Abstract. Anthropogenic land-use and land-cover change activities play a critical role
in Earth system dynamics through significant alterations to biogeophysical
and biogeochemical properties at local to global scales. To quantify the
magnitude of these impacts, climate models need consistent land-cover change
time series at a global scale, based on land-use information from
observations or dedicated land-use change models. However, a specific
land-use change cannot be unambiguously mapped to a specific land-cover
change. Here, nine translation rules are evaluated based on assumptions
about the way land-use change could potentially impact land cover. Utilizing
the Global Land-use Model 2 (GLM2), the model underlying the latest Land-Use
Harmonization dataset (LUH2), the land-cover dynamics resulting from
land-use change were simulated based on multiple alternative translation
rules from 850 to 2015 globally. For each rule, the resulting forest cover,
carbon density and carbon emissions were compared with independent
estimates from remote sensing observations, U.N. Food and Agricultural
Organization reports, and other studies. The translation rule previously
suggested by the authors of the HYDE 3.2 dataset, that underlies LUH2, is
consistent with the results of our examinations at global, country and grid
scales. This rule recommends that for CMIP6 simulations, models should (1) completely clear vegetation in land-use changes from primary and secondary
land (including both forested and non-forested) to cropland, urban land and
managed pasture; (2) completely clear vegetation in land-use changes from
primary forest and/or secondary forest to rangeland; (3) keep vegetation in
land-use changes from primary non-forest and/or secondary non-forest to
rangeland. Our analysis shows that this rule is one of three (out of nine)
rules that produce comparable estimates of forest cover, vegetation carbon
and emissions to independent estimates and also mitigate the anomalously
high carbon emissions from land-use change observed in previous studies in
the 1950s. According to the three translation rules, contemporary global
forest area is estimated to be 37.42×106 km2, within the range
derived from remote sensing products. Likewise, the estimated carbon stock
is in close agreement with reference biomass datasets, particularly over
regions with more than 50 % forest cover.
Land Cover Change Assessment of Vaal Harts Irrigation Scheme using Multi-temporal Satellite Sata