Appendix
This appendix contains the equations applied to convert the output from the GTAP Model to mass of production and area of agricultural land. The term scenario country is used to designate the country in which the demand for wheat is changed, and the term initial indicates the state before the change in demand. Indices r and c are used for region and crop sector, respectively.
To calculate the initial area of cultivable land used by a crop sector in a region (Au,cult,c,r), it is assumed that the distribution of cropland between crop sectors is equal to the distribution of the area harvested.
Au,cult,c,r = Hc,r / Htot,r∙Acrop,r(3)
where
Hc,r is the area harvested in 2001
Htot,r is the total area harvested in 2001
Acrop,r is the total cropland area
Data on area harvested in the eight crop sectors of the 22 GTAP regions is compiled by manually grouping the data from FAOSTAT (2007) covering more than 200 countries and 146 primary crops.
On the basis of Eq. 3, the change in area in a crop sector (ΔAu,cult,c,r) is calculated from
ΔAu,cult,c,r = Au,cult,c,r ∙ qlnd,cult,c,r(4)
where
qlnd,cult,c,r is the relative change in cultivable land being utilised (GTAP output)
The initial annual yield per hectare in a crop sector (Yc,r) is calculated from
Yc,r = Qc,r / Au,cult,c,r(5)
where
Qc,r is the initial production in crop sector c
Production data for the eight crop sectors of the 22 GTAP regions is compiled in the same manner as described for area harvested.
The change in production caused by change in area in a crop sector (ΔQA,c,r) is calculated from
ΔQA,c,r = Yc,r ∙ ΔAu,cult,c,r(6)
The change in production caused by demand driven intensification in a crop sector (ΔQI,d,c,r) is calculated from
ΔQI,d,c,r = Qc,r ∙ qo,c,r – ΔQA,c,r(7)
where
qo,c,r is the relative change in production in crop sector c (GTAP output)
The change in yields in a crop sector (ΔYc,r) is calculated from
ΔYc,r = ΔQI,d,c,r / (Au,cult,c,r + ΔAu,cult,c,r)(8)
The net expansion on cultivable land in a region (ΔAu,cult,r) is calculated from
ΔAu,cult,r = Au,cult,r ∙ qo,cult,r(9)
where
Au,cult,r is the initial area of available cultivable land being utilised (see Fig. 2)
qo,cult,r is the relative change in available cultivable landbeing utilised (GTAP output)
The change in wheat production caused by expansion in the scenario country (ΔQE,wht,r) is calculated from
ΔQE,wht,r = ΔAu,cult,r ∙ Ywht,r(10)
where
Ywht,r is the initial wheat yield per hectare where r is the scenario country
The change in wheat production caused by displacement of other crops in the scenario country (ΔQC,wht,r) is calculated from
ΔQC,wht,r = (ΔAu,cult,wht,r – ∑ΔAu,cult,c,r) ∙ Ywht,r(11)
where
ΔAu,cult,wht,r is the change in area in the wheat sector where r is the scenario country
∑ΔAu,cult,c,r is the sum of area changes in all crop sectors where r is the scenario country
The change in wheat production caused by livestock displacement in the scenario country (ΔQL,wht,r) is calculated from
ΔQL,wht,r = ΔQA,wht,r – ΔQE,wht,r – ΔQC,wht,r(12)
where
ΔQA,wht,r is the total change in wheat production where r is the scenario country
The net expansion on grazable land in a region (ΔAu,graz,r) is calculated from
ΔAu,graz,r = Au,graz,r ∙ qo,graz,r(13)
where
Au,graz,r is the initial area of available grazable land being utilised (see Fig. 2)
qo,graz,r is the relative change in available grazable landbeing utilised (GTAP output)
Data on production (Q) of milk and meat (bovine, equine, sheep and goat) in 2001 is retrieved from FAOSTAT (2007) for all countries available (155). These data are sorted in GTAP regions (index r) and GTAP livestock sectors (index l).
The total change in production in a livestock sector (ΔQl,r) is calculated from
ΔQl,r = Ql,r ∙ qo,l,r(14)
where
Ql,r is the initial production in livestock sector l (FAOSTAT data)
qo,l,r is the relative change in production in livestock sector l (GTAP output)