All over the world, people are engaging in massive tree-planting campaigns to help stop climate change — but will it do any good? Previous research has emphasized that planting trees can’t be our only climate change mitigation strategy, but a new study from researchers at the University of Exeter paints an even bleaker picture.

Historically, scientists have believed that tress can slow climate change by sequestering carbon, removing it from the air and storing it in their wood. While the ability of trees to store carbon is helpful, ecologists say that it’s the carbon storage of the entire ecosystem is important too.

These ecologists measured stored carbon in a Northern Scotland ecosystem — both above and below ground — in experimental areas where trees had been planted either 12 or 39 years previously. They then compared this ecosystem to nearby control areas where the natural heather moorland had been left undisturbed.

Surprisingly, researchers found that plots with trees did not have greater ecosystem carbon storage than the undisturbed sections. Even though the trees themselves stored carbon, this was counter-acted by a decrease in the organic carbon present in the soils where the trees were growing.

This doesn’t mean that planting trees can’t be helpful in certain cases — reforesting areas that once had trees could have many benefits. But this study stresses that planting trees is not a one-size-fits-all solution and that it shouldn’t be done indiscriminately. In areas that haven’t historically had trees, or in places with large amounts of organic carbon present in the soil, planting trees might not be beneficial at all.