Europe’s forest coverage has increased by 10% since 1750, but forest management methods have changed dramatically. According to a study published in the journal Science, this has led to a slight increase in global temperatures. EURACTIV’s partner Journal de l’Environnement reports.
The results of the study published on Thursday (4 February) may come as something of a surprise. The fact that the world’s forests absorb a quarter of all greenhouse gas emissions – against half for the oceans – means they are generally considered as one of our main allies against climate change.
But carbon is not the be all and end all when it comes to a forest’s impact on the climate, and a host of other factors must be considered.
Kim Naudts, a researcher form the French Climate and Environment Sciences Laboratory (LSCE) set out to do just that. He and his research team analysed the evolution of Europe’s forests since 1750. On the surface, the results appeared encouraging: after shrinking by 190,000 km² until 1850, the continent’s forest cover then increased by 386,000 km² by 2010, a net gain of 10% in 260 years.
But other factors must be taken into account. Firstly, Europe has lost 436,000 km² of hardwood forest since 1850, while coverage of conifers, a better commercial investment, has increased by 633,000 km². Secondly, 218,000 km² of coppice has been converted into high forest. And thirdly, 85% of European forests are now commercially exploited.
A temperature increase of 0.12 °C
As a result, Europe’s forests now hold 3.1 billion tonnes less carbon than they did in 1750. The switch from deciduous to coniferous forests is responsible for a 0.12°C temperature rise in the lower atmosphere, because less light is reflected from the winter snows in coniferous forests than in deciduous forests. Softwood trees, which keep their foliage throughout the winter, reduce the reflective capacity of the ground by 1%.
Outside Europe, this kind of forestry policy, integrating the fight against climate change and the cultivation of wood, is being widely emulated. China plans to plant 772,000 km² of trees, the USA 254,000 km² and Russia 170,000 km². Between 64% and 72% of the world ‘s forests are commercially exploited, and switching from deciduous to coniferous species is commonplace.
Refining forest management
According to the researchers, any plan to fight global warming based on land use should “of course integrate forest coverage, but also take into account how the forest in managed, because they do not all contribute to climate change mitigation”.
“The challenge now is to know if it is possible to find a strategy that will bring down the temperature while allowing the production of wood and other ecosystem services,” they added.
An Italian study, also published in Science on Thursday (4 February), examined the effects of global deforestation between 2003 and 2012 on climate change. The researchers concluded that deforestation would raise the temperature by approximately 1°C in the temperate and tropical zones, and in more than 2°C in arid zones, but would have no effect on the Boreal region.