Input data set: Land Use (ISIMIP4)

Description:

Annual land-use state of every grid cell, derived from the CMIP7 input4MIPs UofMD Land-Use Harmonization (LUH3) dataset and delivered on the ISIMIP 0.25° and 0.5° grids. Five datasets share this description; each is a separate file and a separate specifier.

landuse-totals gives the aggregate categories: cropland (total, irrigated and rainfed), pastures, and forests and natural vegetation. Together with urban areas and the static ice and water fractions these sum to one per grid cell.

landuse-5crops gives the five LUH3 crop functional types (C3 annual, C4 annual, C3 nitrogen-fixing, C3 perennial and C4 perennial) each split into rainfed and irrigated area. The two perennial types are additionally split into food and feed production on the one hand and dedicated second-generation bioenergy plantations on the other. It also carries the pasture total, so a crop model can read cropland and pasture from one file.

landuse-pastures splits the pasture total into managed pasture and rangeland.

landuse-urbanareas gives the urban area fraction.

landuse-forests-and-natural-vegetation gives the primary and secondary vegetation state, each separated into forest and non-forest land, together with the mean biomass carbon density and the mean age of secondary vegetation.

All fractions are fractions of the whole grid cell, not of its land area. Ice and water are held static and have already been subtracted upstream (no renormalization is needed or applied).

Users needing cropland resolved into the fifteen ISIMIP crop groups should use landuse-15crops instead, documented under Land Use 15crops (ISIMIP4).

Variables: landuse-5crops (c3ann_irrigated, c3ann_rainfed, c4ann_irrigated, c4ann_rainfed, c3nfx_irrigated, c3nfx_rainfed, c3per_irrigated_food, c3per_rainfed_food, c3per_irrigated_bf, c3per_rainfed_bf, c4per_irrigated_food, c4per_rainfed_food, c4per_irrigated_bf, c4per_rainfed_bf, pastures), landuse-forests-and-natural-vegetation (primary_forests, primary_nonforests, secondary_forests, secondary_nonforests, secondary_mean_biomass, secondary_mean_age), landuse-pastures (managed_pastures, rangeland), landuse-totals (cropland_rainfed, cropland_irrigated, cropland_total, pastures, forests_and_natural_vegetation), landuse-urbanareas (urbanareas)

Time step: annual

Spatial resolution: 0.25° × 0.25° (15arcmin) and 0.5° × 0.5° (30arcmin), global

Unit: 1 (grid-cell fraction), except secondary_mean_biomass in kg m-2 and secondary_mean_age in years

Format: NetCDF4-classic

Period (ISIMIP4b): 1850–2021 for histsoc and 1850soc; 2022–2100 for 2021soc, ssp1vlsoc-noadapt and ssp3hsoc-noadapt

Period (ISIMIP4a): 1850–2025 for all scenarios, published as two files split at the 1900/1901 boundary

Filenames carry the resolution as 15arcmin or 30arcmin.

Derived from the CMIP7 input4MIPs UofMD Land-Use Harmonization (LUH3) dataset, using the multiple-states land-state fractions together with the multiple-management irrigation and bioenergy fractions. Project page: https://luh.umd.edu/

Historical: UofMD-landState-3-1-2
SSP1-VL: UofMD-landState-vl-3-1-1
SSP3-H: UofMD-landState-h-3-1-1

All three were taken at input4MIPs publication version v20260408.

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 v1.2 for CMIP7 Historical (LUH3 v1.2), source_id UofMD-landState-3-1-2, https://doi.org/10.5281/zenodo.19261724 — used for histsoc, 1850soc, 1901soc and 2021soc

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario VL v1.1 for ScenarioMIP (LUH3-VL v1.1), source_id UofMD-landState-vl-3-1-1, https://doi.org/10.5281/zenodo.19353397 — used for ssp1vlsoc-noadapt

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario H v1.1 for ScenarioMIP (LUH3-H v1.1), source_id UofMD-landState-h-3-1-1, https://doi.org/10.5281/zenodo.19354835 — used for ssp3hsoc-noadapt

References for the LUH methodology:
Hurtt et al. (2020), Geoscientific Model Development, https://doi.org/10.5194/gmd-13-5425-2020
Chini et al. (2021), Earth System Science Data, https://doi.org/10.5194/essd-13-4175-2021

Fractions are of the whole grid cell, not of its land area. Ice and water are held static in LUH3 and already subtracted upstream, so the categories of landuse-totals plus urban areas plus ice and water sum to one per cell. Do not renormalize to land area.

Irrigation is a share of the crop area, not of the grid cell. In the LUH3 source the irrigated fraction is defined relative to the area of its crop functional type, and the published irrigated and rainfed variables are already the product of the two. They can be added and compared directly with the crop-type totals.

Annual values are interpolated. The LUH3 reconstruction is anchored on decadal to centennial steps for much of the historical period, and the intervening years are interpolated. Smooth year-to-year behaviour in the early record is a property of that interpolation, not observed interannual variability.

The two resolutions do not give the same global totals. The 0.5° product is conservatively remapped from the native 0.25° grid and renormalized over the land area of each coarser cell, so a global area total computed from a 30arcmin file exceeds the same total from the 15arcmin file by about 1 %, concentrated in coastal cells. Use the 15arcmin files when the global total matters.

Sums close to within numerical tolerance, not bit-exactly. The category sums hold to about 1e-6 after aggregation and remapping. Clamp or renormalize consistently if an exact closure is required.

LUH2 in the vegetation variable names is not a stale reference. It is the upstream term for the potential-vegetation classification that separates forest from non-forest land, which LUH3 inherits unchanged.

Plantation area is not published. The LUH3 pltns state is all-zero in this release and is excluded from every dataset in the family rather than shipped as an empty variable. Dedicated bioenergy plantations are instead carried by the four perennial bf variables of landuse-5crops.

2021soc means different things in the two rounds. Under ISIMIP4b it holds the 2021 state fixed across the 2022–2100 future window; under ISIMIP4a it holds the same state fixed across the full 1850–2025 historical period, as a present-day baseline.

Under ISIMIP4a the value for 2025 repeats 2024, the last observed year.