Amplifying effects of land-use change on future atmospheric CO2 levels

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 ofthe 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 effectland-use change; carbon cycle; future scenarios

The establishment of the High Level Panel of Experts on food security and nutrition (HLPE). Shared, independent and comprehensive knowledge for international policy coherence in food security and nutrition

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

Écobilans de biocarburants : une revue des controverses

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=129National audienceLife-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)

IMACLIM-R: a modelling framework to simulate sustainable development pathways

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.

Implementation of REDD+ in sub-Saharan Africa: state of knowledge, challenges and opportunities

Deforestation and forest degradation represent an important part of global CO2 emissions. 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 TgCO2 yr−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 policie

IMACLIM-R: a modelling framework to simulate sustainable development pathways

International audienceTo 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