Geography Reference
In-Depth Information
Climate
change
Total Factor
Productivity
Biomass
Energy Price
Income
Population
Local taxes & Subsidise
Demand
for
Crop,Livestoch,&
foerst Products
Supply
of Crop,Livestoch,Biomass energy,&
forest Products
Local Price
Land Use
Land Cover
World Market
Stand-alone or EBR
Greenhouse Gas Emissions
Biophysical diversity
Fig. 2.3
Land use allocation framework of GCAM
2.3.2 Key Methods and Models to Combine Emission
Scenarios with Land Use Changes
2.3.2.1 GCAM Model
GCAM is a dynamic recursive model of land use and land cover, economy,
agriculture, and energy, which fully integrates the energy and agriculture systems
with economic equilibrium in the energy and agriculture markets (Wise et al.
2009
). GCAM consists of four modules, i.e., Edmonds-Reilly-Barnes model (ERB)
(Edmonds et al.
1997
), Agriculture and Land use simulation model (AgLU) (Sands
and Leimbach
2003
; Thomson et al.
2005
), Model for the Assessment of Green-
house gas Induced Climate Change (MAGICC) (Wigley and Raper
1992
), and
Regional Climate Change Scenario Generator (SCENGEN) (Hulme et al.
1995
).
The inputs of GCAM include capital, labor, initial land use allocation, all of which
need to be provided by researchers.
The land allocation diagram (Fig.
2.3
) shows how land is allocated among
alternative land uses types, selection of land use is based on maximizing economic
return at a region, profit per hectare is equal to revenue (yield per hectare times
price received) less production cost (yield per hectare times nonland cost per unit
of output). This relationship is shown in Eq. (
2.15
)
pr
i
;
l
;
m
;
p
¼ y
i
;
l
;
m
;
p
P
i
;
l
;
m
G
i
;
l
;
m
ð
2
:
15
Þ
where pr
i
;
l
;
m
;
p
is the economic return of the land as a profit rate ($/ha-yr), y
i
;
l
;
m
;
p
is
yield per hectare for land use i in region j at location p (calories/ha). P
i
;
l
;
m
is the
market price for the product produced by land use i (units $/yield units: calories or
m
3
). G
i
;
l
;
m
is the non-land cost per unit of output in land use (units are $/yield units:
calories or m
3
), i is an index for land use type. l is the region index. p is an index
for geographical location within a region.
While calculating profit rate pr of forest products is different somewhat because
of the time lag between planting and harvest. The profit rate expression for forest
