Trees are considered a critical tool in the push to slow the effects of excessive carbon emissions on the global climate, but a recent study calls their contribution into question. According to a report from CS Monitor, some trees may actually be doing more harm than good when it comes to fighting climate change.

A recent study from scientists in France’s Laboratoire des Sciences du Climat et de L’Environnement suggests that not all trees are created equally when it comes to taking carbon out of the atmosphere. Europe’s two-hundred-year effort to manage forests may not have been doing the rest of the world any favors.

“Two and a half centuries of forest management in Europe have not cooled the climate,” the study said. Despite the total forest growth in Europe approaching about 10 percent since 1750, average temperatures in the continent have risen by about 0.12 degrees centigrade during the same time frame.

Researchers believe that the discrepancy may have something to do with the species of trees that have gained prevalence in Europe’s forests. Because many countries have decided to plant dark evergreen trees like pines and spruces, an excess amount of sunlight is absorbed, resulting in an overall increase in average temperature on the continent.

Other varieties of trees, like oaks and maples, have a tendency to reflect more sunlight than their coniferous cousins. Because evergreens are so dark, they trap more of the sun’s radiation near the surface of the Earth, making the temperature in Europe warmer on average.

Despite Europe’s efforts to manage their forests, it may turn out to be a thorn in the side of the continent’s ambitious climate goals. The study’s authors said that increased demand for the fast-growing wood from coniferous trees has outpaced the growth of trees that reflect more sunlight, which has resulted in an overall increase in absorbed solar radiation.

While the trees in Europe are still converting carbon dioxide into oxygen through the process of photosynthesis, they may still be having a warming effect on the climate.

The study, published in the journal Science, can be found here.