A recent study led by the US Geological Survey published in the journal Environmental Research Letters used ST-Sim to estimate the ecosystem carbon balance for the continental United States (CONUS) over the period from 1973 to 2010.  The study used remotely sensed data to estimate the effects of land use and land cover change on ecosystem carbon balance.  The study estimates that on average, ecosystems in CONUS have  been a net carbon sink (254 TG Carbon per year) but that there is much inter annual variability.  Forests are the largest carbon sink and the size of the sink due to forests has declined by 35% over the study period.  The reasons for the decline in the size of the forest carbon sink are forest ageing and a reduction in the total area of forests in CONUS.  The historic ecosystem carbon balance is more uncertain prior to 1985 when remotely sensed data sets of wildfire and other disturbances became available.  In future, the model developed in this study could be used to evaluate the effects of alternative land use policies on future ecosystem carbon balance.