Worksheet(s) in the FABLE Calculator:
⇒ 4_calc_land
⇒ 4_data_land
We represent 6 land cover types in the FABLE Calculator: pasture, cropland, urban area, forest, new forest, other natural land. Computed changes in area of pasture, cropland, urban and new forest induce changes in area of forest and other natural land as the total land area cannot expand. For each land cover type, we first compute the initial area at the beginning of the period using 2000 historical data as the base year and the feasible computed area at the end of the previous period for the other time steps.
The difference between the targeted pasture area for each time step which is computed in the previous steps (cf. Pasture) and the initial pasture area at the beginning of the time step corresponds to the targeted pasture area change (expansion or reduction) (Figure 6). The targeted pasture change is compared with the maximum pasture expansion which depends on the selected land scenario (cf. Land availability) e.g. in the No Expansion scenario, there is no pasture expansion possible after 2015. In case the targeted expansion is higher than the maximum expansion, the maximum value is used to compute the feasible pasture area. The same is done for cropland. The targeted cropland area is computed as the sum of computed harvested area by crop in previous steps (cf. Crops) plus the area for "other crops" which results from the difference of cropland area in 2000 and the sum of harvested area by crop in the FAO database. The discrepancy between reported cropland and the sum of harvested area can be explained by missing crops in the FAO database but also because arable land includes "temporary meadows for mowing or pasture, land under market and kitchen gardens and land temporarily fallow (less than five years)" (FAO), which are not yet explicitly taken into account in the FABLE Calculator. The area under "other crops" is set constant at 2000 levels for the whole period of simulation. Targeted urban area is computed based on historical expansion rates computed based on ESA-CCI land cover maps from 2000 and 2005 but capped at 3.5% of total land area maximum. Depending on the Afforestation scenario which is selected (cf. Afforestation), there might be some land which is taken out of pasture, cropland and/or other natural land to be converted into new forest. In this case, the afforested area is removed from the initial land area before the land expansion/reduction is computed.
Targeted deforestation is computed as the share of the total expansion which occurs at the expense of forests and the total targeted expansion which is computed by adding cropland, pasture, and urban area expansion. The share of the expansion which occurs on forest is based on FAO data over 2000-2005 but can also be changed through land scenario (cf. Land availability) e.g. in the No deforestation scenario, the share is set to zero. This targeted deforestation is compared with the maximum deforestation which is computed as the initial forest area at the beginning of the period minus the forest within protected areas. The computed deforestation cannot be higher than the maximum deforestation.
The initial other natural land category in 2000 is computed as the difference between the total land area of the country/region minus pasture, cropland and urban areas. It can thus include quite heterogeneous land types and degree of wilderness. The maximum other natural land which can be converted to productive land use is computed as the initial other natural land at the beginning of the period, minus the area within protected areas and minus the area which is targeted for afforestation. The targeted other natural land change is the sum of the targeted productive land use expansion minus the computed deforestation which already accommodates for some of the targeted expansion, and the targeted reduction of productive land area. The computed other natural land change cannot be higher than the maximum available other natural land area. In the of case a targeted expansion which could not be met through available forest and other natural land area, productive land use should be adjusted.
Excess land expansion is computed as the difference between targeted and feasible expansion (Figure 7). The adjustment is allocated between pasture and cropland area proportionally to their role in total expansion of agricultural land. The adjustment factor for pasture and cropland is computed as the maximum feasible pasture area over the targeted pasture area and the maximum feasible cropland area over the targeted cropland area. Urban and afforested area are excluded from the adjustment.
Next Section: 3.5 Feasible production, trade, and consumption