Climate change effects on community structure and the carbon cycle

Climate change is real. It is expected to be the major threat to biodiversity and one of the main factors affecting human health and well-being over the coming decades. There is ample evidence that ecological responses are already occurring at the individual species level. But scaling from populations through to communities, let alone ecosystems, will be challenging (Montoya & Raffaelli 2010). For a compilation of papers on this topic, you can have a look at the issue I edited together with Dave Raffaelli on “The effects of climate change on biotic interactions and ecosystem services”.

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We use ecological theory and manipulative mesocosm experiments to investigate the effects of climatic warming on community structure and ecosystem service supply. In particular, we have shown that warming will change the biomass distribution across trophic levels and that it will benefit small organisms (Yvon-Durocher et al. 2011a), in agreement with the metabolic theory of ecology. Also, it will affect microbial process rates, like the biomass flux from bacteria to their consumers (Sarmento et al. 2010).

We are studying how climatic warming will affect one of the most important services provided by ecosystems: the carbon cycle, which modulates climate change via the regulation of atmospheric CO2. Increasing temperatures will affect the metabolic balance between the photosynthetic fixation and respiratory release of CO2. We have generated qualitative and quantitative predictions for changes in the metabolic balance that fitted our experimental results (Yvon-Durocher et al. 2010). Ecosystem respiration increased at a faster rate than primary production, and thus warming reduced carbon sequestration. This can be simply explained by differences in the sensitivity of both processes to temperature changes. Also, we have demonstrated that methane emission will increase really fast in a warmer world, a positive feedback not reported before (Yvon-Durocher et al. 2011b).

Mesocosms