Search

The global food system is failing to deliver sufficient and nutritious food to all, while damaging the earth and unsustainably drawing down its resources. We argue that trees and forests are essential to solving these challenges. We outline the current contributions of trees and forests to the global food system and present recommendations to leverage these contributions as part of the efforts to reshape food systems to better support healthy diets and environmental sustainability. Trees and forests provide nutrient-rich foods, incomes for food security, ecosystem services for food production, and add resilience to food systems. At the same time, trees and forests protect biodiversity and mitigate climate change through carbon sequestration. We recommend four approaches to realise the full potential of trees and forests to contribute to healthy and sustainable food systems: scaling up current tree-based food production, reorientating some agricultural investments towards nutrient-dense food production, repurposing production incentives from support of calorie-rich but nutrient-poor foods to support nutrient-dense foods, and integrate nutrition objectives into forest conservation and restoration programmes. Trees and forests have important roles to play in the transformation of our food systems, but more needs to be done to ensure that these roles are realised. [Abstract copyright: Copyright © 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.]

Non

While the policy momentum behind ecosystem restoration has never been stronger, restoration finance remains insufficient. A crucial information gap to unlock finance is the lack of robust and consistent data on the costs and benefits of restoration. This is due in part to the wide variety of contexts, interventions and objectives of restoration projects, and to the absence of well-defined standards and protocols for cost and benefit data collection. To fill this gap, we developed a standard framework to assess the costs and benefits of restoration projects and specific restoration interventions. The associated template for data collection, which was tested for usability during a piloting phase, is the first output of The Economics of Ecosystem Restoration (TEER), a multi-partner initiative under the aegis of the UN Decade on Ecosystem Restoration. It is the first attempt ever to improve the robustness and comparability of data on the economics of ecosystem restoration collected from the field at a global scale. Widespread adoption of this framework and associated template by a wide range of organizations implementing or financing restoration would allow for standardised data to be fed into a jointly owned database of restoration costs and benefits and serve as a basis for the further investigation of the economics of ecosystem restoration, including cost-benefits analysis. Better information on costs and benefits will help to inform acurate budgeting access to finance for restoration projects, and make them more likely to achieve their set goals and desired quantitative outcomes (e.g. area restored).

The International Rubber Study Group (IRSG), with the International Rubber Research and Development Board (IRRDB), the CGIAR research program on Forests, Trees and Agroforestry (FTA) led by CIFOR, and the French Agricultural Research Centre for International Development (CIRAD), ran an open digital workshop on natural rubber systems and climate change on 23–25 June 2020, attended by more than 500 scientists and stakeholders. The purpose of the workshop was to review recent research results on impacts of climate change on rubber production, potential means of adaptation and contribution to mitigation of climate change, and to identify knowledge and research gaps as well as recommendation for action. This document brings together the extended abstracts of the presentations and summaries of the discussions held during the workshop.

Forests, trees and agroforestry are part of major land-use transitions worldwide, with an impact on the balance between the global issues of planetary boundaries and local concerns about livelihoods and peoples’ rights. The 17 Sustainable Development Goals (SDGs) include complex trade-offs between various local and global interests in forests or derived land uses that require effective science-policy boundary work. Use-oriented research carried out by FTA connects three knowledge systems: the various scientific disciplines, local ways of knowing, and the way public discourses and policy reforms (re)frame issues, articulate common goals and seek effective means of implementation. Place-based, context-responsive sustainable development solutions need to build on identities and core values. These interact with socially contextualized rights, knowledge, markets, local ecosystem services and global teleconnections. This is an introduction to the FTA Highlights of a Decade series, which showcases the main findings, results and achievements of the CGIAR Research Program on Forests, Trees and Agroforestry (FTA) from 2011 to 2021. FTA, the world’s largest research-for-development partnership on forests, trees and agroforestry, started in 2011. This series features the work undertaken under the FTA program by its strategic partners: Center for International Forestry Research-World Agroforestry (CIFOR-ICRAF), The Alliance of Bioversity and CIAT, Centro Agronomico Tropical de Investigacion y Ensenanza (CATIE), French Agricultural Research Centre for International Development (CIRAD), Tropenbos International and International Bamboo and Rattan Organisation (INBAR); and other national and international partners. A decade of research and action by the FTA program has deepened the understanding of the roles of trees in farms and forests on the planet and of land-use and tree-use options in context. It has supported new market connections (traditional and new tree-based food, energy, biomaterials, environmental services), contributed to the emergence of more inclusive business models for tree-based value chains, informed the agendas of national and global forest, climate and food policy and facilitated new forms of governance for the “global commons.” All the work presented in this introduction and in the FTA highlights series was undertaken as part of the FTA program. The series aims to show the extent of actual contributions of FTA to research and development challenges and solutions over a decade, and indirectly, in doing so, to also provide a perspective on the genesis, history and evolving narratives on the related development issues.

The CGIAR Research Program on Forests, Trees and Agroforestry (FTA) organized over 10 days from 14 to 25 September 2020 its decadal conference. The fully digital event titled Forest, trees and agroforestry science for transformational change gathered more than 500 scientists from the programme and its working partners, from 69 countries across the globe, with more than 100 presentations and 40 posters. The conference also featured a set of science – policy – implementation panel discussions, including around controversial issues, with high profile scientists and key stakeholders, as well as a series of keynote speeches. The present publication gathers the 179 abstracts accepted for the conference. It constitutes a vivid illustration of the research developed by the program and its collaborative partners worldwide. All the material and presentations over the course of the 10-day conference is freely accessible on the FTA website: https://www.foreststreesagroforestry.org/fta-2020-science-conference-forests-trees-and-agroforestry-science-for-transformational-change/

Forest and landscape restoration (FLR) provides a framework for implementing restorative interventions that collectively address major environmental challenges such as soil and land degradation, biodiversity loss, water scarcity, lack of sustainable rural livelihoods, and climate change mitigation and adaptation. Restorative interventions can take many forms, which vary in cost, trajectory and specific economic and social outcomes; likewise, their benefits accrue to various actors and stakeholders. Over the last decade, the CGIAR Program on Forests, Trees and Agroforestry (FTA) has undertaken innovative basic and applied research across different scientific disciplines on the multiple dimensions of FLR for improving policy and practice and facilitating the uptake of new knowledge, tools and approaches — both from the top down and the bottom up. This publication presents key FTA outputs on forest and landscape restoration from 2011 to 2021. Many of them have contributed to informing the implementation of FLR interventions at multiple scales of work. These outputs are presented according to five broad areas of influence: (i) contributions to restoration science; (ii) contributions to global narratives and discourses; (iii) contributions to policy and governance; (iv) focusing on actors on the ground; and (v) contributions to national and international dialogues. The last section discusses ways to move forward.

Key messages Forests, trees and agroforestry play a key, often undervalued, role to support food security and nutrition (FSN), in its four dimensions (availability, access, utilization and stability). Forests, trees and agroforestry provide: (i) diverse and nutritious foods (such as nuts, oils, vegetables – leaves, flowers, roots –, fruits, bushmeat, fish, herbs, saps, mushrooms, tubers and insects), and feed for livestock; (ii) bioenergy for cooking and boiling water; (iii) income and employment (both formal and informal); and (iv) ecosystem services indispensable for agriculture and food production, now and in the future. All these contributions need to be better considered by policies aiming at strengthening food security and nutrition, towards SDG2. The contributions of forests and trees to FSN allow a broader and richer understanding of the notion of people’s “forest dependence”, with local to national and global dependences. Maximizing the contributions of forests, trees and agroforestry to FSN requires policy coherence and integrated landscape approaches. Agricultural policies need to better integrate the specificities of tree crops and the multiple benefits provided by the integration of trees in farming systems.

Land use is a central issue for the achievement of the Sustainable Development Goals (SDGs) and of the Paris Agreement on Climate Change. Plantations of all major tropical commodities are expanding quickly. This creates opportunities for development. It also raises concerns about the impacts of these plantations on the environment, landscapes and livelihoods. Natural rubber is a particularly interesting example to consider in the perspective of sustainable development of a commodity’s producing countries and value chains. This paper is a collaboration between the Forests, Trees and Agroforestry (FTA) research program of the CGIAR (FTA n.d.) and the International Rubber Study Group (IRSG) (IRSG n.d.). FTA works across a range of plantations, value chains and tree crop commodities, from timber, palm oil, cacao, coffee and tea to bamboo, rattan and rubber, among others.

Despite the high level of political engagement and the wide range of organizations involved in restoration projects from local to global levels, beyond some success stories, restoration is not happening at scale. To address this issue, three CGIAR Research Programs (CRPs) – Forests, Trees and Agroforestry (FTA); Policies, Institutions and Markets (PIM) and Water, Land and Ecosystems (WLE) – decided to bring together their expertise in a joint stocktaking of CGIAR work on restoration. This publication illustrates with concrete examples the powerful contribution of forest and landscape restoration to the achievement of most, if not all the 17 sustainable development goals. It can be used to support the design of future restoration activities, programs and projects. We hope that this document will help upscale restoration efforts and deliver enhanced impact from our CGIAR research.

Nudging the development trajectory of tropical landscapes towards sustainability requires a global commitment and policies that take diverse contexts and forest transitions into account. Out-scaling and upscaling landscape-level actions to achieve sustainable development goals globally need to be based on understanding of extrapolation domains and interconnectivity of products and services. We evaluated three portfolios of tropical landscape observatories and quantified extrapolation domains across ecological zones, stages of forest transition, human development index (HDI), population density and potential prominence of four dominant tropical tree crops (arabica coffee, cacao, rubber and oil palm). The ASB Partnership for Tropical Forest Margins portfolio was focussed on active humid forest margins and the Poverty and Environment Network on early stages of forest transition. The portfolio of sentinel landscapes of the Forests, Trees and Agroforestry (FTA) research programme provides a 5% sample of pantropical area, 8% of people, 9% of tree cover and 10–12% of potential tree crop presence, with quantified biases across zones, transition stages and HDI. In the ‘water tower’ configuration, relatively high population density coincides with biodiversity, coffee expansion and contested ecosystem services. The extrapolation domain of the FTA portfolio includes trade-off (tree loss) and synergy (restoration) phases of tropical forest transition.EDITED BY Paolo Omar Cerutti EDITED BY Paolo Omar Cerutti

Resume La question de la durabilite des regimes et des systemes alimentaires suscite un interet grandissant, tant de la part de diverses disciplines scientifiques que de la communaute internationale dans le contexte de l’appel des objectifs de developpement durable a l’eradication de la faim et de la malnutrition. Le but de cet article est d’examiner certains des liens entre les deux notions de regime et de systeme alimentaires durables afin de faciliter leur mise en œuvre. Le concept de regime alimentaire durable a ete defini en 2010, combinant deux perspectives totalement differentes : celle de la nutrition, centree sur les individus, et celle de la durabilite globale, dans toutes ses dimensions : environnementale, economique et sociale. Le point de vue de la nutrition peut etre facilement lie a l’objectif de l’amelioration de la sante. La perspective de durabilite pose un probleme plus complexe d’analyse. Nous proposons qu’elle soit apprehendee comme la contribution d’un regime alimentaire a la durabilite des systemes alimentaires. Une telle approche, couvrant les trois dimensions du developpement durable, permet d’identifier les interactions et les interrelations entre les systemes alimentaires et les regimes alimentaires. Elle offre la possibilite de trouver des leviers de changement vers la durabilite. Les regimes alimentaires sont a la fois le resultat du fonctionnement des systemes alimentaires et des moteurs de changement systemique. Les facteurs de changement pour chacun des acteurs au sein des systemes alimentaires, consommateurs, entreprises, etc., sont differents et peuvent etre declenches par des preoccupations differentes (sante, environnement, aspects sociaux et culturels). La prise en compte de ces differentes dimensions et motivations peut encourager la transition vers des regimes alimentaires durables, en fonction des specificites de chaque systeme alimentaire. L’adoption de regimes alimentaires durables peut etre facilitee et activee par la structure des systemes alimentaires, ainsi que par des politiques et des incitations appropriees.

Deforestation and forest degradation represent an important part of global CO2emissions. The identification of the multiple drivers of land-use change, past and present forest cover change and associated carbon budget, and the presence of locally adapted systems to allow for proper monitoring are particularly lacking in sub-Saharan Africa (SSA). Any incentive system to reduce emissions from deforestation and forest degradation (REDD+) will have to overcome those limits. This paper reviews the main challenges to implementing effective REDD+ mitigation activities in SSA. We estimate that SSA is currently a net carbon sink of approximately 319 TgCO2yr−1. Forest degradation and deforestation put the forest carbon stock at risk (mean forest carbon stock is 57,679 TgC). Our results highlight the importance of looking beyond the forest sector to ensure that REDD+ efforts are aligned with agricultural and land-use policies.

Sustainable diets and sustainable food systems are increasingly explored by diverse scientific disciplines. They are also recognised by the international community and called upon to orient action towards the eradication of hunger and malnutrition and the fulfilment of sustainable development goals. The aim of the present paper is to briefly consider some of the links between these two notions in order to facilitate the operationalisation of the concept of sustainable diet. The concept of sustainable diet was defined in 2010 combining two totally different perspectives: a nutrition perspective, focused on individuals, and a global sustainability perspective, in all its dimensions: environmental, economic and social. The nutrition perspective can be easily related to health outcomes. The global sustainability perspective is more difficult to analyse directly. We propose that it be measured as the contribution of a diet to the sustainability of food systems. Such an approach, covering the three dimensions of sustainability, enables identification of interactions and interrelations between food systems and diets. It provides opportunities to find levers of change towards sustainability. Diets are both the results and the drivers of food systems. The drivers of change for those variously involved, consumers and private individuals, are different, and can be triggered by different dimensions (heath, environment, social and cultural). Combining different dimensions and reasons for change can help facilitate the transition to sustainable diets, recognising the food system's specificities. The adoption of sustainable diets can be facilitated and enabled by food systems, and by appropriate policies and incentives.

International audience; The expansion of crop and pastures to the detriment of forests results into an increase in atmospheric CO2. A first obvious cause is the loss of forest biomass and soil carbon during and after conversion. A second, generally ignored cause, is the reduction of the residence time of carbon when for example forests or grasslands are converted to cultivated land. This decreases the sink capacity of the global terrestrial biosphere, and thereby may amplify the atmospheric CO2 rise due to fossil and land-use carbon release. For the IPCC-A2 future scenario, characterized by high fossil and high land-use emissions, we show that the land-use amplifier effect adds 61 ppm extra CO2 in the atmosphere by 2100 as compared to former treatment of land-use processes in carbon models. Investigating the individual contribution of each of the 6 land-use transitions (forest - crop, forest - pasture, grassland -crop) to the amplifier effect indicates that the clearing of forest and grasslands to arable lands explains most of the CO2 amplification. The amplification effect is 50% higher than in a previous analysis by the same authors which did not consider neither the deforestation to pastures nor the ploughing of grasslands. Such an amplificationeffect is further examined in sensitivity tests where the net primary productivity is considered independant of atmospheric CO2. We also show that land-use changes which have already occurred in the recent past have a strong inertia at releasingCO2, and will contribute to about 1/3 of the amplification effect by 2100. These results suggest that there is an additionnal atmospheric benefit of preserving pristine ecosystems with high turnover times.

A model is presented here, which attempts to determine interactions between change in land use and concentration of atmospheric CO2 over the 1700-2100period. The main impact of the conversion of forests to agricultural areas is the increase of atmospheric CO2 because of the losses of biomass and soil carbon in favour of the atmosphere. This raise will probably increase in the next years, correlated with the proportion of cultivated areas. We show here that this first-order effect is amplified by the correlative decrease of terrestrial sinks of CO2; in fact, as forests are replaced by cultivated parcels, carbon residence time in biosphere decreases, as well as sequestration ability of these ecosystems. This amplification effect leads to an additional increase in atmospheric CO2, which could reach 100 ppm in 2100. The uncertainties on the range of such an increase are important since they cumulate both uncertainties on the behaviour (sink or source) of terrestrial ecosystems in the future and inherent uncertainties of the modeling of carbon fluxes linked to changing land uses. . . Such an additional increase in CO2 is partially limited by the ocean reservoir and by the existing CO2 sinks in primary non-anthropologically disturbed ecosystems. The results imply that conservation ofprimary forests, for which primary productivity and carbon time of residence are high, is an efficient strategy for greenhouse effect mitigation. © 2003 Academie des sciences. Publie par Elsevier SAS. Tous droits reserves.

Climate change policies need to consider the contribution of each emitting region to the increase in atmospheric carbon dioxide. We calculate regional attributions of increased atmospheric CO2 using two different assumptions about land sinks. In the first approach, each absorber region is attributed 'domestic sinks' that occur within its boundaries. In the second, alternative approach, each emitter region is attributed 'foreign sinks' that it created indirectly through its contribution to increasing CO2. We unambiguously attribute the largest share of the historical increase in CO2 between pre-industrial times and the present-day period to developed countries. However, the excess CO2 in the atmosphere since pre-industrial times attributed to developing countries is greater than their share of cumulative CO2 emissions. This is because a greater fraction of their emissions occurred more recently. If emissions remain high over the coming decades, the share of excess CO2 attributable to developing countries will grow, and the sink service provided by forested regions-in particular those with tropical forest-to other regions will depend critically on future tropical land-use change.

Following the 2007-2008 food crisis, improvements of world food governance was at the centre of international discussions, leaning towards a new Global Partnership for Agriculture, Food Security and Nutrition. In this process, the issue of the management of various streams of knowledge appeared a central element to allow for better policy coordination, and led to the creation of the High Level Panel of Experts on food security and nutrition (HLPE). Here we describe the genesis and unveil the rationale underneath the creation of this expert process aiming at a better shared understanding of food insecurity of its causes and of potential remedies, and at helping policy-makers to look forward to emerging issues. Drawing lessons from other international expert processes at the interface between expertise and decision-making, we describe the internal rules of the expertise process, as well as the "boundary rules" that frame relations and exchanges between the expert body and decision makers, and show how critical the "fine-tuning" of those rules is not only for the expert process, but also, for the political negotiation platform itself., Suite à la crise alimentaire de 2007-2008, la réforme de la gouvernance alimentaire mondiale a été au centre des discussions internationales, orientées vers la création d'un partenariat mondial pour l'agriculture, la sécurité alimentaire et la nutrition. Dans ces débats, la question de la confrontation des courants de connaissances a été identifiée comme élément déterminant pour permettre une meilleure coordination des politiques. Ceci a conduit à la création du Groupe d'experts de haut niveau sur la sécurité alimentaire et la nutrition (HLPE). Nous décrivons ici la genèse et les sous-jacents de ce panel d'experts qui vise à une compréhension partagée de l'insécurité alimentaire, de ses causes et des remèdes possibles, et qui ambitionne d'aider les décideurs à anticiper les questions émergeantes. En tirant les leçons d'autres processus internationaux d'expertise à l'interface entre science et décision (GIEC, IAASTD), nous décrivons les règles internes du HLPE, ainsi que ses règles qui définissent son interface avec les organes de décision. Nous soulignons l'importance que revêtent ces règles, jusque dans leur détail, tant pour le processus d'expertise lui-même, que pour le bon fonctionnement de la plate-forme de négociation politique.

International audience; 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 sectorspecific dynamic modules now concerning energy, transportation and industry. This paper provides the general rationale of the model and the description of all its components.

On the eve of the 15th climate negotiations conference in Copenhagen, the pressure to assess all climate mitigation options is mounting. In this study, a bio-physic model and a socio-economic model were designed and coupled to assess the carbon sequestration potential of agricultural intensification in Senegal. The biophysical model is a multiple linear regression, calibrated and tested on a dataset of long-term agricultural trials established in West Africa. The socio-economic model integrates both financial and environmental costs related to considered practice changes. Both models are spatially explicit and the resulting spatial patterns were computed and displayed over Senegal with a geographic information system. The national potential from large-scale intensification was assessed at 0.65-0.83 MtC. With regards to local-scaled intensification as local projects, the most profitable areas were identified in agricultural expansion regions (especially Casamance), while the areas that meet the current financial additionality criteria of the Clean Development Mechanism were located in the northern part of the Peanut Basin. Using the current relevant mode of carbon valuation (Certified Emission Reductions), environmental benefits are small compared to financial benefits. This picture is radically changed if "avoided deforestation", a likely consequence of agricultural intensification, is accounted for as the greenhouse gases sink capacity of projects increases by an average of a hundred-fold over Senegal.

We adapted an integrated model, RESPONSE, to assess the cost-optimized timing of oceanic, geological, and biological carbon sequestration versus fossil emission reduction to mitigate climate change in a context of uncertainty and learning about the magnitude of climate sensitivity to greenhouse-gas forcing. We find that the replacement of abatement measures in the energy sector by various sequestration measures can cut total mitigation policy costs by up to 35% for the Intergovernmental Panel on Climate Change (WMO and UNEP) A1B and A2 emissions scenarios. Biological carbon sequestration and carbon capture and geological or oceanic storage (CCS) contribute to relaxing carbon constraints on the energy sector while adapting to the level of climatic uncertainties. Afforestation, the most flexible option, is helpful in the short run to prevent excessively fast warming, while CCS in geologic or oceanic reservoirs is useful primarily in the longer run to mitigate against overshooting a desired temperature ceiling. In cases of leaky storage, CCS may be less appropriate than emission reduction to stabilize climate, especially if high reference emissions and/or high climate sensitivity are expected. Worst-case scenarios of high emissions and climate sensitivity might preclude to a certain extent the use of carbon sequestration as a substitute for fossil energy reductions. Therefore, the design of optimal sequestration policies depends critically on the anticipation of (1) long-term emission trends and (2) the effective value of the climate sensitivity.

Article publié dans la revue Natures, Sciences, Sociétés, 16:4, Octobre-Décembre, 2008, pp. 337-347 http://www.nss-journal.org/index.php?option=com_article&access=doi&doi=10.1051/nss/2008064&Itemid=129; National audience; Life-Cycle-Analyses of biofuels: a review of controversies. This review of Life-Cycle- Analyses of biofuels synthesizes a wide range of questions raised by the increasing production of biofuels and by agendas aimed at boosting biofuels in future energy consumption. It also shows that current LCAs must be deepened or harmonized in some methodological aspects, and that they remain restricted in number as well as focused on only few North-American and West-European agro-industries. Expanding these analyses to other contexts, biomasses and agricultural modes of production would prove beneficial chiefly for two reasons: (1) there are almost no other ways of exploring and identifying sustainable reservoirs of bioenergies, (2) the LCA results turn out to be highly susceptible on the one hand to the agricultural techniques applied (motorization, chemical inputs, irrigation) in specific ecosystems (climate and soil types), on the other hand to arbitrations relating to the use of co-products (animal feed, soil enhancement, co-production of energy).; Cette revue d'écobilans de biocarburants synthétise un ensemble de questions soulevées par l'émergence de la production de biocarburants et la place ambitionnée pour ces derniers dans les consommations énergétiques à venir. Elle montre également que les écobilans réalisés à ce jour doivent être approfondis et harmonisés sur certains aspects méthodologiques, et qu'ils demeurent restreints en nombre tout en étant largement centrés sur quelques agro-industries nord-américaines et ouest-européennes. Il serait bénéfique d'élargir ces analyses à d'autres contextes, biomasses et modes agricoles de production pour deux grandes raisons : (i) la recherche de réservoirs durables de bioénergies l'impose, (ii) le résultat des écobilans s'avère fortement sensible, d'une part aux techniques agricoles employées (motorisation, intrants chimiques, irrigation) dans des écosystèmes spécifiques (types de climat et de sol), d'autre part aux arbitrages relatifs à la valorisation des coproduits (alimentation animale, amélioration des sols, coproduction d'énergie).

International audience; A new momentum is underway to account for emissions from "avoided deforestation and degradation" at the United Nations Framework Convention on Climate Change (UNFCCC). This paper assesses the feasibility of one of the Reducing Emissions from Deforestation and Degradation (REDD) mechanisms currently discussed, namely that of "Compensated Reduction", in the case of Cameroon. Here we assess the differential revenues that a farmer could get from 1 ha of land out of two alternative land-uses: shifting cultivation, the traditional land-use pattern in southern Cameroon, or carbon credits as compensation for the conservation of primary forest. It is found that a break-even price of $2.85/t of carbon dioxide equivalent would level shifting cultivation with "Compensated Reduction". This result suggests that at current carbon prices, and independently form variations in the discount rate, it could already be more profitable to preserve the primary forest rather than to log it in order to grow crops. © 2008 Elsevier B.V. All rights reserved.

This paper addresses the timing of the use of biological carbon sequestration and its capacity to alleviate the carbon constraint on the energy sector. We constructed a stochastic optimal control model balancing the costs of fossil emission abatement, the opportunity costs of lands allocated to afforestation, and the costs of uncertain climate damages. We show that a minor part of the sequestration potential should start immediately as a 'brake', slowing down both the rate of growth of concentrations and the rate of abatement in the energy sector, thus increasing the option value of the emission trajectories. But, most of the potential is put in reserve to be used as a ''safety valve'' after the resolution of uncertainty, if a higher and faster decarbonization is required : sequestration cuts off the peaks of costs of fossil abatement and postpones the pivoting of the energy system by up to two decades., Cet article traite du tempo de l'utilisation de la séquestration biologique de carbone, et de sa capacité d'alléger la contrainte carbone pesant sur le secteur énergétique. Nous avons construit un modèle de contrôle optimal stochastique, mettant en balance les coûts de réduction des émissions fossiles, les coûts d'opportunité des terres destinées à l'afforestation, et les coûts de dommages climatiques incertains. Nous montrons qu'une petite partie du potentiel de séquestration doit être utilisée immédiatement tel un "frein" à l'augmentation des concentrations de CO2 et aux efforts de réduction d'émissions dans le secteur énergétique, jouant donc à accroitre la valeur d'option des trajectoires d'émission de court terme. La majeure partie du potentiel de séquestration est réservée à un usage potentiel ultérieur à la résolution des incertitudes climatiques, au cas où une "mauvaise surprise" imposerait des taux de décarbonisation très élevés. Dans ce cas, l'utilisation de la séquestration biologique arase jusqu'à 40% du pic de coût de réduction fossile et permet de différer la date de pivotement du secteur énergétique de jusqu'à deux décades.

International audience; This chapter uses the mass-conservation equations for CO2 and its isotopomers 13CO2 and CO18O that can be used to infer globally biospheric and oceanic net fluxes in the case of 18C, and gross terrestrial biospheric fluxes in the case of 18O. The quantitative use of atmospheric measurements of 13C and 18O in CO2 to better constrain those fluxes requires knowledge of various processes specific to each isotopomer. The chapter is divided into two parts, one on each isotope. For 13C, it reviews existing work that calculated isofluxes either using global estimates or derived isofluxes from spatially and temporally explicit models. In addition, it estimates the magnitude of new isofluxes that were not addressed in former studies. These cover the effects of biomass burning, rock weathering and volcanism, and the oxidation of reduced carbon gases into CO2 within the atmosphere.

We constructed a model to analyze the interactions between land-use change and atmospheric CO2 during the recent past and for the future. The primary impact of the conversion of forested lands to cultivated lands is to increase atmospheric CO2, via losses of biomass and soil carbon to the atmosphere. This increase is likely to continue in the next decades, but its magnitude can vary according to each land-use scenario. We show that this first-order effect is further amplified by the correlated diminution of terrestrial sinks, because when croplands replace forests, the turnover time of excess carbon in the biosphere decreases, and hence the sink capacity of terrestrial ecosystems decreases. This effect acts to further increase by up to 100 ppm the CO2 level reached by 2100, and it is of the same order of magnitude, although smaller, than climate-carbon feedbacks. Uncertainties on the magnitude of this land-use induced effect are large, because of uncertainties in the sink role of terrestrial ecosystems in the future and because of uncertainties inherent to the modeling of land-use induced carbon emissions. Such an extra rise in atmospheric CO2 is however partially offset by the ocean reservoir and by sinks operating over undisturbed, pristine ecosystems, suggesting that conserving pristine forests with long turnover times might be efficient in mitigating the greenhouse effect