استراتژی های جنگل کاری و انطباق مدیریت الوار در سیاست آب و هوایی.تجزیه و تحلیل تعادل عمومی قابل محاسبه

This paper analyzes the role of forest-based carbon sequestration in a unilateral EU27 emissions reduction policy under a Global Computable General Equilibrium (CGE) framework. Forestry mitigation is introduced into the model relying on carbon sequestration curves provided by a global forestry model. The structure of the original CGE is extended to consider land use change and timber supply effects, resulting from the use of forest sinks to reduce carbon emissions. Results show that afforestation and timber management could lead to substantially lower policy costs. By using forest-carbon sinks it is possible to achieve the 30% emissions reduction target with an additional European effort of only 0.2% of GDP compared with the cost of a 20% emissions reduction without forestry. Carbon price is also reduced, by approximately 30% in 2020. European forest-carbon sequestration may have, however, the perverse effect of increasing timber production in areas of the world which already have high deforestation rates. A sensitivity analysis on main parameters confirms the robustness of our results. Highlights ► We analyze the role of forest carbon sequestration in stabilizing climate, in Europe. ► We use a Computable General Equilibrium model to analyze forest carbon effects. ► The inclusion of afforestation and timber management leads to lower policy costs. ► Carbon price drops by around 30% in 2020 reducing the leakage effect. ► European forest-carbon sequestration may increase tropical deforestation.

Forests provide several economic and environmental services (Schulze et al., 2000), such as water flow regulation, recreation, esthetic values, and carbon sequestration. Although a detailed carbon plan has not yet been articulated in any specific legislation, the direction of the international debate on forest-carbon intends to strengthen the already existing policies on forestry, and to extend its contribution. In addition to the next phase (2013–2020) of the European Unions' Emissions Trading Scheme (EU-ETS), international forest-carbon has been central for deliberations to the climate change policies proposed in Brazil, which launched the Amazon Fund in 2008, in Australia, in Japan, and in the United States. Aiming to enhance the use of forest-carbon sinks, in 2008, the United Nations created the Reducing Emissions from Deforestation and Forest Degradation Program (UN-REDD) and recognized the role of conservation, and sustainable management of forests to enhance forest-carbon stocks in developing countries. In 2009, the Copenhagen Accord clearly stated the need to develop mechanisms to reward sustainable land-use practices developing forest-carbon sequestration. Accordingly, the range of climate mitigation options of the forestry sector was expanded through the REDD + mechanism, which is based on a payment system for developing countries that reduce emissions by avoiding deforestation and enhances forest-carbon stock through sustainable management.1 The REDD + mechanism has been acknowledged, within the international debate, as a key target for a future binding agreement on climate change mitigation. While the international debate has been centered on avoided deforestation (AD), the annual volume of transaction for afforestation (AR) projects, in both voluntary and compliance markets have been growing in time, and it surpasses the value of AD projects. Today it represents 60% of the total volume of forest-based projects, corresponding to approximately 8 Mt CO2 (Hamilton et al., 2010).2 An extensive number of studies have estimated costs of forest-carbon sequestration, which highly depend on different assumptions, parameters, methodologies, and definitions. Richards and Stokes (2004) provide a useful summary of these estimates. After describing the major differences among the surveyed models, it concludes that carbon cost estimates range from 26–550 USD per t/CO2. Similarly, van Kooten and Sohngen (2007) more recently report that costs of sequestering forest-carbon are around 3–280 USD per t/CO2 and that Europe is the highest cost region. Both studies have identified three different approaches for cost analysis: bottom-up engineering cost studies,3 econometric studies of foresters' revealed preferences,4 and sector optimization models.5 The first set of models does not consider economic agents' responses when assessing the cost-effectiveness of a specific forest-investment activity. The second approach uses observed landowners' choices on land use to derive a relationship between land use change decisions and prices in the agricultural and forestry sectors. Finally, the third approach has the advantage of endogenizing agricultural and timber prices as a function of landowners' decision. Although most of these studies are not directly comparable, they share the conclusion that forestry provides cost-efficient mitigation opportunities, suggesting that significant amounts of carbon can be sequestered for less than 50$ per ton (see also Rose et al., 2008 and Lubowski et al., 2006). Linking a forestry model with a global climate economic model Sohngen and Mendelsohn (2003) and Tavoni et al. (2007) have concluded that forestry can contribute for around 1/3 of total CO2 abatement. These studies, however, provide a unified assessment of the forest sector, without disentangling the individual contribution of different forestry practices. In contrast, researchers who have focused on afforestation–reforestation (AR) and timber management (TM) potential to reduce CO2 emissions have usually dealt with specific geographic areas in the US and have normally relied on a partial equilibrium view, ignoring the general equilibrium aspects of the problem.6 In this paper we use a global computable general equilibrium model (CGE), to explore both direct and indirect socio-economic effects of AR-TM in Europe. The policy exercise assumes that Europe independently commits to reduce CO2 emissions below 1990 levels, by 20% and 30% in 2020. Similarly to Sohngen and Sedjo (2006) we do not restrain our analysis to afforestation practices but consider also timber management (TM) as an additional carbon abatement option. As a result, we have modified the original Intertemporal Computable Equilibrium System (ICES) model to capture the different impacts resulting from these two activities. Following the distinction in Richards and Stokes (2004), we investigate “secondary”, other than “primary” costs and benefits of AR-TM. In particular we examine the changes in policy costs, carbon sequestered, land-use change (converting timber-forests or agricultural land into carbon-forest land), as well as land and timber market prices. Finally, we observe the magnitude of leakage for the case of AR activities, often neglected by the literature and addressed only to the AD practices. By providing a multi-country, multi-sectoral account of the world economy, in which national economies are represented as a system of markets interconnected by domestic and international flows of input, goods and services, CGE models are particularly apt to analyze carbon leakage. 7 We believe that our investigation contributes to the current discussion on carbon sinks by analyzing the role of forests in Europe under a domestic climate change mitigation policy. We add to the literature by exploring global effects and by considering the “higher order” or general equilibrium outcomes determined once all adjustment mechanisms at play in the economic system have occurred. In fact, as CGE models are characterized by market interdependence, they are particularly pertinent to capture reallocation effects affecting the entire economic system. The paper is organized in 5 remaining sections. Section 2 briefly presents the model. It also describes the main changes implemented in the model and the methodology used to derive the cost curve. Section 3 draws the key results while Section 4 develops a sensitivity analysis on main coefficients. Section 5 concludes. In Appendix A, a more detailed description of the ICES model is provided.

In this paper, using a modified version of the ICES model, we study the socio-economic impacts of introducing European forest mitigation within the EU27 emissions abatement portfolio. Two independent mitigation policies are simulated for EU27: a 20% and 30% GHGs emissions reduction by 2020. To this aim ICES has been modified to include a forest-based carbon sequestration supply function, derived from a partial equilibrium model of the forestry sector. Therefore, an additional carbon mitigation option is introduced into the original ICES model. Further adjustments have allowed us to assess land competition effects for the changes in agricultural land availability and prices and timber supply change. Results show that a 20% reduction in emissions by 2020, when forestry is not included in the overall mitigation portfolio, implies a reduction in the EU27 GDP of approximately 1% compared with the baseline, a cost which increases to almost 2% when the target is more stringent (30%). The corresponding contraction of fossil fuel use drives a drastic drop in their prices. The decline of the prices of agricultural land in EU27 is more modest, 1.6%, and 2.3%, respectively. The independent EU27 policy raises the competitiveness of foreign-produced goods. Fossil fuels use increases in the regions outside the policy boundaries generating the well-known leakage effect. According to the IPCC (2007) definition for carbon leakage, this increase in outside emissions offsets EU27 emissions reduction efforts by 26% for the 20% scenario and by 28% for the 30% scenario. The inclusion of the AR-TM activities generates several important implications. Forestry-based carbon sequestration accounts for approximately 20% of the EU27 emissions mitigation efforts, reducing carbon prices by 27% ($31.42/t CO2) and 30% ($50.61/t CO2) for the 20% and 30% emissions reduction targets. Policy costs are also significantly reduced, making it possible to achieve the 30% emissions reduction target with an additional European effort of only 0.2% of GDP compared with the cost of a 20% emissions reduction without afforestation. When forestry sinks are used, European land prices increase due to the reduction in available agricultural land. This increase is, however, marginal. Interestingly, we observe that an EU unilateral policy, which actively uses forestry mitigation may create a perverse effect: timber production increases in areas of the world where deforestation of tropical or old-growth forests is currently taking place. Finally, our results revealed to be robust to sensitivity analysis on the main parameters concerning the introduction of a forest-based supply curve in our model. Although forestry mitigation should be part of a cost-effective climate policy, forests alone are not sufficient to achieve ambitious emissions cut targets. Accordingly, their ability to sequester carbon has to be considered as complementary to the development of an energy-based abatement strategy. This paper constitutes a first attempt to address the role of European forests in a climate change policy within a computable general equilibrium framework. Accordingly, the lack of other CGE studies on this subject does not allow us to establish a direct comparison of our results. Finally, an alternative approach to the one performed in this study consists in directly endogenizing land competition and forest-based carbon sequestration in a global CGE modeling framework. Such an exercise could be undertaken by coupling ICES with a land use model or by directly changing the model to the GTAP-AEZ database. While we recognize its importance we leave this exercise for future work.