### 2.27.4.1. LUH2 Transient Land Use and Land Cover Change Dataset[¶](#luh2-transient-land-use-and-land-cover-change-dataset "Permalink to this headline")

To coordinate the processing and consistency of LULCC data between the historical period (1850-2015) and the six SSP-RCP (2016-2100) scenarios derived from Integrated Assessment Models (IAM), the University of Maryland and the University of New Hampshire research groups (Louise Chini, George Hurtt, Steve Frolking and Ritvik Sahajpal; luh.umd.edu) produced a new version of the Land Use Harmonized version 2 (LUH2) transient datasets for use with Earth System Model simulations. The new data sets are the product of the Land Use Model Intercomparison Project (LUMIP; [https://cmip.ucar.edu/lumip](https://cmip.ucar.edu/lumip)) as part of the Coupled Model Intercomparison Project 6 (CMIP6). The historical component of the transient LULCC dataset has agriculture and urban land use based on HYDE 3.2 with wood harvest based on FAO, Landsat and other sources, for the period 850-2015. The SSP-RCP transient LULCC components (2015-2100) are referred to as the LUH2 Future Scenario datasets. The LULCC information is provided at 0.25 degree grid resolution and includes fractional grid cell coverage by the 12 land units of:

Primary Forest, Secondary Forest, Primary Non-Forest, Secondary Non-Forest,

Pasture, Rangeland, Urban,

C3 Annual Crop, C4 Annual Crop, C3 Perennial Crop, C4 Perennial Crop, and C3 Nitrogen Fixing Crop.

The new land unit format is an improvement on the CMIP5 LULCC datasets as they: provide Forest and Non Forest information in combination with Primary and Secondary land; differentiate between Pasture and Rangelands for grazing livestock; and specify annual details on the types of Crops grown and management practices applied in each grid cell. Like the CMIP5 LULCC datasets Primary vegetation represents the fractional area of a grid cell with vegetation undisturbed by human activities. Secondary vegetation represents vegetated areas that have recovered from some human disturbance; this could include re-vegetation of pasture and crop areas as well as primary vegetation areas that have been logged. In this manner the land units can change through deforestation from Forested to Non Forested land and in the opposite direction from Non Forested to Forested land through reforestation or afforestation without going through the Crop, Pasture or Rangeland states.

The LUH2 dataset provides a time series of land cover states as well as a transition matrices that describes the annual fraction of land that is transformed from one land unit category to another (e.g. Primary Forest to C3 Annual Crop, Pasture to C3 Perrenial Crop, etc.; Lawrence et al. 2016). Included in these transition matrices is the total conversion of one land cover type to another referred to as Gross LULCC. This value can be larger than the sum of the changes in the state of a land unit from one time period to the next known as the Net LULCC. This difference is possible as land unit changes can occur both from the land unit and to the land unit at the same time. An example of this difference occurs with shifting cultivation where Secondary Forest can be converted to C3 Annual Crop at the same time as C3 Annual Crop is abandoned to Secondary Forest.

The transition matrices also provide harmonized prescriptions of wood harvest both in area of the grid cell harvested and in the amount of biomass carbon harvested. The wood harvest biomass amount includes a 30% slash component inline with the CMIP5 LULCC data described in (Hurtt et al. 2011). The harvest area and carbon amounts are prescribed for the five classes of: Primary Forest, Primary Non-Forest, Secondary Mature Forest, Secondary Young Forest, and Secondary Non-Forest.

Additional land use management is prescribed on the Crop land units for nitrogen fertilization and irrigation equipped land. The fertilizer application and the the irrigation fraction is prescribed for each Crop land unit in a grid cell individually for each year of the time series. The wood harvest and crop management are both prescribed spatially on the same 0.25 degree grid as the land use class transitions.

