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GTAP Resource #1591

"Incorporating Agro-Ecologically Zoned Land Use Data into the GTAP Framework"
by Lee, Huey-Lin

Land use, land-use change and forestry (LULUCF) activities have been perceived as a relatively cost-effective option to mitigate climate change due to greenhouse gas (GHG) emissions. LULUCF may contribute to abatement of emissions by increasing carbon storage in forests (the so-called sinks: enhancing afforestation and forest management, while curbing deforestation). Article 3 of the Kyoto Protocol makes provision for the Annex I parties to take into account removals and emissions due to LULUCF activities since 1990 (e.g., afforestation, reforestation, deforestation and other agreed land use changes) to meet their commitment targets of greenhouse gas emission abatement. In the seventh Conference of the Parties (COP7) to the UNFCCC held in Marrakesh, October/November 2001, the parties finally agreed to include land-based carbon sequestration in their 2008-2012 GHG emissions reduction targets. The COP9, held in Milan, December 2003, has reached consensus for the rules of accounting for LULUCF projects in the Clean Development Mechanism (CDM) for the first commitment period (2008-2012) of the Kyoto Protocol. Along with such policy commitments, research on Integrated Assessment (IA) of climate change has recently been advancing towards the LULUCF embraced analysis.
In the 2002 MIT workshop (GTAP Website, 2002), co-sponsored by the U.S. EPA, MIT, and the Center for Global Trade Analysis, the idea of identifying agro-ecological zoning in the GTAP model was sparked in the discussion among the participating experts. The recognition of various agro-ecological zones (AEZ) is believed to be a more realistic approach in modelling land use change in GTAP, where land is mobile between crop, livestock and forestry sectors within, but not across, AEZ’s. In the standard GTAP model, land is assumed to be transformable between uses of crop growing, livestock breeding, or timber plantation, regardless of climatic or soil constraints. The fact is that most crops can only grow on lands that is under certain temperature, moisture, soil type, land form, etc.. The same concern arises for land use by the livestock and the forestry sectors. Lands that are suitable for growing wheat may not be good for rice cultivation alike, even under transformation at a reasonable cost. The introduction of the agro-ecological zoning in GTAP helps to clear up the counterfactual assumption in inter-sectoral land transition, and permit a sound presentation of sectoral competition for land.
In this paper, we describe a GTAP based CGE model, named GTAP-AEZ, which identifies six agro-ecological zones (AEZ) for the U.S., China, and rest of world. We follow the FAO fashion of agro-ecological zoning (FAO, 2000; Fischer et al, 2002) to identify lands located in six zones. Lands located in a specific AEZ have similar (or homogenous) soil, landform and climatic characteristics. The six AEZs range over a spectrum of length of growing period (LGP) for which their climate characteristics can support for crop growing. AEZ 1 covers the land of the temperature and moisture regime that is able to support length of growing period (LGP) up to 60 days per annum. On the other end of the LGP spectrum, lands in AEZ 6 can support a LGP from 270 to 360 days per annum. Crop growing, livestock breeding, and timber plantation are dispersed on lands of each AEZ of the six, whichever meets their climatic and edaphic requirements. We assume that transition of land in a specific AEZ can occur only between sectors that the land is appropriate for their use.
In GTAP-AEZ, we recognize a unique production function for each of the land-using sectors located in a specific AEZ. For example, the paddy rice sector located in AEZ 1 has a different production function from the paddy rice sector located in AEZ 6. This is to identify the difference in the productivity of land of different climate characteristics. Nevertheless, all the paddy rice sectors located in the six AEZs produce homogenous output to meet market demand.
The AEZ land data of the GTAP-AEZ model are compiled from a data set of land acreage and production of 19 crops and 3 species of timber located in 18 agro-ecological zones (6 AEZs coupled with 3 climate zones—boreal, temperate, tropical). The crop land data are provided by Dr. Navin Ramancutty of the Center for Sustainability and Global Environment (SAGE), University of Wisconsin-Madison. The timber land data are provided by Dr. Brent Sohngen of Ohio State University. These authors will also be presenting their work at the GTAP conference.
In GTAP-AEZ, we associate methane (CH4) and nitrous oxide (N2O) emissions to their emitting sources (or drivers). For example, we link methane emissions from paddy rice cultivation to the land used in the paddy rice sector of GTAP-AEZ. We treat methane emissions as input to the paddy rice growing, and permit limited substitution of other input for emissions according to estimates of the marginal cost of abatement, following the approach of Hyman (2001).
At present, GTAP-AEZ is a comparative static model and so is not suited to long run analysis of climate change policy. However, for purposes of illustration and analysis, we run a simulation in which U.S. seeks to cut its GHG emissions by 5%. We compare the results of two scenarios: (1) the tax is imposed only on CO2 emissions from fossil fuel combustion, and (2) the tax is imposed on CO2 from combustion, CH4 and N2O from all sources. Preliminary results show that the carbon tax in scenario (1) required to attain a 5% reduction in total GHG emissions of the U.S. is about USD$15 (in 1997 USD). On the other hand, the carbon tax in scenario (2) required to attain a 5% reduction in U.S. total GHG emissions is only USD$5. This conforms with empirical findings presented at a recent meeting of the Energy Modeling Forum (EMF) at Stanford University (EMF, 2003; study results scheduled to publish in a special issue of The Energy Journal in Fall 2004) where it was concluded that multi-gas mitigation helps to reduce cost of emissions abatement. Results associated with land transition between using sectors are currently under examination.

EMF. (2003). EMF 21: Multi-Gas Mitigation and Climate Change. The Energy Modeling Forum (EMF), Stanford University, Palo Alto, CA. Available:
FAO. (2000). Land Cover Classification System: Classification Concepts and User Manual (with CD-Rom). Rome: Food and Agriculture Organization (FAO) of the United Nations.
Fischer, G., van Velthuizen, H., Shah, M., and Nachtergaele, F. (2002). Global Agro-Ecological Assessment for Agriculture in the 21st Century: Methodology and Results (Research Report RR-02-02). Laxenburg, Austria: International Institute for Applied Systems Analysis (IIASA) and Food and Agriculture Organization (FAO) of the United Nations (UN).
GTAP Website. (2002). Workshop: Incorporation of Land Use and Greenhouse Gas Emissions into the GTAP Data Base. Center for Global Trade Analysis (GTAP), Purdue University, West Lafayette, IN. Available:
Hyman, R. C. (2001). A More Cost-Effective Strategy for Reducing Greenhouse Gas Emissions: Modeling the Impact of Methane Abatement Opportunities. Unpublished Master thesis, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Resource Details (Export Citation) GTAP Keywords
Category: 2004 Conference Paper
Status: Published
By/In: Presented at the 7th Annual Conference on Global Economic Analysis, Washington DC, USA
Date: 2004
Created: Lee, H. (5/22/2004)
Updated: Bacou, M. (5/22/2004)
Visits: 5,244
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