European forests are reaching saturation point as carbon sinks, claims a new study appearing in the publication ‘Nature Climate Change’ and featuring in a BBC News article. The report states that the amount of CO2 absorbed by the European forest has been diminishing since 2005 as a result of declining volumes of trees, deforestation and the impact of natural disturbances.
The authors of the report, which include a team of seven climate scientist headed by Dr Gert-Jan Nabuurs from Wageningen University and Research Centre, Netherlands, said the continent's forests had been recovering in recent times after centuries of previous decline and that this growth had provided a "persistent carbon sink" which it had been hoped would continue for decades to come.
However, the team's study has offered stark warnings that the carbon sink provided by this huge eco-system is now approaching saturation point:
"The stem volume increment rate (of individual trees) is decreasing and thus the sink is curbing after decades of increase," the report warns.
“Land use is intensifying, leading to deforestation and carbon losses. Natural disturbances such as wildfires are increasing and, as a consequence, so are the emissions of CO2. All of this together means that the increase in the size of the sink is stopping; it is even declining a little," concludes Dr Nabuurs; "we see this as the first signs of a saturating sink" he is reported to have told BBC News.
The study’s conclusions confirm the headline assumption that the forest in Europe is growing, but cautioned that the rate of growth is slowing. Dr Nabuurs said the rate of afforestation was in decline because a sizeable proportion of the European forest is now mature stands of trees planted in the early part of the 20th Century in post-war Europe.
"These forests have now reached 70-80 years old and are starting a phase in the life of a tree where the growth rate starts to come down," he explained. "So you have large areas of old forest and even if you add these relatively small areas of new forest, this does not compensate for the loss of growth rate in the old forests".
However, these mature woodlands are widely recognised as habitats for natural biodiversity. This could even lead to the problem of having to make a choice between a forests' ecological value and its effectiveness at sequestering CO2.
Commenting on the study, John Roche, spokesperson for industry environmental group FOPAP, states that the findings are significant because they highlight the fact that trees eventually get old and die; an element of carbon sequestration modelling he says is often overlooked, “When policymakers are making decisions about how to effectively utilise a forest and determining its efficacy as a carbon sink, they need to understand that no matter how much CO2 a tree absorbs in its lifetime it will return its entire carbon stock to the atmosphere when it dies. This means that the capacity for a forest to act as a carbon sink will always eventually diminish.”
This latest study of the European forest backs up the conclusion of the similar 2011 State of Europe's Forests report, that trees cover almost half of Europe's land area and absorb about 10% of its annual CO2 emissions. Roche says that this statistic, as impressive as it may seem, is meaningless when put into context with the emissions that are not absorbed by the forest.
“90% of man-made CO2 in Europe is not absorbed by the European forest. Considering that the forest already covers half of Europe, it would take a forested area some five times bigger than the whole of continental Europe to capture these emissions; the world simply does not have the space.”
Roche does believe, however, that the truth of the state of the European forest could present an opportunity for the printing and paper industries:
“In the report, Dr Nabuurs says it is time to concentrate on continuous wood production again to rejuvenate the forests through a continuous flow of wood products. I agree wholeheartedly with this. It is FOPAP’s long assertion that the only way to actively remove CO2 from the atmosphere is to use trees for paper and other wood-based products before they grow too old and replace them with younger, CO2-hungry saplings. Among other things, this means recycling less paper to encourage the demand for trees which, in turn, would help bring the European forest back to health. It would seem that Dr Nabuurs and his team have arrived at the same conclusion from a different perspective. Nevertheless, it is the same conclusion.”
A copy of the original article as it appeared in Nature Climate Change can be purchased here: http://www.nature.com/nclimate/journal/v3/n9/full/nclimate1853.html
A copy of the related BBC News article can be found on its website here:
A copy of the news article as it appears on the European Forests Institute website can be found here: http://www.efi.int/portal/news___events/news/?bid=1253