Forests in Europe have dwindled to such an extent that they can no longer absorb as much carbon dioxide as they have, scientists recently reported in Nature Climate Change. Since 2005, the continent’s trees have not been absorbing as much atmospheric CO2 as they previously had, the result of a declining number of trees, deforestation and the impact of natural disturbances.
In fact, forests in Europe may have reached a “saturation point” such that they are no longer able to keep up with the amount of carbon released into the atmosphere as a result of human activity.
Trees play a key role in the carbon cycle, in which carbon is transferred among land, the sea and the atmosphere. Along with the ocean, soil, rocks and fossil fuels, forests and groves of trees serve as carbon sinks, storing carbon and keeping it from being recycled between the land and the atmosphere.
Wildfire and other natural disturbances are releasing more carbon into the atmosphere. But human activity is the main culprit. The Industrial Revolution, which started in Great Britain, altered the carbon cycle as humans began to burn fossil fuels. Huge quantities of carbon that had long been stored in the geosphere were released into the atmosphere as a result.
Meanwhile, the biosphere (the parts of the earth where living organism dwell) has shrunk due to the clearing of land as cities have grown and the construction of more factories, train tracks, roads, etc. The biosphere removes carbon from the atmosphere via photosynthesis; its reduction over time means that carbon sinks are being overtaxed.
In other words, planting trees to replenish forests in Europe can only make so much of a difference. The rapid industrialization in countries such as Brazil, China and India have also sped up the rate at which carbon is released into the atmosphere.
Old Forests Can Only Absorb So Much Carbon
The study’s findings are in apparent contradiction to the 2011 State of Europe’s Forests report in 2011, according to which forest cover in Europe has been increasing, to the point that trees cover almost half of Europe’s land and absorb 10 percent of the continent’s annual greenhouse gas emissions.
The researchers acknowledge that, after centuries of decline and deforestation, forests in Europe have been making a comeback. But as study co-author Gert-Jan Nabuurs of the Netherland’s Wageningen University and Research Center says to the BBC, the rate of afforestation — the planting of trees where none had been before — has been slowing.
Plus, in many forested areas, trees planted in the early 20th century or after World War II predominate. These trees, which are 70 to 80 years old, provide a key habitat for many types of wildlife and support biodiversity. But they “are starting a phase in the life of a tree where the growth rate starts to come down,” says Nabuurs. In comparison, areas with new forests which would have greater growth are relatively small.
Restoring Carbon Sink Is an International Effort
The study’s findings could have implications for European Union and member states’ climate mitigation efforts to reduce emissions. While we certainly need to maintain old forests, Nabuurs also says that, given the rise in carbon emissions globally, “maybe it is time to concentrate more on continuous wood production again and rejuvenate forests again, so then you have growing forests and a continuous flow of wood products,” to restore the carbon sink.
As many forests in Europe are maintained by small holders, a “pan-European, legally binding agreement on forest management” is needed, to “balance the ecological value of forests against the trees’ commercial and climate mitigation value.”
More than 40 nations have been working on such an agreement since 2011, but so far been unable to come to an accord about technicalities. European Union forestry ministers are to meet in mid-November and are hoping to create a draft accord about forest policy among nations.
While the Nature Climate Change study looks specifically at forests in Europe, its findings have ramifications for other parts of the world including south America and countries including Indonesia. Rainforests have been, and are being, cleared there at an alarmingly fast rate in the name of development. Palm oil plantations have replaced the forests in some areas but, as a 2012 Nature Climate Change study projected, those in Indonesia could emit over 558 million metric tons of CO2 by 2020, more than the amount of fossil fuel emissions from Canada.
If nothing else, the Nature Climate Change study is a powerful reminder of what trees do for us. They not only provide shade and shelter and food for all kinds of wildlife, but they help store the carbon we are sending into the atmosphere in amounts and at a speed never before known in the earth’s history.
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