon sequestration in terrestrial ecosystems on Hawaii Island.