European forests are expanding. This trend, observed over the last two decades, suggests that European forests already serve to mitigate climate change by providing a sink for atmospheric carbon dioxide. The sink could be enhanced through forest management if it was tailored to fit such goal.
There are basically two strategies for managing expanding European forests: one may increase either the stock of wood or its annual increment. The stock of wood increases with forest age. In Europe, where most forests are managed, the forest age depends on the length of harvest cycles. Delayed harvest increases the carbon sink with an annual magnitude that lies in the range of 1–2% of the baseline carbon stock [1].
The harvest, however, cannot be delayed indefinitely: trees are not immortal, and hence they should be harvested before stand break-up (the stage when a large portion of trees dies within a short period of time due to age-related causes). The annual increment of wood peaks much earlier than stand break-up begins. Therefore, the maximum available stock of wood and the maximum available increment of wood cannot be achieved at the same harvest age. Maximization of the stock and maximization of its increment are mutually exclusive goals. This raises an important question: Which of them is more appropriate to the task of enhancing the forest carbon sink? The answer to this question could be found in the paper [2] that appeared in Carbon Balance and Management.
The climatic effects of afforestation are not limited to removing carbon dioxide from the atmosphere. Expanding European forests changes the physical characteristics of the land surface controlling the energy and water exchange between the land and the atmosphere, and thus may either amplify or reduce the local effects of global warming. Another paper [3] that appeared in Carbon Balance and Management shows that the regional expansion of forests may reduce the effects of global warming in some places of Europe.
The idea that afforestation may change local climate is two hundred year old. In 1809, V. Ia. Lomikovskii planted tall trees around plowed fields in the Poltava Province of Ukraine. The scientific principles of protective afforestation were elaborated by V. V. Dokuchaev and G. N. Vysotskii at the end of the 19th century [4]. An impressive experiment, known as the Stalin’s plan for the transformation of nature [5], was done in the middle of the past century. However, there were little or no efforts to evaluate the validity of the idea with climate models, and so one would be interested to see model projections of how the climate may change in Poltava if European forests will expand to their natural extent [3].
It seems that these two papers [2-3] could be a good start for a thematic series, that would pull together various research and give us a better understanding of the climate benefits of European forests. We are now inviting submissions to add to this series, and to further our understanding of the climate benefits of afforestation.
[1] Georgii A Alexandrov. Carbon stock growth in a forest stand: the power of age. Carbon Balance and Management 2007, 2:4 [http://www.cbmjournal.com/content/2/1/4]
[2] Georg E Kindermann, Stefan Schörghuber, Tapio Linkosalo, Anabel Sanchez, Werner Rammer, Rupert Seidl and Manfred J Lexer. Potential stocks and increments of woody biomass in the European Union under different management and climate scenarios. Carbon Balance and Management 2013, 8:2 [http://www.cbmjournal.com]
[3] Borbala Galos, Stefan Hagemann, Andreas Haensler, Georg Kindermann, Diana Rechid, Kevin Sieck, Claas Teichmann and Daniela Jacob. Case study for the assessment of the biogeophysical effects of a potential afforestation in Europe. Carbon Balance and Management 2013, 8:3 [http://www.cbmjournal.com]
[4] P. D. Nikitin. Polezaschitnoe lesorazvedenie. Big Soviet Encyclopedia. [http://bse.sci-lib.com/article090695.html], (in Russian).
[5] Stephen Brain. The Great Stalin Plan for the Transformation of Nature. Environmental History 2010, 15 (4): 670-700.
