Man-made forests contribute to climate warming rather than cooling it: study

Man-made forests are commonly recognized as key strategies for climate mitigation, but a new study said Thursday that Europe's managed forests are contributing to climate warming rather than countering it.

"Our study shows that historical land-cover changes and forest management in Europe did not mitigate climate warming," Chen Yiying, who took part in the research while studying at the Institute Pierre Simon Laplace in France, wrote in an email to Xinhua.

"This is surprising as it goes against the current assumption that all forests and all sustainable forest management cool the climate," said Chen, now research fellow at the National University of Singapore.

The study, published in the U.S. journal Science, reconstructed 260 years of historical land use in Europe and improved a complex computer model to calculate the amount of carbon, energy and water that is trapped or released by managing a forest.

By doing this, the researchers could analyze the effect of historical afforestation and forest management on the carbon balance and the contemporary climate.

The study showed that land-use changes since 1750 have increased Europe's forest area by 10 percent and put over 85 percent of the forests under management.

Meanwhile, strong favoritism of foresters to plant more commercially valuable trees -- such as Scot pines, Norway spruce and beech -- has resulted in reforestation of 633,000 square km of conifers at the expense of broadleaved forests, which decreased by 436,000 square km since 1850.

"Over the past 260 years, a lot of broadleaf forests have been converted into conifer forests which resulted in large scale tree species changes form deciduous (bright color) to evergreen (dark color)," Chen said.

"As the results, the European's forest management changes the surface energy budget and traps heat in the near surface atmosphere," which contributed to climate warming rather than mitigating it.

Besides, converting a natural forest to a man-made forest caused carbon stored in the biomass, litter, dead wood and soil of the forest to be released to the atmosphere.

Although Europe's forest management has a little contribution to regional warming, it does not strongly contribute to global warming, Chen noted.

"It shapes our understanding of the climate effects of forest management," Chen said of the study's significance. "It shows that we should be careful when planning large-scale changes in land-use because the net effects may be different than the anticipated outcome." Endit