Renaud Crassous’s research while affiliated with International Research Center on Environment and Development, French National Centre for Scientific Research and other places

Interactions between food demand, biomass energy and forest preservation are driving both food prices and land-use changes, regionally and globally. This study presents a new model called Nexus Land-Use version 1.0 which describes these interactions through a generic representation of agricultural intensification mechanisms within agricultural lands. The Nexus Land-Use model equations combine biophysics and economics into a single coherent framework to calculate crop yields, food prices, and resulting pasture and cropland areas within 12 regions inter-connected with each other by international trade. The representation of cropland and livestock production systems in each region relies on three components: (i) a biomass production function derived from the crop yield response function to inputs such as industrial fertilisers; (ii) a detailed representation of the livestock production system subdivided into an intensive and an extensive component, and (iii) a spatially explicit distribution of potential (maximal) crop yields prescribed from the Lund-Postdam-Jena global vegetation model for managed Land (LPJmL). The economic principles governing decisions about land-use and intensification are adapted from the Ricardian rent theory, assuming cost minimisation for farmers. In contrast to the other land-use models linking economy and biophysics, crops are aggregated as a representative product in calories and intensification for the representative crop is a non-linear function of chemical inputs. The model equations and parameter values are first described in details. Then, idealised scenarios exploring the impact of forest preservation policies or rising energy price on agricultural intensification are described, and their impacts on pasture and cropland areas are investigated.

Interactions between food demand, biomass energy and forest preservation are driving both food prices and land-use changes, regionally and globally. This study presents a new model called Nexus Land-Use version 1.0 which describes these interactions through a generic representation of agricultural intensification mechanisms. The Nexus Land-Use model equations combine biophysics and economics into a single coherent framework to calculate crop yields, food prices, and resulting pasture and cropland areas within 12 regions inter-connected with each other by international trade. The representation of cropland and livestock production systems in each region relies on three components: (i) a biomass production function derived from the crop yield response function to inputs such as industrial fertilisers; (ii) a detailed representation of the livestock production system subdivided into an intensive and an extensive component, and (iii) a spatially explicit distribution of potential (maximal) crop yields prescribed from the Lund-Postdam-Jena global vegetation model for managed Land (LPJmL). The economic principles governing decisions about land-use and intensification are adapted from the Ricardian rent theory, assuming cost minimisation for farmers. The land-use modelling approach described in this paper entails several advantages. Firstly, it makes it possible to explore interactions among different types of biomass demand for food and animal feed, in a consistent approach, including indirect effects on land-use change resulting from international trade. Secondly, yield variations induced by the possible expansion of croplands on less suitable marginal lands are modelled by using regional land area distributions of potential yields, and a calculated boundary between intensive and extensive production. The model equations and parameter values are first described in details. Then, idealised scenarios exploring the impact of forest preservation policies or rising energy price on agricultural intensification are described, and their impacts on pasture and cropland areas are investigated.

Interactions between food demand, biomass energy and forest preservation are driving both food prices and land-use changes, regionally and globally. This study presents a new model called Nexus Land-Use which describes these interactions through a generic representation of agricultural intensification mechanisms. The Nexus Land-Use model equations combine biophysics and economics into a single coherent framework to calculate crop yields, food prices, and resulting pasture and cropland areas within 12 regions inter-connected with each other by international trade. The representation of cropland and livestock production systems in each region relies on three components: (i) a biomass production function derived from the crop yield response function to inputs such as industrial fertilisers ; (ii) a detailed representation of the livestock production system subdivided into an intensive and an extensive component, and (iii) a spatially explicit distribution of potential (maximal) crop yields prescribed from the Lund-Postdam-Jena global vegetation model for managed Land (LPJmL). The economic principles governing decisions about land-use and intensification are adapted from the Ricardian rent theory, assuming cost minimisation for farmers. The land-use modelling approach described in this paper entails several advantages. Firstly, it makes it possible to explore interactions among different types of demand for biomass for food and animal feed, in a consistent approach, including indirect effects on land-use change resulting from international trade. Secondly, yield variations induced by the possible expansion of croplands on less suitable marginal lands are modelled by using regional land area distributions of potential yields, and a calculated boundary between intensive and extensive production. The model equations and parameter values are first described in detail. Then, idealised scenarios exploring the impact of forest preservation policies or rising energy price on agricultural intensification are described, and their impacts on pasture and cropland areas are investigated.

This article explores the critical role of labour market imperfections in climate stabilisation costs formation. To do so, we use a dynamic recursive energy-economy model that represents a second best world with market imperfections and short-run adjustments constraints along a long-term growth path. We show that the degree of rigidity of the labour markets is a central parameter and we conduct a systematic sensitivity analysis of the model results to this parameter. When labour markets are represented as highly flexible, the model results are in the usual range of existing literature, i.e. less than 2% GDP losses in 2030 for a stabilisation target at 550ppm CO 2 equivalent. But when labour markets rigidities are accounted for, mitigation costs increase dramatically. In a second time, the article identifies accompanying measures, namely labour subsidies, which guarantees against the risk of large stabilisation costs in the case of high rigidities of the labour markets. That vision complements the usual view that mitigation is a long-term matter that depends on technology, innovation, investment and behavioural change. Here we add the warning that mitigation is also a shorter-term issue and a matter of transition on the labour market.

To assess the sustainability of future development pathways requires models to compute long-run Economy?Energy?Environment scenarios. This paper presents the IMACLIM-R framework, aimed at investigating climate, energy and development inter-related issues. The model was built in an attempt to address three methodological challenges: to incoporate knowledge from economics and engineering sciences, to support the dialogue with and between stakeholders, to produce scenarios with a strong consistency, concerning especially the interplay between development patterns, technology and growth. These goals led to the development of a recursive structure articulating a static general equilibrium framework, including innovative features and sector-specific dynamic modules now concerning energy, transportation and industry. This paper provides the general rationale of the model and the description of all its components.

This paper proposes to test the global hybrid computable general equilibrium model Imaclim-R against macroeconomic data. To do so, it compares the modeled and observed responses of the Indian economy to the rise of oil price during the 2003-2006 period. The objective is twofold: first, to disentangle the various mechanisms and policies at play in India's economy response to rising oil prices and, second, to validate our model as a tool capable of reproducing short-run statistical data. With default parameterization, the model predicts a significant decrease in the Indian growth rate that is not observed. However, this discrepancy is corrected if three additional mechanisms identified by the International Monetary Fund are introduced, namely the rise in exports of refined oil products, the imbalance of the trade balance allowed by large capital inflows, and the incomplete pass-through of the oil price increase to Indian customers. This work is a first step toward model validation, and provides interesting insights on the modeling methodology relevant to represent an economy's response to a shock, as well as on how short-term mechanisms - and policy action - can smooth the negative impacts of energy price shocks or climate policies.

Tropical deforestation is responsible for 15-20% of total man-made emissions of greenhouse gases. In December 2007, at the international conference of Bali, the United Nations acknowledged that a viable solution to climate change must include a mechanism to limit deforestation and forest degradation. Today, the most widely used economic tool to reduce emissions is carbon markets: caps on emitters, and trade allowed between emitters and reducers, drive a price signal on carbon and provide incentives to control emissions. This report examines the different possibilities to broaden the range of this tool so that it helps reduce emissions from deforestation. The three main possibilities presented are a tax-based fund, the use of auctions revenues, and the issuance of tradable credits. The report does not discuss other instruments unrelated to carbon-related payments. We first summarize existing information on the causes of deforestation, and the impact forest loss has on the global climate. To the contrary of a commonly held view, we find that farmers, more than loggers, are driving deforestation. Some, mostly in Africa, cut the forest to grow staple crops, while others, especially in South America, do so in response to the increasing demand for commercial crops and cattle. Building on this analysis, we describe the different possibilities to link carbon markets to the fight against deforestation. In the latter case of the issuance of tradable credits, we find that while carbon markets could substantially increase the amount of funding available to develop projects and programs that reduce deforestation, demand for carbon credits must keep up with this potential new source of supply, probably around one billion ton of CO 2 per year. As an analysis conducted by EDF shows, the emission caps currently advocated by the European Commission for Europe and by the Lieberman-Warner bill for the US would create enough demand to generate a price signal around 20 €/tCO 2 . Other solutions such as reserve prices in auctions or credits banking have been put forward to mitigate the risk of too many deforestation credits flooding carbon markets.

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An hybrid framework coupling the bottom-up energy sector WEM model with the top-down general equilibrium model IMACLIM -R is implemented to capture the macro economic feedbacks of Chinese and Indian economic growth on energy and emissions scenarios. The iterative coupling procedure captures the detailed representation of energy use and supply while ensuring the microeconomic and macroeconomic consistency of the different scenarios studied. The dual representation of the hybrid model facilitates the incorporation of energy sector expertise in internally consistent scenarios. The paper describes how the hybrid model was used to assess the effect of uncertainty on economic growth in China and India in the energy and emissions scenarios of the International Energy Agency.