Planting trees may alleviate global warming in Europe

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As a result of human industrial activities, atmospheric carbon is increasing. This increase has significantly contributed to the climate change that we are experiencing in the world today, and the increasingly worrying predicted changes in climate in the near future. Much scientific research and effort is therefore currently being put into mitigating for these changes in order to ensure environmental stability.

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Deforestation has widely been discussed as a major contributor to increasing atmospheric CO2 and subsequently climate change. Most of this discussion revolves around the ability of forests to act as a ‘carbon sink’- storing carbon as vegetative biomass and preventing it from entering the atmosphere. However, the capability of forests to affect their environment is not limited to carbon sequestration. Forest cover also has significant biogeophysical effects due to alterations to the physical characteristics of the land caused by forest cover. Trees play an important part in influencing important interactions in energy and water flow between the land and the atmosphere. For example, deciduous trees have a large leaf area and low aerodynamic resistance, therefore lending this type of tree to enhanced evapotranspiration compared to other vegetation, cooling the surrounding air, and leading to cooler surface temperatures.

Image attributed to Luc Viatour/www.Lucnix.be

On a global scale, whether afforestation (planting trees in new areas) could have enough effect in a carbon sequestration sense to mitigate for deforestation is yet to be determined. However, in exciting new research published in Carbon Balance and Management  Gálos et al have investigated the potential biogeophysical effect of afforestation, which is an important mitigation strategy, in Europe. The team investigated using a regional climate model called REMO, developed by the Max Planck Institute for Meteorology, to model precipitation and temperature, using carbon projections from the A2 IPCC-SRES simulation. Predicted changes in climate due to projected increase in atmospheric CO2 and other greenhouse gases result in a large increase in variability and higher probability of extreme weather conditions in comparison with today. As the only continent with a significant increase of forest cover in recent times, it is important that the potential effects of this mitigation strategy are investigated.

The study demonstrates that in most parts of the temperate zone, afforestation could lead to cooler and wetter summers, and the probability of dry days and warm temperature extremes would increase.  Dr Borbála Gálos who led this study explained, “While we realize that the amount of afforestation included in our model is unrealistic in practice, even a more modest  program of planting trees could theoretically reduce the effect of climate change in Northern Europe. There is less of an effect in more southerly regions due to complex issues including soil moisture content. However, even in these areas, forest cover can provide localized benefits by making the surrounding air moister and cooler, sequestering carbon, protecting biodiversity and air quality, and preventing soil erosion.”

This study is published today in a new thematic series on ‘Climatic benefits of forests in Europe’. This series aims to provide a widely accessible forum for the discussion of the use of reforestation and afforestation to mitigate for local and regional climate change in Europe. For further information about this series, please contact editorial@cbmjournal.com.