Land-Use Harmonization 2: New Features and New Scenarios

Land use and land cover change are known to be significant drivers of regional and global changes to the biogeochemical and biophysical properties of the Earth surface, with resulting implications for the climate system, carbon stocks, biodiversity, and economic resilience. To incorporate these effects into Earth System Models and Dynamic Global Vegetation Models, new gridded datasets of land-use states and transitions have been developed and adopted as a required forcing for CMIP6 experiments. These Land-Use Harmonization 2 (LUH2) datasets make use of new historical data from HYDE and FAO (for years 850 to 2015), as well as new Shared Socio-economic Pathways (SSPs) from Integrated Assessment Models (for years 2015 to 2100). The LUH2 harmonization strategy estimates fractional land-use patterns (at 0.25 degrees spatial resolution, globally), underlying land-use transitions, key agricultural management information, and resulting secondary lands annually while minimizing the differences between the end of the historical reconstruction and IAM initial conditions, and working to preserve future changes projected by the IAMs. The LUH2 datasets have now been finalized and include more than 20 different historical and future scenarios spanning a wide range of alternative future land uses, from increased deforestation to significant global afforestation. Each scenario involves more than 100 possible land-use transitions (between 12 different land-use states) in each grid-cell, annually. In this presentation we will highlight some of the newer features of LUH2, such as data layers describing important land-management practices; new representations of shifting cultivation; and the "added tree cover" needed to capture the intended forest cover gains from IAM scenarios. In addition, we will also share several of the most recent LUH2 scenarios including "high" and "low" historical reconstructions; new scenarios for SSP1 RCP1.9 and SSP5 RCP3.4OS; and the extensions of SSP5 RCP8.5, SSP5 RCP3.4OS, and SSP1 RCP2.6 for the years 2100 to 2300. Finally, we will describe several novel uses of LUH2 data in scientific studies outside of CMIP6, such as the annual Global Carbon Budget and TRENDY studies; the impact studies of ISIMIP2b; and new work extending the annual LUH2 data for use in monthly carbon forecasting models.