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dimanche 20 mars 2016

Problèmes d'alimentation en vue à cause du réchauffement climatique

Nous apprenons par Carbonbrief que des problèmes d'alimentation sont envisagés avec une surmortalité liée au réchauffement climatique:
  • While the number of people dying from malnutrition around the world is expected to fall in coming decades, scientists say the benefits will be partly counteracted by the impacts of climate change on the availability of fruit, vegetables and staple crops, such as wheat and sorghum.
Cette information a attiré les sarcasmes habituels de Benoit Rittaud qui, pour nous "prouver" que ce ne sont que balivernes, ne trouve rien de mieux que nous montrer des courbes s'arrêtant au mieux en 2015, tirées du site de la FAO:
  • Évolution du nombre de personnes sous-alimentées dans le monde
  • Évolution de la quantité de nourriture par habitant par région du monde
  • Adéquation moyenne de l’offre alimentaire dans le monde

Plusieurs remarques à propos de ces courbes:
  1. elles sont historiques et ne présagent en rien de ce que sera le futur, elles peuvent donc très bien s'inverser
  2. personne ne nie que le nombre de personnes sous-alimentées dans le monde a baissé
  3. personne ne nie que la quantité de nourriture par habitant dans le monde a augmenté
  4. personne ne nie que l'offre alimentaire dans le monde s'est améliorée
Les allégations de Benoit Rittaud sont ce que l'on appelle un strawman.

Au contraire il est bien dit dans l'article de Carbonbrief:
  • While the number of people dying from malnutrition around the world is expected to fall in coming decades...
Mais c'est pour ajouter:
  • ...scientists say the benefits will be partly counteracted by the impacts of climate change on the availability of fruit, vegetables and staple crops, such as wheat and sorghum.
Ainsi deux études récentes sont parues:
  1. Timescales of transformational climate change adaptation in sub-Saharan African agriculture
  2. Global and regional health effects of future food production under climate change: a modelling study
La première est donc focalisée sur la zone sub-saharienne:
  • Climate change is projected to constitute a significant threat to food security if no adaptation actions are taken1, 2. Transformation of agricultural systems, for example switching crop types or moving out of agriculture, is projected to be necessary in some cases3, 4, 5. However, little attention has been paid to the timing of these transformations. Here, we develop a temporal uncertainty framework using the CMIP5 ensemble to assess when and where cultivation of key crops in sub-Saharan Africa becomes unviable. We report potential transformational changes for all major crops during the twenty-first century, as climates shift and areas become unsuitable. For most crops, however, transformation is limited to small pockets (<15% of area), and only for beans, maize and banana is transformation more widespread (~30% area for maize and banana, 60% for beans). We envisage three overlapping adaptation phases to enable projected transformational changes: an incremental adaptation phase focused on improvements to crops and management, a preparatory phase that establishes appropriate policies and enabling environments, and a transformational adaptation phase in which farmers substitute crops, explore alternative livelihoods strategies, or relocate. To best align policies with production triggers for no-regret actions, monitoring capacities to track farming systems as well as climate are needed.
La seconde est globale et régionale:
  • Background - One of the most important consequences of climate change could be its effects on agriculture. Although much research has focused on questions of food security, less has been devoted to assessing the wider health impacts of future changes in agricultural production. In this modelling study, we estimate excess mortality attributable to agriculturally mediated changes in dietary and weight-related risk factors by cause of death for 155 world regions in the year 2050.
  • Findings - The model projects that by 2050, climate change will lead to per-person reductions of 3·2% (SD 0·4%) in global food availability, 4·0% (0·7%) in fruit and vegetable consumption, and 0·7% (0·1%) in red meat consumption. These changes will be associated with 529 000 climate-related deaths worldwide (95% CI 314 000–736 000), representing a 28% (95% CI 26–33) reduction in the number of deaths that would be avoided because of changes in dietary and weight-related risk factors between 2010 and 2050. Twice as many climate-related deaths were associated with reductions in fruit and vegetable consumption than with climate-related increases in the prevalence of underweight, and most climate-related deaths were projected to occur in south and east Asia. Adoption of climate-stabilisation pathways would reduce the number of climate-related deaths by 29–71%, depending on their stringency.
  • Interpretation - The health effects of climate change from changes in dietary and weight-related risk factors could be substantial, and exceed other climate-related health impacts that have been estimated. Climate change mitigation could prevent many climate-related deaths. Strengthening of public health programmes aimed at preventing and treating diet and weight-related risk factors could be a suitable climate change adaptation strategy.

Mais ce n'est pas grave doit se dire Benoit Rittaud, les morts attendues devraient se produire essentiellement en Asie du sud et de l'est, donc loin de son petit jardin à la française dans lequel il pourra continuer à faire pousser ses tomates sans être trop perturbé par le réchauffement climatique.

Tout comme Philippe Verdier  qui demande "Devons-nous trouver pénible de pouvoir plus souvent déjeuner en extérieur au printemps et en automne ?".

Honnêtement je suis d'accord avec lui, je trouve bien agréable de pouvoir bénéficier de ma terrasse plus longtemps dans l'année, cependant je ne sais pas si l'on a demandé leur avis à ceux qui n'ont pas de terrasse...


 

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